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Introduction
It has long been recognized that certain reptilian
and amphibian groups once thrived at higher lat-
itudes than they do today (e.g., Matthew 1939;
Estes 1970; see also von Zittel 1901). Dermatemy-
didae (Hay 1908, although Hay included taxa that
are unrelated [see, e.g., Joyce 2007]), Crocodylia
(Estes and Hutchison 1980; Markwick 1998;
Eberle et al. 2010) and Boinae (Holman 2000) are
obvious examples. The self-consistent view devel-
oped, supported by more direct climatologic data
from the Neogene, that a warmer Earth had per-
mitted modern tropical taxa to occur outside their
present ranges and that later Cenozoic climatic
cooling drove these taxa toward the equator (e.g.,
de Fejérváry 1935; Matthew 1939; Böhme 2003).
Near the boundary between the Eocene and
Oligocene epochs, in particular in the earliest
Oligocene, a profound transition took place in the
global climate system (Prothero 1994). Average
global sea surface temperature declined by about
4 °C over the course of 300,000 years, with higher
latitudes experiencing larger drops (Liu et al.
2009). The East Antarctic Ice Sheet expanded rap-
idly (Miller et al. 1991; Coxall et al. 2005). The
The Evolution of Mid-latitude Faunas during the Eocene:
Late Eocene Lizards of the Medicine Pole Hills Reconsidered
Krister T. Smith
Department of Paleoanthropology and Messel Research, Senckenberg Research Institute,
Senckenberganlage 25, 60325 Frankfurt am Main, Germany
—email: krister.smith@senckenberg.de
Abstract
The Medicine Pole Hills local fauna of the late Eocene (Chadronian) of North Dakota affords an ex-
ceptional view of a terrestrial community in central North America prior to the climatic deteriora-
tion of the earliest Oligocene. The recovery of hundreds of new squamate specimens—particularly
abundant dermal skull bones—gives occasion for a re-evaluation of that portion of the assemblage.
This work represents the first attempt to associate significant amounts of cranial material from a
large number of closely related species. New material of Polychrus charisticus suggests it lies outside
the crown of Polychrus (monkey lizards). One previously known but unnamed species is a crown
iguanine (true iguana) related to Dipsosaurus dorsalis (the Desert Iguana). Another lies within
crown Corytophaninae (basilisks) on the stem of Laemanctus + Corytophanes. New material of Tu-
berculacerta pearsoni indicates that its proposed relation to Phrynosomatinae (fence lizards, horned
lizards, and others) was probably in error; however, a well-supported alternative hypothesis has not
emerged. Unusual similarities are reported between Hoplocercinae (spiny-tailed and dwarf igua-
nas) and Cypressaurus, but more material from the latter taxon is needed for a firm phylogenetic
determination. The presence of a diploglossine (galliwasp) in the assemblage is confirmed and two
additional small anguids are reported: an annielline (the last known central North American record
of the California limbless lizard lineage) and a gerrhonotine (alligator lizard). On the basis of the
new specimens, the number of independent iguanid lineages is reduced from eight to five. How-
ever, the higher-taxonomic diversity of Iguanidae in the late Eocene is strengthened. Eocene lizard
faunas in central North America show considerable faunal continuity, consistent with the notion
that middle and high latitudes were warmer in the late Eocene than previously thought. Late Eocene
faunas are still dominated by lineages with exclusively tropical living representatives but also in-
clude several lineages that today remain extratropical.
Keywords
Greenhouse climate, climate change, Squamata, Iguanidae, Anguidae, Eocene, biogeography
Bulletin of the Peabody Museum of Natural History 52(1):3–105, April 2011.
© 2011 Peabody Museum of Natural History, Yale University. All rights reserved. • http://www.peabody.yale.edu
global character of these changes as well as proxy
measurements of the partial pressure of atmos-
pheric CO
2
support declining greenhouse gas
concentrations as a primary forcing mechanism
(DeConto and Pollard 2003; Pagani et al. 2005;
Zanazzi et al. 2007; Liu et al. 2009; Pearson et al.
2009), rather than regional changes like the open-
ing of ocean gateways (e.g., Exon et al. 2004).
Zanazzi and co-workers (2007) conducted the
most recent geochemical analysis of climates
in the Rocky Mountain interior across the
Eocene–Oligocene boundary interval. These
authors examined the relationship between ␦
18
O
in fossil bone and tooth enamel and interpreted
changes in these two repositories over the course
of no more than 400,000 years as reflecting an 8.2
± 3.1 °C decline in mean annual temperature. At
the same time, it has been argued that smaller and
more gradual decreases in temperature occurred
in other parts of North America (such as on the
western coast of mid-latitude North America
[Retallack et al. 2004] and around the Greenland
Sea [Eldrett et al. 2009]). Thus, theories of climate
change now have a firmer evidentiary basis, even
if details remain to be worked out.
Yet, Matthew’s (1939:120) observation, with
regard to the relationship between climate and
evolution, that the “evidence from fossil lizards is
very slight” still largely holds true today. The fos-
sil record of lizards in the Tertiary has seen only
modest improvements in the intervening decades.
The reasons Matthew gave—the scant and frag-
mentary nature of the fossil specimens—are still
an obstacle. But obstacles may be overcome, and
the advent of screenwashing (Hibbard 1949) to
supplement quarrying and surface-collecting has
greatly increased the quantity of available raw
material. The decades since Gilmore (1928) have
also seen increasing emphasis on the precise phy-
logenetic relations between fossil and living taxa
(Gauthier 1982; Estes 1983). We need no longer
be content, like Matthew, with the mere assign-
ment of a species to a “family.”
To understand the nature of the squamate
response to Eocene–Oligocene climatic deterio-
ration in central North America, Smith (2006a)
examined the lizards of a rich, late Eocene assem-
blage from North Dakota and found this group
of poikilothermic reptiles to be more diverse than
previous collections had suggested (Emry 1973;
Hutchison 1992; Sullivan and Holman 1996).
However, his taxonomic conclusions were lim-
ited by near-exclusive reliance on dentigerous ele-
ments, principally dentaries and maxillae. New
collections derived from recent excavations of the
same locality by Dean Pearson (Pioneer Trails
Regional Museum, Bowman, North Dakota) and
Allen Kihm (Minot State University, Minot,
North Dakota) as well as re-examination of pre-
viously dry-screened material has turned up a
wealth of new elements belonging to the same
taxa, as well as remains of two previously unrec-
ognized lineages in the assemblage. The new spec-
imens, especially the abundant dermal cranial
remains of iguanians, permit a far more detailed
understanding of the morphology and relation-
ships of the taxa concerned. New cranial elements
of the taxon Tinosaurus, which was first recog-
nized by Pearson (1998), have already provided
clues to the relationships of that lineage (Smith,
submitted). In this work, the remainder of the
nonserpentian squamates are considered. This
work represents the first attempt to fully associate
significant amounts of cranial material with a
fairly large set of closely related species, in partic-
ular five species attributed to the clade Iguanidae.
Abbreviations used in this paper are as fol-
lows: AMNH, American Museum of Natural His-
tory, New York, NY, USA; CM, Carnegie Museum
of Natural History, Pittsburgh, PA, USA; FMNH,
Field Museum of Natural History, Chicago, IL,
USA; MCZ, Museum of Comparative Zoology,
Harvard University, Cambridge, MA, USA;
PTRM, Pioneer Trails Regional Museum, Bow-
man, ND, USA; SMF, Senckenberg Research
Institute, Frankfurt am Main, Germany; UF, Uni-
versity of Florida Museum of Natural History,
Gainesville, FL, USA; UMMZ, University of
Michigan Museum of Zoology, Ann Arbor, MI,
USA; YPM, Peabody Museum of Natural History,
Yale University, New Haven, CT, USA.
Age of the Fauna
The Chadron Formation of the Medicine Pole Hills
of southwestern North Dakota (Figure 1) preserves
a rich vertebrate fauna (the Pioneer Trails Regional
Museum site V89002) of late Eocene age (Leonard
1922; Pearson 1993; Kihm et al. 2001; Smith 2006a;
Kihm and Schumaker 2008). The geology of the
general area has been discussed by Murphy and co-
workers (1993), and that of the site by Pearson and
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
4
Hoganson (1995). The fossiliferous deposits
unconformably overlie the Paleocene Tongue
River Formation. They are disjunct from other
parts of the Chadron Formation and have previ-
ously been correlated with the Chalky Buttes Mem-
ber (e.g., Hoganson et al. 1998), but recent work on
the heavy mineral assemblage of the site suggests
that the two sedimentary packages had different
source regions (Webster and Kihm 2009). Thus,
whereas a Chadronian (late Eocene) age for the site
is not in question (Pearson and Hoganson 1995;
Hoganson et al. 1998), its exact age is less certain.
The best published constraint on the age of the
fauna is the identification by Heaton and Emry
(1996) of the leptomerycid artiodactyl Leptomeryx
yoderi (or a slightly different, more primitive
form) in the Medicine Pole Hills. Prothero and
Emry (1996) suggested that L. yoderi be the defin-
ing taxon of the late early Chadronian. The upper
limit of the stratigraphic range of the species in the
proposed type section, Flagstaff Rim (Prothero
and Emry 1996), is about 15 m (50 ft) below Ash
B (cf. Emry 1973 and Heaton and Emry 1996;
Prothero and Emry 2004). The Medicine Pole
Hills specimens most closely match those of
Quarry A at Flagstaff Rim (Heaton and Emry
1996), which is about 50 m below the ash layer. On
the other hand, the oldest localities above the
known range at which L. yoderi is considered not
to be present at Flagstaff Rim are perhaps 15 m
above the ash (see Heaton and Emry 1996).
Of these three possibilities—correlating with
the population of Leptomeryx yoderi at Quarry A
that is most similar, with the upper end of the
demonstrated range of L. yoderi, or with the low-
est locality above its known range where L. yoderi
is definitely not present (that is, assuming the true
range of L. yoderi extended until an infinitesimal
distance below said locality)—the last is the most
conservative option for the purpose of establish-
ing minimum ages of divergence. The youngest
age for the Medicine Pole Hills fauna is thus esti-
mated as follows. Obradovich and co-workers’
(1995) revised
40
Ar/
39
Ar date on Ash B is 35.41 ±
0.14 Ma. By conservatively assuming the youngest
end of the error range (cf. Benton and Donoghue
2007) and using an average sediment accumula-
tion rate for the interval between Ashes B and F,
based on dates in Swisher and Prothero (1990)
and stratigraphic thickness from Emry (1973), the
15 m above Ash B should represent about 0.045
million years. Therefore, the minimum age of the
Late Eocene Lizards of the Medicine Pole Hills • Smith
5
Figure 1. The northern Great Plains, showing the location of the Medicine Pole Hills.
fauna is taken to be 35.2 Ma. Because of these
assumptions, this date is 0.5 million years younger
than the estimated upper boundary of the late
early Chadronian given by Prothero and Emry
(2004). Hopefully other taxa will provide for a
more precise geochronologic placement of the
Medicine Pole Hills local fauna.
Systematic Paleontology
A set of orientations is assumed below to describe
isolated elements that almost certainly deviate
from the original but inexactly known orienta-
tions. For the maxilla, the parapet of the jaw is
assumed to extend anteroposteriorly (although it
is usually oblique to that axis) and the lateral sur-
face of the facial process is assumed to be vertical.
The dorsal surface of the prefrontal overlying
the nasal capsule is assumed to be horizontal
(although it is usually inclined anteriorly); the
medial edge of the prefrontal is assumed to be
longitudinal (although it is usually oblique). The
exterior surfaces of the jugal, postorbital, and
squamosal are taken to be lateral.
Much of the morphology of the coronoid and
compound bone relates to the various portions
of the trigeminal musculature. Unfortunately,
despite many published studies of these muscles
(e.g., Lakjer 1926; Oelrich 1956; Harris 1963;
Avery and Tanner 1971; Costelli 1973), there is
no careful account of their precise insertions in
particular iguanids, nor of the relation between
these insertions and the various osteological fea-
tures of the bones. The dissections required to
ground such a description are beyond the scope of
this work. Thus, the present account is restricted
to an osteological phenomenology. Hopefully
future studies will provide further insight.
There is considerable additional material
beyond what is described here, notably countless
osteoderms and vertebrae. With effort some of
these might ultimately be assignable to the taxa
recognized here.
Informal taxonomy follows Smith (2006a);
MPH refers to the Medicine Pole Hills local
fauna. Below are genus descriptions and
remarks for Sauropithecoides gen. nov. (page 7),
Queironius gen. nov. (page 30), Orithyia gen.
nov. (page 56), Tuberculacerta (page 82),
Cypressaurus (page 86), Palaeoxantusia (page 89),
Peltosaurus (page 95), Helodermoides (page 96)
and Saniwa (page 96).
Squamata Oppel, 1811
Iguanidae Bell, 1825
Remarks
In 1989 the family Iguanidae (sensu Boulenger 1885) was split
into 8 (later, 11) families because evidence of its monophyly
was lacking (Frost and Etheridge 1989; Frost et al. 2001). Sub-
sequently, molecular (Macey et al. 1997; Schulte et al. 1998, 2003)
and morphological (Smith 2009a) evidence for monophyly has
been accumulating. Taxonomy of Iguanidae here follows Schulte
and co-workers (2003), where the clade has its more traditional
composition. Smith (2009a) found evidence for a division of
Iguanidae into two clades: Clade A, comprising Crotaphytinae,
Iguaninae + Hoplocercinae, and Polychrotinae* + Corytophan-
inae; and Clade B, comprising Oplurinae, Tropidurinae* and
Phrynosomatinae. Other hypotheses of iguanid phylogeny
based on morphological evidence exist (Conrad and Norell
2007; Conrad et al. 2007; Conrad 2008), and those based on
molecular-genetic data are strongly divergent (Schulte et al.
1998, 2003). Although my discussions of character distribution
and polarity implicitly assume a dichotomy between Clade A
and Clade B, my systematic conclusions—where they are drawn
at all—are not strongly dependent on broad-scale phylogenetic
structure, because the species are deeply nested within
Iguanidae (except for Polychrus charisticus, within groups
whose monophyly is not in question).
Iguanidae is a principally New World clade. However,
until recently few Paleogene fossil iguanids have been allied with
particular iguanid groups.
Polychrotinae* Macey, Larson,
Ananjeva et Papenfuss, 1997
Remarks
Polychrotinae* is a group of New World lizards, referred to by
Etheridge and de Queiroz (1988) as the “anoloids,” which
includes more than 400 species. These are divided into several
distinct clades: Anisolepini (including the genera Anisolepis,
Enyalius and Urostrophus); Leiosaurini, including the genera
Aperopristis, Diplolaemus, Leiosaurus and Pristidactylus; the
eponymous genus Polychrus (monkey lizards), with six cur-
rently recognized species (Frost et al. 2001); and, following Poe
(2004), the hyperdiverse genus Anolis (which some authors
break into numerous genera). Anisolepini and Leiosaurini are
exclusively found in tropical and temperate South America,
Polychrus is tropical and principally South American, and Ano-
lis is widely distributed in tropical North and South America
and the Caribbean.
Apart from the late Eocene Polychrus charisticus (see
immediately below), fossil polychrotines may include the
early Eocene taxa Anolbanolis (Smith 2009b, in press) and
Afairiguana avius (Conrad et al. 2007), as well as several late
Cenozoic remains (Etheridge 1964, 1965, 1966a; Pregill 1981;
Pregill et al. 1988).
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
6
Sauropithecoides Smith, gen. nov.
Type species. Polychrus charisticus Smith, 2006a.
Diagnosis
. As for the type and only known species.
Etymology
. From sauros (Gr. “lizard”) and pithekos (Gr. “ape,
monkey”), because members of this taxon look like living
monkey lizards (Polychrus) but seem to lie outside the mod-
ern radiation.
Sauropithecoides charisticus
(Smith, 2006a)
Figures 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24
Polychrus charisticus Smith, 2006a:6.
Xenosaurid MPH-1 Smith, 2006a:29.
Holotype
. PTRM 1841 (partial right maxilla; Smith 2006a, fig.
4.1–2).
Paratypes
. See Smith (2006a).
Newly referred specimens. Both specimens of Xenosaurid MPH-
1 as well as the following: PTRM 19003 (right prefrontal; Figure
10), 19008 (frontal fragment; Figure 12D–F), 19009 (frontal frag-
ment; Figure 12A–C), 19010 (partial parietal; Figure 18A–C),
19011 (partial parietal), 19012 (partial parietal; Figure 18D–F),
19014 (partial left postorbital; Figure 16), 19037 (partial premax-
illa; Figure 2D), 19038 (premaxilla; Figure 2A–C), 19039 (partial
premaxilla; Figure 2E), 19040, 19041 (partial right dentaries),
19042 (premaxilla fragment), 19043 (right maxilla fragment),
19044 (jaw fragment), 19045 (partial left maxilla; Figure 4E),
Late Eocene Lizards of the Medicine Pole Hills • Smith
7
Figure 2. Premaxilla of Sauropithecoides charisticus. A–C, PTRM 19038 (nearly complete element) in anterodor-
sal, posteroventral, and right lateral views, respectively. D, PTRM 19037 (nearly complete element) in anterodor-
sal view. E, PTRM 19039 (partial element) in anterodorsal view. Abbreviations: a.pm.f., anterior premaxillary
foramina; in, median internasal scale; in.pr., incisive process; inL, inR, left and right medial-most internasal scales;
mx.fac., maxillary facet; n.fac., nasal facet; n.pr., nasal process of premaxilla; pinL, pinR, left and right medial-
most postinternasal scales; p.pm.f., posterior premaxillary foramen; prL, prR, left and right postrostral scales.
19046 (left maxilla fragment), 19078 (partial left dermarticular),
19079 (partial dermarticular; Figure 24), 19087 (left jugal frag-
ment; Figure 14), 19091 (partial left ectopterygoid; Figure 8B–E),
19094 (partial right ectopterygoid; Figure 8A), 19109 (partial left
prefrontal), 19132 (partial right squamosal; Figure 20), 19138 (left
maxilla fragment; Figure 4D), 19217, 19218 (partial left maxil-
lae), 19219, 19220, 19221, 19222 (left maxilla fragments), 19223,
19224 (right maxilla fragments), 19225 (jaw fragment), 19226
(right maxilla fragment), 19227 (partial left dentary), 19228 (left
dentary fragment), 19229 (dentary fragment), 19230 (jaw frag-
ment), 19231 (dentary fragment), 19232 (jaw fragment), 19323
(partial right coronoid; Figure 22), 19326 (left articular fragment),
19349 (partial left prefrontal), 19382 (jaw fragment), 19384 (left
dentary fragment), 19385 (right dentary fragment), 19386, 19387
(left maxilla fragments), 19388 (right dentary fragment), 19389
(premaxilla fragment), 19390 (right dentary fragment), 19391
(jaw fragment), 19392 (right maxilla fragment), 19459 (partial
premaxilla), 19460, 19475 (left maxilla fragments), 19496 (partial
right maxilla; Figure 4F), 19497 (right maxilla fragment), 19498
(left maxilla fragment), 19518 (partial left maxilla), 19519, 19522
(right maxilla fragments), 19531 (premaxilla fragment), 19553
(partial right nasal; Figure 6), 19579 (partial right maxilla; Figure
4A–C), and 19580 (right maxilla fragment).
Emended diagnosis
. An iguanid similar to (most) living Poly-
chrus in the following derived features: broad, polygonal rugosi-
ties cover all dorsally facing dermal skull bones; multiple
anterior premaxillary foramina, colinearly arrayed parallel to
jaw parapet; nasal process of premaxilla broadly expanded,
strongly overlapping premaxillary process of maxilla; premax-
illary process elongate, with strong crista lateralis that slightly
overhangs tooth row; slight overhang of premaxillary process
by anterior margin of facial process; tooth crowns striated; and
low and square coronoid process of coronoid. Differs from
(most) living Polychrus in having the following plesiomorphies:
seven or fewer premaxillary teeth; foramen present in prefrontal
just anterior to frontal facet in paranasal recess; lacrimal broadly
exposed along orbital margin (also in P. femoralis); postfrontal
discrete; postorbital without strong canthal crest; and nuchal
fossa on posterior margin of parietal exposed dorsally and
bounded ventrally by long, sharp-edged crest. Additionally dif-
fers from all species of Polychrus except perhaps P. peruvianus
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
8
Figure 3. Premaxilla of selected members of Polychrotinae*. A–C, Polychrus gutturosus (UF 49377). D–F, Ano-
lis garmani (UF 42404). First column, Anterodorsal view. Second column, Posteroventral view. Third column,
Right lateral view. Abbreviations: in.pr., incisive process; mx.fac., maxillary facet; n.fac., nasal facet; n.pr., nasal
process of premaxilla; p.pm.f., posterior premaxillary foramen.
in usually having a median element in the internasal scale row.
Autapomorphies include the following: unicuspid tooth series
extends as far back as posterior end of palatine process of max-
illa, tooth tips generally moderately recurved (also in P.
femoralis), anteroposteriorly foreshortened nasal bone, ptery-
goid process of ectopterygoid very shallowly oriented, circular
lacrimal facet on prefrontal, and quadratojugal process on jugal.
Description
PREMAXILLA
Smith (2006a) described this element under the heading
Xenosaurid MPH-1. As discussed below, it is referable to Sauro-
pithecoides charisticus. The new specimens clarify the morphol-
ogy of and variation in this element.
Description: PTRM 19038 is the most complete specimen
known. The tip of the nasal process, broken in the described
premaxilla, is triangular (Figure 2A, B). On its ventral surface to
either side of the mid-line is a triangular facet for the anterome-
dial process of the nasal (n.fac.). The right facet in PTRM 19038
has an acute anterior end, whereas the left one terminates
bluntly (in no other specimen are the facets as well preserved).
The margin of the nasal process also varies slightly bilaterally in
this specimen. The median keel on the interior surface of the
nasal process is well defined between the nasal facets. The lateral
wings of the nasal process, which project out over the premax-
illary process of the maxilla, as indicated by the maxillary facets
(Figure 2B, mx.fac.), differ somewhat in width, and thus the
extent of premaxillary overlap of the maxilla also differs. The
incisive process (in.pr.) is not always clearly bilobed. In PTRM
Late Eocene Lizards of the Medicine Pole Hills • Smith
9
Figure 4. Maxilla of Sauropithecoides charisticus. A–C, PTRM 19579 (anterior portion of right element, com-
prising premaxillary process and anterior base of facial process) in lateral, dorsal and ventral views, respectively.
D, PTRM 19138 (anterior portion of left element, comprising premaxillary process) in medial view. E, PTRM
19045 (middle fragment of left element, comprising much of section with facial process) in dorsomedial view.
F, PTRM 19496 (middle fragment of right element, comprising section with palatine articulation). Abbreviations:
a.i.a.f., anterior inferior alveolar foramen; cr.tv., crista transversalis; fa.pr., facial process; j.fac., jugal facet; pl.fac.,
palatine facet; pl.fl., palatal flange; pm.fac., premaxillary facet; prf.fac., prefrontal facet; s.a.f., superior alveolar
foramen; sn.a.f., subnarial arterial foramen; v.fac., vomerine facet.
19037 the two halves are completely fused, but PTRM 19459 is
like the first-described specimen, PTRM 1986.
Anterior premaxillary foramina are multiple and arranged
in more or less a single row (Figure 2A, a.pm.f.). The foramina
are generally bilaterally symmetrical (Figure 2D, E). The rugosi-
ties on the exterior surface are considerably taller in some spec-
imens (PTRM 19039) than in others (PTRM 19037). (These are
assumed to be rugosities rather than osteoderms, following
Etheridge and de Queiroz [1988], despite the lack of develop-
mental data on the fossil species.) In all specimens there is a pri-
mary pair of scales lying immediately dorsal to the jaw parapet;
on the basis of comparison with living Polychrus, these are taken
to be the postrostral scales (prL, prR). On the basis of the same
comparisons, the scales posterior to the postrostrals are taken to
be internasals. In several specimens the mid-line internasals
occur as a pair (Figure 2A, D, inL, inR; Smith 2006a, fig. 19-1).
In PTRM 19039, however, the internasal scale row includes a
median scale (Figure 2E, in), which is in turn succeeded by a
scale pair, called here the postinternasals (Figure 2D pinL, pinR).
Even where the mid-line internasals are paired, the precise rela-
tion of the scales varies. In PTRM 19037, slight contact between
scales prL and inR excludes prR and inL from contacting each
other and, similarly, contact between scales inL and pinR
excludes contact between inR and pinL (Figure 2D); this is also
the case in PTRM 1986 (Smith 2006a, fig. 19-1). The arrange-
ment is reversed in PTRM 19038 (Figure 2A).
Four specimens (including PTRM 1986) have seven tooth
positions, one (PTRM 19037) has only six. The teeth are far
from being the columnar structures seen in worn specimens
(such as PTRM 1986 and 19038); they are conical, sharply
pointed (tapering beginning below the parapet) and moderately
to strongly lingually curved.
Comparisons:
Smith (2006a) originally described certain dermal
cranial elements with broad “osteoderms” (premaxilla, indeter-
minate element) as Xenosaurid MPH-1, believing that the differ-
ence in sculpture these showed with regard to Polychrus
charisticus was too great for them to be accommodated in the
latter, despite the similarity in size and the shared, derived pre-
maxillary–maxillary relationship, as indicated by the articulation
facets. Subsequent examination of living Polychrus revealed that
many species of this genus show exactly the same kind of hetero-
geneity of dermal bone sculpture, with small, irregular rugosi-
ties on the lateral surfaces of the skull and large, more regular
rugosities on the skull roof. This is an aspect of the morphology
of crown Polychrus. Specimens assigned to Xenosaurid MPH-1
are therefore referred to Sauropithecoides charisticus.
Anterior premaxillary foramina are present in several
iguanids (see Smith 2009a, 2009b), particularly in members of
Clade A exclusive of Crotaphytinae and Anolis. However, they
are multiple only in Polychrus and in some members of Iguani-
nae; in the latter clade, they are arrayed atop one another or are
haphazardly distributed. Multiple foramina arrayed colinearly
along the parapet were found in all living species of Polychrus in
which the premaxilla was sufficiently exposed (in the illustrated
specimen of P. gutturosus [Figure 3A] the main body and lateral
processes of the bone are damaged). The arrangement of these
foramina unites Sauropithecoides charisticus exclusively with
Polychrus.
An expanded nasal process of the maxilla is common in
species that make up Clade A. In most Anolis, however, the
nasal process is narrow (Figure 3D, E), which Smith (2009a)
considered a reversal. The nasal process is even more expanded
in most Polychrus, especially basally, so much so that it overlies
and articulates dorsally on the anterior end of the premaxillary
process of the maxilla (Smith 2006a). (In the more recently
examined P. liogaster, however, the overlap is effectively
nonexistent, which I consider a reversal.) This apomorphy
evolved independently in Enyalioides oshaughnessyi (Smith
2006a). The degree of expansion in Polychrus varies, however.
In P. gutturosus, the width of the nasal process is not greater
than in the (locally) primitive condition shown by most coryto-
phanines and hoplocercines (Figure 3A, B). In P. marmoratus
the nasal process is also narrow by comparison with other Poly-
chrus—not wider than the premaxilla at its base —and the lat-
eral margin of the nasal process between the maxillary and nasal
articulations is distinctly concave. The lateral margin is also con-
cave in P. acutirostris and P. liogaster. In P. peruvianus and P.
femoralis, in contrast, the nasal process is extremely broad and
has a straight-to-convex margin between said articulations.
Polychrus peruvianus and P. femoralis are not thought to be par-
ticularly closely related (Frost et al. 2001). Sauropithecoides
charisticus shows the highly derived condition seen in the latter
two species.
Members of Polychrus, like many other polychrotines (e.g.,
Etheridge 1959; Etheridge and de Queiroz 1988), tend to have
strong rugosities on the skull that are better developed than in
other iguanian clades (except part of Hoplocercinae and some
Mongolian acrodontans). Their topographic extent is inter-
specifically (as well as probably ontogenetically) variable. They
are highly developed on all dorsally facing dermal skull bones in
P. acutirostris, P. femoralis and P. peruvianus. In P. liogaster, P.
marmoratus and P. gutturosus, on the other hand, they are
reduced on the anterior portion of the skull and extremely weak
or absent on the nasal process of the premaxilla (Figure 3A).
Outgroup comparisons with polychrotines (Anisolepis undula-
tus, Urostrophus vautieri, Enyalius iheringii, Pristidactylus
torquatus, some Anolis; Figure 3D) suggest that at least some
rugosities on the nasal process are expected to be present on the
stem of Polychrus (complete reduction in P. gutturosus and P.
marmoratus is derived). However, whether the great ventral
extent of the rugosities seen in some Polychrus is primitive for
the crown is uncertain: character optimization on the best pres-
ent estimate of Polychrus phylogeny (Frost et al. 2001) is
ambiguous. Whatever the case, Sauropithecoides charisticus
shows the more common condition in Polychrus.
The median rostral scale is bordered posteriorly by a pair
of postrostral scales in living Polychrus as well as Sauropithe-
coides charisticus. The following internasal row, however, seems
to include a median scale in most living Polychrus: P. acutirostris
(de Avila Pires 1995, fig. 37), P. femoralis (pers. obs.), P. liogaster
(de Avila Pires 1995, fig. 41) and P. marmoratus (de Avila Pires
1995, fig. 43; pers. obs.). In P. peruvianus MCZ 18776, however,
the mid-line internasals are paired (unknown in P. gutturosus).
In Anolis, the postrostral scales (like those of much of the rest of
the body) tend to be very small; the mid-line postrostrals seem
to be variably paired or to include a median scale, but the cor-
respondence between individual postrostral scales in Polychrus
and Anolis is far from clear. The same applies to the South
American anoloids (Anisolepini and Leiosaurini; see, e.g.,
Etheridge 1969). Thus, the feature can only clearly be evaluated
in species with large postrostral scales: S. charisticus and Poly-
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
10
chrus. The former shows a condition that seems to be uncom-
mon in Polychrus.
The number of premaxillary teeth (6 to 7; mode of 7) in
Sauropithecoides charisticus is low as compared with living Poly-
chrus. Polychrus acutirostris has 8 (N ⫽ 1); P. femoralis has 9 (N ⫽
1); P. gutturosus has at least 8 (N ⫽ 2; Figure 3B); P. liogaster
has 8 (N ⫽ 1); P. marmoratus has 8 to 10, with a mode of 8 (N ⫽
12); and P. peruvianus has 10 or more (N ⫽ 1). Most examined
Anolis have 10 or more premaxillary teeth (Figure 3E; the
number was as low as 7 in one A. chlorocyanus). But all other
examined polychrotines have 7 or fewer (usually fewer). Fur-
thermore, stem members of Corytophaninae have 7 (Smith
2009b). If Anolis and Polychrus are sister taxa (Frost et al. 2001;
Smith 2009a) and a premaxillary tooth count greater than 7 is
primitive for that clade, then the condition in S. charisticus could
be a reversal. However, if tooth count increased independently
in Anolis and Polychrus (see Smith, in press), then the low count
in S. charisticus would be a plesiomorphy, pushing it outside
crown Polychrus.
MAXILLA
Newly referred maxillae provide more data on this element than
the hypodigm.
Description:
PTRM 19579 preserves the most complete premax-
illary process of any specimen thus far. It is highly elongate (Fig-
ure 4A). As in the paratype PTRM 5373, the lateral rim of the
premaxillary process rises toward the premaxillary facet (Figure
4B, pm.fac.), whereafter it decreases again. The dorsal portion of
the premaxillary facet is triangular in dorsal view, tapering pos-
teriorly. Its medial rim is joined anteriorly by the crista transver-
salis (cr.tv.), which runs obliquely (mostly anteriorly) from the
base of the facial process. The subnarial arterial foramen (sn.a.f.)
is an elongate slit just lateral to the crista; from it, a groove runs
anteriorly, parallel to the crista. The dorsal surface of the pre-
maxillary process, exclusive of the premaxillary facet, forms a
closed basin, concave in transverse and sagittal cross section. The
anterior inferior alveolar foramen (a.i.a.f.) is raised above its floor.
The premaxilla also articulated very briefly on the ventral sur-
face of the premaxillary process of the maxilla (Figure 4C,
pm.fac.). A small posterior projection along the lingual margin
of the maxilla was present; in PTRM 19579 this projection was
rounded and extended only as far as the anteroposterior mid-
point of the first maxillary tooth, but in PTRM 19139 it was
longer and sharper. The vomerine facet on the anteromedial pro-
jection of the premaxillary process is an elongate surface,
smoothly convex in transverse cross section (Figure 4D, v.fac.).
The facial process is most complete in the holotype, but it
was not described in much detail. In one of the new specimens,
an elongate facet is preserved on the medial surface of the pos-
terior portion of the facial process (Figure 4E, fa.pr.). Although
it is possible that this facet is related to the lacrimal, given the
shortness of the nasal (see below), it is more probably a partic-
ularly strongly developed facet for the prefrontal (prf.fac.). The
palatine process is merely a weak medial swelling of the palatal
shelf, atop which the palatine articulated (Figure 4F, pl.fac.). The
superior alveolar foramen is somewhat open (s.a.f.), but not for
a space of more than about two to two and one-half teeth; in
one specimen it shows a clear division at its base into anterior
and posterior openings.
One unusual feature of the dentition of this species is that
the teeth are unicuspid for much of the tooth row (Smith
2006a). The well-preserved teeth of PTRM 19138 (Figure 4D)
show that the fourth tooth has a weak but distinct mesial carina,
which is lacking on the first tooth. Unicuspid teeth can be
demonstrated as far back as the anterior end of the jugal artic-
ulation in PTRM 19217. The tips of anterior and middle teeth
are also somewhat recurved.
Other significant features of the maxilla have already been
described (Smith 2006a).
Comparisons:
Distinct accessory cusps are present on more ante-
rior teeth in other species of Polychrus. In P. acutirostris both
mesial and distal cusps are present by the 4th maxillary tooth, in
P. femoralis by the 3rd, in P. gutturosus (Figure 5A, B) and P. lio-
gaster by the 7th, in P. marmoratus by the 6th, and in P. peru-
vianus by about the 7th. Accessory cusps often occur somewhat
later in absolute terms in Anolis (Figure 5D, E; as far back as the
10th or 12th is not uncommon), but this is still more anterior
than in Sauropithecoides charisticus with respect to the palatine
process. In Enyalius iheringii both accessory cusps are present
by the 7th tooth, in Anisolepis undulatus by the 7th, and in
Urostrophus vautieri by the 8th. These data clearly establish that
the extreme posterior extent of the unicuspid teeth in S. charis-
ticus—at least as far back as the end of the palatine process—is an
autapomorphy of the species. The curvature of the tooth tips also
falls in this category (although this is also seen in P. femoralis).
Sauropithecoides charisticus shares the weakness of its pala-
tine process with many other members of Clade A (Figure 5C,
F). This is a plesiomorphy (Smith 2009a).
The shape of the vomerine facet in Sauropithecoides charis-
ticus is similar to that in Polychrus gutturosus (Figure 5B). Other
species of Polychrus were not available as disarticulated skele-
tons. The facet was generally flatter in examined Anolis, and in
A. garmani it additionally has a longitudinal slit (Figure 5E).
Specimens from the polychrotine clades Anisolepini and
Leiosaurini were unavailable as disarticulated skeletons. At pres-
ent, the evolution of the vomerine facet in Polychrotinae* is
poorly constrained.
Still other features of Sauropithecoides charisticus are of
uncertain evolutionary significance for want of adequate com-
parative osteological material. What is interpreted as a pre-
frontal facet in S. charisticus is much more strongly marked than
the equivalent facet in Polychrus gutturosus (Figure 5C) and is
unusual in Iguania. The concavity of the anterior margin of the
premaxillary process in Sauropithecoides charisticus is similar
to that in Anolis (Figure 5F). The superior alveolar foramina in
P. gutturosus are two distinct openings, both located at the level
of the palatine process and not set in a distinct gutter (Figure
5C), unlike in S. charisticus. These characters may be examined
when additional disarticulated specimens of Polychrus and
other polychrotines become available.
NASAL
A single specimen, PTRM 19553, is tentatively identified as a
nasal of Sauropithecoides charisticus. The size of the element and
the morphology and size of its rugosities are consistent with this
interpretation, although the morphology of its undersurface
departs somewhat from that in most other examined iguanids.
There is no other obvious candidate for the identification in
terms of taxon or element.
Late Eocene Lizards of the Medicine Pole Hills • Smith
11
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
12
Figure 5. Left maxilla of selected members of Polychrotinae*. A–C, Polychrus gutturosus (UF 49377). D–F, Ano-
lis garmani (UF 42404). First column, Lateral view. Second column, Medial view. Third and fourth columns,
Dorsal view. Abbreviations: a.i.a.f., anterior inferior alveolar foramen; cr.tv., crista transversalis; ec.fac., ectoptery-
goid facet; fa.pr., facial process; j.fac., jugal facet; l.fac., lacrimal facet; pl.pr., palatine process; prf.fac., prefrontal
facet; s.a.f., superior alveolar foramen; sn.a.f., subnarial arterial foramen; v.fac., vomerine facet.
Figure 6. Probable right nasal of Sauropithecoides charisticus (PTRM 19553). A, Dorsal view. B, Ventral view.
Dashed lines indicate the probable original course of the bone margins. Abbreviations: fr.fac., frontal facet;
mx.fac., maxillary facet; pm.fac., premaxillary facet; prf.fac., prefrontal facet.
Description: The dorsal surface is covered by rugosities similar
to those on the premaxilla (Figure 6A). The anteromedial
process and some of the anterior margin of the bone are broken
off (a possible outline, based in part on the nasal facet of the pre-
maxilla, is shown with a dashed line in Figure 6). What is inter-
preted as the right anterolateral corner curves ventrally for
articulation on the maxilla (Figure 6B, mx.fac.); this ventral cur-
vature, indeed, is the reason it is identified as a right nasal rather
than a left. Only a small corner of the premaxillary facet
(pm.fac.) is visible in ventral view; it is assumed that the facet
was primarily developed on the dorsal surface of the broken
anteromedial process of the bone. A more or less continuous
articulation facet runs from the maxillary facet to the postero-
medial corner of the bone, where the facet is broader (Figure
6B); probably the lateral portion of this corresponds to the pre-
frontal facet (prf.fac.) and the posteromedial portion to the
frontal facet (fr.fac.), although a clear division is not apparent.
The edge of the bone is broken here, so the frontal facet was
presumably distinctly longer than preserved. The portion of the
ventral surface that would directly have overlain the cartilagi-
nous nasal capsule is smooth. This surface is divided into ante-
rior and posterior portions by an oblique, slightly arcuate ridge
running posteromedially from the maxillary facet. Anterior to
this ridge, the bone is thin and distinctly concave; posterior to it,
the bone is flat. A prominent foramen pierces the bone near the
posterior margin of the posterior portion. The ridge possibly cor-
responds to the division between the cupula and tectum nasi of
the nasal capsule (cf. Hallermann 1994), the zona annularis of
Oelrich (1956). On the whole, the bone is anteroposteriorly short.
Comparisons:
The nasal is not well exposed in most available
skeletal specimens of Polychrus, so comparisons are limited. It
Late Eocene Lizards of the Medicine Pole Hills • Smith
13
Figure 7. Right nasal of selected members of Polychrotinae* and Corytophaninae. A, B, Polychrus gutturosus
(UF 49377). C, D, Anolis garmani (UF 42404). E, F, Basiliscus basiliscus (UF 99655). G, H, Laemanctus longipes
(UF 66061). First and third columns, Dorsal view. Second and fourth columns, ventral view. Abbreviations:
f.fac., frontal facet; mx.fac., maxillary facet; pm.fac., premaxillary facet.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
14
is fairly short as compared with polychrotines and corytopha-
nines (Figure 7), which is an autapomorphy of the species.
The anterolateral corner of the nasal bears a small anterior
projection that overhangs the external naris in Polychrus
femoralis FMNH 81405, P. liogaster AMNH R101460 (strongly
so), P. marmoratus MCZ 74150 (but not FMNH 42501), P. gut-
turosus MCZ 46441 (but not UF 49377; Figure 7A) and P. acu-
tirostris SMF 24870 (left side only). This is distinct from, but
possibly related to, the overhang of the premaxillary process by
the facial process (see Smith 2006a). (It is unknown in P. peru-
vianus, because tissue obscures the relevant region in the only
skeletal specimen.) The presence of such a projection cannot be
excluded in Sauropithecoides charisticus, because the anterolat-
eral corner is broken. Such a projection was not observed in
corytophanines (Figure 7E, G) or other polychrotines (e.g., Fig-
ure 7C), except Anisolepis undulatus, where it seems to arise
from the maxilla, not the nasal; this character bears further
examination in Polychrus. It is clearly intraspecifically variable,
but its presence in a certain proportion could be an autapomor-
phy of the clade.
In Polychrus marmoratus FMNH 42501 (Digimorph.org
2002–2005) there is a large frontonasal fontanelle that is not
present in P. marmoratus MCZ 74150. The fontanelle was not
observed in other Polychrus. The articulations on the single
known nasal of Sauropithecoides charisticus would appear to
exclude the possibility of a fontanelle in that individual, which
is taken to be the primitive condition on the basis of outgroup
comparison.
The oblique ridge observed on the ventral surface of the
nasal in Sauropithecoides charisticus is absent in Polychrus guttur-
osus (Figure 7B), but it is found in P. femoralis and might be pres-
ent in P. marmoratus FMNH 42501 (Digimorph.org 2002–2005,
slices xy88 ff.). Understanding its phylogenetic significance in
Polychrus will require more specimens from additional species.
The strong ventral deflection of the anterolateral process of
the nasal was not found in examined polychrotines (Figure 7D)
other than Polychrus. (The deflection seems to be absent in P.
liogaster, perhaps related to the very strong development of an
anterior process.) The absence of deflection is possibly related to
a restriction of the lateral extent of the nasal in most poly-
chrotines, for a distinct deflection is also seen in living coryto-
phanines (Figure 7F, H). In Polychrus, the deflection was found
in all species in which it could be checked (Figure 7B), that is,
excepting P. peruvianus, in which skin still covers the snout and
the exact bone boundaries are unknown in the only skeletal spec-
imen. This may well be a reversal in Polychrus, in which case its
presence in Sauropithecoides charisticus would tie it to that clade.
ECTOPTERYGOID
An ectopterygoid morphotype is tentatively associated here on
the basis of size, iguanid morphology, complementarity of artic-
ulation with the jugal, and the fact that another morphotype is
associated with the new iguanine described below.
Description:
The posterior face of the bone, which contributes
to the coronoid recess, is flat in sagittal cross section (Figure 8A,
B). The pterygoid facet (pt.fac.) that incises it tapers and deep-
ens laterally and terminates in a more (Figure 8B) or less (Fig-
ure 8A) rounded point; small tongue-and-groove structures
mark the medial portion of the facet. Opposite the facet, on the
anterior face of the bone, is a small fossa (Figure 8C). The ptery-
goid process extends medially at a very shallow angle (Figure
8A, B). In fact, the dorsal margin of the bone is more distinctly
concave than the ventral margin.
The anterolateral process of the bone is robust and was
probably quite extensive, but it is broken in even the most com-
plete specimen (Figure 8D). The maxillary facet (mx.fac.)
encompasses the entire lateral margin of the bone, but it is most
medially extensive just anterior to the transverse level of the
pterygoid process; it is pierced at this point by a foramen. The
ventrolateral edge of the bone is slightly concave.
The lateral surface of the bone is triangular in shape (Figure
8E). It is dominated by the concave facet for the jugal (j.fac.), the
center of which is pierced by a foramen that may communicate
Figure 8. Ectopterygoid of Sauropithecoides charisticus. A, PTRM 19094 (partial right element) in posterior
view. B–E, PTRM 19091 (partial left element) in posterior, anterior, ventral and lateral views, respectively. Abbre-
viations: al.pr., anterolateral process; j.fac., jugal facet; mx.fac., maxillary facet; pl.pr., posterolateral process;
pt.fac., pterygoid facet; pt.pr., pterygoid process.
with the one penetrating the lateral margin of the posterior face
at mid-height in PTRM 19091 (Figure 8B). The dorsal corner of
the posterolateral process is well developed but more acute and
less extensive than the ventral corner.
Comparisons:
The preservation of this morphotype and the
dearth of disarticulated specimens of living species permit only
modest comparisons with living Polychrus. The maxillary facet
is broadly developed on the ventral surface of the ectopterygoid
in Sauropithecoides charisticus, as in Polychrus gutturosus (Figure
9A), but unlike many living Anolis (Figure 9E). Disarticulated
members of Anisolepini and Leiosaurini were unavailable, but a
mediolaterally extensive maxillary facet is also seen in living cory-
tophanines and in the stem corytophanines Geiseltaliellus maar-
ius (Smith 2009a) and Suzanniwana patriciana (Smith 2009b).
Thus, this feature may be a plesiomorphy of Sa. charisticus.
In Polychrus gutturosus there is a small foramen located
within the maxillary facet (Figure 9A). A foramen is absent on
the ventral surface of the ectopterygoid in articulated specimens
of P. acutirostris, P. femoralis and P. liogaster, suggesting that it
might open in the maxillary facet in these species as well. In Sauro-
pithecoides charisticus the foramen is at the edge of the facet.
In corytophanines (except Corytophanes hernandesii, where a
homolog could not be found, even in a disarticulated specimen),
the foramen is located medially to the facet. This is also the posi-
tion observed in Enyalius iheringii and in Anolis (Figure 9E). On
the other hand, articulated specimens of Anisolepis undulatus and
Urostrophus vautieri did not show a foramen outside the maxil-
lary facet, suggesting it may intersect the facet in these taxa. Fur-
thermore, there seems to be intraspecific variation in the stem
corytophanine Suzanniwana patriciana (see Smith 2009b, figs.
2H, J), which invites caution. The position of this feature may be
of phylogenetic utility when its distribution, especially in living
polychrotines, is better understood.
The ectopterygoid of Sauropithecoides charisticus appears
to be similar to that of all living Polychrus in having a stronger
ventral than dorsal corner of the posterolateral process (Figure
9D). The ventral corner is especially well developed in P. acu-
tirostris. Both corners appear reduced in most Anolis (Figure
9H; Smith 2009b). However, other examined polychrotines
seem to conform to the Polychrus pattern, which is taken to be
primitive.
The pterygoid process of the ectopterygoid of Sauropithe-
coides charisticus takes an exceedingly shallow course, extend-
ing almost directly medially. This distinguishes it from almost
all other examined polychrotines (Figure 9C, G). Only Poly-
chrus liogaster and P. marmoratus even approach S. charisticus.
Thus, the extremely shallow angle of the pterygoid process is
considered an autapomorphy of S. charisticus.
PREFRONTAL
A prefrontal morphotype is associated here on the basis of size,
relative abundance and the similarity of dermal sculpture to the
other dermal skull bones.
Description: PTRM 19003, a right element, is nearly complete
but stream-worn; it lacks the ventral portion of the palatine
process and the anterior flange overlapped by the facial process
of the maxilla (Figure 10). Unless otherwise expressed or
implied, the description is based on this specimen. The dorsal
surface of the bone is covered with large, polygonal dermal
rugosities (Figure 10A). The elongate, oblique rugosity on the
anterolateral margin of the prefrontal is common to PTRM
19003 and 19109. The apical surfaces of all rugosities are pene-
trated by many small foramina, from some of which extend
grooves that incise the surface of the rugosities. The prefrontal
boss is subdued in PTRM 19003 (Figure 10A, B), but in PTRM
19109 it is much more prominent.
The long frontal process (Figure 10A, B, f.pr.) tapers pos-
teriorly. Its ventral edge is continuous anteriorly with the antor-
bital flange (Figure 10B, ant.fl.). In PTRM 19109 this flange is
pierced by a prominent foramen. The articulation facet for the
Figure 9. Left ectopterygoid of selected members of Polychrotinae*. A–D, Polychrus gutturosus (UF 49377).
E–H, Anolis garmani (UF 42404). First column, Ventral view. Second column, Anterior view. Third column,
Posterior view. Fourth column, Lateral view. Abbreviations: al.pr., anterolateral process; mx.fac., maxillary facet;
pl.pr., posterolateral process; pt.fac., pterygoid facet; pt.pr., pterygoid process.
Late Eocene Lizards of the Medicine Pole Hills • Smith
15
frontal is concave in transverse cross section (Figure 10C, f.fac.),
but the degree of concavity changes longitudinally. Distally on
the process the concavity is very shallow and essentially the
entire surface is directed dorsomedially. Proximally, the con-
cavity becomes more prominent, the lateral portion of the sur-
face curving to overhang the facet, implying a ridge on the
frontal. The facet tapers anteriorly to an acute point. Proximally
in PTRM 19003 a ridge neatly bisects the angle formed by the
margins of the facet; the ridge is absent in PTRM 19109.
The excavation for the nasal capsule, or the paranasal
recess, is an extensive concavity (Figure 10C, pn.rec.). The dor-
sal wall of the recess has a longitudinal medial incision, pre-
sumably the articulation facet of the nasal (n.fac.). The
posterior wall of the recess (i.e., the antorbital flange) meets
the frontal facet at high angle and an oblique ridge is formed
at their junction. A large foramen opens medially into the
recess just anterior to the frontal facet in both specimens; in
PTRM 19109 it is located more ventrally. Apart from this fora-
men, the surface of the recess is smooth. The recess reaches
its greatest lateral extent near the dorsal edge of the bone. The
palatine process (pl.pr.), as noted above, is broken. However,
near the ventralmost preserved part of the bone in PTRM
19003, the ventromedially extending floor of the recess makes
a sudden turn toward the ventral, a deflection that on the basis
of comparison with living taxa marks the dorsal-most extent
of the palatine articulation on the prefrontal (pl.fac.). The pala-
tine process is slightly more complete in PTRM 19109 and
preserves a more extensive palatine facet, which has subdued,
rounded margins as well.
The anterolateral edge of the bone has a groove for artic-
ulation with the maxilla (Figure 10D, mx.fac.). On the basis of
comparison with living corytophanines and polychrotines,
presumably the ventral ridge bounding this groove would
have projected anteriorly, deep to the facial process of the
maxilla. In all specimens the lacrimal facet (l.fac.) is an oval,
anterolaterally directed depression surrounded by a projecting
rim; its floor evinces weak surficial irregularities. The ventral
rim of the facet is prominent and distinct in PTRM 19003,
such that the lacrimal foramen (l.f.) was bordered dorsolater-
ally by the prefrontal, but in PTRM 19109 the rim is anteriorly
incomplete. Laterally, the antorbital flange of the bone does
not terminate abruptly in a sharp edge at the lacrimal foramen
but curves anteriorly.
Comparisons:
The prefrontal boss of Sauropithecoides charisti-
cus is variable in prominence, sometimes comparable to that of
Basiliscus, sometimes more like that of Polychrus gutturosus
(Figure 11A–C) and Laemanctus. In Anolis the boss can also be
prominent in the sense of projecting strongly laterally (Figure
11E, F); it tends to form an elongate canthal ridge (Smith
2009b), as also seen in other Polychrus (e.g., P. marmoratus and
P. peruvianus) and some other polychrotines.
A rounded lacrimal facet, bounded not only dorsally and
posteriorly but also ventrally by a projecting rim, was taken by
Smith (2009b) to be an autapomorphy of Corytophaninae and
part of its stem, first known in Suzanniwana patriciana. Funda-
mentally, this change involves a ventrolateral projection of the
prefrontal distinct from the flange overlain by the maxilla. The
facet in Sauropithecoides charisticus—clearly rounded, with dis-
tinct margins—corresponds best to the condition in Basiliscus,
Corytophanes and Su. patriciana. Given its relationship to
Polychrus (Smith 2006a and below), the round facet of Sa.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
16
Figure 10. Right prefrontal of Sauropithecoides charisticus (PTRM 19003). A, Dorsal view. B, Lateral view. C,
Medial view. D, Anterior view. Abbreviations: ant.fl., antorbital flange; f.fac., frontal facet; f.pr., frontal process;
l.f., lacrimal foramen; l.fac., lacrimal facet; mx.fac., maxillary facet; n.fac., nasal facet; pl.fac., palatine facet; pl.pr.,
palatine process; pn.rec., paranasal recess; prf.boss, prefrontal boss.
charisticus is presently best interpreted as an autapomorphy,
but it is also worth noting that disarticulated specimens of poly-
chrotines other than Anolis are almost nonexistent.
In Suzanniwana patriciana (Smith 2009b, fig. 2M) and liv-
ing corytophanines and polychrotines (Figure 11D), the antor-
bital flange is emarginated between the frontal and palatine
articulations. The emargination can be absent when the pala-
tine and frontal closely approach one another (e.g., Anisolepis
undulatus and many Anolis; Figure 11H), simply because there
is no space to build a concavity. This concavity is exaggerated
in some Su. patriciana and in Basiliscus by the ventral extension
of a small process that partially (B. basiliscus) or wholly (B.
plumifrons) encloses what could be a branch of the palatine
ramus of the facial or the maxillary division of the trigeminal
(see Oelrich 1956), creating a small foramen in the antorbital
flange. A notch is also seen in some Anolis and Urostrophus vau-
tieri; a possibly related foramen is found in Ani. undulatus.
Sauropithecoides charisticus, like Polychrus, lacks a process or
foramen.
The foramen found in Sauropithecoides charisticus just
anterior to the ridge separating the frontal articulation facet
from the paranasal recess has a homolog in Laemanctus
longipes (where it is relatively small) and Basiliscus. In Coryto-
phanes hernandesii, this foramen is posteriorly displaced and
lies near the anterior end of the frontal facet (it is dual on one
side in UF 72492). Smith (2009b) did not describe the medial
surface of the prefrontal of Suzanniwana patriciana very care-
fully, but two uncatalogued new specimens from the type local-
ity have a small foramen just anterior to the frontal facet,
similar to the location in Basiliscus and L. longipes. The fora-
men is absent in Polychrus gutturosus (Figure 11D), at least in
a similar position, and one could not be discerned in computed
tomography (CT) scans of P. marmoratus (Digimorph.org
2002–2005). A foramen is present anterior to the frontal facet
in Pristidactylus torquatus and perhaps also in Leiosaurus cata-
marcensis (Digimorph.org 2002–2005, slice xy70). When there
is an obvious foramen in Anolis, it is sometimes located ante-
rior to the frontal facet (e.g., A. cristatellus), sometimes within
the anterior end of the facet (e.g., A. chlorocyanus and A. dis-
tichus) and sometimes on a broad ridge in between (e.g., A.
extremus); other times the foramen seems to be absent (Figure
11E, H). The occurrence and position of the foramen in Sa.
Late Eocene Lizards of the Medicine Pole Hills • Smith
17
Figure 11. Right prefrontal of selected members of Polychrotinae*. A–D, Polychrus gutturosus (UF 49377). E–H,
Anolis garmani (UF 42404). First column, Dorsal view. Second column, Anterior view. Third column, Lateral
view. Fourth column, Medial view. Abbreviations: f.fac., frontal facet; f.pr., frontal process; l.fac., lacrimal facet;
mx.fac., maxillary facet; n.fac., nasal facet; pl.fac., palatine facet; pl.pr., palatine process; pn.rec., paranasal recess;
prf.boss, prefrontal boss.
charisticus is probably primitive, based on the morphology seen
in Corytophaninae and Pristidactylus. The absence of the fora-
men in Polychrus might be an autapomorphy of the crown
clade, which would suggest Sa. charisticus lies outside it.
The curious strong ridge bisecting the tapering anterior
end of the frontal facet in some Sauropithecoides charisticus
is found in Polychrus gutturosus as well (Figure 11D). How-
ever, it appears to be absent in P. marmoratus on the basis of
CT scans (Digimorph.org 2002–2005, slices xy139 ff.). There
is a very subdued structure similar to a ridge in Laemanctus
longipes UF 66061. A ridge was absent in Basiliscus and Cory-
tophanes as well as in uncatalogued topotypic specimens of
Suzanniwana patriciana (pers. obs.). The ridge was absent
in all examined Anolis (Figure 11E, H) and, apparently, in
Pristidactylus torquatus and Leiosaurus catamarcensis
(Digimorph.org 2002–2005, slices xy81 ff. and xy64 ff.,
respectively). The presently known distribution of this fea-
ture would suggest that it independently evolved in the Poly-
chrus lineage and perhaps some Laemanctus. The degree of
intraspecific variation is unknown. The occurrence of the
ridge in some Sa. charisticus might provide a degree of cor-
roboration for affinities with Polychrus, once the distribution
of the feature in that taxon is better known.
The palatine facet is strongly marked in Polychrus guttur-
osus (Figure 11D). In particular, a flange projects medially from
the palatine process of the prefrontal to brace the dorsal end of
the prefrontal process of the palatine, creating a deep concavity.
This seems not to be true of P. marmoratus FMNH 42501 (Digi-
morph.org 2002–2005, xy148 ff.) or P. femoralis. In other poly-
chrotines and corytophanines where this could be studied, the
contact is merely an abutting one. Thus, there is no evidence
that the deep facet for the palatine is anything other than an
autapomorphy of P. gutturosus.
In almost all members of Iguanidae, the lacrimal bone is
exposed along the orbital margin between the anterior end of
the jugal and the prefrontal. In many living Polychrus, however,
a posteroventral projection of the lacrimal facet meets the jugal
to exclude the lacrimal from the orbital margin. This feature is
intraspecifically variable (Frost et al. 2001) and can even vary
slightly bilaterally. But even when the lacrimal is not completely
excluded, its exposure on the orbital margin is usually reduced
as compared with non-Polychrus. The lacrimal was completely
excluded in P. acutirostris (N ⫽ 1) and P. peruvianus (N ⫽ 1).
The lacrimal was at least partly excluded from the orbital mar-
gin in P. gutturosus (N ⫽ 2), as can be seen also from the mor-
phology of the lacrimal facet (Figure 11B, C). The abundance of
specimens of P. marmoratus (N
⫽ 10) provides the best under-
standing of intraspecific variation; the lacrimal was completely
excluded from the orbital margin on both sides in seven speci-
mens and incompletely excluded on at least one side in the
remaining three. Excluding from consideration P. liogaster, in
which the lacrimal is poorly exposed in the single existing oste-
ological specimen, P. femoralis (N ⫽ 1) is unique in the genus
in having a large and broadly exposed lacrimal. The morphol-
ogy of the lacrimal facet on the prefrontal in Sauropithecoides
charisticus implies that the lacrimal was broadly exposed at the
orbital margin. Once again, the phylogenetic position of P.
femoralis (Frost et al. 2001) makes the status of this feature as an
autapomorphy of crown Polychrus ambiguous, a problem that
the morphology of S. charisticus does little to resolve. However,
the degree of variation in P. femoralis is unknown.
FRONTAL
A frontal morphotype is associated here on the basis of iguan-
ian morphology, size, relative abundance and the similarity of
its dermal sculpturing to that of other dermal cranial bones.
Description:
The dorsal surface of the bone is covered in irreg-
ular polygonal rugosities (Figure 12A, D). These rugosities seem
more subdued on PTRM 19009 than on PTRM 19008, which is
possibly attributable to the abrasion suffered by the latter. The
rugosities along the orbital margin show there to have been a
periorbital row of scales. The posterior end of the nasal facet is
not preserved in any specimen. The dorsal surface of the bone
is basically flat in both transverse and sagittal cross sections (see
Figure 12D and 12C, F, respectively). The posterior margin of
the frontal containing part of the parietal foramen (p.f.) is pre-
served.
The posterior portion of the prefrontal facet is confined to
the ventral surface of the bone (Figure 12B, C). At midorbit
there are strong supraorbital flanges (Figure 12E, so.fl.) lateral to
the cristae cranii (cr.cr.), which decrease in width anteriorly and
posteriorly. These flanges probably reduced the extent of lateral
constriction of the frontal between the orbits. The arcuate cristae
cranii in the preserved portion of the bone are broad and
rounded in cross section. They do not approach one another
particularly closely. Medial to each crista cranii and extending
from midorbit a short distance posteriorly is a shallow groove
for the attachment of the planum or solium supraseptale (so.ss.).
The ventral surface of the posterior portion of the bone is
smooth. The ventral surface of the anterior portion is more
deeply excavated.
Comparisons: The parietal organ in Polychrus peruvianus might
not be externally exposed. There is an extremely small fissure in
the appropriate place in this species (confined to the frontal, but
contiguous with the frontoparietal suture) and the correspon-
ding median scale on the dorsal surface of the roofing bones is
depressed on the surface, but a distinct parietal foramen to
house the parietal organ on the external surface is lacking. A
clear foramen is also lacking in P. marmoratus. (There seems to
be an error in the Frost et al. 2001 data matrix. Character 50 of
their appendix 3 does not correspond to the written description
of that character, which regards the presence of a parietal fora-
men. There may have been a frame-shift to the right in the
matrix.) Notably, Frost and co-workers (2001) found these
species to be sister taxa. A clear foramen is present, however, in
P. acutirostris, P. femoralis and P. gutturosus (Figure 13A) and
in each case the foramen is confined to the frontal but contigu-
ous with the frontoparietal suture. In Anolis a foramen is pres-
ent, but it is frequently completely excluded from the frontal
(Etheridge 1959; Williams 1989; Figure 13D). In other poly-
chrotines, the foramen is contiguous with the frontoparietal
suture. The presence and position of the foramen in Saurop-
ithecoides charisticus would seem to be primitive.
The supraorbital flanges are strong in all living species of
Polychrus (Figure 13B) and are extremely well developed in
some (e.g., P. peruvianus, P. acutirostris and P. liogaster). Sauro-
pithecoides charisticus is similar to Polychrus in this respect.
However, the grooves for the solium supraseptale approach one
another more closely in living Polychrus than in S. charisticus,
and also more closely than in the stem corytophanine Suzanni-
wana patriciana (Smith 2009b, fig. 2R). On the other hand, the
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
18
grooves approach one another very closely in many other living
polychrotines, including Anolis (Figure 13E), and in some cory-
tophanines. Thus, there is some interspecific variation within
closely related taxa.
The frontal of Sauropithecoides charisticus seems to be less
arched than in Polychrus gutturosus (Figure 13C), but this
species may be unusual in this respect, on the basis of examina-
tion of articulated skulls of other species.
JUGAL
A single jugal fragment, PTRM 19087, is associated on the basis
of weak sculpturing and size. This association is further sup-
ported by the apparently complementary morphology of the
ectopterygoid morphotype associated here.
Description: Only the angle of the bone is preserved (Figure 14).
As compared even with the lateral surface of the facial process
of the maxilla, the sculpture on the lateral surface of the jugal is
weak (Figure 14A). As on the facial process of the maxilla and
not as on the dorsally facing dermal skull bones, scale margins
are not clearly demarcated. There is a curvilinear row of regu-
larly spaced foramina that pierce the lateral surface; grooves
extend from several of them, but without a clear pattern. The
orbital and ventral margins project laterally. There was a small
quadratojugal process (qj.pr.), which is broken.
The bone is mediolaterally thin. The dorsal surface of sub-
orbital ramus is weakly convex in cross section (Figure 14A, B,
so.ra.). Two foramina pierce this surface at the base of the tem-
poral ramus (Figure 14B, tm.ra.). The coronoid recess (cn.rec.)
on the posteromedial surface of the temporal ramus is broad
and shallow. The ectopterygoid articulation (ec.fac.) is a com-
plex surface, generally convex toward the center. The dorsal and
ventral corners of the posterolateral process of the ectoptery-
goid both left their impression here; the latter was distinctly
stronger than the former, which is consistent with the associ-
ated ectopterygoid morphotype (see above).
Comparisons: A distinct quadratojugal process, as seen in Sauro-
pithecoides charisticus, is generally absent in Polychrus. In par-
ticular, it is absent in P. acutirostris, P. gutturosus (Figure 15A),
P. liogaster, P. marmoratus and P. peruvianus and is present only
in P. femoralis. Outside of Polychrus, a strong angle (a 90° corner
on the posteroventral margin of the jugal) is frequently present
in Anolis (Figure 15C), sometimes forming a distinct quadroju-
Late Eocene Lizards of the Medicine Pole Hills • Smith
19
Figure 12. Frontal of Sauropithecoides charisticus. A–C, PTRM 19009 (right anterior portion) in dorsal, ventral
and right lateral views, respectively. D–F, PTRM 19008 (central portion) in dorsal, ventral and left lateral views,
respectively. Abbreviations: cr.cr., crista cranii; p.f., parietal foramen; prf.fac., prefrontal facet; so.fl., supraorbital
flange; so.ss., groove for attachment of solium supraseptale.
gal process; a distinct process is notably absent in A. richardii
and A. princeps. The process is absent in Anisolepini but present
in some members of Leiosaurini (e.g., weakly in Pristidactylus
torquatus, which is similar to many Anolis). Given current
understanding of Polychrus phylogeny (Frost et al. 2001), the
quadratojugal tubercle is an autapomorphy of S. charisticus.
In species of Polychrus, except for P. femoralis, the lateral
surface of the jugal, like that of the maxilla, does not possess
such well-defined polygonal rugosities as the dorsally facing
bones of the skull. This is consistent with the morphology
observed in Sauropithecoides charisticus.
POSTFRONTAL
No such element was recognized, nor is the posterolateral cor-
ner of the frontal known. The morphology of the postorbital
provides the only evidence here (assuming that element is cor-
rectly associated).
Description: The scar on the postorbital (see below) indicates
that the postfrontal was well developed and not fused to the
postorbital.
Comparisons: In all living species of Polychrus, the postfrontal
seems to be fused to the postorbital, such that the combined
bone has a forked dorsomedial end that wraps around the fron-
toparietal corner. The only other polychrotine known to me in
which this is the case is Leiosaurus bellii (Smith 2009a). The
postfrontal is discrete in stem corytophanines and discrete or
absent in Basiliscus (Smith 2009a). The fusion of the postfrontal
is thus an autapomorphy of crown Polychrus and the discrete-
ness of the postfrontal in Sauropithecoides charisticus suggests it
lies outside that crown.
POSTORBITAL
A single postorbital, PTRM 19014, is associated on the basis of
sculpturing, size and iguanid morphology.
Description: The lateral surface is dominated by two large
rugosities (Figure 16A), one on the middle of the dorsal ramus
(do.ra.), the other ventral to the first, along the ventral margin
of the bone. The latter may have continued onto the jugal.
Because the former is set away from the orbital margin of the
bone, this margin is convex in coronal cross section. The dor-
sal ramus expands slightly distally, and its end bears two facets
(Figure 16A–C), an anterior one for the postfrontal (pof.fac.)
and a posterior one for the parietal (p.fac.). A short but distinct
process, best developed medially, would probably have inserted
beneath the frontoparietal corner along the mutual suture of
those bones; its original extent is unknown. The medial surface
of the bone is smooth and weakly concave. The posterior ramus
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
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Figure 13. Frontal of selected members of Polychrotinae*. A–C, Polychrus gutturosus (UF 49377). D–F, Anolis
garmani (UF 42404). First column, Dorsal view. Second column, Ventral view. Third column, Right lateral
view. Abbreviations: cr.cr., crista cranii; n.fac., nasal facet; p.f., parietal foramen; pof.fac., postfrontal (or post-
frontal part of postorbitofrontal) facet; prf.fac., prefrontal facet; so.fl., supraorbital flange; so.ss., groove for attach-
ment of solium supraseptale.
(po.ra.) tapers strongly as far as it is preserved and presumably
this tapering continued to its distal end; its original posterior
extent is unknown. The inflection in the ventrolateral edge just
posterior to the dorsal ramus (Figure 16A) possibly then marks
the boundary between the jugal and squamosal articulations.
However, the morphology of the ventral edge is unusually
uneven (Figure 16D) and it is yet possible that much of it is actu-
ally broken and abraded. In any case, the anterior ramus is
mediolaterally thin.
Comparisons:
All living species of Polychrus have a well-devel-
oped canthal crest on the postorbital. This crest consists of a
longitudinally arrayed set of prominent, laterally directed
rugosities. This crest is absent in most other polychrotines,
including Anolis (although there can be an elaborate postorbital
rugosity; Figure 17A), Anisolepini and the leiosaur Pristidacty-
lus torquatus, although a similar crest was found in Enyalius
iheringii. Such a crest is also absent in Corytophaninae and its
stem members Suzanniwana patriciana and Geiseltaliellus spp.
(Smith 2009a, 2009b). The strong canthal crest thus seems to
be an autapomorphy of Polychrus and its absence in Saurop-
ithecoides charisticus would exclude the species from the crown.
PARIETAL
A parietal morphotype is associated on the basis of size, relative
abundance and the similarity of its sculpture to that of other
dermal skull elements.
Description: The parietal table is covered with irregular, gener-
ally polygonal rugosities (Figure 18A, D). Their form does not
deviate markedly from what has already been described for the
other dorsally facing dermal skull bones. The body of the pari-
etal (that is, excluding the supratemporal processes) is antero-
posteriorly short, its minimum width exceeding its minimum
Late Eocene Lizards of the Medicine Pole Hills • Smith
21
Figure 14. Left jugal of Sauropithecoides charisticus (PTRM 19087). A, Lateral view. B, Medial view. Abbrevia-
tions: cn.rec., coronoid recess; ec.fac., ectopterygoid facet; qj.pr., quadratojugal process; so.ra., suborbital ramus;
tm.ra., temporal ramus.
Figure 15. Left jugal of selected members of Polychrotinae*. A, B, Polychrus gutturosus (UF 49377). C, D, Ano-
lis garmani (UF 42404). First column, Lateral view. Second column, Medial view. Abbreviations: cn.rec., coro-
noid recess; ec.fac., ectopterygoid facet; mx.fac., maxillary facet; po.fac., postorbital facet; qj.pr., quadratojugal
process; so.ra., suborbital ramus; tm.ra., temporal ramus.
length (Figure 18A). The preserved portion of the bone does
not contain any part of the parietal foramen, but this is to be
expected, since the anteromedian portion of the bone is missing.
The parietal table projects strongly laterally over the supratem-
poral fossa (Figure 18B, C, st.fos.), forming what Lang (1989)
called adductor crests. PTRM 19012 indicates that the
supratemporal fossa becomes visible in dorsal view only along
the posterior half of the parietal table (Figure 18D). Anteriorly,
the descensus parietalis (desc.p.), which forms the floor of the
fossa, terminates in a facet for the postorbital articulation (Fig-
ure 18B, po.fac.); the facet is medially extensive and suggests
that a significant portion of the process underlying the fron-
toparietal corner is missing from the postorbital (see above), if
it is accurately associated.
The supratemporal fossa continues posteriorly onto the
anterolateral face of the supratemporal process (Figure 18D,
st.pr.). No facet for the supratemporal bone is preserved there
and the original length of the process is unknown. On its pos-
teromedial surface is an elongate fossa for the insertion of the
nuchal musculature (Figure 18D, F, nuc.fos.), presumably m.
spinalis capitis or m. articulo-parietalis, or both (following Tsui-
hiji 2005). The ventral surface of the supratemporal process is
not clearly demarcated from the underside of the body of the
parietal, or the cranial vault (Figure 18B, E). There is no evi-
dence of a pineal fossa (see Smith 2009b). A foramen is present
proximally on the ventral surface of the process. The recessus
processi ascendentis, which received the processus ascendens
of the synotic tectum, is dorsoventrally flattened in cross sec-
tion (Figure 18F). It opens well anterior of the posterior margin
of the bone and is continued posteriorly to the margin by what
Klembara and Green (2010) called a parietal trough, which
widens in the same direction (Figure 18B).
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
22
Figure 16. Left postorbital of Sauropithecoides charisticus (PTRM 19014). A, Lateral view. B, Medial view. C,
Dorsal view. D, Ventral view. Abbreviations: an.ra., anterior ramus; do.ra., dorsal ramus; p.fac., parietal facet;
po.ra., posterior ramus; pof.fac., postfrontal facet.
Figure 17. Left postorbital of Anolis garmani (UF 42404). A, lateral view. B, anterior view. C, medial view. Abbre-
viations: an.ra., anterior ramus; do.ra., dorsal ramus; po.ra., posterior ramus; pof.fac., postfrontal facet; sq.fac.,
squamosal facet.
Comparisons: The degree of development of the adductor crest
varies considerably in living Polychrus. In P. acutirostris, P.
femoralis and P. peruvianus the crest is very strong and most of
the supratemporal fossa is obscured in dorsal view. This mor-
phology is considered derived (see Lang 1989). In P. marmora-
tus and P. gutturosus, in contrast, the crest is weak, exposing
most of the supratemporal fossa in dorsal view (Figure 19A).
These two species are not closely related, according to Frost and
co-workers (2001). Polychrus liogaster is intermediate. The posi-
tion of P. gutturosus makes the evolution of this feature in Poly-
chrus ambiguous. The well-developed adductor crests shown
by Sauropithecoides charisticus are consistent with a relation-
ship to some part of the total clade of Polychrus, but determin-
ing precisely at which level requires additional data from other
characters.
The relative length of the parietal table varies considerably
in polychrotines. Some species of Polychrus stand out has hav-
ing elongate tables. In P. acutirostris the ratio of mid-line length
of the parietal table to width of the frontoparietal suture is 0.63;
in P. femoralis, this ratio is 0.58. Other members of Polychrus
have a ratio lower than 0.55: P. peruvianus (0.53), P. marmora-
tus (0.47) and P. gutturosus (0.51; Figure 19A). Sauropithecoides
charisticus also has a fairly low ratio (0.51). Outside of Polychrus
there is also much variation. In the leiosaur Pristidactylus
torquatus it is only 0.54. Among examined anisolepinins, Enyal-
ius iheringii had a ratio of 0.68 and for Anisolepis undulatus it is
0.63, but for Urostrophus vautieri only 0.52. Homologous points
of comparison are difficult to establish for species with a Y-
shaped parietal table (Figure 19C). Anolis princeps, with a nearly
V-shaped but technically still trapezoidal parietal table, showed
a ratio of 0.48. This distribution of biometric data makes it dif-
ficult to determine character polarity. Possibly this feature will
be of use on a more local level or after denser species sampling.
In polychrotines of the clades Leiosaurini and Anisolepini,
the fossa formed on the posterior margin of the parietal by the
development of a near-horizontal flange for the insertion of the
nuchal musculature is extensive, running much of the length of
the supratemporal process. In many species of Anolis and in liv-
ing corytophanines, the fossae are developed on the underside
of the parietal and a distinct flange is often absent (Figure 19D);
the fossae are small and semiventrally located already in the
stem corytophanine Suzanniwana patriciana (Smith 2009b). In
Polychrus the extent of the fossa is greatly reduced, the flange
terminating abruptly at a point no further posterolaterally than
the edge of the parietal table. In P. acutirostris the flange is essen-
tially absent. Of all species it is best developed in P. gutturosus
(Figure 19A). With regard to the extent of the fossa and the
development and sharpness of the flange, the condition in
Sauropithecoides charisticus departs from the usual condition
in Polychrus and is more similar to polychrotines other than
Anolis. This feature is potentially also a plesiomorphy of Sa.
charisticus that would exclude it from the crown of Polychrus;
however, primitive stem representatives of Anolis are desirable
to confirm local character polarity.
Late Eocene Lizards of the Medicine Pole Hills • Smith
23
Figure 18. Parietal of Sauropithecoides charisticus. A–C, PTRM 19010 (left anterior portion) in dorsal, ventral
and left lateral views, respectively. D–F, PTRM 19012 (right posterior portion) in dorsal, ventral and posterior
views, respectively. Dashed lines indicate the probable original course of the bone margins. Abbreviations: desc.p.,
descensus parietalis; nuc.fos., nuchal fossa; po.fac., postorbital facet; rec.pr.asc., recessus processi ascendentis;
st.fos., supratemporal fossa; st.pr., supratemporal process.
The recessus processi ascendentis is clearly located on the
ventral side of the parietal in Corytophaninae and Polychroti-
nae* (Smith 2009a, 2009b). The condition in Sauropithecoides
charisticus is similar to that of Polychrus gutturosus (Figure 19B)
and not as extreme as in many Anolis (Figure 19D).
SQUAMOSAL
A single squamosal specimen is tentatively associated here on
the basis of size and iguanid morphology. It is not considered in
the diagnosis of the species.
Description:
PTRM 19132 is a partial right element comprising
the posterior end and much of the anterior rod of the bone. It
is quite abraded. The anterior rod is nearly circular in cross sec-
tion, only slightly taller than wide (Figure 20A, B). The rod
increases in height posteriorly as the ventral and particularly the
dorsal margins become drawn out into flanges. At its posterior
end the bone has a weak ventral and a strong dorsal process
(vn.pr. and do.pr., respectively). The lacuna in the dorsal process
implies it was significantly longer than preserved. The posterior
margin of the ventral process is concave where it articulated on
the quadrate (q.fac.). The posterior margin of the bone as a
whole appears convex in side view, but a straight posterior mar-
gin cannot be ruled out because the dorsal process is broken
and abraded.
Comparisons:
In all examined species of Polychrus there are lat-
eral eminences on the main rod of the squamosal that are con-
tinuous with the canthal ridge on the postorbital. In P.
acutirostris, P. liogaster, P. marmoratus and P. gutturosus (Fig-
ure 21A) these eminences are very low and smooth. In P. peru-
vianus and P. femoralis they are clear and distinct rugosities, as
on the postorbital. That these eminences are lacking in Sauro-
pithecoides charisticus might suggest—if the squamosal is cor-
rectly attributed—that the species is outside of crown Polychrus.
However, this feature might not be independent of the postor-
bital crest (see above).
Smith (2009b) noted variation in Polychrotinae* in the
length of the ventral process of the squamosal, but the length of
the dorsal process also varies. In all Polychrus examined (espe-
cially P. femoralis, P. liogaster, P. peruvianus and P. gutturosus;
Figure 21A) the dorsal process is highly elongate, distinctly taller
than the height of the main rod of the bone at its middle. The
height of the dorsal process is variable in Anolis but frequently
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
24
Figure 19. Parietal of selected members of Polychrotinae*. A, B, Polychrus gutturosus (UF 49377). C, D, Anolis
garmani (UF 42404). First column, Dorsal view. Second column, Ventral view. Abbreviations: add.cr., adduc-
tor crest; desc.p., descensus parietalis; p.f., parietal foramen; pin.fos., pineal fossa; po.fac., postorbital facet;
rec.pr.asc., recessus processi ascendentis; st.fac., supratemporal facet; st.fos., supratemporal fossa; st.pr., supratem-
poral process.
short (Figure 21D). The process is elongate in Pristidactylus
torquatus, Leiosaurus catamarcensis and Enyalius iheringii and
moderately long in Anisolepis undulatus and Urostrophus vau-
tieri. A long dorsal process is also characteristic of the coryto-
phanines Laemanctus and Corytophanes (see below), as well as
Geiseltaliellus maarius (Smith 2009a). Although the conclusion
is not without uncertainty (the dorsal process is short in the
squamosal associated with Suzanniwana patriciana: Smith
2009b), possibly a long dorsal process is primitive for Poly-
chrotinae*. If so, the probable presence of a long dorsal process
of the squamosal associated with Sauropithecoides charisticus
could be a plesiomorphy.
The parietal facet of the squamosal in Polychrus gutturosus,
the only disarticulated specimen of the genus available, is very
distinct (Figure 21B). Although of interest, the state of this fea-
ture in polychrotine taxa other than Anolis is uncertain for want
of disarticulated specimens.
There is little indication of curvature of the squamosal in
PTRM 19132 except at its posterior end, which is a common
morphology for Clade A iguanids. In examined hoplocercines
(see also Estes et al. 1988, fig. 16 on Morunasaurus annularis) the
anterior rod of the bone is straight for most of its length; the
squamosal begins to curve medially toward its posterior end at
approximately the same place where the dorsal flange begins to
grow. The angle formed by the lateral margins of the squamosal
at its posterior and anterior end is small. (Curvature is present
somewhat farther anteriorly in Enyalioides oshaughnessyi, but
the angle remains small.) Most examined iguanines show a
Late Eocene Lizards of the Medicine Pole Hills • Smith
25
Figure 20. Right squamosal tentatively referred to Sauropithecoides charisticus (PTRM 19132). A, Lateral view.
B, Dorsal view. C, Medial view. Abbreviations: do.pr., dorsal process; q.fac., quadrate facet; vn.pr., ventral process.
Figure 21. Right squamosal of selected members of Polychrotinae*. A–C, Polychrus gutturosus (UF 49377).
D–F, Anolis garmani (UF 42404). First column, Lateral view. Second column, Medial view. Third column,
Dorsal view. Abbreviations: do.pr., dorsal process; p.fac., parietal facet; po.fac., postorbital facet; q.fac., quadrate
facet; vn.pr., ventral process.
similar morphology, although the curve encompasses more of
the rod in Dipsosaurus dorsalis and especially Conolophus sub-
cristatus. Crotaphytines are similar to hoplocercines. In the
corytophanines Laemanctus and especially Basiliscus, the ante-
rior rod is even straighter and the curvature more restricted to
the posterior end of the bone. (In Corytophanes it is difficult to
judge because of the peculiar morphology of the squamosal.) In
contrast, in some polychrotines, including Enyalius iheringii
and most species of Polychrus (P. femoralis, P. marmoratus, P.
peruvianus and P. gutturosus; Figure 21C), the entire posterior
half of the squamosal is strongly medially bent and the angle
formed between the anterior and posterior portions of the
squamosal can exceed 75°). Some Anolis show this morphology
as well (e.g., A. princeps), but in most the curvature is more gen-
tle (Figure 21F). This condition is considered derived and to
have evolved before crown Polychrus. Probably the squamosal
associated with Sauropithecoides charisticus lacked this strong
bowing, which would suggest that the species is outside crown
Polychrus, assuming the bone is properly attributed. This must
be seen as tentative at present until more complete specimens
are discovered and referral made more secure.
DENTARY
Specimens are associated here on the basis of size and relative
abundance. Tooth morphology also ties it to the maxilla. The
new specimens provide little additional data on its morphology
beyond what was described by Smith (2006a).
CORONOID
A single coronoid is associated here on the basis of size and the
presence of apomorphies of polychrotines or Polychrus.
Description:
PTRM 19323 is a partial right element lacking
much of the anteromedial and posteromedial processes. The
coronoid process (cn.pr.) has a rounded tip rounded in medial
(Figure 22A) and lateral (Figure 22C) aspect. Its posterior mar-
gin is straight and roughly vertical, whereas the anterior margin
is slightly convex and oblique. On the anterodorsal margin of
the bone is an elongate, slightly rugose patch (Figure 22A). In
posterolateral view the coronoid process is nearly quadrangular,
with a flattened (though still convex) dorsal edge (Figure 22B).
The medial edge of this quadrangle is formed by the medial crest
of the bone, which descends the posteromedial process (pm.pr.).
The lateral crest terminates ventrally in a small, posteriorly
deflected projection. Ventrally the quadrangular posterolateral
face is divided into two surfaces, a flat medial portion and a con-
cave lateral portion, which are separated by a rounded step.
Dorsally, these two surfaces become indistinct and the face is
uniformly concave.
The dorsal portion of the dentary facet extends slightly up
onto the lateral surface of the coronoid (Figure 22C, d.fac.). An
anterolateral process of the coronoid is absent. Apically, the
medial surface of the coronoid process is nearly flat, but basally
and between the anteromedial and posteromedial processes it
becomes concave (Figure 22A). The ventral margin of the bone
between said processes is strongly concave. The articulation sur-
faces for the dentary (d.fac.) and surangular (sa.fac.) are found
on the lateral surfaces of the respective processes (Figure 22C).
Comparisons:
One of the most noteworthy characteristics of
the coronoid of Sauropithecoides charisticus is the quadrangu-
lar shape of the coronoid process in posterolateral view:
dorsoventrally short with parallel sides. In examined corytopha-
nines the medial and lateral crests converge distally and the
process as a whole is relatively taller. In examined members of
Leiosaurini and Anisolepini the process is relatively short, as in
S. charisticus, but the medial and lateral crests still clearly con-
verge toward the apex. The process is variable in Anolis; gener-
ally it has convergent crests (e.g., A. princeps), but the degree of
convergence can be low (e.g., A. cuvieri) and sometimes the
crests are more or less parallel (e.g., A. garmani; Figure 23E), at
least distally. The process is generally relatively low, as in other
polychrotines, but it can be tall (e.g., A. garmani; Figure 23E). In
contrast, some species of Polychrus—namely, P. acutirostris and
P. gutturosus (Figure 23B)—have a coronoid process that is both
low and quadrangular. In P. marmoratus, however, the crests
are slightly convergent and in P. femoralis, P. liogaster and P.
peruvianus they are distinctly so. Thus, S. charisticus shares the
shape of its coronoid process uniquely with species of Polychrus
and this morphology is considered derived. Whether these
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
26
Figure 22. Right coronoid of Sauropithecoides charisticus (PTRM 19323). A, Medial view. B, Posterolateral
view. C, Lateral view. Abbreviations: am.pr., anteromedial process; cn.pr., coronoid process; d.fac., dentary facet;
pm.pr., posteromedial process; sa.fac., surangular facet.
features were present in the common ancestor of Polychrus,
however, is ambiguous at present.
A strong anterolateral process of the coronoid is present
in all Anolis (Etheridge and de Queiroz 1988; Frost and
Etheridge 1989; Figure 23F), but is absent in Polychrus (Figure
23C) and other polychrotines. The absence of an anterolateral
process in Sauropithecoides charisticus is thus primitive and
merely excludes the species from crown Anolis.
A strong posterolateral process of the coronoid is rare in
Squamata, including Iguanidae (Lang 1989). Yet a small pro-
jection from the ventral end of the lateral crest, extending pos-
teriorly along the lateral margin of the anterior surangular
foramen, seems to be present in all corytophanines except
Basiliscus galeritus (Lang 1989; pers. obs.). A strong process is
found in the stem corytophanine Geiseltaliellus (Rossmann
2000; Smith 2009a). A distinct posterior projection is absent in
Pristidactylus torquatus and Enyalius iheringii. A distinct but
weak projection is present in Urostrophus vautieri, and in
Anisolepis undulatus the presence of a small projection could
be masked by the growth of a small flange between it and the
posteromedial process of the coronoid, which overlaps the
surangular. A similar problem is encountered in many Anolis
(e.g., A. princeps). In spite of this flange, a projection is present
and distinct in some species (e.g., A. cuvieri and A. garmani;
Figure 23F) and both flange and projection are absent in still
others (e.g., A. richardii). Among Polychrus, a small posterior
projection was found in P. acutirostris, P. femoralis, P. gutturo-
sus (Figure 23B, C) and P. peruvianus. In P. marmoratus MCZ
74150, a flange over the top of the surangular is present and a
projection is not distinct (pers. obs.); but in P. marmoratus
FMNH 42501 (Digimorph.org 2002–2005), the projection is
present. This distribution suggests that projection is likely prim-
itive for the total clade of Polychrus and its occurrence in Sauro-
pithecoides charisticus does not help to constrain the
relationships of that species.
DERMARTICULAR
A dermarticular morphotype is tentatively associated here on
the basis of iguanid morphology, size and relative abundance.
However, it lacks several features common to Anolis and Poly-
chrus (see below) and its attribution is thus regarded as tentative,
pending recovery of more complete specimens. It is not con-
sidered in the diagnosis.
Description: PTRM 19079 comprises only the dermal prearticu-
lar and endochondral articular. The surangular was incompletely
fused to these elements and was lost after death, leaving a facet
ventrally (Figure 24C, sa.fac.) and a rugose patch around the
anterolateral portion of the articular, which is partly abraded (Fig-
ure 24A, ar.). The articular surface was surrounded (except pos-
teriorly) by a projecting medial rim for the attachment of the
articular capsule; the margin of the surface is elsewhere abraded.
The articular surface is weakly divided into facets for the lateral
and medial portion of the articular condyle of the quadrate. A
strong, triangular retroarticular process (ra.pr.) projects posteri-
orly. It is broken distally in all specimens. Its dorsal surface forms
an elongate basin at whose anteromedialmost corner is the rela-
tively large foramen chorda tympani (f.c.t.). The medial crest that
bounds the basin (me.cr.) diminishes in strength posteriorly,
whereas the tympanic crest (ty.cr.) remains tall (Figure 24B).
Late Eocene Lizards of the Medicine Pole Hills • Smith
27
Figure 23. Left coronoid of selected members of Polychrotinae*. A–C, Polychrus gutturosus (UF 49377). D–F,
Anolis garmani (UF 42404). First column, Medial view. Second column, Posterolateral view. Third column, Lat-
eral view. Abbreviations: al.pr., anterolateral process; am.pr., anteromedial process; cn.pr., coronoid process;
d.fac., dentary facet; pm.pr., posteromedial process; sa.fac., surangular facet.
The strong angular process projects ventromedially from
the level of the articular surface, curving slightly anteriorly (Fig-
ure 24B, C, an.pr.). A medially concave sheet of bone connects
the angular and retroarticular processes. The edge of this sheet
is slightly concave in dorsal view (Figure 24A), but slightly con-
vex in medial view (Figure 24B). Viewed ventrolaterally, the
posterior portion of the bone forms a largely flat, triangular
surface (Figure 24C). The triangle is bisected by a weak longi-
tudinal ridge that diminishes in prominence anteriorly, dis-
appearing by the transverse level of the articular surface. A small
foramen perforates this surface just medially to the anterior end
of the ridge.
Comparisons: The medial crest is greatly reduced in many
polychrotines, with some notable exceptions. It is absent in
most examined species of Polychrus (Figure 25A) and repre-
sented only by a very low swelling in P. peruvianus. It is highly
reduced in Anolis (Figure 25E) and Urostrophus vautieri as
well. On the other hand, a weak but distinct crest is present in
Enyalius iheringii and Anisolepis undulatus, and a strong crest
is found in Pristidactylus torquatus. Distinct crests are found
in living corytophanines. Present data suggest at a minimum
that Sauropithecoides charisticus, with its well-developed
medial crest, lies outside crown Polychrus. If Anolis and Poly-
chrus are sister taxa (Frost et al. 2001; Smith 2009a), then it is
even implied that S. charisticus lies outside this clade. How-
ever, the retroarticular process in Anolis is hardly plesiomor-
phic in other regards and the compound bone of stem Anolis
is unknown.
Yet another similarity between Anolis and Polychrus is the
location of the foramen chorda tympani. In Polychrus, the fora-
men is not located posterior to the transverse midpoint of the
articulation for the medial half of the quadrate, but rather at the
posteromedial corner of the articular surface (Figure 25A). This
is particularly clear in P. peruvianus, in which a remnant medial
crest remains. This position is also seen in Anolis and Anisolepis
undulatus, but not Pristidactylus torquatus or Urostrophus vau-
tieri. Regardless of the primitive condition in Polychrotinae*, if
Anolis and Polychrus are sister taxa, this position should have
obtained in their most recent common ancestor. That it is not
the case in the dermarticular associated with Sauropithecoides
charisticus suggests that this feature might represent a reversal
or that the attribution of the element is incorrect.
The retroarticular process of all Polychrus is also highly
reduced in length (Figure 25A, B). In particular, it is no longer
than the length of the (endochondral) articular bone. A longer
retroarticular process is taken to be primitive, on the basis of its
occurrence in examined members of Leiosaurini, Anisolepis
undulatus, Anolis (Figure 25D, E) and Corytophaninae. Thus,
these data suggest that Sauropithecoides charisticus lies outside
the crown of Polychrus, assuming the dermarticular is properly
associated.
The angular process lies in a plane nearly parallel with the
articular surface in Polychrus and Anolis (Figure 25A, D). This
was also the case in other examined polychrotines except Pris-
tidactylus torquatus, and the steeper angle seen in the dermar-
ticular associated with Sauropithecoides charisticus would have
to be an autapomorphy.
The flange connecting the angular and retroarticular
processes is highly reduced in most Polychrus, such that the
angular process takes on a fingerlike form (Figure 25B, C). The
angular process in P. femoralis has a similar length and orienta-
tion to that of other species, but it is connected by a strong flange
with the retroarticular process. A weaker flange is seen in P. lio-
gaster. A well-developed flange is present in Leiosaurini,
Anisolepini and Anolis. Thus, while a flange is expected at the
base of the Polychrus stem, the evolution of this feature in Poly-
chrus is ambiguous, given the position and morphology of the
two divergent species.
The compound bone of Polychrus shows other noteworthy
features, such as a circular tubercle anterolateral to the articular
surface (Figure 25B, C), which in other polychrotines (and
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
28
Figure 24. Dermarticular (⫽articular + prearticular) of Sauropithecoides charisticus (PTRM 19079). A, Dorsal
view. B, Medial view. C, Posteroventral view. Abbreviations: an.pr., angular process; ar., (endochondral) artic-
ular; f.c.t., foramen chorda tympani; me.cr., medial crest; ra.pr., retroarticular process; sa.fac., surangular facet;
ty.cr., tympanic crest.
P. femoralis) is much elongate (Figure 25E, F). Discussion of
such features is best deferred until the relevant parts of the com-
pound bone of Sauropithecoides charisticus are discovered.
Remarks
Smith (2006a) previously articulated five apomorphies that link
this species with Polychrus: extension of the premaxillary
process of the maxilla; dorsal overlap of the premaxilla onto the
premaxillary process; slight overhang of the premaxillary
process by the anterior margin of the facial process; a dorsolat-
erally projecting lip of bone on the lateral margin of the pre-
maxillary process; and tooth crown striations. This character
evidence remains. In the newly identified elements described
here, there are two more features that support this conclusion:
anterior premaxillary foramina multiple and anterior premax-
illary foramina arrayed colinearly on parapet of jaw. An addi-
tional potential synapomorphy of S. charisticus and Polychrus is
that the anterolateral corner of nasal is downturned (if the con-
dition in Polychrus is a reversal).
Sauropithecoides charisticus uniquely shares additional fea-
tures with most species of Polychrus, especially the massive
expansion of the premaxillary nasal process, well-developed and
relatively large rugosities developed over the entire dorsally fac-
ing portion of the skull, and strong adductor crests on the pari-
etal. Yet the plesiomorphic states of these characters in P.
gutturosus render their status in the last common ancestor of
Polychrus ambiguous.
As many as six derived features of Polychrus are lacking in
Sauropithecoides charisticus, suggesting that it lies outside the
crown. The primitive states of these features shown by the fos-
sil species are the following: seven or fewer premaxillary teeth;
foramen present in prefrontal just anterior to frontal facet,
within paranasal recess (needs confirmation in other Polychrus
species); lacrimal not excluded from orbital margin by apposi-
tion of jugal and prefrontal (assuming condition in P. femoralis
is a reversal); postfrontal and postorbital discrete; posterior
ramus of postorbital lacks rugosities that form canthal crest; and
nuchal fossa on posterior margin of parietal broadly exposed
dorsally and bounded ventrally by long, sharp-edged crest. If
the dermarticular bone is properly referred, the plesiomorphy
of a well-developed retroarticular process in S. charisticus would
also exclude it from crown Polychrus.
Smith (2006a) also gave the following two features as
autapomorphies of Sauropithecoides charisticus: simplified
tooth crowns, which lack accessory cusps far back along the
tooth row; and the greater extent of overlap of the premaxillary
process by the premaxilla. The new specimens clarify that tooth
crowns are unicuspid as far back as the end of the palatine
process of the maxilla. The second feature is probably related to
the expansion of the nasal process; its evolution is uncertain at
present (given the morphology in Polychrus gutturosus), but the
early age of the fossil suggests that this feature may have evolved
early on the stem of Polychrus, with a reversal in P. gutturosus.
Newly identified autapomorphies of S. charisticus include
recurved tips of anterior teeth (also seen in P. femoralis), antero-
posteriorly short nasal, pterygoid process of ectopterygoid
extending at extremely shallow angle (nearly directly medially),
circular lacrimal facet on prefrontal, and quadratojugal process
present. If the dermarticular bone is properly referred, several
additional features might also be autapomorphic: the ventro-
medial (oblique) orientation of the angular process, the strength
of the medial crest of the retroarticular process, and the posi-
tion of the foramen chorda tympani.
The conclusion that the predominantly South American
lineage Polychrus was present in the late Eocene of North
America (Smith 2006a) is strengthened by apomorphic
Late Eocene Lizards of the Medicine Pole Hills • Smith
29
Figure 25. Right compound bone of selected members of Polychrotinae* and Corytophaninae. A–C, Polychrus
gutturosus (UF 49377). D–F, Anolis garmani (UF 42404). First row, Medial view. Second row, Dorsal view.
Third row, Posterolateral view. Abbreviations: an.fac., angular facet; an.pr., angular process; ar., (endochondral)
articular; f.c.t., foramen chorda tympani; par., prearticular; ra.pr., retroarticular process; sa., surangular.
evidence from newly identified elements. Sauropithecoides
charisticus had the gestalt of Polychrus, but with a less angular
temple region. Its skull would have looked a great deal like that
of P. femoralis FMNH 81405 (Figure 26). Smith (2006a) origi-
nally placed the species in Polychrus out of taxonomic conser-
vatism, but because the new data suggest it lies outside the crown
of Polychrus (the modern radiation), the erection of a new
generic name is now justified (cf. de Queiroz and Gauthier 1992).
Iguaninae Cope, 1886
Remarks
Iguaninae, with eight extant genera, encompass the true iguanas
(Etheridge 1982; de Queiroz 1987). The basalmost living mem-
ber of the clade seems to be Dipsosaurus dorsalis (Norell and de
Queiroz 1991; Schulte et al. 2003), the desert iguana of the
American Southwest. Apart from Sauromalus, also found north
of Mexico, remaining taxa are confined to the tropical Ameri-
cas and tropical Pacific islands. Several early Miocene fossils
cannot be rejected as iguanines (see summary in de Queiroz
1987), but the earliest fossil with clear affinities is the middle
Miocene Armandisaurus explorator, which is related to D. dor-
salis (Norell and de Queiroz 1991).
Queironius Smith, gen. nov.
Type species. Queironius praelapsus sp. nov.
Diagnosis
. As for the type and only known species.
Etymology. After Kevin de Queiroz, in recognition of his con-
tribution to the systematics of Iguanidae in general, and of
Iguaninae in particular, and to the way in which we conceive of
these taxa.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
30
Figure 26. Skull of Polychrus femoralis (FMNH 81405). A, Dorsal view. B, Lateral and slightly anterior view.
Queironius praelapsus
Smith, sp. nov.
Figures 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47
Iguanid MPH-1 Smith, 2006a:10.
Holotype
. PTRM 19499 (left dentary; Figure 43).
Paratypes. PTRM 19016 (partial right prefrontal; Figure 33),
19017 (partial frontal; Figure 35D–F), 19018 (frontal fragment;
Figure 35A–C), 19019 (partial left postorbital; Figure 39), 19047
(partial right dentary), 19048 (partial left dentary), 19050 (left
dentary fragment), 19064, 19066 (partial premaxillae), 19086
(partial left jugal), 19088 (partial left jugal; Figure 37E, F), 19092
(left ectopterygoid; Figure 31), 19093 (partial right ectoptery-
goid), 19139 (left maxilla fragment; Figure 29A–C), 19141 (right
maxilla fragment), 19151 (partial premaxilla), 19233, 19234 (left
maxilla fragments), 19236 (right maxilla fragment; Figure 29J),
19237 (left maxilla fragment; Figure 29I), 19241 (partial left den-
tary), 19242 (left dentary fragment), 19243 (partial left dentary),
19244 (left dentary fragment), 19245, 19246 (partial right den-
taries), 19247 (right dentary fragment), 19249 (partial right den-
tary), 19250, 19251 (right dentary fragments), 19254 (partial
premaxilla), 19255 (partial premaxilla; Figure 27D–F), 19304,
19305, 19308, 19309 (partial premaxillae), 19324 (partial right
coronoid; Figure 45), 19337 (frontal fragment), 19361 (left jugal
fragment), 19362 (left jugal fragment; Figure 37A–D), 19379
(frontal fragment; Figure 35G, H), 19380 (frontal fragment),
19393 (right dentary fragment), 19394 (partial right dentary),
19395 (right dentary fragment), 19396 (partial right dentary),
19447 (right prefrontal fragment), 19457 (left maxilla fragment;
Figure 29D, E), 19458 (partial right dentary), 19500? (left den-
tary fragment), 19530 (left maxilla fragment), 19535 (premax-
illa; Figure 27A–C), 19554 (right maxilla fragment), 19571
(partial left maxilla; Figure 29F), 19572 (left maxilla fragment),
19581 (left maxilla fragment; Figure 29G, H), 19583 (right den-
tary fragment), 19584, 19587 (partial right dentaries), 19783
(parietal fragment; Figure 41).
Referred specimen. PTRM 19077 (partial right compound
bone; Figure 47).
Diagnosis
. An iguanid similar to (most) living iguanines in the
following derived features: accessory cusps (variably) present on
premaxillary teeth; mesial accessory cusp often appearing before
distal cusp; keel on ventral surface of nasal process between nasal
articulations triangular in cross section, not thin and bladelike;
ventral corner of posterolateral process of ectopterygoid exposed
laterally beneath angle of jugal; prefrontal boss broad and low;
strong expansion of orbital face of jugal anterior to ectoptery-
goid; and anterolateral process of coronoid present. Similar to
Dipsosaurus dorsalis (and Armandisaurus explorator, where
known) in the following derived features: nasal process of pre-
maxilla significantly overlapped by nasal bones, overlapped sur-
face broad and dorsally flat; blunt posterior end of maxilla; broad
maxillary facet on ectopterygoid; dual articulation of pterygoid
on ectopterygoid; prefrontal boss developed primarily dorsally;
and dual foramina on orbital face of temporal ramus of jugal.
Differs from D. dorsalis (and A. explorator, where known) in
having the following plesiomorphies: anterior premaxillary
foramina absent, nasal process of premaxilla relatively broad and
parallel-sided, only a weak gutter on the palatal shelf of the max-
illa, a very weak and rounded palatine process of the maxilla,
dorsal portion of postorbital curves medially, parietal foramen
broadly contiguous with frontoparietal suture, posteromedial
process of coronoid long, and angular process directed ven-
tromedially. Differs from almost all iguanines in having par-
allel-sided cheek teeth. The following three features are
autapomorphic: strong dorsal displacement of anterior infe-
rior alveolar foramen on facial process of maxilla, very shal-
lowly directed pterygoid process of ectopterygoid, and very
shallowly directed temporal ramus of jugal (possibly related).
Etymology
. From prae (L. “before”) and lapsus (L. “fall, stum-
ble”) → Engl. prelapsarian, referring to the idyllic state of man
before the mythic fall from grace and loss of innocence and par-
adise, as mid-latitude North America was still relatively warm
and humid in the late Eocene.
Description
PREMAXILLA
A premaxillary morphotype is associated with this species on
the basis of size and relative abundance. The association is fur-
ther supported by the presence of iguanine features.
Description: PTRM 19535 is an essentially complete element
(missing a few tooth crowns and the tip of the nasal process) and,
unless otherwise expressed or implied, forms the basis of the
description. The nasal process near its base is anteroposteriorly
thick and oval in cross section, its anterior as well as posterior
surfaces weakly convex and its lateral margins bluntly rounded
(Figure 27A–C, n.pr.). The anterior face becomes somewhat
more flattened distally (Figure 27A) and the posterolateral sur-
faces flatter (Figure 27B), giving this portion of the process a tri-
angular cross section. The anterior face of the nasal process is
smooth, but distally there is a V-shaped step marking the extent
of overlap by the nasal bones on the nasal process (Figure 27A,
n.fac.). The apex of the V lies a quarter-length down the nasal
process as preserved; ventral to this apex, the nasal facets become
increasingly restricted until they disappear from exterior view
more than halfway down the process. At the base of the nasal
process, the anterior surface curves ventrally into the parapet of
the jaw (Figure 27C). The nasal process extends posterodorsally
at a high angle to the horizontal. Distally, there is an inflection in
the anterior surface of the process associated with the nasal facet
(Figure 27C). The width of the nasal process increases very
slightly from its basal to middle portion (Figure 27A, D).
Proximally on the nasal process, the posterior surface is
already more acutely convex than the anterior one and a strong
but rounded median keel develops distally (Figure 27C). The
keel is flanked on either side by an extensive nasal facet; the
facets do not meet on the preserved portion of the bone,
although they approach one another distally. Just posterior to
the expanded base of the nasal process are the posterior pre-
maxillary foramina (Figure 27B, E, p.pm.f.), set in small depres-
sions. In some specimens (PTRM 19254, 19255, 19304 and
19535) these are essentially dual on each side, one lying behind
the other; the posterior hole in each pair seems to run ventrally
to pierce the palate, whereas the anterior one extends anteroven-
trally into the bone. However, in other specimens (PTRM
Late Eocene Lizards of the Medicine Pole Hills • Smith
31
19064, 19066, 19151, 19308 and 19309) the posterior premax-
illary foramen is more clearly single (PTRM 19305 is interme-
diate). Lateral to the base of the nasal process in some specimens
(e.g., PTRM 19255, 19304, 19308 and 19535) is a well-devel-
oped foramen on each side (Figure 27C, F, acc.f.). These foram-
ina probably do not correspond to anterior premaxillary
foramina (which usually pierce the anterior face of the premax-
illa); others lack these foramina or have only very small openings
that may be associated with the maxillary overlap, suggesting
that the anterior twig of the ethmoidal nerve extended through
connective tissue lateral to the nasal process and onto the snout
in all specimens. On the dorsal surface of the lateral process of
the premaxilla is a facet for the overlap of the premaxillary
process of the maxilla (Figure 27A, C, F, mx.fac.); in some
specimens (e.g., PTRM 19064 and 19309) the facet is more
clearly marked. Prominent ridges extend posteroventrally from
the base of the nasal process, enclosing between them an hour-
glass-shaped space (Figure 27B), which would have received the
anterior part of the cartilaginous nasal septum (see Oelrich
1956); ventrally they broaden to form small lappets contiguous
with the palatal shelf of the bone. The incisive process (in.pr.)
projects anteroventrally from them; it is bifurcated posteriorly
but fully fused anteriorly.
Seven tooth spaces are indicated in each of six specimens
(PTRM 19064, 19066, 19304, 19308, 19309 and 19535). These
teeth are high-crowned, roughly half their height projecting
above the parapet of the jaw. The teeth are parallel-sided for
most of their height, but they taper abruptly near the tip, espe-
cially on the mesial side, forming sharp and slightly lingually
deflected tips. Teeth are poorly preserved in most specimens,
but some allow determinations with regard to accessory cuspa-
tion. The first tooth pair is clearly unicuspid in PTRM 19305
(other teeth lost); all teeth are unicuspid in PTRM 19309;
mesial but not distal “shoulders” are present on the first tooth
pair in PTRM 19254 (other teeth lost); and mesial accessory
cusps were distinctly developed on the first tooth pair in PTRM
19255 (Figure 27D; the cusp seems to have been broken off on
right side).
The anterior face of the nasal process in PTRM 19309 has
a small (0.5 mm diameter) puncture mark where the surface of
the bone has clearly been crushed inward, creating an arcuate
rupture.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
32
Figure 27. Premaxilla of Queironius praelapsus. A–C, PTRM 19535 in dorsal, posterior and right lateral views,
respectively. D–F, PTRM 19255 in anterodorsal, posteroventral, and right lateral views, respectively. Abbrevia-
tions: acc.f., accessory foramen; in.pr., incisive process; mx.fac., maxillary facet; n.fac., nasal facet; n.pr., nasal
process; p.pm.f., posterior premaxillary foramen.
Comparisons: The presence of accessory cusps on the premax-
illary teeth of some Queironius praelapsus is a derived feature it
shares with several members of Iguaninae (Cope 1886; de
Queiroz 1987). Moreover, distal accessory cusps, when present
in iguanians, usually first occur more anteriorly than mesial
accessory cusps. However, this generalization is not infrequently
violated in Iguaninae (e.g., Sauromalus obesus, Cyclura cornuta
SMF 72159, Ctenosaura similis and Ct. pectinata), where mesial
cusps often precede distal ones. To be sure, where exactly the
first accessory cusps occur is difficult to tell in iguanines with
serrate teeth (i.e., Iguana and Cyclura). Moreover, there can be
considerable individual variation. For instance, in Brachylophus
fasciatus SMF 81156 mesial accessory cusps alone are developed
on the right side of the premaxillary teeth, whereas on the left
side the distal cusps are predominant or exclusive. Finally, in
several taxa (e.g., Amblyrhynchus cristatus, Conolophus sub-
cristatus and Dipsosaurus dorsalis; Figure 28A) all teeth have
both mesial and distal accessory cusps; this renders the state at
the base of Iguaninae uncertain, because the ancestral condi-
tion in the lineage leading to the basalmost living taxon, D. dor-
salis, is unknown. The occurrence of mesial accessory cusps
alone on the premaxillary teeth of some specimens of Q. prae-
lapsus is thus suggestive of iguanine relationships, but the great
amount of variation requires that larger sample sizes will be nec-
essary to draw a stronger conclusion.
Seven premaxillary teeth seem to be the norm for Queiro-
nius praelapsus, which also is the modal number for nearly all
living iguanines (Figure 28B, H) except Sauromalus (Figure
28E) and Cyclura (de Queiroz 1987), but the evolution of tooth
count outside of Iguaninae is complicated (Smith 2009b).
The premaxillary tooth count of Q. praelapsus is consistent
with iguanine relations. Notably, however, Armandisaurus
explorator has only six (Norell and de Queiroz 1991).
In some iguanines (de Queiroz 1987) and other iguanids
(Etheridge 1966b), the nasal bones are apposed until close to
their anterior ends and the nasal process of the premaxilla does
not achieve much dorsal exposure between them. Another
aspect of mutual relationship of the nasals is the proportion of
the nasal process of the premaxilla that they completely overlap.
In Brachylophus fasciatus and Sauromalus obesus (Figure 28D),
roughly one-third of the nasal process is completely covered by
the nasals; the figure is 40% in Dipsosaurus dorsalis (Figure 28A)
and approximately 16% and 24% in Amblyrhynchus cristatus
and Conolophus subcristatus, respectively. In other iguanines—
Ctenosaura (Figure 28G), Iguana and Cyclura—the nasals do
not so extensively cover the nasal process. In neither B. fascia-
tus nor S. obesus is the dorsal surface of the covered portion of
the nasal process entirely flat; instead, it is lenticular in cross sec-
tion, at least proximally (Figure 28F), although distally it
becomes flat in S. obesus (Figure 28D). Thus, in extent of cov-
erage by the nasals (taking into account the breakage to the tip
in PTRM 19535), the nasal process of Queironius praelapsus is
more similar to that of D. dorsalis, B. fasciatus and S. obesus. It
is conceivable that this is plesiomorphy, not apomorphy, given
the usual hypotheses of relationship among these taxa (de
Queiroz 1987; Sites et al. 1996). In S. obesus, the extent of nasal
overlap seems to depend on posterior growth of the nasal
process, which contacts the anterior end of the frontal, whereas
this is not the case in D. dorsalis or
B. fasciatus, suggesting the
possibility of independent evolution. In having a dorsal surface
that is proximally flat beneath the nasals, the nasal process in
Q. praelapsus is uniquely similar to that of D. dorsalis, which
may be a synapomorphy of the two lineages.
In iguanines the ventral keel on the nasal process of the
premaxilla is less sharp than in other members of Clade A
(Corytophaninae, Crotaphytinae, Hoplocercinae and Poly-
chrotinae*), even taxa with slender nasal processes such as Gam-
belia wislizenii, Laemanctus longipes and Anolis (Figure 3E), in
large part because the nasal facets are not as deep (Figure 28B,
E, H). Queironius praelapsus shows the iguanine condition,
which is considered derived.
The length of the nasal process seems to be relatively
greater in iguanines than in some other iguanids of Clade A.
The ratio of process length to premaxillary basal width was close
to 1 in measured corytophanines (0.9 in Basiliscus basiliscus and
1.0 in Laemanctus longipes and Corytophanes hernandesii) and
hoplocercines (1.1 in Enyalioides oshaughnessyi and Hoplocer-
cus spinosus). Polychrotines are highly variable: 0.85 in Poly-
chrus gutturosus, 1.4 in Anolis princeps (also high in many other
Anolis), 1.25 in Pristidactylus torquatus, 1.5 in Enyalius iheringii,
and greater than 1.5 in Urostrophus vautieri. The ratio was
greater than 1 in all iguanines (1.5 in Dipsosaurus dorsalis, 1.6 in
Sauromalus obesus and 1.5 in Ctenosaura similis; see
Figure 28). The ratio in Gambelia wislizenii was 1.4, however,
and in Crotaphytus collaris it was 1.6. Whereas the evolution of
a long nasal process in Anolis is easily attributable to the elon-
gation of the snout in this taxon, the evolution of the character
closer to the base of Clade A is less certain, given the length of
the process in Crotaphytinae and Iguaninae. The ratio was
greater than 1.3 in Queironius praelapsus, which is consistent
with a relationship to Iguaninae, if not indicative of one.
Furthermore, the nasal process in Queironius praelapsus
is parallel-sided and relatively broad for a considerable distance
above its base, as Smith (2009a) argued is the case primitively for
Clade A exclusive of Crotaphytinae, secondarily lost in taxa like
Dipsosaurus dorsalis (Figure 28A), Anolis and Laemanctus
(including L. serratus, not examined in Smith 2009a). A slen-
der, strongly tapering nasal process may be an additional
synapomorphy of D. dorsalis and Armandisaurus explorator,
which also shows this feature (Norell and de Queiroz 1991). The
condition in Q. praelapsus is considered primitive.
Smith (2009b) noted the “general” presence of anterior
premaxillary foramina in Iguaninae. Among taxa presently
available to me they are generally found in Dipsosaurus dorsalis
(Figure 28A), Cyclura cornuta, Iguana iguana, Ctenosaura sim-
ilis (Figure 28G) and the Galápagos iguanines. They are also
usually present in Sauromalus obesus
(Figure 28D), but are
found rather far laterally on the premaxilla and can be unilateral
or incomplete. They are present in the single known specimen
of Armandisaurus explorator (Norell and de Queiroz 1991, fig.
1–2). In contrast, in two good specimens of Brachylophus fascia-
tus they seem to be absent (possibly there is a tiny, related fora-
men unilaterally in SMF 81134).
The orientation of the nasal process of the premaxilla indi-
cates an animal with a tall snout, but the anterior margin of the
bone is not arched as in Dipsosaurus dorsalis (Figure 28C) or
Sauromalus obesus (Figure 28F). It is more similar to that of
Ctenosaura similis (Figure 28I).
The slight increase in the width of the nasal process from
its basal to middle portions is also seen in Ctenosaura similis
(Figure 28G), whereas in Dipsosaurus dorsalis and Sauromalus
obesus the process tapers (Figure 28A, D).
Late Eocene Lizards of the Medicine Pole Hills • Smith
33
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
34
Figure 28. Premaxilla of selected members of Iguaninae. A–C, Dipsosaurus dorsalis (CM 144937). D–F, Sauro-
malus obesus (UF 45624). G–I, Ctenosaura similis (UF 67982). First column, Dorsal view. Second column, Pos-
terior view. Third column, Right lateral view. Abbreviations: a.pm.f., anterior premaxillary foramen; in.pr.,
incisive process; mx.fac., maxillary facet; n.fac., nasal facet; n.pr., nasal process; p.pm.f., posterior premaxillary
foramen.
MAXILLA
Several partial maxillae and fragments are associated here on
the basis of similarity of tooth form. No specimen is close to
complete, but in combination they give a fairly detailed portrait
of the bone and its variability.
Description:
The dorsal surface of the premaxillary process is
bounded laterally by a thick, rounded ridge, which rises gradu-
ally posteriorly to form the anterior margin of the facial process
(Figure 29A, D, fa.pr.). This ridge also curves medially at its
anterior end to form a short rise at the anterior end of the pre-
maxillary process where it overlapped the premaxilla (Figure
29A, pm.pr.). Thus, the premaxillary process has a dorsal sur-
face that is concave in both sagittal and transverse section (Fig-
ure 29B). The crista transversalis (cr.tv.) decreases in height as
it crosses the premaxillary process to join the medial margin of
the bone (Figure 29A, D). It has a markedly more sagittal orien-
tation and greater dorsal extent in PTRM 19139 than in PTRM
19457. The anterior inferior alveolar foramen (a.i.a.f.) opens
near the junction of the crista transversalis and the facial process,
well above the floor of the premaxillary process. The subnarial
arterial foramen (sn.a.f.) opens onto the floor of the premaxil-
lary process; it is very large in PTRM 19457, but may have been
smaller in PTRM 19139. It is continued anteromedially by a
deep trough. The premaxillary facet on the underside of the
anterior margin of the bone has a triangular posterior extension
along the palatal margin (Figure 29C, pm.fac.), which implies a
corresponding process on the premaxilla. The medial portion of
the palatal flange is not complete in any specimen.
The anterior margin of the facial process rises nearly ver-
tically (Figure 29D). The process is mediolaterally thin, but its
anterior edge is thickened (Figure 29E). The facial process in
PTRM 19457, where it is most complete, shows a distinct inflec-
tion in the anterior margin; dorsal to this point there is a slightly
thickened, flattened surface that probably marks the ventral-
most extent of the nasal (n.fac.), although it does not show any
rugosities commonly associated with such structures. The facial
process curves gradually medially toward its distal end. The
more posterior portion of the facial process is not well preserved
in any specimen.
The superior alveolar foramen seems to be largely
“unroofed” (Smith 2006a); that is, to sit in a fairly extensive gut-
ter (Figure 29F). A gutter is not seen in PTRM 19139 or 19457
(Figure 29E), so clearly it did not extend to the anterior end of
the facial process, but its exact extent is uncertain because all
specimens are fragmentary. In the specimen most completely
preserving the palatal flange (pl.fl.), PTRM 19571, the anterior
inferior alveolar foramen lies about midway between the poste-
rior end of the “roof” and the anterior end of the premaxillary
process (Figure 29F), but a second opening (acc.f.) is also pres-
ent anterior to the main opening. The jugal facet (j.fac.) reaches
the posterior margin of the gutter (Figure 29I).
The palatine process is weak (Figure 29G, pl.pr.). The max-
illary process of the palatine clasps it and the portion of the pala-
tine facet (pl.fac.) on the underside of the palatal flange is
somewhat less extensive than the portion on its upper side (Fig-
ure 29G, H). Anteriorly, the palatine facet tapers but deepens.
The posterior end of the maxilla is preserved in only one
specimen, PTRM 19236. It ends bluntly (Figure 29J). The facial
process is completely reduced at this point. A flange for the jugal
articulation projects laterally well over the tooth row (j.fac.).
A ridge separates the jugal facet from the medial one for the
ectopterygoid (ec.fac.). The latter is mediolaterally extensive.
Posteriorly, it is directed predominantly dorsomedially and
evinces a small longitudinal ridge. Anteriorly, the facet is con-
cave in transverse cross section and faces more or less dorsally.
The jugal articulated on the flat, weakly striated dorsal surface
of the palatal flange anterior to the ectopterygoid facet.
The antepenultimate tooth is only about 20% shorter than
the tooth two spaces in front of it. The last two tooth spaces in
this specimen are empty, but they are expected to have been
much shorter.
Comparisons: Many iguanines—Dipsosaurus dorsalis (Figure
30C), Iguana iguana, Conolophus subcristatus, Sauromalus obe-
sus (Figure 30F) and Ctenosaura similis (Figure 30I)—have a
fairly strong lateral ridge on the premaxillary process, like
Queironius praelapsus. In some others (Cyclura cornuta and
Brachylophus fasciatus), the dorsal surface of the premaxillary
process is transversely flat. Where a ridge is present, it is often
coincident with or scarcely separate from the lateral margin of
the groove for the subnarial artery (Figure 30F). In larger igua-
nines, the ridge may curve medially away from the lateral mar-
gin of the bone, forming an oblique, anterolaterally directed
surface on the premaxillary process. A strong ridge is also pres-
ent in hoplocercines, but is not generally found in crotaphytines
or corytophanines. A strong ridge is present in Polychrus (Smith
2006a), Pristidactylus torquatus, Enyalius iheringi and some
Anolis, but not in Urostrophus vautieri or Anisolepis undulatus.
The presence of a lateral ridge may be plesiomorphic.
In iguanines there is a tendency for the anterior inferior
alveolar and subnarial arterial foramina to combine, especially
in larger species like Ctenosaura similis (Figure 30I), but also in
Brachylophus fasciatus. They may be separated by only a small
bridge of bone (Figure 30F) and sometimes only unilaterally. In
Dipsosaurus dorsalis they are distinct (Figure 30C), as they also
are in Queironius praelapsus and most other iguanids. Indeed,
their separation is an autapomorphy of Iguanidae (Smith
2009a). This is a plesiomorphy of Q. praelapsus.
In some Dipsosaurus dorsalis the anterior inferior alveolar
foramen is located well above the dorsal surface of the premax-
illary process on the anterior margin of the facial process. This
dorsal position is also seen in Enyalioides oshaughnessyi and
Hoplocercus spinosus, but in neither of them is it as dorsally dis-
placed as in Queironius praelapsus. This is an autapomorphy of
the fossil species.
A tall posterior portion of the crista transversalis, as seen in
Queironius praelapsus, is not usual in iguanines. The crista is low
in Dipsosaurus dorsalis (Figure 30B), Brachylophus fasciatus,
Sauromalus obesus (Figure 30E) and Amblyrhynchus cristatus.
It is more extensive in Ctenosaura similis (Figure 30H), Cyclura
cornuta and Conolophus subcristatus. It is also more extensive in
the hoplocercines Enyalioides oshaughnessyi and Hoplocercus
spinosus, which may suggest it is a locally primitive character.
In curving gradually medially toward its distal end, the
facial process of Queironius praelapsus is similar to that of igua-
nines (Figure 30A, D, G) and most hoplocercines, but unlike
that of polychrotines, corytophanines or crotaphytines (Smith
2006a). (In Enyalioides oshaughnessyi it shows a corytophanine-
like sharp bend near the distal end.)
A distinct inflection of the anterior margin of the facial
process marking the nasal articulation is seen in Sauromalus
Late Eocene Lizards of the Medicine Pole Hills • Smith
35
obesus (Figure 30E), but the inflection is far more subdued in
Dipsosaurus dorsalis (Figure 30B) and Ctenosaura pectinata
(Figure 30H). Queironius praelapsus is similar to S. obesus in
this respect.
Smith (2006a) noted the occurrence of an extensive gutter
on the dorsal surface of the palatal flange of the maxilla in sev-
eral iguanids, including iguanines (Figure 30C, F, I). The gutter
in Queironius praelapsus, although not especially well character-
ized by existing specimens, seems not to be as anteriorly exten-
sive as that of iguanines, corytophanines and perhaps
hoplocercines. It was certainly not as extensive as the gutter
of Dipsosaurus dorsalis, which extends to the anterior end
of the facial process. CT scans of Brachylophus fasciatus
(Digimorph.org 2002–2005, slices xy89 ff.) suggest that the
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
36
Figure 29. Maxilla of Queironius praelapsus. A–C, PTRM 19139 (anterior portion of left element comprising
most of premaxillary process) in lateral, dorsal and ventral views, respectively. D, E, PTRM 19457 (anterior por-
tion of left element comprising anterior base of facial process) in lateral and medial views, respectively. F, PTRM
19571 (partial left element) in dorsal view. G, H, PTRM 19581 (middle fragment of left element) in dorsal and
medial views, respectively. I, PTRM 19237 (slightly more posterior middle fragment of left element) in dorsal
view. J, PTRM 19236 (posterior fragment of right element) in dorsal view. Abbreviations: acc.f., accessory fora-
men; a.i.a.f., anterior inferior alveolar foramen; cr.tv., crista transversalis; ec.fac., ectopterygoid facet; fa.pr., facial
process; j.fac., jugal facet; n.fac., nasal facet; pl.fac., palatine facet; pl.fl., palatal flange; pl.pr., palatine process;
pm.fac., premaxillary facet; pm.pr., premaxillary process; sn.a.f., subnarial arterial foramen.
gutter is relatively shorter in this species too. Thus, the extent of
the gutter is more variable in living iguanines than available dis-
articulated specimens would suggest. The condition in Queiro-
nius praelapsus could be primitive.
In having a weak palatine process, Queironius praelapsus is
similar to members of Clade A (Figure 30C, F, I) exclusive of
Crotaphytinae. Differences obtain among iguanines—the
process is small but sharp in Dipsosaurus dorsalis (Figure 30C),
larger but rounded in Sauromalus obesus (Figure 30F)—but in
general the palatine process here differs from that seen in Clade
B, in which the process is generally sharp and strong. Queironius
praelapsus is very similar to Ctenosaura similis in this respect, a
resemblance that is primitive.
Queironius praelapsus is most similar to Sauromalus obe-
sus (Figure 30F) and, less so, Dipsosaurus dorsalis (Figure 30C),
among available disarticulated iguanines in having a strongly
dorsomedially oriented posterior portion of the ectopterygoid
facet. The facet is directed almost entirely dorsally in Ctenosaura
similis (Figure 30I), as it also is in examined members of Cory-
tophaninae, Polychrotinae* and Crotaphytinae.
The posterior end of the maxilla is very blunt in Dipsosaurus
dorsalis, almost flat (Figure 30C), in contrast to all other igua-
nines (Figure 30F, I). This is not necessarily related to a decrease
in tooth number (compare tooth counts in D. dorsalis and Sauro-
malus obesus), but to a truncation of the edentulous posterior
process of the maxilla. The posterior end of the maxilla is much
blunter in Queironius praelapsus than in most other iguanines,
but Cyclura cornuta and the Galápagos iguanines come close.
The partial flattening of the posterior end of the maxilla in Q.
praelapsus is an apomorphy uniting it with D. dorsalis.
The parallel-sided tooth crowns separate Queironius prae-
lapsus from nearly all living members of Iguaninae, in which
the tooth crowns of posterior teeth, at least, flare apically (Fig-
ure 30B, E, H). In the relatively small-bodied Ctenosaura quin-
quecarinata, however, the teeth are similar to many other
iguanids in not flaring (de Queiroz 1987), which is presumably
a reversal. Its status in Q. praelapsus—plesiomorphy or autapo-
morphy—is unknown.
ECTOPTERYGOID
Two ectopterygoids (PTRM 19092 and 19093) are associated
here on the basis of size and relative abundance; the association
is further buttressed by the presence in this ectopterygoid mor-
photype of apomorphies appearing (almost exclusively) in
Iguaninae.
Description: The anterolateral process is broken in both speci-
mens, so its exact length and course cannot be determined
Late Eocene Lizards of the Medicine Pole Hills • Smith
37
Figure 30. Left maxilla of selected members of Iguaninae. A–C, Dipsosaurus dorsalis (UF 55334). D–F, Sauro-
malus obesus (UF 45624). G–I, Ctenosaura similis (UF 67982). First column, Lateral view. Second column,
Medial view. Third column, Dorsal view. Abbreviations: a.i.a.f., anterior inferior alveolar foramen; cr.tv., crista
transversalis; ec.fac., ectopterygoid facet; fa.pr., facial process; j.fac., jugal facet; l.fac., lacrimal facet; n.fac., nasal
facet; pl.pr., palatine process; s.a.f., superior alveolar foramen; sn.a.f., subnarial arterial foramen.
(Figure 31A, al.pr.). The maxillary facet (mx.fac.), which occu-
pies the whole of the anterolateral process and runs posteriorly
toward the posterolateral process (pl.pr.) of the bone, is deep
and mediolaterally extensive. Its ventrolateral edge is asymmet-
rically concave and the ventral corner of the posterolateral
process is developed into an elongate wedge (Figure 31B), which
would have inserted between the jugal and maxilla to be
exposed in lateral view (see also description of jugal below).
Most of the lateral surface is occupied by the concave jugal facet
(j.fac.), which is punctured at its deepest point by a foramen.
The delicate pterygoid process extends at a shallow angle
ventromedially (Figure 31C, pt.pr.). On the posterior face of the
bone is the broad pterygoid facet (Figure 31D, pt.fac.), which is
overhung by a strong corner of the dorsal margin (Figure 31A,
D), marking the medial edge of the coronoid recess (cn.rec.).
The pterygoid also had an anterior articulation on the ectoptery-
goid (Figure 31A, C, pt.fac.(a)); this accessory articulation is sep-
arated dorsally, ventrally and laterally by a strongly developed
transverse ridge from the (plesiomorphic) posterior articula-
tion. The posterior face of the bone is pierced near its lateral
edge by a foramen (Figure 31D) that may have communicated
with the one in the jugal facet.
Comparisons: The exposure of the ventral corner of the pos-
terolateral process of the ectopterygoid between the jugal and
the posterior end of the maxilla is found in many members of
Iguaninae as well as in Crotyphytinae (Lang 1989; McGuire
1996). The ventral corner is developed into a strong wedge in
isolated elements of Dipsosaurus dorsalis (cf. Figure 32D), but
not in Sauromalus obesus or Ctenosaura similis (Figure 32H, L).
It is not known whether a strong wedge is formed in all taxa in
which the ectopterygoid is laterally exposed, although it seems
a distinct possibility in Brachylophus fasciatus. Queironius prae-
lapsus has a wedge-shaped ventral corner and apparently
showed lateral exposure, which features would link that species
with Crotaphytinae or Iguaninae, at least.
The posterior end of the maxilla of Dipsosaurus dorsalis is
especially blunt and mediolaterally broad in comparison with
other iguanines (see above), which may be partly responsible
for the great breadth of the maxillary facet on the ventral surface
of the lateral portion of the ectopterygoid (Figure 32A). The
ratio of two measurements of the ectopterygoid—the transverse
distance from the lateral edge of the bone to the medialmost
extent of the maxillary facet and to the tip of the pterygoid
process—is about one-third (0.32) in D. dorsalis. In contrast,
the ratio is one-fourth or less in other iguanines: 0.24 in Sauro-
malus obesus (Figure 32E) and 0.22 in Ctenosaura similis (Fig-
ure 32I). Other examined iguanids in Clade A show similar
ratios (see Smith 2009b, fig. 4; also Figure 9A, E, and later fig-
ures), suggesting that this is the primitive state. I conclude that
Queironius praelapsus, with a ratio of 0.33, shows exclusive
derived similarity in this regard to D. dorsalis, with the nontriv-
ial caveat that most iguanines were not available as disarticu-
lated specimens.
Another derived similarity of Queironius praelapsus to
Dipsosaurus dorsalis (both examined specimens) is the dual
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
38
Figure 31. Left ectopterygoid of Queironius praelapsus (PTRM 19092). A, Ventral view. B, Lateral view. C, Ante-
rior view. D, Posterior view. Abbreviations: al.pr., anterolateral process; cn.rec., coronoid recess; j.fac., jugal facet;
pl.pr., posterolateral process; pt.fac., pterygoid facet; pt.fac.(a), supplementary anterior portion of pterygoid
facet; pt.pr., pterygoid process.
articulation for the pterygoid on the ectopterygoid. Smith (sub-
mitted) notes that this articulation, in which a strong transverse
ridge divides the two portions of the articulation (Figure 32A,
B), is present in the acrodontan Leiolepis belliana but not other
acrodontans; curiously, a stem representative of Leiolepis might
also be present in the Medicine Pole Hills (Smith, submitted).
The feature is not present in other iguanids, including other
iguanines (Figure 32F, J), and is therefore considered a derived
feature where it occurs. The form of the ectopterygoid-ptery-
goid articulation in Armandisaurus explorator (Norell and de
Queiroz 1991, figs. 1B, 2B) suggests this feature might be pres-
ent there as well, but CT scans will be required to confirm that.
The shallowness of the pterygoid process in Queironius
praelapsus is noteworthy. It is shallower, in fact, than in any
examined living iguanine (Figure 32C, G, K). Amblyrhynchus
cristatus (not measured) comes closest to the fossil species.
Other members of Clade A also generally have steep pterygoid
processes (Figure 9C, later figures) and so are closer to the igua-
nine condition. The shallow condition is considered derived
and constitutes another autapomorphy of Q. praelapsus.
The corner of bone hanging over the posterior pterygoid
facet and marking the medial edge of the coronoid recess is well
developed in most iguanines. This is true as well of some mem-
bers of Clade A, such as Crotaphytus collaris, Enyalioides lati-
ceps, Laemanctus longipes, the leiosaur Pristidactylus torquatus
and some Anolis (e.g., A. garmani). The corner is poorly devel-
oped, however, in the iguanines Dipsosaurus dorsalis and
Amblyrhynchus cristatus and other members of Clade A, includ-
ing many hoplocercines, Anisolepini, Polychrus and Gambelia
wislizenii. Queironius praelapsus shows the more common igua-
nine condition. This feature seems to be fairly plastic and poten-
tial ontogenetic variability has not been explored.
PREFRONTAL
A prefrontal morphotype best represented by PTRM 19016 is
associated on the basis of iguanid morphology and size; the
Late Eocene Lizards of the Medicine Pole Hills • Smith
39
Figure 32. Left ectopterygoid of selected members of Iguaninae. A–D, Dipsosaurus dorsalis (CM 144937). E–H,
Sauromalus obesus (UF 45624). I–L, Ctenosaura similis (UF 67982). First row, Ventral view. Second row, Ante-
rior view. Third row, Posterior view. Fourth row, Lateral view. Abbreviations: al.pr., anterolateral process;
“cn.rec., coronoid recess; j.fac., jugal facet; mx.fac., maxillary facet; pl.pr., posterolateral process; pt.fac., ptery-
goid facet; pt.fac.(a), supplementary anterior portion of pterygoid facet; pt.pr., pterygoid process.
association is further supported by the presence of iguanine
apomorphies.
Description: PTRM 19016 is a fragmentary right element, lack-
ing most of the frontal process, the palatine process and the
maxillary flange that articulated deep to the facial process of the
maxilla. Its dorsal surface is dominated by an extensive, low,
pentagonal prefrontal boss (Figure 33A, prf.boss). Anteriorly
and laterally its sculpture is dominated by radial grooves, the
deepest and widest of which begins at the center of the boss and
extends anteromedially; there are also many tiny, widely sepa-
rated foramina, which toward the center of the bone are set in
small pits. A ridge of bone, likewise sculptured, extends poste-
riorly from the posteromedial corner of the boss, merging with
the orbital margin. A longitudinal groove developed dorsolat-
erally on the medial edge of the prefrontal marks the nasal artic-
ulation (n.fac.).
The lateral half of the anterior margin of the prefrontal boss
is undercut by a groove into which the posterior margin of the
facial process of the maxilla inserts (Figure 33B, mx.fac.). This
groove shallows somewhat medially. The floor of the facet is
lined with many small foramina. A ridge of bone, the anterolat-
eral portion of the broken palatine process, extends ventrally
from the anterolateral corner of the prefrontal boss (Figure 33B,
C, pl.pr.). On the anterior surface of this ridge is the lacrimal
facet (l.fac.). This facet is smooth except for a tiny foramen near
its dorsal edge.
The paranasal recess is deep (Figure 33D, pn.rec.). Its mar-
gins are broken nearly everywhere, so that the contacts with the
palatine and frontal cannot be studied. However, even the pre-
served portions show that the floor of the recess extends ventro-
medially for a distance exceeding the mediolateral width of the
roof without showing any ventral inflection that would mark
the dorsal-most extent of the palatine articulation. Thus, the
palatine seems not to have extended far up the medial edge of
the antorbital flange in this species.
Comparisons: A prefrontal boss, the rugose patch developed on
the prefrontal at the anterior corner of the orbit that anchors
connective tissue (Oelrich 1956), is considered to be an autapo-
morphy of Iguania (Estes et al. 1988). In Iguaninae, except for
Cyclura and adult Iguana iguana among examined specimens,
it is typically much broader and lower than in other iguanians,
including other iguanids. This is a unique apomorphy linking
the Queironius praelapsus with Iguaninae.
In Dipsosaurus dorsalis (Figure 34A), the prefrontal boss is
found primarily on the dorsal surface of the prefrontal (that is,
it is not at a marked angle to the dorsal surface, although this
surface curves anteroventrally). In other examined iguanines—
Brachylophus fasciatus, Sauromalus obesus (Figure 34E),
Amblyrhynchus cristatus, Conolophus subcristatus and Cteno-
saura similis (Figure 34I)—the boss is clearly directed laterally.
The boss is drawn out into a strong and comparatively narrow
process in subadult and adult Cyclura cornuta, but juveniles
were unavailable. Although adult Iguana iguana have bosses
that are drawn out posteriorly and relatively small in cross-sec-
tional area, juveniles show broader, lower bosses like those seen
in B. fasciatus, which suggests an ontogenetic transformation
among some larger iguanines. In some hoplocercines like
Enyalioides oshaughnessyi the prefrontal boss (much more
restricted) is also directed more laterally. The dorsal direction of
the boss is potentially a synapomorphy of D. dorsalis and
Queironius praelapsus.
In Iguaninae the palatine articulation on the palatine process
is considerably restricted (Figure 34B, F, J). This is also true in
Hoplocercinae. In other members of Clade A (Corytophaninae,
Crotaphytinae and Polychrotinae*), the palatine extends farther
dorsally along the palatine process, and the frontal and palatine
facets consequently approach closely (e.g., Figure 11D, H).
Restricted dorsal extent of the palatine may well be the primitive
state for Iguania, as it appears to be present in Acrodonta and
Sphenodon. This feature could represent a reversal in Iguaninae
and Hoplocercinae, depending on the topology in Iguanidae.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
40
Figure 33. Partial right prefrontal of Queironius praelapsus (PTRM 19016). A, Dorsal view. B, Anterior view.
C, Lateral view. D, Medial view. Abbreviations: l.fac., lacrimal facet; mx.fac., maxillary facet; n.fac., nasal facet;
pl.pr., palatine process; pn.rec., paranasal recess; prf.boss, prefrontal boss.
FRONTAL
A frontal morphotype is associated on the basis of iguanian
morphology, size and relative abundance.
Description:
The anteriormost portion and the distal end of the
posterolateral process are lacking in all specimens. The frontal
has an hourglass shape (Figure 35A, D). The dorsal surface is
lightly sculpted in larger specimens (Figure 35A, D, G), but
sculpture is absent in the smallest specimen (PTRM 19337).
Posteriorly, around the parietal foramen (p.f.), which strongly
(Figure 35D) or weakly (Figure 35G) invades the frontal, this
sculpture consists of grooves largely tangential to the margins of
the foramen and low, elongate eminences. In most places, the
small size of the grooves suggests that the eminences raised
between them were not individually associated with epidermal
scales; there is little indication (by groove depth or width, for
instance) of where scale boundaries lay. Sculpture is poorly
developed on the periorbital ridges. In PTRM 19018, the emi-
nences of the sculpture are somewhat larger in scale (Figure
35A). The medial half of the posterior margin is weakly but
asymmetrically concave (Figure 35D, G); the lateral half of the
posterior margin is nearly straight (Figure 35D). The dorsal
surface of the frontal is generally flat between the orbits (Figure
35A, G), but in PTRM 19017 there is a weak concavity (Figure
35D) and in PTRM 19337 there is a strong one. In lateral view,
the frontal is very weakly arched (Figure 35F).
Although the tip of the right posterolateral corner is bro-
ken in the most complete specimen, the distal end of the post-
frontal facet is preserved (Figure 35E, pof.fac.), implying that
this element was well developed. The prefrontal facet is a pos-
teriorly tapering triangular depression with one apex close to
the dorsal margin of the bone (Figure 35C, F, prf.fac.). The post-
frontal and prefrontal were very widely separated on the orbital
margin. Two small foramina pierce the lateral surface of the
right crista cranii, one just anterior to the postfrontal facet, the
other farther anteriorly, both well behind the point of greatest
interorbital constriction.
The cristae cranii are low (Figure 35B, E, H, cr.cr.). They
increase only slightly in height anteriorly, although approaching
the prefrontal facet the rate of change increases. In cross sec-
tion, the cristae are rounded along their entire preserved extent,
the ventrolateral and ventromedial surfaces meeting one
another at a blunt apex. Supraorbital flanges are not developed.
The cristae are widely separated, even at midorbit. Medial to the
base of the cristae are small bilateral grooves, marking the
attachment of the solium supraseptale (so.ss.; de Beer 1937; Oel-
rich 1956). In midsagittal section, the ventral surface is convex,
as the bone thins anteriorly and posteriorly from midorbit. A
median longitudinal ridge is not developed posteriorly except in
PTRM 19018, where it is broad and low (Figure 35B).
In ventral view, along the lateral half of the frontoparietal
suture, several anteroventrally trending grooves and ridges are
Late Eocene Lizards of the Medicine Pole Hills • Smith
41
Figure 34. Right prefrontal of selected members of Iguaninae. A–D, Dipsosaurus dorsalis (CM 144937). E–H,
Sauromalus obesus (UF 45624). I–L, Ctenosaura similis (UF 67982). First row, Lateral view. Second row, Medial
view. Left element in third row, Anterior view. Right element in third row, Dorsal view. Abbreviations: f.fac.,
frontal facet; f.pr., frontal process; l.fac., lacrimal facet; mx.fac., maxillary facet; pl.fac., palatine facet; pl.pr., pala-
tine process; pn.rec., paranasal recess; prf.boss, prefrontal boss.
visible, which were complemented by ridges and grooves,
respectively, on the parietal.
Comparisons: In many living iguanines there is a tendency for
the parietal foramen to be shifted anteriorly. Generally, it is
contiguous with the frontoparietal suture, but predominantly
found in the frontal (Figure 36D, G). (Other iguanids in which
the parietal foramen is shifted forward include Basiliscus,
Corytophanes and Jamaican Anolis: e.g., Etheridge 1959.) The
foramen is developed entirely within the frontal bone in Dip-
sosaurus dorsalis (Figure 36A) and Armandisaurus explorator
(Norell and de Queiroz 1991) and in some Sauromalus obesus,
among other species (de Queiroz 1987). The parietal foramen
in Queironius praelapsus is contiguous with the suture, but
possibly more equally distributed between frontal and pari-
etal (unfortunately, the single known parietal of Q. praelapsus
is too incomplete to check this). A similar position is seen in
hoplocercines, which retain the foramen. The position of the
foramen in Q. praelapsus seems to be primitive.
Many other characters of the frontal of Queironius praelap-
sus are primitive: the absence of supraorbital flanges, the general
lack of a median ridge on the ventral surface posteriorly and the
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
42
Figure 35. Frontal of Queironius praelapsus. A–C, PTRM 19018 in dorsal, ventral, and right lateral views, respec-
tively. D–F, PTRM 19017 in dorsal, ventral and left lateral views, respectively. G, H, PTRM 19379 in dorsal and
ventral views, respectively. Abbreviations: cr.cr., crista cranii; p.f., parietal foramen; pof.fac., postfrontal facet;
prf.fac., prefrontal facet; so.ss., groove for attachment of solium supraseptale.
wide separation of the cristae cranii (see Figure 36B, E, H). The
very slight curvature of the frontal in lateral view is similar to
what is seen in Sauromalus obesus (Figure 36F) and not as
strong as seen in Dipsosaurus dorsalis (Figure 36C). In at least
some larger iguanines curvature is absent (Figure 36I).
The rugosities on the frontal of Queironius praelapsus are
smaller in scale than those of most iguanines (Figure 36A, D),
although a similar sculpture was seen in large (but not small)
Cyclura cornuta and in places in one Ctenosaura similis (Figure
36G). Only one of the fossil specimens, PTRM 19018, showed
sculpture more like that of other iguanines.
JUGAL
A jugal morphotype is associated with this species on the basis
of size, absence of sculpture laterally, iguanid morphology and
relative abundance. The association is further supported by an
iguanine autapomorphy.
Description:
The lateral surface is smooth (Figure 37A). It is
pierced by several small foramina of nearly equal size (the anteri-
ormost one is slightly larger than the others). These are divisible
into a curvilinear row of foramina that parallels the ventral mar-
gin of the bone and two additional foramina dorsal to these. The
Late Eocene Lizards of the Medicine Pole Hills • Smith
43
Figure 36. Frontal of selected members of Iguaninae. A–C, Dipsosaurus dorsalis (CM 144937). D–F, Sauroma-
lus obesus (UF 45624). G–I, Ctenosaura similis (UF 67982). First row, Dorsal view. Second row, Ventral view.
Third row, Right lateral view. Abbreviations: cr.cr., crista cranii; n.fac., nasal facet; p.f., parietal foramen; pof.fac.,
postfrontal facet; prf.fac., prefrontal facet; so.ss., groove for attachment of solium supraseptale.
curvilinear row approaches slightly closer to the ventral margin
posteriorly. The ventral margin of the jugal is broadly rounded. A
shallow impression, the maxillary facet (mx.fac.), is present on
the ventral margin of the suborbital ramus (so.ra.) of the bone,
marking the articulation of the posterior continuation of the facial
process of the maxilla. The curve traced by the dorsal margin of
the facet extends at first anterodorsally, but then it shifts toward
the horizontal, suggesting that the jugal was probably broadly
exposed in lateral view. The depth of the suborbital ramus is vari-
able, but can be considerable (cf. Figures 37A and E).
The dimension of the lateral surface of the jugal perpendi-
cular to the orbital margin is greatest near the angle. The
dorsoventral height of the suborbital ramus seems to be nearly
constant, as far as the ramus is preserved, whereas the tempo-
ral ramus tapers strongly (Figure 37E, tm.ra.). The temporal
ramus curves distinctly medially (Figure 37F), suggesting that
the skull was relatively broad and rounded in cross section, or
at least not laterally compressed. The temporal ramus also takes
a very shallow course with respect to the horizontal (36°). At the
distalmost preserved end of the ramus, on the orbital face of the
bone, is the anterior end of the postorbital facet (po.fac.). Prox-
imal to this facet are two small foramina (Figure 37E, F), also
seen in PTRM 19086.
Ventrally, the maxillary facet has a weak, lateral ridge (Fig-
ure 37B) that would have inserted in the shallow jugal groove of
the posterior process of the maxilla. Medial to the ridge, the ven-
tral surface of the jugal forms a flat, anteriorly expanding, acute
triangle whose medial edge is marked by a tiny, sharp ridge that
becomes increasingly prominent posteriorly toward the apex.
The ventral surface is pierced by a row of several small foram-
ina, which parallels the medial edge of the triangle. Distinct from
the dominant maxillary facet on the ventral surface is a small
facet at the angle of the bone for the ectopterygoid (ec.fac.). This
facet received the wedge supported by the ventral corner of the
posterolateral process of that bone, clearly implying that the
wedge was exposed laterally on the skull.
The main ectopterygoid facet is a prominent, elongate,
anteriorly tapering feature found on the medial face of the bone
(Figure 37C, E, ec.fac.). The orbital face of the suborbital ramus
changes significantly in shape and orientation dorsolaterally to
this facet. Posteriorly it is weakly convex in cross section. How-
ever, the orbital face is strongly medially expanded anteriorly
(Figure 37D, F), correlated with the expanding, triangular ven-
tral surface that articulates on the maxilla and acquires a
strongly concave shape in cross section. Dorsal to the midpoint
of the ectopterygoid facet, the orbital face in PTRM 19362 shows
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
44
Figure 37. Jugal of Queironius praelapsus. A–D, PTRM 19362 (base of suborbital ramus of left element) in lat-
eral, ventral, medial and dorsal views, respectively; E, F, PTRM 19088 (partial left element) in medial and dor-
sal views, respectively. Abbreviations: ec.fac., ectopterygoid facet; mx.fac., maxillary facet; po.fac., postorbital
facet; so.ra., suborbital ramus; tm.ra., temporal ramus.
a small, roughly circular depression with two tiny foramina at
the base.
Comparisons: In comparison with the width of the temporal
ramus perpendicular to the orbit, the suborbital ramus of the
jugal is tall in Queironius praelapsus (extremely so in some spec-
imens). Similar proportions are seen in Dipsosaurus dorsalis
(Figure 38A); the suborbital ramus is somewhat less tall in
Ctenosaura similis (Figure 38G) and much less so in Sauroma-
lus obesus (Figure 38D). The very delicate character of the sub-
orbital ramus of S. obesus is probably autapomorphic, given
comparisons with Crotaphytinae and Hoplocercinae. The
extreme height of the suborbital ramus in some specimens of
Q. praelapsus might provide support for a relationship with D.
dorsalis, although it would be desirable also to study other dis-
articulated specimens as well as Armandisaurus explorator in
this respect.
One outstanding feature of the jugal of Queironius prae-
lapsus is medial expansion of the orbital face of the jugal ante-
rior to the anterolateral process of the ectopterygoid. This
expansion was observed in many iguanids of the clade Iguani-
nae, including adults of Brachylophus fasciatus, the Galápagos
iguanines, Sauromalus obesus (Figure 38F), juvenile and adult
Ctenosaura similis (Figure 38I), Iguana iguana and Cyclura cor-
nuta. In S. obesus and B. fasciatus, however, the expansion is
notably weaker than in other iguanines, weaker in fact than in
Q. praelapsus. In S. obesus, this may be related to the great rela-
tive length of the anterolateral process of the ectopterygoid,
which limits expansion of the orbital face of the jugal until just
behind the lacrimal foramen (Figure 32E). An expansion is vir-
tually absent in Dipsosaurus dorsalis (Figure 38C) and Arman-
disaurus explorator (Norell and de Queiroz 1991, fig. 1A). A
weak expansion is seen in several other iguanids—for example,
Oplurus cuvieri (but not Chalarodon madagascariensis), Crota-
phytus collaris (but not Gambelia wislizenii) and Polychrus (but
not Enyalius iheringii)—but in none of them, or in examined
members of Acrodonta, was the expansion as strong or as clear
as in Iguanini (i.e., Iguaninae exclusive of D. dorsalis and B. fas-
ciatus). The strong expansion of the jugal in Q. praelapsus would
unite it with Iguanini.
The dual foramen on the orbital face of the temporal ramus
of the jugal is unusual in Iguanidae. In Iguaninae the foramen is
dual in multiple examined Dipsosaurus dorsalis (Figure 38B), but
it was found otherwise only in one adult Iguana iguana. The
foramen is absent in Sauromalus obesus (Figure 38E), at least on
the orbital face of the temporal ramus; it might also be absent in
Amblyrhynchus cristatus. The state of this character in Arman-
disaurus explorator is uncertain. The foramen is single in other
iguanines (Figure 38H) as well as in polychrotines, corytopha-
nines (although the foramen has a tendency to be absent in Cory-
tophanes and Laemanctus) and crotaphytines. Hoplocercines
show a more complicated pattern; the foramen is dual in
Enyalioides spp. but single in Hoplocercus spinosus. The best pres-
ent hypothesis—assuming H. spinosus is the basalmost diverging
Late Eocene Lizards of the Medicine Pole Hills • Smith
45
Figure 38. Left jugal of selected members of Iguaninae. A–C, Dipsosaurus dorsalis (CM 144937). D–F, Sauro-
malus obesus (UF 45624). G–I, Ctenosaura similis (UF 67982). First row, Lateral view. Second row, Medial view.
Third row, Dorsal view. Abbreviations: ec.fac., ectopterygoid facet; mx.fac., maxillary facet; po.fac., postorbital
facet; so.ra., suborbital ramus; tm.ra., temporal ramus.
lineage in Hoplocercinae (Torres-Carvajal and de Queiroz
2009)—is that the dual foramina are autapomorphic of D. dor-
salis. The presence of this feature in Queironius praelapsus would
tie it to D. dorsalis or possibly I. iguana among iguanines.
The degree of concavity of the orbital face of the jugal
seems to show considerable ontogenetic variation, being promi-
nently developed in juveniles (especially posteriorly, around the
angle of the jugal) and subtler in adults of Iguana iguana and
Ctenosaura similis (Figure 38I). Among examined hoplo-
cercines, strong concavity was observed in Enyalioides oshaugh-
nessyi but not Hoplocercus spinosus.
Marked medial curvature of the temporal ramus is found
in many members of Clade A, including hoplocercines (e.g.,
Enyalioides laticeps and Hoplocercus spinosus), crotaphytines
and some polychrotines and corytophanines. It is also found in
iguanines like Dipsosaurus dorsalis (Figure 38C), but is essen-
tially absent in some larger iguanines like Ctenosaura similis
(Figure 38I) and also Sauromalus obesus (Figure 38F). The
broad distribution of curvature in Clade A suggests it is a ple-
siomorphy of Queironius praelapsus.
Finally, the very shallow angle of the temporal ramus to
the horizontal was not encountered in any examined iguanine
and is an autapomorphy of Queironius praelapsus. It suggests a
certain depression of the skull and for this reason is possibly
related to the shallow angle taken by the pterygoid process of
the ectopterygoid.
POSTFRONTAL
The postfrontal was well developed (see description of
frontal above and postorbital below). An isolated element
was not identified.
POSTORBITAL
A single postorbital specimen is tentatively associated here on
the basis of size and because (1) it displays iguanid morphology
and (2) morphological evidence has already tied postorbital
morphotypes to the other two common iguanids, Sauropithe-
coides charisticus and the new corytophanine described below.
Description: PTRM 19019 is a left element lacking the tip of the
anterior ramus, much of the posterior ramus and most of the
ventral margin of the bone. The lateral surface is smooth, with
only weak rugosities on the anterior ramus (Figure 39A, an.ra.).
Along the orbital margin the lateral surface has a flangelike
expansion to which the supraorbital fascia would have attached
(cf. Oelrich 1956); this expansion nearly doubles the mediolat-
eral width of the bone at mid-height, as compared with the pre-
served portion of the anterior ramus (Figure 39B). However,
this expansion has no anterior component and does not inter-
rupt the curvature of the orbital margin in lateral aspect (Figure
39A). On the anterolateral edge of the dorsal ramus (do.ra.) is a
strong postfrontal facet whose ventralmost extent lies just dor-
sal to the apex of the expansion (Figure 39B, pof.fac.). A small
foramen pierces the facet near mid-height. Conceivably, the dis-
tal part of the facet marks the articulation on the posterior edge
of the parietal rather than the postfrontal, but there is no divi-
sion of the facet that would imply this. The bone thins pos-
terodorsally toward the dorsal edge of the posterior ramus
(Figure 39A, C, po.ra.). The bone as a whole is laterally bowed:
the medial edge of the bone in anterior aspect is distinctly con-
cave. Additionally, the posterior ramus seems to have curved
distinctly medially.
Comparisons: A lateral expansion of the orbital margin that is
separated from the postfrontal suture, as seen in PTRM 19019,
is also found in the earliest Eocene polychrotine Anolbanolis
banalis (Smith 2009b), although there the expansion usually has
an anterior component that interrupts the curvature of the
orbital margin in lateral view. Similar expansions are seen in
several polychrotines, particularly members of Anisolepini and
some Polychrus. (Smith [2009b] lacked skeletons of Anisolepini
and did not note their similarity to A. banalis.) These expansions
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
46
Figure 39. Partial left postorbital of Queironius praelapsus (PTRM 19019). A, Lateral view. B, Anterodorsal
view. C, Medial view. Abbreviations: an.ra., anterior ramus; do.ra., dorsal ramus; po.ra., posterior ramus; pof.fac.,
postfrontal facet.
may be seen as modifications of postorbital tubercles, which are
present in many iguanids, especially members of Clade A. These
tubercles or flanges are generally lacking (at least on the postor-
bital) in Hoplocercinae. A flangelike expansion is seen in
Brachylophus fasciatus and some Dipsosaurus dorsalis (Figure
40A, B), whereas an expansion of any kind is absent in
Sauromalus obesus (Figure 40D, E). In other iguanines like
Ctenosaura similis the postorbital shows a broad, rugose expan-
sion, which could be homologous with the flange seen in some
D. dorsalis, but is largely restricted to the dorsal part of the bone
along the postfrontal articulation (Figure 40G, H). That is, the
flange is dorsally displaced in these taxa. In many living igua-
nines (D. dorsalis, Amblyrhynchus cristatus, Conolophus sub-
cristatus) the expansion also has an anterior component. This
feature is probably a plesiomorphy of Queironius praelapsus.
A dorsoventrally extensive postfrontal articulation, like
that seen in Queironius praelapsus, is also found in all examined
iguanines (see Figure 40B, H) except Sauromalus obesus (Fig-
ure 40E), where it is strongly reduced. An extensive articulation
is also seen in many polychrotines and in hoplocercines. The
articulation is smaller (or indeed, with the postfrontal, absent)
in most corytophanines and in crotaphytines. The postfrontal
seems to be fused to the postorbital in Polychrus (see above),
but in the stem taxon Sauropithecoides charisticus the facet
indicates a small articulation (see above). A large postfrontal
articulation is probably a primitive feature of little use in deter-
mining the relationships of Q. praelapsus.
In Dipsosaurus dorsalis (Figure 40B), Sauromalus obesus
(Figure 40E) and Conolophus subcristatus among iguanines, the
element is nearly straight in anterior profile. In other iguanines,
however, there is a medial curvature of the dorsal ramus that
begins just dorsal to the ventralmost extent of the lateral postor-
bital expansion (Figure 40H). This curvature is also found in
most other members of Clade A. In crotaphytines the slight
curvature occurs somewhat more ventrally. In corytophanines
and polychrotines the curvature is sharper. In examined hoplo-
cercines, curvature, when present (e.g., Enyalioides oshaugh-
nessyi), is also mostly confined to the distal portion of the dorsal
ramus and in Hoplocercus spinosus the curvature is almost
absent. Thus, the straight postorbital of D. dorsalis and
S. obesus is probably autapomorphic. Queironius praelapsus is
primitive.
The posterior ramus of the postorbital has a markedly
thicker dorsal margin than in comparably sized members of
Iguaninae (Dipsosaurus dorsalis, Sauromalus obesus, Brachylo-
phus fasciatus) and Hoplocercinae (Hoplocercus spinosus).
Whether this was true of the unpreserved remainder of the
ramus is unknown.
Late Eocene Lizards of the Medicine Pole Hills • Smith
47
Figure 40. Left postorbital of selected members of Iguaninae. A–C, Dipsosaurus dorsalis (CM 144937). D–F,
Sauromalus obesus (UF 45624). G–I, Ctenosaura similis (UF 67982). First column, Lateral view. Second column,
Anterodorsal view. Third column, Medial view. Abbreviations: an.ra., anterior ramus; do.ra., dorsal ramus; j.fac.,
jugal facet; po.ra., posterior ramus; pof.fac., postfrontal facet.
PARIETAL
A single parietal fragment, PTRM 19783, is associated here on
the basis of iguanian morphology, size and the relative abun-
dance of other elements of Queironius praelapsus.
Description:
Only the right posterolateral portion of the main
body of the bone is preserved (Figure 41). The parietal table is
smooth (Figure 41A). It is trapezoidal, showing no indication of
posterior constriction that would result in a V- or Y-shaped
table. The slopes of the supratemporal fossa (st.fos.) are roughly
45° to the vertical, and the adductor crests do not project. Pos-
teriorly there is a small, rounded facet on the lateral side of the
bone (Figure 41C); it is situated at an angle to the supratempo-
ral fossa and faces ventrolaterally. Anteriorly, the lateral edge of
the bone is broken, so it cannot be determined what lay anterior
to the facet. It is also possible that the facet is artifactual (two
small foramina near its dorsal edge are suggestive of spongiosa,
but these may themselves just be artifacts of corrosion). At pres-
ent, the best hypothesis is that the facet is real, although it is not
clear what the facet represents. Posteriorly, the nuchal fossa is
very deep (Figure 41A, nuc.fos.), undercutting the posterior
margin of the parietal table. The recessus processi ascendentis
is located just under the posterior edge of the bone (Figure 41B,
rec.pr.asc.). It forms a flattened oval in cross section. The ven-
tral surface of the bone is otherwise smooth.
Comparisons:
The parietal table is trapezoidal in Dipsosaurus
dorsalis (Figure 42A) as well as Sauromalus obesus (Figure 42D)
and part of Ctenosaura (Etheridge and de Queiroz 1988). The
trapezoidal condition is considered primitive (Etheridge and de
Queiroz 1988; Frost and Etheridge 1989), modified to a V- or Y-
shape in Brachylophus and Iguanini (Figure 42G). If the rela-
tively large size of the parietal with respect to other elements is
taken to indicate that PTRM 19783 represents an adult individ-
ual, then the trapezoidal condition in Queironius praelapsus is
either primitive or an autapomorphy allying it with Sauroma-
lus or part of Ctenosaura (cf. de Queiroz 1987).
The curious facet seen on the lateral margin of the parietal
of Queironius praelapsus has an uncertain significance. It is
almost surely not associated with the supratemporal, whose
anterior end in Iguaninae runs on the medial side of the
supratemporal process (de Queiroz 1987) and which, in cases
where it runs broadly on the lateral side (the primitive condition
in Iguanidae), does not form a facet at marked angle to the
supratemporal fossa. A more or less similar facet was not found
in any iguanine (Figure 42F, I) except Dipsosaurus dorsalis CM
144937 (Figure 42C) and, less clearly, UF 55334 (but not CM
40505). Where present in this species, the facet is located just
posteriorly to a slight ventral expansion of the ventral edge of the
supratemporal fossa (descensus parietalis); the expansion,
which sometimes has a frilled appearance, serves apparently for
attachment of the ligament connecting the epipterygoid with
the parietal. However, the distal tip of the epipterygoid is pro-
vided with a separate posterior facet in these two specimens
(especially CM 144937) and this facet is set off at an angle.
Assuming the facet in PTRM 19783 is not artifactual (see
description), it could represent the same facet seen in some D.
dorsalis. However, it would then suggest an unusually posterior
attachment point for the epipterygoid. Clearly, more complete
fossil specimens are desirable before any conclusions are drawn.
There is otherwise not a great deal of phylogenetic infor-
mation preserved on the parietal. The great depth of the nuchal
fossa—by comparison with Dipsosaurus dorsalis (Figure 42A),
Sauromalus obesus (Figure 42D) and the Galápagos iguanines—
is potentially autapomorphic, but adequate comparison cannot
be made with many taxa with Y-shaped parietals (Figure 42G).
The reduction in the recessus processi ascendentis in S. obesus
(Figure 42E) is presumably autapomorphic by comparison with
other iguanids (e.g., Figure 42B, H).
DENTARY
Dentary specimens are associated here on the basis of characters
described in Smith (2006a), which are also exemplified by the
holotype, described below.
Description: The dentary was briefly described by Smith (2006a)
on the basis of partial specimens. Of the new specimens, the
holotype, PTRM 19499, is noteworthy in being the most
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
48
Figure 41. Parietal fragment (right posterior portion) of Queironius praelapsus (PTRM 19783). A, Dorsal view.
B, Lateral view. C, Ventral view. Abbreviations: nuc.fos., nuchal fossa; rec.pr.asc., recessus processi ascendentis;
st.fos., supratemporal fossa; st.pr., supratemporal process.
complete known specimen and also one of the largest (Figure
43). The description below, unless otherwise expressed or
implied, is based on it. This left dentary has a tooth row length
of 16.8 mm; excluding the last six teeth, it is about 16% larger
than the specimen illustrated by Smith (2006a, fig. 5). The
Meckelian groove is fused as far posteriorly as the the boundary
between teeth 21 and 22 (Figure 43A). Anteriorly, it is open for
a space of about four teeth (M.gr.). Posteriorly, it opens like a V,
at whose apex the anterior inferior alveolar foramen would have
been located (a.i.a.f.); this apex is located well above mid-height
on the nontooth-bearing portion. The medial surface of the
bone is flat but somewhat oblique, undercutting the dental
lamella that bears the teeth. An extremely narrow subdental
shelf can be discerned on the anterior half of the bone, but it
diminishes posteriorly and is absent entirely on the latter half
(Figure 43B). The ventral margin of the bone is essentially
straight, except at the anterior end, where it curves slightly
upward (Figure 43A, C). However, in one of the smallest spec-
imens (PTRM 19396), the ventral margin is very slightly con-
cave (anterior end unknown). Seven irregularly spaced and
sized mental foramina are present laterally (Figure 43C, me.f.),
the last located at the transverse level of the 16th tooth (cf.
PTRM 1822, described in Smith 2006a). The lateral face of the
dentary is everywhere convex in transverse cross section. Ven-
trally, there is a weak, longitudinal fossa developed for m.
genioglossus, which extends as far posteriorly as the level of the
12th tooth.
The coronoid facet is horizontally floored and undercuts
the posterodorsalmost corner of the bone, but not the tooth row
(Figure 43A, cn.fac.). The floor of the facet curves ventromedi-
ally, becoming an intramandibular lamella (im.l.) of moderate
size to brace laterally the anteromedial process of the coronoid.
As a distinct lamella it does not extend more than four tooth
spaces anteriorly, although it is continued for a short distance
more by a weak swelling on the roof of the intramandibular
canal. It does not come close to the intramandibular septum.
On the lateral side of the posterodorsal corner of the bone is an
anteriorly tapering facet (Figure 43C, cn.fac.), marking the
Late Eocene Lizards of the Medicine Pole Hills • Smith
49
Figure 42. Parietal of selected members of Iguaninae. A–C, Dipsosaurus dorsalis (CM 144937). D–F, Sauroma-
lus obesus (UF 45624). G–I, Ctenosaura similis (UF 67982). First column, Dorsal view. Second column, Ven-
tral view. Third column, Right lateral view. Abbreviations: ept.fac., epipterygoid facet; nuc.fos., nuchal fossa;
rec.pr.asc., recessus processi ascendentis; st.fos., supratemporal fossa; st.pr., supratemporal process.
articulation of an anterolateral process of the coronoid that
extended as far as the boundary between the ultimate and
penultimate tooth.
Although the dentary tube is filled with sediment, and the
end of the intramandibular septum consequently cannot be seen,
enough of the sediment could be removed to determine that the
ratio of the length of the intramandibular septum to tooth-row
length is 0.7 or less. PTRM 19246 suggests that the intramandibu-
lar septum may have been considerably shorter than this.
PTRM 19499 has 26 tooth spaces, although most teeth are
broken off (Figure 43A). The tips of remaining teeth seem to be
rounded and abraded. The eighth tooth has distinct accessory
cusps (set off by labial and lingual grooves from the central
cusp), although they are not highly developed; the seventh tooth
has a distinct distal cusp, but whether a mesial cusp was present
as well is difficult to determine. In PTRM 19243, a small speci-
men, the fifth tooth shows a well-developed mesial shoulder
(though no distinct cusp) and nothing distally; the fourth tooth
is simple. As on the premaxilla, the mesial edge of the tooth is
more strongly angled than the distal, and the tips of the teeth
are distolingually decurved. In the midsized PTRM 19395 there
is a distal shoulder with the slightest of labial grooves on the
sixth tooth, and probably a mesial one as well; certainly there is
a distinct mesial cusp on the seventh. In PTRM 19249, a very
small specimen, the fifth tooth has a distinct distal cusp (mesial
edge broken). In the large PTRM 19244, neither the fifth nor
the sixth tooth has accessory cusps or even shoulders. In PTRM
19242, also large, the fourth tooth has a mesial shoulder (distal
edge broken) and the fifth tooth distinct (if weak) mesial and
distal cusps. Together these specimens paint a portrait in which
accessory cusps appear far anteriorly (generally by the fifth
tooth) and precedence of the mesial cusp is common.
Although tooth crowns (above the parapet) are straight
and parallel-sided throughout the tooth row, the bases of mid-
dle and posterior teeth frequently evince a curious distal curva-
ture (e.g., PTRM 1822: Smith 2006a, fig. 5; PTRM 19583; PTRM
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50
Figure 43. Left dentary of Queironius praelapsus (holotype, PTRM 19499). A, Medial view. B, Dorsal view. C,
Lateral view. Abbreviations: a.i.a.f., anterior inferior alveolar foramen; an.pr., angular process; cn.fac., coronoid
facet; im.l., intramandibular lamella; M.gr., Meckelian groove; me.f., mental foramina; sa.pr., (base of) surangu-
lar process.
19581: Figure 29H). In PTRM 19583, the accessory cusps flare
slightly near their tips. PTRM 19587, a smaller specimen, has
unusually stocky (short-crowned) teeth near the posterior open-
ing of the Meckelian groove, but the central cusps of the teeth
and the orientation of the medial surface of the dentary other-
wise agree exactly with other specimens.
The angular process does not seem to be broken, but it is
rounded by stream-wear (Figure 43A, an.pr.). The notch above
it, separating the angular from surangular processes, does not
cut deep, and although only the base of the surangular process
(sa.pr.) is preserved, it must have had a much larger base than
the angular process.
The dentary does not seem to increase significantly in
depth in later ontogeny. In the large holotype, the ratio of den-
tary depth at the notch for the anterior inferior alveolar fora-
men to dentary length to this transverse level is 0.27. In PTRM
19458, a small specimen (half the size of the holotype), the ratio
is approximately 0.25. In PTRM 19396, much smaller still, the
ratio cannot be estimated, but the edge of the subdental lamina
seems to have about the same curvature.
Comparisons:
Tooth count in the holotype, one of the largest
specimens, is similar to counts observed in Gambelia, Basilis-
cus and Polychrus. A high count (31) was found in Enyalioides
oshaughnessyi SMF 67590, but one Morunasaurus annularis
had only about 25 (see Estes et al. 1988, fig. 16) and Hoplocer-
cus spinosus MCZ 20679 had 17. Among iguanines, counts
above 25 were observed in adult Ctenosaura spp. (Figure 44G),
Cyclura spp. and Iguana iguana. However, all Sauromalus spp.
(Figure 44D) and especially Dipsosaurus dorsalis (Figure 44A)
and Brachylophus fasciatus had counts lower than 25 in all
examined specimens. Counts above 25 are unusual in Clade B,
especially in Tropidurinae and Oplurinae; they were observed
in Uta stansburiana, Sceloporus cyanogenys, Petrosaurus
mearnsi and Cophosaurus texanus. Thus, tooth count alone
provides little constraint on the relationships of Queironius
praelapsus.
A well-developed anterolateral process of the coronoid,
indicated by a facet on the posterolateral margin of the dentary,
is a derived feature present in Anolis, Iguaninae, Hoplocerci-
nae, Leiocephalus and Liolaemini (e.g., Frost and Etheridge
1989). This feature would unite Queironius praelapsus with any
of these. However, the strength of the process varies. In Dip-
sosaurus dorsalis (Figure 44B, cn.fac.) and Armandisaurus
explorator (Norell and de Queiroz 1991, fig. 1C), it barely
reaches as far anteriorly as the ultimate tooth, whereas in Sauro-
malus obesus it is longer, reaching the boundary between the
penultimate and antepenultimate tooth (Figure 44E), and in
Brachylophus fasciatus one tooth farther. In many of the larger
iguanines (Iguana, Cyclura, the Galápagos iguanines) the
process, although strong, usually only reaches the level of the
ultimate tooth, because the coronoid as a whole is located rela-
tively more posteriorly (Figure 44H). In Enyalioides oshaugh-
nessyi, the anterolateral process extends along the tooth row for
a space of four teeth, but in Hoplocercus spinosus it reaches only
the penultimate tooth (pers. obs.), and in Morunasaurus
Late Eocene Lizards of the Medicine Pole Hills • Smith
51
Figure 44. Left dentary of selected members of Iguaninae. A–C, Dipsosaurus dorsalis (UF 55334). D–F, Sauro-
malus obesus (UF 45624). G–I, Ctenosaura similis (UF 67982). First column, Medial view. Second column, Lat-
eral view. Third column, Dorsal view. Abbreviations: a.i.a.f., anterior inferior alveolar foramen; an.pr., angular
process; cn.fac., coronoid facet; M.gr., Meckelian groove; me.f., mental foramina; sa.pr., surangular process.
annularis only the ultimate tooth (see Estes et al. 1988, fig. 16).
The length of the process in Q. praelapsus thus does not seem to
be much different from what is seen in D. dorsalis, large igua-
nines and some hoplocercines and is probably (locally) primi-
tive. The coronoid in Q. praelapsus lacked the broad ventral
expansion seen in many iguanines.
Few iguanines were available as disarticulated specimens,
yet some remarks on the main coronoid facet will be useful.
The condition in Queironius praelapsus likens that of adult
Ctenosaurus similis in having a brief, horizontally floored
coronoid facet, which curves ventromedially and is continu-
ous with a short intramandibular lamella (Figure 44G). In Dip-
sosaurus dorsalis, there is a short, horizontally floored facet,
but it does not curve ventromedially, and the lamella is entirely
absent (Figure 44A). In Sauromalus obesus, there is no hori-
zontally floored facet; instead, the short (vertical) lamella con-
tinues posteriorly and the coronoid is applied to its medial side
(Figure 44D).
As in Queironius praelapsus, the Meckelian groove was
open anteriorly for a space of four to five teeth in all examined
iguanines (Figure 44A, D, G) except Brachylophus fasciatus,
where the anterior opening terminated by tooth 2–3.
The subdental shelf of Queironius praelapsus is compara-
ble in development to that of most iguanines (Figure 44C, F, I).
The angular process has a smaller base than the surangu-
lar process in living iguanines, including Dipsosaurus dorsalis
(Figure 44A) and Sauromalus obesus (Figure 44D). This is also
true of some hoplocercines (Enyalioides oshaughnessyi, E. lati-
ceps, Morunasaurus annularis). A distinct angular process is
lacking in Hoplocercus spinosus, but if it were present, it would
be smaller than the surangular process, as deduced from the
available space. This feature is thus probably primitive for
Iguaninae and its occurrence in Queironius praelapsus does not
help to constrain the relationships of that taxon.
CORONOID
A single coronoid is associated here on the basis of size and
complementary relations with the holotype dentary.
Description: PTRM 19324 is a partial right element lacking the
anteromedial process and the tips of the anterolateral and pos-
teromedial processes. The coronoid process is rounded in medial
(Figure 45A) and lateral (Figure 45B) aspects. The medial crest
of the coronoid, which descends the posteromedial process (Fig-
ure 45A), is sharp, extremely well developed and makes the bone
mediolaterally wide. Near the top of the medial crest is a
dorsoventrally elongate, rugose patch, slightly expanded posteri-
orly. On the anteromedial side of the tip of the coronoid process
is another rugose area, with a small ridge running down its mid-
dle. Little can be said of the morphology of the anteromedial
process (am.pr.), but the posteromedial process (pm.pr.) is nearly
complete. It grows larger distally, not only anteroposteriorly but
also mediolaterally, forming a medially directed tubercle. On the
ventral surface is an articulation facet for the prearticular (pra.fac.).
The posterior margin of the posteromedial process was at least
weakly concave, surrounding the anterior end of the Meckelian
fossa; a (broken) flange (Figure 45, dashed lines) would have over-
lapped the dorsomedial surface of the surangular.
The lateral and posterolateral surface of the coronoid
process is complex (Figure 45B). A weak, low, rounded crest
runs into the anterolateral process (al.pr.); for this reason its
ventral portion is considered to represent the lateral crest of the
bone. Dorsally, this ridge cuts obliquely across the posterolateral
face of the coronoid process. Posteromedially to this ridge, the
surface of the bone is concave, except where it joins the dorsally
convex portion of the bone that lay atop the surangular. Antero-
lateral to the ridge are two distinct surfaces: a flat, ventral one
and a dorsal one bounded by a strong lateral ridge. The antero-
lateral process (al.pr.) of the bone is relatively short.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
52
Figure 45. Partial right coronoid of Queironius praelapsus (PTRM 19324). A, Medial view. B, Lateral view.
Dashed lines indicate the probable original course of the bone margins. Abbreviations: al.pr., anterolateral
process; am.pr., anteromedial process; cn.pr., coronoid process; d.fac., dentary facet; pm.pr., posteromedial
process; pra.fac., prearticular facet; sa.fac., surangular facet.
Comparisons: The anterolateral process of the coronoid was
discussed above in conjunction with the facet it forms on the
dentary.
The coronoid process in Queironius praelapsus is rela-
tively short by comparison with many iguanines, including
Dipsosaurus dorsalis (Figure 46A) and Armandisaurus
explorator, Sauromalus obesus (Figure 46C), Ctenosaura sim-
ilis (Figure 46E), Iguana iguana and Conolophus subcristatus.
On the other hand, the process is relatively short in Ambly-
rhynchus cristatus and Cyclura cornuta. As discussed above
under Sauropithecoides charisticus, the process is tall in Cory-
tophaninae. It is generally short in Polychrotinae* (except
some Anolis) and also short in examined hoplocercines and
crotaphytines. The complicated distribution of the height of
the process in Iguaninae makes it difficult to ascertain what
the primitive state is.
A concavity in the posterior margin of the posterolateral
process that surrounds the anterior end of the Meckelian fossa
is present to a greater or lesser extent in all iguanines (e.g.,
Ctenosaura similis, Figure 46E) except Dipsosaurus dorsalis (Fig-
ure 46A). To be sure, the concavity is very weak in some species,
such as Sauromalus obesus (Figure 46C). And in D. dorsalis the
concavity is absent, because of reduction in the extent of the
posteromedial process. Whereas the concavity is very weak or
absent in hoplocercines and some other members of Clade A,
there is no indication that the extent of the ventromedial process
has been reduced. The reduction of that process in D. dorsalis is
autapomorphic. Whether the concavity is present in Arman-
disaurus explorator is an important question in this regard, but
with current preparation this feature cannot be studied (see
Norell and de Queiroz 1991).
The morphology of the posterolateral face of coronoid
process in Queironius praelapsus is unique among examined
iguanids. It is unfortunately impossible to establish any homolo-
gies between the surfaces of the fossil and those of other igua-
nines without dissection to determine the various insertion
points of the trigeminal musculature and associated connective
tissue structures. Many iguanines, for instance, have a nearly
vertical crest dividing the posterior surface of the coronoid
process (Figure 46B, F), which does not have an obvious
homolog in Q. praelapsus. Likewise, it is unclear what the
homologies are of the surfaces anterior to the lateral crest in the
fossil species.
In Dipsosaurus dorsalis, like Queironius praelapsus, there is
a distinct, flattened, rugose, slightly posteriorly expanded surface
near the top of the medial crest (Figure 46A). This surface was
absent in other examined iguanines (Figure 46C, E) and hoplo-
cercines (but see Estes et al., 1988, fig. 16, on Morunasaurus
annularis). It could constitute an apomorphy linking Q. praelap-
sus to D. dipsosaurus. It would be desirable to know with what
aspect of the bodenaponeurosis this feature is associated. The
morphology in Armandisaurus explorator is unknown.
The extremely strong medial crest of the coronoid in
Queironius praelapsus is also noteworthy. The living iguanine
that most closely matches the fossil taxon in this respect is
Amblyrhynchus cristatus. In Dipsosaurus dorsalis the crest is
strong (Figure 46A), but not as strong as in A. cristatus or the
fossil taxon. All other examined iguanines have relatively weak
and blunt medial crests (Figure 46C, E). Outside of Iguaninae,
a sharp and moderately strong medial crest was found in exam-
ined hoplocercines (very strong in Enyalioides oshaughnessyi),
Crotaphytus, Basiliscus and many polychrotines. This could be
Late Eocene Lizards of the Medicine Pole Hills • Smith
53
Figure 46. Right coronoid of selected members of Iguaninae. A, B, Dipsosaurus dorsalis (CM 144937). C, D,
Sauromalus obesus (UF 45624). E, F, Ctenosaura similis (UF 67982). First row, Medial view. Second row, Lat-
eral view. Abbreviations: al.pr., anterolateral process; am.pr., anteromedial process; cn.pr., coronoid process;
pm.pr., posteromedial process.
a primitive feature. However, the great strength of the crest in
Q. praelapsus is probably an autapomorphy.
COMPOUND BONE
A single compound bone is associated here on the basis of
iguanid morphology and size.
Description: PTRM 19077 is a partial right element of an onto-
genetically advanced individual, the surangular almost com-
pletely fused with the dermarticular (Figure 47). A strong
tubercle is developed anterior to the articular bone (Figure 47A,
B, ar.). Anterior to the lateral half of the articular facet there is
an oblique flattened area bounded laterally by a ridge that was
probably continuous with the dorsal margin of the surangular.
The posterior surangular foramen (p.sa.f.) is located at the same
transverse level as the aforementioned tubercle and ventral to
the ridge. The medial and lateral portions of the articular facet
are weakly depressed for the halves of the articular condyle of
the quadrate; the articular facet is thus saddle-shaped. A weakly
raised rim surrounds most parts of the articular facet. The facet
is notched, however, anteromedially.
The dorsal surface of the retroarticular process is deeply
concave in transverse cross section, bounded by strong medial
and tympanic crests (Figure 47A, B, me.cr. and ty.cr., respec-
tively). The foramen chorda tympani (f.c.t.) is an elongate struc-
ture opening behind the posteromedialmost corner of the
articular facet (Figure 47A). A curious circular swelling is located
just lateral to this foramen. The angular process extends from
the medial edge of the articular facet at a steep angle to the hor-
izontal, curving slightly anteriorly (an.pr.). It is connected by a
sheet of bone with the medial margin of the retroarticular
process. Posteriorly the edge of this sheet becomes slightly frilled
and curls ventrally (Figure 47C). The sheet is also pierced by an
accessory foramen adjacent to the medial crest at the same trans-
verse level as the foramen chorda tympani (Figure 47B, acc.f.).
In ventrolateral view the bone forms a broad, flat surface
(Figure 47C). A strong ridge, bounded or rather defined by
depressions on either side, runs anteriorly. It decreases abruptly
in prominence and curves slightly toward the anterior base of
the angular process. The ventral portion of the surangular (sa.)
terminates at about the anteroposterior midpoint of the articu-
lar facet. Its medial margin runs anteriorly at first, but then
curves ventromedially toward the angular facet (an.fac.). The
apex of said facet lies medially to the prearticular-surangular
suture. The facet is particularly deep medially.
Comparisons: The anterior edge of the angular process in
Queironius praelapsus is oblique to the horizontal plane, unlike
in Dipsosaurus dorsalis (Figure 48A). This seem to be an autapo-
morphy of D. dorsalis, however, because Brachylophus fascia-
tus, Sauromalus obesus (Figure 48D), Ctenosaura similis (Figure
48G) and other examined iguanines (except Amblyrhynchus
cristatus), as well as examined hoplocercines, show a morphol-
ogy similar to Q. praelapsus.
The medial crest of the retroarticular process is much
lower and blunter in many iguanines, including Brachylophus
fasciatus, Sauromalus obesus (Figure 48E), Cyclura cornuta and
Conolophus subcristatus. It is strong, however, in Dipsosaurus
dorsalis (Figure 48B), Iguana iguana, Ctenosaura similis (Fig-
ure 48H) and Amblyrhynchus cristatus. Among hoplocercines,
the crest is weak in Hoplocercus spinosus, but strong in
Enyalioides oshaughnessyi. This may be a plesiomorphy of
Queironius praelapsus and in any case is consistent with a rela-
tionship to D. dorsalis.
The position of the foramen chorda tympani is compara-
ble to what is seen in many iguanines.
The curvature of the surangular-prearticular suture on the
ventrolateral surface of the bone was also found in Cyclura cor-
nuta. Although this curvature was not clearly present in any
other examined iguanines (Figure 48C, F, I) or hoplocercines,
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
54
Figure 47. Partial right compound bone of Queironius praelapsus (PTRM 19077). Abbreviations: acc.f., acces-
sory foramen; an.fac., angular facet; an.pr., angular process; ar., (endochondral) articular; f.c.t., foramen chorda
tympani; M.fos., Meckelian fossa; me.cr., medial crest; p.sa.f., posterior surangular foramen; ra.pr., retroarticu-
lar process; sa., surangular; sa.fac., surangular facet; ty.cr., tympanic crest.
the entire surangular-prearticular suture seems to take a more
ventromedial course in some taxa; the condition in these taxa is
not necessarily the same as the straight suture of Sauromalus
obesus and Ctenosaura similis (Figure 48F and I).
The angular bone approaches the angular process less
closely in Ctenosaura similis (Figure 48I) than other iguanines
(Figure 48C, F). The close approach in Queironius praelapsus is
considered plesiomorphic by comparison with these other
iguanines and the hoplocercines Hoplocercus spinosus and
Morunasaurus annularis (see Estes et al. 1988, fig. 16).
A departure of the posterior tip of the angular from the
surangular-prearticular suture is not common. The tip and
suture were coincident in Dipsosaurus dorsalis (Figure 48C),
Armandisaurus explorator (Norell and de Queiroz 1991, fig. 1B),
Brachylophus fasciatus SMF 81134, Sauromalus obesus (Figure
48F), Iguana iguana, Cyclura cornuta SMF 33229 and Conolo-
phus subcristatus. Departure from the suture was observed in
Amblyrhynchus cristatus and B. fasciatus SMF 81156, and signif-
icant departure in one subadult C. cornuta (SMF 72159). Where
the posterior end of the angular is very blunt, as in Ctenosaura
similis, it is difficult to define the tip; yet, the angular is symmet-
rically distributed across the suture there (Figure 48I). Among
hoplocercines, slight departure was observed in Hoplocercus
spinosus, but the suture and tip were coincident in Enyalioides
oshaughnessyi. Intraspecific variation and the distribution in
outgroups make it difficult to assess any pattern of evolution at
present.
The ventrolateral surface of the retroarticular process is
often smooth in iguanines. A ridge as sharp as seen in Queiro-
nius praelapsus was not observed in any other taxon (Figure
48C, F, I) and could constitute an autapomorphy of the fossil
species. Yet there can be considerable intraspecific variation. In
Brachylophus fasciatus SMF 81156 the surface is smooth, but in
B. fasciatus SMF 81134 there is a long, broad ridge in the same
position as in Q. praelapsus. A broader and more poorly defined
ridge is seen in some Dipsosaurus dorsalis (Figure 48C) and in
Enyalioides oshaughnessyi.
An accessory foramen like the one medial to the medial
crest in Queironius praelapsus was otherwise only found in
Cyclura cornuta and Iguana iguana. Multiple small foramina
were found in some Brachylophus fasciatus; a single foramen
was found unilaterally in Dipsosaurus dorsalis CM 144937. It is
unclear whether these structures are all homologous. The acces-
sory foramen in Q. praelapsus possibly constitutes an autapo-
morphy, if it is consistently present, but further data are clearly
required.
Remarks
Queironius praelapsus is united with Iguaninae by the following
four synapomorphies: accessory cusps on premaxillary teeth
(variable); keel on ventral surface of nasal process between nasal
articulations triangular, not thin and bladelike; exposure of ven-
tral corner of posterolateral process of ectopterygoid beneath
angle of jugal; and broad and low prefrontal boss. Other char-
acters possibly uniting Q. praelapsus with Iguaninae or some
part thereof, but which have significant caveats associated with
them: mesial accessory cusp usually appears earlier than distal
accessory cusp (all teeth have accessory cusps in basal
Late Eocene Lizards of the Medicine Pole Hills • Smith
55
Figure 48. Right compound bone of selected members of Iguaninae. A–C, Dipsosaurus dorsalis (CM 144937).
D–F, Sauromalus obesus (UF 45624). G–I, Ctenosaura similis (UF 67982). First column, Medial view. Second
column, Dorsal view. Third column, Lateral view. Abbreviations: an.fac., angular facet; an.pr., angular process;
ar., (endochondral) articular; cn.fac., coronoid facet; f.c.t., foramen chorda tympani; M.fos., Meckelian fossa;
me.cr., medial crest; par., prearticular; ra.pr., retroarticular process; sa., surangular; ty.cr., tympanic crest.
Dipsosaurus dorsalis); strong expansion of orbital face of jugal
anterior to ectopterygoid articulation (absent in D. dorsalis and
known stem); and anterolateral process of coronoid present (if
not a synapomorphy of Iguaninae and Hoplocercinae; also
found in Anolis, Leiocephalus and Leiolaemini: e.g., Etheridge
and de Queiroz 1988).
Queironius praelapsus is united with Dipsosaurus dorsalis
by the following seven synapomorphies: exterior surface of nasal
process flat where it is completely overlain by the nasal bones;
partly blunted posterior end of maxilla; very broad maxillary
facet on ectopterygoid; dual articulation of pterygoid on
ectopterygoid; prefrontal boss developed primarily dorsally;
dual foramina on orbital face of temporal ramus of jugal; and
flattened, rugose, slightly posteriorly expanded surface near top
of medial crest of coronoid.
Queironius praelapsus lacks the following eight apomorphies
present in Armandisaurus explorator (where known) and Dip-
sosaurus dorsalis: anterior premaxillary foramina; nasal process
narrow and tapering; strong gutter on the palatal shelf of the max-
illa; small but sharp palatine process of the maxilla; dorsal por-
tion of postorbital does not curve medially; parietal foramen
strongly displaced anteriorly (entirely developed, if not isolated,
in the frontal); posteromedial process of coronoid foreshortened;
and angular process of prearticular extends ventromedially.
Three apparent autapomorphies of Queironius praelapsus
are strong dorsal displacement of anterior inferior alveolar fora-
men on facial process of maxilla; very shallow angle of the ptery-
goid process of the ectopterygoid; and (if this is independent)
very shallowly directed temporal ramus of jugal.
In summary, there is considerable evidence that Queiro-
nius praelapsus is in the total clade of Iguaninae. Within that
clade, there is considerable evidence that it is related to Dip-
sosaurus dorsalis. Most compelling here are characters of the
premaxilla and ectopterygoid. Q. praelapsus lacks the one pre-
viously published autapomorphy of D. dorsalis that can be
ascertained in available material. If D. dorsalis is the basalmost
extant lineage of Iguaninae (Norell and de Queiroz 1991;
Schulte et al. 2003), then the absence of some autapomorphies
in a 35-million-year-old fossil species would hardly be surpris-
ing. However, it also lacks a feature that has previously been
recognized as autapomorphic of (crown) Iguaninae—flared
tooth crowns—suggesting convergent evolution in Dipsosaurus
and the remainder of Iguaninae or a reversal in Q. praelapsus
(whose history cannot be very ancient). The flaring of the tooth
crowns has a clear adaptive explanation (Hotton 1955).
Thus far the earliest known iguanine with clear phyloge-
netic relationships is the stem dipsosaur Armandisaurus
explorator, known from the early middle Miocene Skull Ridge
Member of the Tesuque Formation of northern New Mexico,
USA (Tedford 1981; Norell and de Queiroz 1991). The White
Operation Quarry, from which the specimen derives
(Barghoorn and Tedford 1993; Norell and de Queiroz 1991), is
located 2.5 to 3.0 m below the No. 4 White Ash (Galusha and
Blick 1971; Barghoorn and Tedford 1993), which has been dated
by
40
Ar/
39
Ar methods at 15.30 ± 0.05 Ma (youngest date cited in
Tedford et al. 2004). Thus, Queironius praelapsus extends the
minimum age for the basal divergence in Iguaninae backward
by some 20 million years.
Armandisaurus explorator shows two apomorphies of
Dipsosaurus dorsalis: parietal foramen developed entirely
in frontal, and loss of lateral process of palatine posterior to
maxillopalatine foramen (Norell and de Queiroz 1991). Addi-
tionally, if the phylogenetic position of Queironius praelapsus
supported above is correct, it suggests that other features com-
mon to A. explorator and D. dorsalis may be synapomorphies:
anterior premaxillary foramina; absence of expansion of jugal
anterior to ectopterygoid (reversal); and possibly flared cheek
teeth. Hopefully, CT scans of A. explorator will enable examina-
tion of other features noted here.
Smith (2006a) noted the similarity between his Vertebra
Type 1 and presacral vertebrae of basal iguanines, in particular
Dipsosaurus and Brachylophus (de Queiroz 1987). The morphol-
ogy of these vertebrae—especially the accessory articulations—
would be consistent with their association with Q. praelapsus,
given the phylogenetic position discussed above. Caudal verte-
brae of the iguanine type (Etheridge 1967) have not yet been dis-
covered.
Corytophaninae Macey, Larson,
Ananjeva et Papenfuss, 1997
Remarks
Corytophaninae is a distinctive clade comprising three living
genera—Basiliscus (basilisks), Corytophanes (helmeted basilisks)
and Laemanctus (casque-heads)—and nine recognized living
species (Lang 1989). They are restricted to tropical Central and
equatorial South America. The stem representatives Suzanni-
wana and Geiseltaliellus are known from the early Eocene of the
Nearctic and Palearctic, respectively (Smith 2009a, 2009b).
Orithyia Smith, gen. nov.
Type species. Orithyia oaklandi sp. nov.
Diagnosis
. As for the type and only known species.
Etymology. After the Athenian princess Orithyia, who accord-
ing to legend was carried away to the north by Boreas, who cov-
eted her.
Orithyia oaklandi Smith, sp. nov.
Figures 49, 51, 53, 55, 57, 59, 61, 63, 65,
67, 68, 70
cf. Aciprion sp. Smith, 2006a:16.
Iguanid MPH-3 Smith, 2006a:17.
Type specimen. PTRM 5198 (partial right dentary; Smith 2006a,
fig. 8).
Paratypes
. All specimens referred to cf. Aciprion sp. and to
Iguanid MPH-3 by Smith (2006a) as well as the following:
PTRM 19000 (partial parietal; Figure 63), 19001 (partial frontal;
Figure 57), 19002 (partial left maxilla), 19004 (partial premax-
illa; Figure 49A–C), 19005 (partial left postorbital; Figure 61),
19006 (partial frontal), 19007 (partial left jugal; Figure 59), 19015
(right prefrontal; Figure 55), 19033 (right ectopterygoid; Figure
53A–C), 19053 (partial left dentary), 19054 (partial right den-
tary), 19055 (left maxilla fragment), 19056 (dentary fragment),
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
56
19058, 19059 (jaw fragments), 19060 (left maxilla fragment),
19062 (partial right maxilla; Figure 51K), 19067 (premaxilla
fragment), 19080 (left dermarticular fragment; Figure 70D),
19082 (partial right coronoid; Figure 68), 19084 (left jugal frag-
ment), 19089 (right jugal fragment), 19111 (left prefrontal frag-
ment), 19114, 19115 (frontal fragments), 19133 (partial right
ectopterygoid; Figure 53D, E), 19140 (partial left maxilla; Figure
51D–F), 19142 (left maxilla fragment), 19143 (right dentary
fragment), 19144 (jaw fragment), 19239 (right maxilla fragment;
Figure 51A–B), 19256 (partial premaxilla), 19257–19259 (par-
tial left dentaries), 19260 (left dentary fragment), 19261 (partial
right dentary), 19264, 19265 (right dentary fragments), 19266
(right maxilla fragment), 19268–19270 (right maxilla frag-
ments), 19271 (partial left maxilla; Figure 51G–I), 19272 (par-
tial left maxilla), 19273–19276 (left maxilla fragments), 19277
(dentary fragment), 19278 (jaw fragment), 19279 (right maxilla
fragment), 19280 (right dentary fragment), 19281 (right maxilla
fragment), 19282 (left dentary fragment), 19283, 19284 (jaw
fragments), 19285 (left maxilla fragment), 19286 (dentary frag-
ment), 19288, 19290 (jaw fragments), 19291 (maxilla fragment),
19325 (partial right compound bone; Figure 70A–C), 19338
(partial left ectopterygoid), 19381 (frontal fragment), 19397,
19399 (partial right dentaries), 19400 (left dentary fragment;
Figure 67A–C), 19402 (partial left dentary), 19404, 19405 (left
maxilla fragments), 19406, 19407 (dentary fragments), 19408
(jaw fragment), 19449 (partial left jugal), 19451 (partial right
maxilla), 19452, 19453 (left maxilla fragments), 19454 (partial
right maxilla), 19456 (jaw fragment), 19462 (partial right den-
tary; Figure 67D), 19504 (partial left dentary), 19505 (right den-
tary fragment), 19506 (jaw fragment), 19507 (right maxilla
fragment), 19534 (partial premaxilla; Figure 49D–F), 19551 (left
dermarticular fragment), 19573 (partial right maxilla; Figure
51C), 19574 (partial left maxilla), 19575 (partial right maxilla),
19576 (partial right maxilla; Figure 51J), 19577, 19578 (right
maxilla fragments), 19585 (partial left dentary), 19586 (partial
right dentary).
Referred specimen. PTRM 19334 (partial right squamosal;
Figure 65).
Diagnosis. An iguanid lizard similar to Corytophaninae in the
following derived features: continuous jugal buttress on maxilla;
Late Eocene Lizards of the Medicine Pole Hills • Smith
57
Figure 49. Premaxilla of Orithyia oaklandi. A–C, PTRM 19004 (partial element) in dorsal, ventral and right lat-
eral views, respectively. D–F, PTRM 19534 (partial element) in dorsal, posterior and right lateral views, respec-
tively. Abbreviations: in.pr., incisive process; mx.fac., maxillary facet; n.fac., nasal facet; n.pr., nasal process;
p.pm.f., posterior premaxillary foramina; v.pm.f., ventral premaxillary foramina.
convex dorsal margin of posterior ramus of postorbital; and Y-
shaped parietal. Similar to Laemanctus and Corytophanes in the
following derived features: medial folding of facial process
occurs low on maxilla; slightly more oblique relationship
between main body of ectopterygoid and lateral margin; (pos-
sibly) poor development of periorbital scale row; angulation
toward ventral in ventral margin of frontal process of prefrontal;
prominent ventral keel on anterior ramus of postorbital;
distinct ventral inflection along posterior ramus of postorbital
for squamosal articulation; strong adductor crests of parietal;
junction of adductor crests near level of recessus processi ascen-
dentis; poor division of cerebral hemispheres; and small angu-
lar process of prearticular. Plesiomorphic with respect to
Laemanctus and Corytophanes in the following respects: gutter
on maxilla short; palatine process of maxilla extremely weak;
more gradual posterior decay of facial process of maxilla;
median ventral ridge on frontal between grooves for solium
supraseptale; quadratojugal process of jugal absent; ventral
inflection on posterior ramus of postorbital weak; compound
bone not depressed at articular; and angular process with
anteroventromedial orientation. Autapomorphic in the follow-
ing ways: fossa on orbital surface of antorbital flange of
prefrontal; incision of palatine nerve into medial edge of antor-
bital flange of prefrontal; ridge beneath prefrontal boss bladelike;
(variably) deep longitudinal fossae laterally along cristae cranii;
dual foramina below postorbital facet on jugal; rugosity on lat-
eral surface of surangular opposite coronoid articulation; flange
connecting angular and retroarticular processes nearly absent;
posterodorsally trending ridge on lateral surface of surangular;
and dorsal curvature of retroarticular process.
Etymology. After Jeff Oakland, who so magnanimously permit-
ted excavation of these remains and gave them to science.
Description
PREMAXILLA
A premaxillary morphotype is associated on the basis of iguanid
morphology, size and relative abundance.
Description:
The nasal process is broad (Figure 49A, D, n.pr.),
encompassing at its base more than 50% of the maximal width
of the bone. Posterodorsally it then increases slightly in width
before tapering again (Figure 49A, B). The nasal process thus has
convex lateral margins. Its anterodorsal surface in PTRM 19004
evinces several relatively low, subcircular swellings, approxi-
mately1.5 mm in diameter each (Figure 49A); the basalmost two
are located at approximately the same transverse level, but the
more distal swellings are offset. These swellings probably corre-
spond to epidermal scales. In PTRM 19256, large-scale swellings
(as above) are not distinct, and instead there are many small-
scale rugosities, closer to the morphology of the sculpture on the
frontal and prefrontal (see below). Rugosities are absent in
PTRM 19534, as far as the nasal process is preserved (Figure
49D). A large anterior premaxillary foramen is developed on the
right side near the edge of the nasal process in PTRM 19256 (pos-
sibly also on the left side, which is damaged); such foramina,
however, seem to be absent in the other specimens (Figure 49A,
D). In PTRM 19534 alone there is a pair of tiny foramina at the
base of the nasal process, not far from the mid-line, but these dif-
fer in size and position from the foramen seen in PTRM 19256
and so are probably not homologous with the anterior premax-
illary foramina. The anterior surface of the nasal process curves
ventrally into the parapet of the jaw (Figure 49C, F). At the base
of the nasal process, just visible in anterior view, is the posterior
premaxillary foramen (Figure 49A, F, p.pm.f.), which conveys
the ethmoidal nerve into the body of the bone. The facets for the
maxillary articulation are found on the dorsolateral surface of
the lateral processes (Figure 49F, mx.fac.).
The premaxilla bears seven teeth in PTRM 19004 (Figure
49B), but nine in PTRM 19534 (Figure 49E) and PTRM 19256.
The low count in PTRM 19004 may be a result of the relative
narrowness of the body of the premaxilla, which accentuates
the broad appearance of the nasal process in that specimen. The
teeth all seem unicuspid, but they are poorly preserved in detail.
In PTRM 19256, there is a hint of a distal carina on the crown
of the lateralmost tooth. The incisive process (in.pr.) projects
ventrally from the palatal shelf; it is longer in PTRM 19256 than
in PTRM 19534. On the palatal flange, just lingual to the tooth
bases at the level of the boundary between the second and third
teeth on the right side in PTRM 19004, is a ventral premaxil-
lary foramen (Figure 49B, v.pm.f.). The nasal process in ventral
view bears a strong median keel. This keel is relatively broad
and rounded proximally, but distally it becomes sharper. The
paired nasal facets (n.fac.) extend anteroventrally along the
underside of the nasal process. These cover the entire base of
the nasal process distally, meeting along the ventral surface of
the median ridge, but proximally they taper and terminate
bluntly.
Comparisons:
A mediolaterally broad nasal process was con-
sidered by Smith (2009a) to be a synapomorphy of members of
Clade A, including Corytophaninae (Figure 50A, G) and its
stem (Smith 2009b). Laemanctus, with a strongly tapering nasal
process, shows a reversal (Figure 50D). The broad nasal process
of Orithyia oaklandi is primitive. In general, the shape of the
nasal process as a whole is most similar to that in Corytophanes
(Figure 50G).
Known tooth count in Orithyia oaklandi—7 or 9, with a
mode of 9—is similar to that in members of Corytophaninae
(Lang 1989; Figure 50B, E, H). I have counted as follows: 9 in
Basiliscus galeritus (N ⫽ 1), 7 to 8 in B. vittatus (N ⫽ 2), 8 to
9 in B. basiliscus (N ⫽ 3), 8 to 9 in B. plumifrons (N ⫽ 2), 7 or
9 in Corytophanes hernandesii (N ⫽ 3), 7 or 9 in C. cristatus
(N ⫽ 2), 7 in C. percarinatus (N ⫽ 2), 7 to 9 in Laemanctus
longipes (N ⫽ 3) and 8 in L. serratus (N ⫽ 1). Tooth counts
in Suzanniwana patriciana (Smith 2009b) and Geiseltaliellus
maarius (Smith 2009a) seem to be lower than this, although a
referred premaxilla of Geiseltaliellus sp. has 10 (Augé 2003).
At the least, the count in O. oaklandi does not exclude it from
the crown.
Anterior premaxillary foramina are found in Basiliscus
vittatus, B. basiliscus (variably; Figure 50A), B. plumifrons,
Corytophanes hernandesii (Figure 50G), C. cristatus, C. percar-
inatus and L. serratus. Small bilateral foramina are found in
Basiliscus galeritus, which are also probably homologous,
although they are somewhat more posterolaterally than is
usual. The foramina are absent in examined Laemanctus
longipes (Figure 50D). Larger sample sizes may help to con-
strain the evolution of these foramina in Corytophaninae.
Their rare presence in Orithyia oaklandi provides little addi-
tional guidance at the present time.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
58
Rugosities on the nasal process are uncommon in Coryto-
phaninae. They are absent in all examined specimens of Basilis-
cus and Corytophanes. They were also absent in Laemanctus
longipes, although this is scarcely surprising given the narrow-
ness of the nasal process; there are rugosities here on the facial
process of the maxilla and on the nasals, so one might consider
them to be present at least in this part of the skull. They are pres-
ent in L. serratus UMMZ 149101, in which skull rugosities are
considerably less strongly developed than in the specimen illus-
trated by Etheridge and de Queiroz (1988, fig. 3).
Late Eocene Lizards of the Medicine Pole Hills • Smith
59
Figure 50. Premaxilla of selected members of Corytophaninae. A–C, Basiliscus basiliscus (UF 99655). D–F, Lae-
manctus longipes (UF 66061). G–I, Corytophanes hernandesii (UF 72492). First column, Anterodorsal view.
Second column, Posteroventral view. Third column, Right lateral view. Abbreviations: a.pm.f., anterior pre-
maxillary foramina; in.pr., incisive process; mx.fac., maxillary facet; n.fac. nasal facet; n.pr., nasal process of pre-
maxilla; p.pm.f., posterior premaxillary foramen.
MAXILLA
A maxillary morphotype is associated here on the basis of
iguanid morphology, relative abundance and dental similarity
to the holotype. For further discussion on association, see Com-
parisons below.
Description:
The premaxillary process is represented by several
specimens (particularly PTRM 19239, 19266, 19268, 19269,
19405 and 19573). The dorsal surface of the process is flat and
usually horizontal; in PTRM 19239 (Figure 51A) and 19271,
however, it slopes laterally. A lateral crista is absent in most spec-
imens, although in PTRM 19573 a small rounded ridge is devel-
oped anterolaterally. The anterior margin of the premaxillary
process is smoothly concave (Figure 51C). On the ventral sur-
face of the anterior margin is a mediolaterally continuous facet
for articulation on the premaxilla; this facet indicates a triangu-
lar posteromedial projection of the premaxilla along the palatal
surface. The facet is anteroposteriorly narrow in most speci-
mens, less than the length of a full tooth space, but the well-pre-
served PTRM 19573, in which the facet is distinctly more
extensive, suggests that this narrowness may be artifactual in
some specimens. Along the anteromedial edge of the premax-
illary process is an articulation facet for the vomer. This facet, as
far as it is preserved (most completely in PTRM 19573), con-
sists of a dorsomedially directed surface separated by a longitu-
dinal ridge from a narrower, medially directed surface (Figure
51C, v.fac.). The crista transversalis (cr.tv.) is poorly developed
in all specimens; it varies from a very low swelling (e.g., PTRM
19266) to a sharp-edged if weakly developed crest (e.g., PTRM
19573). In all specimens, the subnarial arterial foramen opens
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
60
Figure 51. Maxilla of Orithyia oaklandi. A, B, PTRM 19239 (anterior fragment of right maxilla) in lateral and
medial views, respectively. C, PTRM 19573 (anterior portion of right maxilla) in medial view. D–F, PTRM 19140
(middle portion of left maxilla) in lateral, medial and dorsal views, respectively. G–I, PTRM 19271 (middle por-
tion of left maxilla) in lateral, medial and dorsal views, respectively. J, PTRM 19576 (middle portion of right
maxilla) in dorsal view. K, PTRM 19062 (midposterior portion of right maxilla) in dorsal view. Abbreviations:
a.i.a.f., anterior inferior alveolar foramen; cr.tv., crista transversalis; ec.fac., ectopterygoid facet; fa.pr., facial
process; j.bt., jugal buttress; j.fac., jugal facet; l.fac., lacrimal facet; pl.fac., palatine facet; pl.pr., palatine process;
s.a.f., superior alveolar foramen; v.fac., vomerine facet.
anteriorly onto the dorsal surface of the premaxillary process,
just lateral to the apex of the crista transversalis; individual vari-
ation in the diameter of the foramen is on the order of a factor
of two.
The anterior edge of the facial process is mediolaterally
thick and anteriorly flattened (Figure 51A). The anterior inferior
alveolar foramen (a.i.a.f.) opens anterodorsally well above the
floor of the premaxillary process in the center of the thickened
edge. It is sometimes recessed into a weak depression (e.g.,
PTRM 19239). Dorsal to the foramen the anterior margin of
the facial process (fa.pr.) turns abruptly posterodorsally. This
indicates the presence of a distinctly dorsomedially folded sur-
face. On the dorsalmost preserved portion of the anteromedial
edge of the facial process is the base of a facet for the nasal. The
most completely preserved facial process is found in PTRM
19271. Here, the posterior margin of the process curves contin-
uously toward the posterior (Figure 51G). In PTRM 19140, in
contrast, there is an inflection point in the posterior continua-
tion of the facial process (Figure 51D) marking the posterior-
most extent of the lacrimal facet (Figure 51E, l.fac.).
The palatal flange becomes distinctly narrower behind the
premaxillary process. In all six specimens in which the feature
can be evaluated (including the rather divergent PTRM 19271),
there is a moderately sized to large foramen opening dorsome-
dially just behind the crista transversalis (Figure 51B, I). Most of
the dorsal surface of the palatal flange seems depressed by com-
parison with its medial margin (Figure 51F, I). A short gutter,
into which the superior alveolar nerve and maxillary artery
plunge, is developed on the dorsal surface posteriorly (s.a.f.).
This gutter generally has a length of three-and-one-half to five-
and-one-half tooth spaces; in one specimen (PTRM 19271),
from an apparently short-snouted animal, it is only two tooth
spaces long. The palatine process (pl.pr.) is merely a weak
expansion of the medial edge of the palatal flange. At its anteri-
ormost end, the palatine articulation was wholly medial. Poste-
riorly, the palatine articulated both dorsally and ventrally on the
palatal flange, implying that the maxillary process of the palatine
was bifurcated. The process is approximately two tooth-spaces
in length and decays gradually in size posteriorly. Beyond it, the
palatine articulates for a short distance on the dorsal surface of
the palatal flange.
The jugal groove (Figure 51F, I–K, j.fac.) is always deep,
but the medial portion of the jugal articulation is variable. In
most specimens (14 out of 20 in which the feature can be eval-
uated), the jugal groove is fully separated from the ectoptery-
goid facet by a jugal buttress (Smith 2009b), an elongate, dorsally
projecting ridge that braces the jugal medially (Figure 51F, K,
j.bt.). When the buttress is present, the jugal groove has a nearly
vertical medial as well as lateral wall. A buttress is developed
posteriorly in another two specimens (PTRM 19055, 19574),
although it does not extend to the anterior end of the jugal
groove. In four specimens, finally, a jugal buttress seems to be
wholly absent on the preserved portion of the bone (Figure 51I, J),
including at least half the jugal groove. In these specimens the
jugal groove is still deep, but it is broader and has a medial mar-
gin oblique to the sagittal plane. The buttress varies in cross-
sectional shape, being taller in some specimens (e.g., PTRM
19140) than in others (PTRM 19454); in some specimens (e.g.,
PTRM 19002) it is broadly rounded, whereas in others it is sharp
(e.g., PTRM 19140). The posterior end of the ectopterygoid facet
(ec.fac.) is not preserved in any specimen.
In four of the more complete specimens the anterior teeth
are taller than middle and posterior teeth (Figure 51E). PTRM
19271 is exceptional in that the middle teeth, around the pala-
tine process, are distinctly taller than anterior or posterior teeth
(Figure 51H). PTRM 19271 is also exceptional in having weak
but distinct accessory cusps on the fourth maxillary tooth (with
intimations on the third). In other specimens in which this can
be determined, the fourth tooth is unicuspid; in most speci-
mens, it is probable that the first accessory cusps appear approx-
imately two tooth spaces in front of the anterior end of the gutter
for the superior alveolar nerve (very roughly the eighth or ninth
tooth position), where weak accessory cusps are seen and a gen-
erally cylindrical tooth form obtains. In PTRM 19575 the tran-
sition seems to have occurred midgutter. The crowns of
posterior teeth are generally parallel-sided, but in some speci-
mens (e.g., PTRM 19575) they are slightly flared. They are also
somewhat labiolingually compressed.
Comparisons: The vomerine facet of Orithyia oaklandi is unlike
that of Basiliscus basiliscus (Figure 52B, v.fac.), Laemanctus
longipes (Figure 52E) or Polychrus gutturosus in being sharply
divided into two surfaces by a longitudinal ridge. Corytophanes
hernandesii is just like O. oaklandi, as is Gambelia wislizenii.
This feature implies slight lateral bifurcation of the anterior end
of vomer. In examined iguanines, the vomerine facet is gener-
ally not so distinct; where it is (e.g., Ctenosaura similis; Figure
30H), it is not bifurcated. The degree of variation in this char-
acter is poorly understood on account of the paucity of disartic-
ulated specimens.
The jugal buttress in Corytophanes hernandesii (Figure 52I)
is lower and more rounded than in Basiliscus basiliscus (Figure
52C) or Laemanctus longipes (Figure 52F), which is possibly an
autapomorphy of the lineage. Nevertheless, the variation
observed in Orithyia oaklandi suggests that a larger sample size
of living corytophanines may reveal additional intra- and inter-
specific variation. In any case, the presence of a jugal buttress in
most specimens of O. oaklandi unites it with Corytophaninae
(see Smith 2009b). A jugal buttress is at least variably present in
early Eocene Suzanniwana sp. (Smith, in press).
The first accessory cusps on maxillary teeth occur some-
what later in most Orithyia oaklandi than in living corytopha-
nines: by the fifth in Basiliscus spp. (Figure 52B), by the fourth
in Corytophanes spp. (Figure 52H), by the eighth in Laemanc-
tus longipes (Figure 52E; observed: fourth to eighth) and by the
fifth or sixth in L. serratus. (For data on polychrotines, see above
under Sauropithecoides charisticus.) Late appearance is possibly
autapomorphic of O. oaklandi. However, the first accessory
cusps occur even later in Geiseltaliellus maarius (Smith 2009a).
The marked medial bend of the facial process of the max-
illa is seen in living members of Polychrotinae* (exaggerated in
Anolis) and Corytophaninae (Smith 2006a). In Laemanctus
(Figure 52D) and Corytophanes (Figure 52G), it occurs rela-
tively lower on the facial process than in polychrotines (except
Anolis) and other corytophanines, including Geiseltaliellus
maarius, where the bend occurs but was not described (see
Smith 2009a, fig. 2). It also occurs low on the facial process in
Orithyia oaklandi, a feature potentially uniting it with Laemanc-
tus and Corytophanes.
As in corytophanines (Figure 52B, E, H) and Geiseltaliellus
maarius (Smith 2009a, figs. 2, 4), the anteromedial edge of the
facial process is blunt in cross section, not sharp, as in Gambelia
Late Eocene Lizards of the Medicine Pole Hills • Smith
61
and Polychrus (Figure 5B). A blunt edge, however, is also seen
in at least some members of Leiosaurini and Anisolepini.
Smith (2006a) noted that a well-developed gutter is devel-
oped on the dorsal surface of the palatal flange of the maxilla in
living corytophanines, iguanines, crotaphytines and certain
members of Clade B. One is present in examined hoplocercines,
although it is shorter than in the aforementioned taxa (Smith
2009a). The presence of a gutter per se seems to be derived in
Iguania (Smith 2009a; contra Smith 2006a), although the supe-
rior alveolar nerve and maxillary artery may pierce the maxilla
in several places. The occurrence of a gutter in Orithyia oak-
landi may unite it with these taxa, but it is distinctly less well
developed than in most of them. In particular, the gutter in dis-
articulated corytophanines is about seven tooth spaces in length
(Figure 52) and in Laemanctus longipes nearly reaches the ante-
rior base of the facial process (Figure 52E). (It does not seem to
be that long in L. serratus, although an exact measurement can-
not be given because a disarticulated specimen was not avail-
able.) The development of the gutter in O. oaklandi is
approximately like that in Hoplocercinae, which would tend to
exclude this species from the corytophanine crown.
The facial process in Corytophanes (Figure 52G) and Lae-
manctus (Figure 52D) decays abruptly posterior to its apex
before diminishing more gently, whereas in Basiliscus (Figure
52A) the decay is gradual. Geiseltaliellus maarius is like Lae-
manctus and Corytophanes (Smith 2009a, figs. 2, 4). In poly-
chrotines of all major clades (except Polychrus gutturosus), the
facial process decays gradually (and even in P. gutturosus it does
not decay as abruptly as in Laemanctus and Corytophanes). An
abrupt initial decay is the norm in Hoplocercinae. However, in
most members of Iguaninae (except Sauromalus obesus) the
decay is more gradual (if not quite so gradual as in Basiliscus).
Given the angle of the posterior remnant in PTRM 19140, it is
impossible that decay of the facial process in Orithyia oaklandi
can have been as abrupt as in Laemanctus and Corytophanes.
Polarity here is presently uncertain within Clade A.
In Basiliscus (Figure 52C) and Polychrus gutturosus, the
palatine process is very weak and essentially the only projecting
portion of the palatal flange is clasped by the palatine. The
process is similarly weak in Geiseltaliellus maarius (Smith
2009a) and Suzanniwana patriciana (Smith 2009b). In Lae-
manctus longipes (Figure 52F) and Corytophanes hernandesii
(Figure 52I) the process is larger (but still bluntly rounded) and
only partly clasped by the palatine. A very weak palatine process
may well be primitive, and this feature of Orithyia oaklandi
would exclude it from Laemanctus + Corytophanes.
ECTOPTERYGOID
An ectopterygoid morphotype is tentatively associated here
principally on the basis of iguanid morphology, size, relative
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
62
Figure 52. Maxilla of selected members of Corytophaninae. A–C, Basiliscus basiliscus (UF 99655). D–F, Lae-
manctus longipes (UF 66061). G–I, Corytophanes hernandesii (UF 72492). First column, Lateral view. Second
column, Medial view. Third column, Dorsal view. Abbreviations: a.i.a.f., anterior inferior alveolar foramen;
cr.tv., crista transversalis; ec.fac., ectopterygoid facet; fa.pr., facial process; j.bt., jugal buttress; j.fac., jugal facet;
pl.pr., palatine process; s.a.f., superior alveolar foramen; sn.a.f., subnarial arterial foramen; v.fac., vomerine facet.
abundance and because ectopterygoids are already associated
with Sauropithecoides charisticus and Queironius praelapsus,
described above. For further discussion on association, see
Comparisons below.
Description: The anterolateral process is moderately long (Fig-
ure 53A, D, al.pr.). It is broken or abraded distally in all speci-
mens, but it does not seem to be significantly incomplete (no
lacuna is exposed at the distal ends). The maxillary facet
(mx.fac.) occupies the entire ventral surface of the anterolateral
process distally. Posteriorly, the maxillary facet becomes increas-
ingly restricted to the lateral margin of the bone and then
abruptly tapers. The posterolateral process (pl.pr.), with its dor-
sal and ventral corners, is poorly preserved in all specimens. The
ventral surface of the ventral corner is clearly thickened (Figure
53A, D), suggesting the presence of a flange to brace the poste-
rior end of the maxilla. In PTRM 19133 there is a foramen just
medial to where this flange would have been located (Figure
53D). The posterior face of the bone, forming the coronoid
recess (cn.rec.) is somewhat oblique in PTRM 19133, rather
than strictly vertical. The main body or neck of the bone extends
posteromedially from the lateral margin.
Laterally, the jugal facet is a concave feature (Figure 53E,
j.fac.); this is not evident in PTRM 19033, presumably due to
stream-wear, but it is expected given the morphology of the
jugal (see above). In the two (worn) specimens in which it can
be judged, the dorsal corner of the posterolateral process (pl.pr.)
is distinctly stronger than the ventral corner (Figure 53B). (In
PTRM 19133 the ventral corner is broken away entirely; Figure
53E.) The pterygoid process is angled ventromedially and
slightly posteriorly (Figure 53B, C, pt.pr.). Virtually its entire
posterior face is occupied by the pterygoid facet (Figure 53C,
pt.fac.), which is deepest laterally. In PTRM 19033 there is a
foramen in the fossa opposite the pterygoid facet, that is, on the
anterior face of the bone (Figure 53A).
Comparisons: One argument against the association of this
ectopterygoid with the jugal is the morphology of the postero-
lateral process, where the dorsal corner seems much stronger
than the ventral corner. On the jugal, in contrast, the ectoptery-
goid facet clearly indicates that the ventral corner is stronger.
This argument, however, would also exclude association of this
ectopterygoid with Sauropithecoides charisticus (the only other
reasonable candidate). Another argument for preferring
Late Eocene Lizards of the Medicine Pole Hills • Smith
63
Figure 53. Ectopterygoid of Orithyia oaklandi. A–C, PTRM 19033 (stream-worn right element) in ventral, lat-
eral and posterior views, respectively. D, E, PTRM 19133 (partial right element) in ventral and lateral views,
respectively. Abbreviations: al.pr., anterolateral process; cn.rec., coronoid recess; j.fac., jugal facet; mx.fac., max-
illary facet; pl.pr., posterolateral process; pt.fac., pterygoid facet; pt.pr., pterygoid process.
Orithyia oaklandi among these two possibilities is the abrupt
decrease in the width of the maxillary facet, which is matched by
a posteriormost maxillary fragment, PTRM 19270. The best
present interpretation of the contradiction with respect to the
posterolateral process of the ectopterygoid is a taphonomic one:
the ventral corner was simply very thin and consequently expe-
rienced greater abrasion. The ventral corner is also more deli-
cate in Laemanctus longipes (Figure 54H) and Corytophanes
hernandesii (Figure 54L). Clearly, better preserved specimens
are desirable.
Smith (2009b) noted that the main body or neck of the
ectopterygoid is generally oriented close to orthogonal to the
bone’s lateral margin in Iguanidae. This includes examined
polychrotines in the following clades: Anisolepini, Polychrus
(for the most part) and Leiosaurini; Anolis is an exception
(Smith 2009b). The neck is also nearly orthogonal in Basilis-
cus basiliscus (78°; Figure 54A), Suzanniwana patriciana
(Smith 2009b) and Geiseltaliellus maarius (Smith 2009a). The
angle is slightly lower in Corytophanes hernandesii (74°; Fig-
ure 54I) and distinctly so in Laemanctus longipes (59°; Figure
54E), which is taken to be apomorphic. The angle in Orithyia
oaklandi (70°) is derived and may provide some measure of
support for a relationship with Laemanctus and Corytophanes.
The angle of the pterygoid process with respect to the ver-
tical is similar to that in Basiliscus (Figure 54B, C) and Laemanc-
tus (Figure 54F, G), as well as that in most polychrotines. The
angle is somewhat steeper in Corytophanes hernandesii (Figure
54J, K), which is taken to be apomorphic. The condition in
Orithyia oaklandi is considered plesiomorphic.
As noted in the description, it is likely that there was a pos-
terior flange on the ectopterygoid of Orithyia oaklandi that
would have clasped the posteromedial end of the maxilla. Such
a flange is seen in living Basiliscus basiliscus (Figure 54D), Lae-
manctus longipes (Figure 54H) and Corytophanes hernandesii
(Figure 54L). The flange is absent in examined disarticulated
Polychrus and most Anolis; it is furthermore absent in Suzanni-
wana patriciana (Smith 2009b) and Geiseltaliellus maarius
(Smith 2009a). Thus, the flange is taken to be apomorphic. Its
presence would not be surprising in O. oaklandi, but it cannot
be considered as established. At the moment this feature is
merely a potential synapomorphy.
The relative size of the dorsal and ventral corners of the
posterolateral process in Polychrotinae* was discussed above
under Sauropithecoides charisticus. The primitive condition
there seems to be one in which the ventral corner is distinctly
stronger. In Suzanniwana patriciana, the two corners are nearly
equal in size, but the dorsal one is slightly stronger (Smith
2009b). In Basiliscus the two corners can have about the same
length, or the ventral corner can be slightly stronger (Figure
54D). In Laemanctus (Figure 54H) and Corytophanes spp. (Fig-
ure 54L), however, the dorsal corner is distinctly stronger. This
condition is taken to be derived and it is absent in Orithyia oak-
landi, judged by its facet on the jugal rather than the poorly pre-
served actual specimens.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
64
Figure 54. Left ectopterygoid of selected members of Corytophaninae. A–D, Basiliscus basiliscus (UF 99655).
E–H, Laemanctus longipes (UF 66061). I–L, Corytophanes hernandesii (UF 72492). First column, Ventral view.
Second column, Anterior view. Third column, Posterior view. Fourth column, Lateral view. Abbreviations:
al.pr., anterolateral process; j.fac., jugal facet; mx.fac., maxillary facet; pl.pr., posterolateral process; pt.fac., ptery-
goid facet; pt.pr., pterygoid process.
PREFRONTAL
This morphotype is associated here on the basis of size, relative
abundance and the occurrence of dermal rugosities on the dor-
sal surface of the larger specimen, which are similar to those on
the frontal.
Description:
PTRM 19015 is nearly complete and the descrip-
tion, unless otherwise expressed or implied, is based on it. It
lacks much of the palatine process and the flange that articu-
lated deep to the facial process of the maxilla. The dorsal surface
in this specimen is smooth (Figure 55A), unlike in the larger
PTRM 19111, which has rugosities similar to those on the
frontal (see below). A row of six foramina penetrates the dorsal
surface near its lateral edge, forming an arc that parallels the
orbital margin; additional foramina are irregularly distributed
on the dorsal surface.
The frontal process tapers distally (Figure 55A, f.pr.). Its
lateral margin is fairly smoothly concave, but the orbital rim is
slightly thickened in one place posterior to the poorly developed
prefrontal boss (prf.boss), forming a small bulge. The orbital
face curves anteroventrally into the antorbital flange (Figure
55B). The undersurface of the frontal process is also sculpted
by five shallow, regularly spaced, anteroposteriorly oriented
grooves of uncertain significance. The ventral extent of the
process is abruptly restricted posteriorly, a fact that is only partly
attributable to abrasion (see also under description of frontal
below).
The frontal facet is medially concave in transverse cross
section along its entire length (Figure 55C, f.fac.). The facet
tapers strongly anteriorly, where it is separated from the
paranasal recess (pn.rec.) by a strong ridge. A foramen opens
medially just in front of this ridge, so closely in fact that the
foramen partly incises the ridge. The paranasal recess is rela-
tively shallow. At the transverse level of the prefrontal boss, the
floor of the excavation makes a sudden turn toward the ventral.
The edge of the antorbital flange is thickened in this location,
which marks the dorsalmost extent of the palatine articulation
(pl.fac.). Anterior to this thickening, there is a shallow cavity
weakly distinguished from the main recess by a broad, low,
posteroventrally trending ridge. The edge of the antorbital
flange between the dorsal extremity of the palatine articulation
and the frontal articulation is distinctly concave (Figure 55B,
C). The edge here is thickened and incised, possibly for the
medial palatine nerve. The ventral portion of the palatine
process (pl.pr.) is broken.
The posterior edge of the facial process of the maxilla
inserts in a groove below the prefrontal boss (Figure 55D,
mx.fac.). A sharp ridge extends ventrally from the prefrontal
boss; this ridge is slightly concave in anterior view (Figure 55D)
and the broken edge (Figure 55B) is consistent with the presence
of a weak groove below the prefrontal boss. Medial to the ridge
on the posterior surface of the antorbital flange in both speci-
mens is a distinct fossa (Figure 55B), whose soft-tissue corre-
lates are uncertain. Anterior to the ridge, ventral to the
prefrontal boss, is a depression in the shape of a parallelogram,
which contributes to the thinness of the ridge (Figure 55D). This
depression is possibly related to the lacrimal articulation, but
more likely the lacrimal articulation was restricted to the wedge-
shaped facet ventral to it (l.fac.). The margins of the facet are all
worn. The facet is directed predominantly anteriorly.
Late Eocene Lizards of the Medicine Pole Hills • Smith
65
Figure 55. Right prefrontal of Orithyia oaklandi (PTRM 19015). A, Dorsal view. B, Lateral view. C, Medial view.
D, Anterior view. Abbreviations: ant.fl., antorbital flange; f.fac., frontal facet; f.pr., frontal process; l.fac., lacrimal
facet; mx.fac., maxillary facet; pl.fac., palatine facet; pl.pr., palatine process; pn.rec., paranasal recess; prf.boss, pre-
frontal boss.
Comparisons: The rugosities seen on the dorsal surface of the
larger prefrontal of Orithyia oaklandi are consistent with the
presence of significant rugosities on other dorsally facing skull
bones. In Basiliscus these bones are smooth (Figure 56A). These
bones are also smooth in most specimens of Geiseltaliellus
(Augé 2003, 2005; Smith 2009a); the prefrontal, but not the
frontal, is also smooth in Suzanniwana patriciana (Smith
2009b). There is a tendency for rugosities to be present in Cory-
tophanes spp. (Figure 56I) and they are moderately to strongly
developed in Laemanctus serratus (Etheridge and de Queiroz
1988, fig. 3; pers. obs.). They are clearly present but less strong
in L. longipes (Figure 56E).
The fossa on the orbital surface of the antorbital flange is
not found, to my knowledge, in any polychrotine or corytopha-
nine and constitutes an autapomorphy of Orithyia oaklandi.
The incision of the medial palatine nerve into the medial edge
of the antorbital flange between the frontal and palatine articu-
lations is not, to my knowledge, seen in any living Polychrus,
nor in corytophanines (Figure 56G, K) apart from certain
derived Basiliscus (Figure 56C) and seems to constitute another
autapomorphy of Orithyia oaklandi.
The palatine articulation on the antorbital flange of the pre-
frontal of Orithyia oaklandi is comparable to that in corytopha-
nines, in which it consists of a simple impression along the medial
edge of the antorbital flange (Figure 56C, G, K). In some Basilis-
cus, the facet is bounded dorsally by a process (Figure 56C), but
this derived feature is not seen in O. oaklandi or other examined
disarticulated corytophanines. The palatine facet in Laemanctus
longipes (Figure 56G) and some Corytophanes hernandesii (Fig-
ure 56K), but not C. percarinatus, seems more dorsally extensive
than in O. oaklandi. In this respect O. oaklandi is primitive.
Large portions of the orbital rim in polychrotines and cory-
tophanines are very thin. This is true dorsally on account of the
development of supraorbital flanges (Smith 2009a, 2009b) and
is true ventrally because the exposed dorsal edge of the jugal is
mediolaterally compressed. In Polychrus, the anterior portion
of the rim is also mediolaterally thin, forming a complete thin
rim around the front of the orbit. On the prefrontal, this thin
rim takes the form of a crest that extends ventrally from the pre-
frontal boss to the lacrimal facet. In extant corytophanines, in
contrast, the ridge beneath the prefrontal boss is thick and
rounded, not sharp (Figure 56D, H, L). The ridge was also thick
and rounded in other polychrotines, except in Anisolepis undu-
latus, in which it was somewhat thinner and sharper. Outgroup
comparison thus implies that this thin ridge is derived and its
presence in Orithyia oaklandi is considered autapomorphic.
Because of breakage, it is not possible at present to compare
the gross morphology of the lacrimal facet of Orithyia oaklandi.
Probably the facet was rounded with a strong ventral margin, on
the basis of the morphology seen in Basiliscus (Figure 56D),
Corytophanes (Figure 56L) and Suzanniwana patriciana (Smith
2009b). Laemanctus longipes departs from the others in this
respect (Figure 56H).
FRONTAL
A frontal morphotype is associated here on the basis of size, rel-
ative abundance and the similarity of its dermal sculpture to
that of one prefrontal and one premaxilla.
Description:
PTRM 19001, missing only its left posterolateral
and anteromedial portions, is the most complete specimen. As
in other iguanids, the bone is constricted between the orbits, giv-
ing it an hourglass shape (Figure 57A, C). In sagittal cross section
it is distinctly dorsally arched (Figure 57B). Nearly the entire dor-
sal surface of the frontal is covered in mound-shaped rugosities
(Figure 57A), each of which was probably overlain by a single
epidermal scale. These rugosities are criss-crossed by tiny, irreg-
ular grooves. Tiny foramina penetrate the surface of the frontal;
where these foramina intersect rugosities, they are unexception-
ally found in the grooves, but there are a few additional foram-
ina on the surface of the bone between the rugosities. The
rugosities on the anterior half of the bone between the prefrontal
facets (prf.fac.) are larger than the others. The rugosities are dis-
tinctly taller in PTRM 19006 than in PTRM 19001; the former is
also larger. Similarly, they are more poorly developed in PTRM
19381, which is also smaller. A well-defined arcuate row of peri-
orbital rugosities is absent and the rugosities along the orbital
margins are subdued: flatter, with smoother apical surfaces and
less well-defined margins. Abrasion, clearly seen at the postero-
lateral corner (see below), might account for their subdued char-
acter. The appertaining scales of many of them seem not to have
been confined to the frontal table, but extended over the orbit.
Anteriorly, between the prefrontal incisions, the lateral
margins of the frontal table are slightly upturned (Figure 57A),
such that this portion of the bone, apart from the rugosities, is
also concave in transverse cross section. Deep facets are incised
bilaterally into the anterior margin of the bone for articulation
with the nasals (n.fac.). The right anterolateral spine of the
frontal table was probably exposed farther anteriorly than the
left one in PTRM 19001. The posterolateral and posteromedial
margins of the nasal facets met one another at a broad but acute
angle. The nasal facets were probably laterally restricted and the
anteromedian spine of the frontal table broad.
The posterolateral corner of the frontal is preserved in two
specimens, PTRM 19114 and 19115, both of which have a well-
developed postfrontal facet. The facet is not seen in PTRM
19001 (Figure 57B), because the corner has been worn away.
The cristae cranii are low and broadly rounded in cross section
(Figure 57C, cr.cr.), increasing slightly in depth from the fron-
toparietal suture toward the prefrontal facet (prf.fac.). Posteri-
orly, the lateral surface of each crista is merely concave, forming
supraorbital flanges (so.fl.), but this concavity deepens anteriorly
in PTRM 19001, forming fossae that strongly undercut the
frontal table and overcut the crista cranii. The surface of the con-
cavity is irregular posteriorly and penetrated by a few tiny
foramina; on the right side, the deepest portion of the fossa con-
sists of two distinct impressions, whereas on the left side the
fossa is not so divided. The fossa on the right side terminates
abruptly near midorbit, whereas that on the left terminates in
the same position but more gradually. These fossae are poorly
developed in PTRM 19006 and are absent entirely in PTRM
19115 and 19381.
From the posterior end of the prefrontal facet, a longitudi-
nal ridge begins to take form, dividing the facet into dorsolater-
ally and dorsoventrally facing surfaces (Figure 57B). For its
posteriormost portion, the scar is confined to the dorsolaterally
facing surface, but anteriorly it expands abruptly to cover almost
the entirety of the ventrolaterally facing surface as well. Anteri-
orly, the ventral portion of the crista is broken and its relation
with the prefrontal and palatine cannot be determined.
The frontal is thickest at midorbit, where the cristae cranii
approach one another closely (Figure 57C). A broad median
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
66
ridge rises from the thin posterior portion of the bone, tapering
smoothly anteriorly and increasing in depth until it reaches the
dorsoventral level of the cristae cranii just posterior to midorbit.
The grooves for the planum or solium supraseptale (so.ss.)
between this ridge and the cristae are deepest at the anteropos-
terior midpoint of the ridge. The grooves disappear at midorbit;
here, the ventral surface of the frontal is flat. More anteriorly, the
ventral surface is increasingly excavated for the olfactory bulbs.
Late Eocene Lizards of the Medicine Pole Hills • Smith
67
Figure 56. Right prefrontal of selected members of Corytophaninae. A–D, Basiliscus basiliscus (UF 99655).
E–H, Laemanctus longipes (UF 66061). I–L, Corytophanes hernandesii (UF 72492). First row, Dorsal view. Sec-
ond row, Lateral view. Third row, Medial view. Fourth row, Anterior view. Abbreviations: ant.fl., antorbital
flange; f.fac., frontal facet; f.pr., frontal process; l.fac., lacrimal facet; mx.fac., maxillary facet; n.fac., nasal facet;
pl.fac., palatine facet; pl.pr., palatine process; pn.rec., paranasal recess; prf.boss, prefrontal boss.
Comparisons: The interorbital portion of the frontal in Orithyia
oaklandi is comparatively narrow. The interorbital width divided
by the greatest frontal width (1.9/6.2 mm) is 0.31 maximally;
given that the corner is also missing, we might reasonably assume
another 1 mm total width, bringing the ratio down to 0.26.
Although this ratio is similar to many Basiliscus (Figure 58A)—
B. basiliscus (3.4/12.7 mm ⫽ 0.27), B. plumifrons (4.9/15.8
mm ⫽ 0.31), B. galeritus (2.7/11.4 mm ⫽ 0.24)—most members
of Corytophanes and Laemanctus have interorbitally broader
frontals (Figure 58D, G): C. percarinatus (3.6/10.9 mm ⫽ 0.33),
C. hernandesii (4.2/12.1 mm ⫽ 0.35), L. longipes (3.8/11.8 mm ⫽
0.32), L. serratus (0.43, based on Etheridge and de Queiroz 1988,
fig. 3). Suzanniwana patriciana and Geiseltaliellus maarius (0.33
each) also have a moderately broad frontal. Broad frontals are
also common in Polychrus and Anolis (see above). Thus, it could
be that species of Basiliscus are apomorphically narrow and a
broader interorbital region is primitive. Alternatively, a narrow
frontal may be an autapomorphy of crown Corytophaninae with
a reversal in Corytophanes + Laemanctus.
Well-developed, relatively large rugosities on the frontal
are characteristic of Laemanctus (Figure 58D; L. serratus can be
extremely rugose). In Corytophanes hernandesii and C. cristatus,
the frontal table is relatively smooth, as it is in most Basiliscus
(Figure 58A). In B. plumifrons and C. percarinatus the frontal
table shows low, irregular rugosities that are not clearly related
to epidermal scales. This is also the case in Suzanniwana patri-
ciana, except for the periorbital series (Smith 2009b).
One interesting aspect of the frontal of Orithyia oaklandi
is the nature of the periorbital scales. They do not form so clear
a curvilinear row; that is at least in part because their medial
margins, rather than running parallel to the arc of the row,
instead contain significant medial, two-sided projections. This
is also true of Laemanctus (Boulenger 1877, pl. VII, fig. 1a, 2,
illustrates this clearly in L. serratus) and Corytophanes (pers.
obs.). In contrast, the scales of the periorbital row in Basiliscus
have straighter medial margins (pers. obs.); thus, the rows are
more clearly defined. This may also have been true of Suzanni-
wana patriciana and Geiseltaliellus maarius (Smith 2009a,
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Figure 57. Frontal of Orithyia oaklandi (PTRM 19001). A, Dorsal view. B, Lateral view. C, Ventral view. Abbre-
viations: cr.cr., crista cranii; n.fac., nasal facet; prf.fac., prefrontal facet; so.fl., supraorbital flange; so.ss., groove
for attachment of solium supraseptale.
2009b). It seems possible that the loss of definition of the peri-
orbital scale row is synapomorphic of Laemanctus and Coryto-
phanes, and first seen in O. oaklandi.
Unfortunately it is not possible to determine whether the
parietal foramen pierced the frontal alone or was contiguous
with the frontal parietal suture. This character varies signifi-
cantly in Corytophaninae (Figure 58A, D, G; see also discus-
sions under Sauropithecoides charisticus and Queironius
praelapsus above) and its determination in Orithyia oaklandi
would do much to clarify the evolution of this character in Cory-
tophaninae (see Lang 1989). At present, one can merely say that
the occurrence of the foramen as far forward as in Basiliscus or
Corytophanes is unlikely.
The sagittal arching of the frontal of Orithyia oaklandi is
similar to that of Corytophanes (Figure 58H) and Basiliscus (Fig-
ure 58B; excepting B. plumifrons). The frontal in Laemanctus
longipes, but not L. serratus, is essentially flat (Figure 58E). In
Geiseltaliellus sp. from the early Eocene site of Prémontré in
France, the frontal is slightly arched (pers. obs.). Thus, the flat
condition in L. longipes is probably derived.
Well-developed longitudinal fossae below frontal table on
lateral face of cristae cranii are not present in most Basiliscus
(Figure 58B, C) or in any examined member of Corytophanes
(Figure 58H, I). They were also absent in examined poly-
chrotines, although the lateral margins of the cristae were very
strongly defined in Anisolepini. Weak fossae are present, how-
ever, in B. galeritus UF 61491. Only in Laemanctus (both
species) are fossae well developed (Figure 58E, F). In Orithyia
oaklandi, the fossae are only variably present; their occurrence
in some proportion may be an autapomorphy of the species.
But the presence of fossae at all provides some support for an
alliance of O. oaklandi with Laemanctus.
The frontal table in Basiliscus has a strong, anteromedian
spine (Figure 58A). This spine is truncated in Laemanctus
Late Eocene Lizards of the Medicine Pole Hills • Smith
69
Figure 58. Frontal of selected members of Corytophaninae. A–C, Basiliscus basiliscus (UF 99655). D–F, Lae-
manctus longipes (UF 66061). G–I, Corytophanes hernandesii (UF 72492). First row, Dorsal view. Second row,
Ventral view. Third row, Right lateral view. Abbreviations: cr.cr., crista cranii; n.fac., nasal facet; p.f., parietal fora-
men; pof.fac., postfrontal (portion of postorbitofrontal) facet; prf.fac., prefrontal facet; so.ss., groove for attach-
ment of solium supraseptale.
longipes (Figure 58D; but not L. serratus) and in Corytophanes
(Figure 58G); in the latter, reduction contributes to a frontonasal
fontanelle. Unfortunately, the relevant region is unknown in
any specimen of Orithyia oaklandi. Basiliscus (Figure 58C) also
show a ventral, median ridge on the frontal in the region of the
olfactory excavation, which begins at or posterior to the trans-
verse level of the posterior end of the nasal facets and grows in
prominence anteriorly. This ridge is absent in Laemanctus
longipes (Figure 58F; but possibly present in L. serratus) and
examined Corytophanes except C. hernandesii UF 72492 (Fig-
ure 58I) and also seems to have been absent in O. oaklandi.
The median posterior ridge in Orithyia oaklandi, which rises
to the depth of the cristae cranii, and the lateral grooves for the
solium supraseptale that bound it are similar to those in Basilis-
cus (Figure 58C) and Suzanniwana patriciana (Smith 2009b). In
Corytophanes spp. the grooves are very reduced and the space
between them is flat (Figure 58H); that is, the ridge is absent. In
Laemanctus longipes, the grooves are also scarcely visible,
bounded medially only by a weak but sharp step medially (Figure
58F); between these medial crests there is, instead of a well-devel-
oped ridge, a shallow concavity that conforms to the expected
shape of the ventral surface in the absence of any median emi-
nence. The condition in O. oaklandi is probably primitive.
The prefrontal facet of Laemanctus longipes is developed
entirely on the ventrolateral surface of the crista cranii (Figure
58F); that is, the facet is not divided by a ridge into dorsolaterally
and ventrolaterally directed portions. In Basiliscus basiliscus, in
contrast, the prefrontal facet in transverse cross section is weakly
divided (Figure 58B); this is not true in B. plumifrons, in which
the facet (although relatively deeper) is unitary and faces laterally.
Corytophanes hernandesii is similar to Orithyia oaklandi in hav-
ing dorsolaterally and ventrolaterally directed surfaces (Figure
58H), although the former is much less extensive than the latter.
This condition may be primitive. It would be desirable to know
whether the ridge is present also in stem corytophanines.
In both Corytophanes hernandesii (Figure 58H) and C.
cristatus, and in Laemanctus longipes (Figure 58F), the ventral
margin of the prefrontal facet evinces a distinct angulation
toward the ventral, just as in Orithyia oaklandi (in which, in fact,
it is even more marked). In Basiliscus spp., in contrast, the ven-
tral margin runs straight until it terminates at the apex of the
crista cranii (Figure 58B). Corytophanes percarinatus and L. ser-
ratus were also like Basiliscus, as were examined members of
the polychrotine clades Leiosaurini and Polychrus; among
members of Anisolepini, Enyalius iheringii has a straight suture,
but Anisolepis undulatus and Urostrophus vautieri show a very
marked angulation. In Anolis, the margin is often straight and
there is even a tendency for there to be a lateral rather than ven-
tral curvature. Thus, the condition in L. longipes and most Cory-
tophanes is at present taken to be derived (with a reversal in C.
percarinatus) and unites O. oaklandi with them; yet, there is
some suggestion of intraspecific variation and larger sample
sizes of all relevant taxa are desirable.
JUGAL
A jugal morphotype is associated here on the basis of size, rela-
tive abundance and complementarity of articulation with the
postorbital.
Description: The morphotype is best represented by PTRM
19007, a left element preserving the angle of the bone, half of
the suborbital ramus and most of the ascending ramus (Figure
59). In this specimen the temporal ramus (tm.ra.), measured
along the lateral surface perpendicular to the orbital margin, is
nearly twice as thick as (1.9 times) the suborbital ramus (so.ra.),
measured at the posterior end of the lateral exposure of the max-
illary facet; this is partly attributable to a posterior expansion of
the temporal ramus, whose posterior margin is distinctly con-
vex in its ventral two-thirds. In PTRM 19449, however, the tem-
poral ramus is more slender and less expanded. The ramus in
this specimen is also more complete and lacks any posterior
deflection of its dorsal tip. The temporal ramus as a whole is
weakly laterally bowed (Figure 59B). In PTRM 19007 its lateral
surface is lightly sculpted, but distinct eminences that would
correspond to epidermal scales are not apparent (Figure 59A);
sculpture is even more subdued in PTRM 19449. A curvilinear
row of at least seven small foramina pierces the lateral surface
(best seen in PTRM 19449), extending halfway up the tempo-
ral ramus; weak grooves extend posteriorly from the dorsalmost
of these. The orbital rim is thickened at the angle of the bone, but
becomes more acute on the suborbital and temporal rami. On
the suborbital ramus, the orbital rim is also bowed outward,
strongly overhanging the ventral edge of the bone. The maxil-
lary facet (mx.fac.) becomes exposed laterally only at the very
anteriormost preserved portion in PTRM 19007, being sepa-
rated from the posteroventral angle by a significant distance.
The postorbital facet is not exposed laterally in said specimen,
but in PTRM 19449 a sliver of the facet is seen laterally on the
distalmost portion of the ramus.
The orbital face of the bone is flat nearly everywhere in
cross section, except at the angle, where it becomes slightly con-
vex (Figure 59B). In all three specimens in which it can be
judged, two longitudinally arrayed foramina pierce this face, the
first located immediately below the postorbital facet (po.fac.).
In PTRM 19007 this facet is roughly V-shaped in cross section,
but in PTRM 19449 it is shallower with a flatter base. The base
of the V in PTRM 19007 forms a deep trough that extends from
the ventralmost end of the facet to the dorsalmost preserved end
of the bone. The lateral limb of the V is long and straight, but the
medial limb is short and complex.
The posteromedial face of the temporal ramus is excavated,
the degree of concavity increasing anteroventrally and reach-
ing a maximum just behind the ectopterygoid articulation (Fig-
ure 59C). This is the coronoid recess (cn.rec.). No foramen
pierces the recess in any specimen. The ectopterygoid articula-
tion surface (ec.fac.) is complex. It encompasses a medial bump
that inserts in a lateral concavity on the ectopterygoid. A small,
tapering facet, which receives the dorsal corner of the postero-
lateral process of the ectopterygoid, extends posterodorsally
from this bump; the facet for the ventral corner of the same
process is distinctly more extensive. A longitudinal groove just
below the orbital face of the suborbital ramus of the jugal would
have received the anterolateral process of the ectopterygoid. The
ectopterygoid would not have achieved exposure laterally on
the skull.
Comparisons:
The temporal ramus is massively posteriorly
expanded in Corytophanes (Lang 1989; Figure 60E), but the pos-
terior margin shows a distinct posterior convexity also in some
Polychrus (P. gutturosus, weakly in P. marmoratus) and in
Basiliscus, in which it is more distally positioned in B. galeritus
and B. basiliscus (Figure 60A) and more proximally positioned
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70
in B. plumifrons. There is no obvious expansion in other Poly-
chrus (P. acutirostris, P. femoralis) or other polychrotines (except
Anisolepis undulatus and Anolis). A distinct expansion is absent
in Geiseltaliellus maarius (Smith 2009a) and Suzanniwana patri-
ciana (Smith 2009b). Outgroup comparison thus suggests the
expansion is derived, and it is possibly characteristic of crown
Corytophaninae. Its occurrence in Orithyia oaklandi is consis-
tent with corytophanine affinities.
In both Laemanctus (Figure 60C) and Corytophanes (Fig-
ure 60E) the posteroventral angle of the jugal is drawn out into
a quadratojugal process. As the angle is rounded in all Basiliscus
(Figure 60A) and in Geiseltaliellus maarius (Smith 2009a) and
Suzanniwana patriciana (Smith 2009b), the rounded condition
is probably primitive for Corytophaninae, as it may be for Igua-
nia (Smith 2009a). Thus, the corner seen in Corytophanes + Lae-
manctus is probably locally derived and its absence in Orithyia
oaklandi would exclude this species from that clade.
In Corytophanes hernandesii and Laemanctus longipes, as
well, the suborbital ramus of the jugal shows a distinct medial
curvature that is absent in Basiliscus and Polychrus. Although
the jugal as a whole is laterally convex in Orithyia oaklandi, this
owes primarily to a medial curvature of the distal portion of
the temporal ramus, and it is presently unknown if the anterior
ramus shows the condition seen in Corytophanes and Lae-
manctus.
The deep trough in the postorbital facet in Orithyia oak-
landi is related to the development of a strong keel on the ven-
tral edge of the postorbital and is discussed below in conjunction
with that element.
The postorbital facet on the jugal only barely achieves lat-
eral exposure in Orithyia oaklandi. Exposure was thus more
restricted in the fossil species than in living corytophanines (Fig-
ure 60A, C, E), which could be an autapomorphy. On the other
hand, lateral exposure of the postorbital facet is also greatly
restricted in Suzanniwana patriciana (Smith 2009b). The
discovery of stem Basiliscus may be necessary to clarify the evo-
lution of this feature.
The lateral exposure of the maxillary facet on the subor-
bital ramus of the jugal is widely separated from the posteroven-
tral corner of the bone in stem corytophanines (Smith 2009a,
2009b), corytophanines (Figure 60A, C, E) and polychrotines.
This aspect of the jugal of Orithyia oaklandi is therefore proba-
bly primitive. The degree of protrusion of the orbital rim of the
suborbital ramus in Orithyia oaklandi is similar to that seen in
some Basiliscus (B. galeritus, B. plumifrons) and Corytophanes
(Figure 60E) and is also conceivably a primitive feature.
The dual foramina below the postorbital facet is a feature
not seen in any examined member of Corytophanes, Laemanc-
tus or Basiliscus. In these taxa, the foramen is single. (In Basilis-
cus and L. serratus, the single foramen is always located
extremely close to the postorbital articulation, generally con-
tiguous with its anterior end.) The foramen was also single in all
examined polychrotines. Thus, the dual condition of the fora-
men is taken to be derived and constitutes an autapomorphy of
Orithyia oaklandi.
POSTFRONTAL
The only information on this element comes from the morphol-
ogy of the frontal.
Description: The morphology of the posterolateral corner of the
frontal indicates that this element was present and well devel-
oped (see above). Whether it was fused to the postorbital can-
not be determined, although fusion is not expected.
Comparisons:
The fate of the postfrontal has been uncertain in
Corytophaninae. The bone is greatly reduced or absent in Basilis-
cus (Etheridge and de Queiroz 1988; Smith 2009a), present and
well developed in Laemanctus (Etheridge and de Queiroz 1988;
Lang 1989) and absent as a discrete element in Corytophanes
Late Eocene Lizards of the Medicine Pole Hills • Smith
71
Figure 59. Partial left jugal of Orithyia oaklandi (PTRM 19007). A, Lateral view. B, Medial view. C, Anterodor-
sal view. Abbreviations: cn.rec., coronoid recess; ec.fac., ectopterygoid facet; mx.fac., maxillary facet; po.fac., pos-
torbital facet; so.ra., suborbital ramus; tm.ra., temporal ramus.
(Frost and Etheridge 1989). Among stem corytophanines, it is
well developed in Suzanniwana patriciana (Smith 2009b), but
highly reduced or absent in Geiseltaliellus maarius (Smith 2009a).
Smith (2009a) noted that when the postfrontal in Iguanidae is
discrete and well developed, it is always found along the anterior
surface of the posterolateral corner of the frontal. Thus, when
the postfrontal is not present as a discrete element, but the pos-
torbital seems to occupy this position (e.g., Polychrus, Leiosaurus
bellii), it is likely that the postfrontal is fused to the postorbital.
Corytophanes shows precisely this morphology (Figure 58I,
pof.fac.), suggesting that the two elements are fused and that the
postorbital spine projecting anteriorly over the orbit is composed
of the postfrontal (not the postorbital). There is no need to pos-
tulate the re-evolution of the postfrontal in Laemanctus. The
presence of a well-developed and discrete postfrontal in Orithyia
oaklandi corroborates this interpretation, given other evidence
supporting its phylogenetic position. Still, developmental data
on Corytophanes are desirable.
POSTORBITAL
A single postorbital, PTRM 19005, is associated here on the
basis of iguanian morphology, size and complementarity of
articulation with the jugal. It additionally shows corytophanine
features.
Description:
The bone is triangular in lateral aspect, with a
dorsoventrally short anterior edge and longer posterodorsal and
ventral edges (Figure 61). Its lateral surface is smooth (Figure
61A). The bone thins posterodorsally and also curves medially,
giving it a laterally convex shape (Figure 61A, C). The anterior
ramus (an.ra.) is broken. The anterior face of what remains
curves smoothly onto the lateral face. It had a complex suture
with the jugal (j.fac.) marked by a strong keel that inserted into
the groove on that bone. (The reduced groove in one jugal spec-
imen, of course, implies variation in the strength of the keel.) It
is partially obscured in lateral view by a ventrally projecting
ridge (Figure 61A). This ridge has an irregular margin and
comes to an end anterior to where the keel does. A longitudinal
facet is also developed between the keel and the main medial
face of the bone (Figure 61C, j.fac.). The posterior termination
of the keel is fairly abrupt.
Dorsally, the orbital face of the postorbital grows in medi-
olateral thickness in consequence of a thick lateral expansion
(Figure 61B). This expansion projects both laterally and anteri-
orly, making the orbital face weakly concave in coronal cross
section. A small foramen pierces the orbital face near mid-
height on the bone (as preserved). At the point of its greatest
prominence, the lateral expansion is continued posteriorly onto
the lateral face of the bone by a broad, low swelling (Figure 61A).
The dorsal ramus (do.ra.) is truncated, but the medial curva-
ture of the exterior face of the bone (Figure 61B) as well as the
medially directed lacuna in the broken edge (Figure 61C) sug-
gest a sharp medial curvature of the dorsal ramus and the pres-
ence of a strong medial process, which presumably underlapped
the frontoparietal corner.
The posterodorsal margin of the posterior ramus is convex
(Figure 61A, po.ra.). The ventrolateral margin of the posterior
ramus is marked by a well-developed longitudinal facet for
reception of the squamosal (sq.fac.). Anteriorly, this facet is con-
tinuous with the jugal facet, from which it is demarcated by only
a very weak step; from anterior to posterior, the step is medial,
suggesting that the tip of the temporal ramus of the jugal might
have laterally overlapped the anterior tip of the squamosal. Near
the jugal–squamosal boundary, the ventral margin of the pos-
terior ramus shows a distinct ventral inflection, enlarging the
articulation surface for the squamosal. The squamosal facet
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Figure 60. Left jugal of selected members of Corytophaninae. A, B, Basiliscus basiliscus (UF 99655). C, D, Lae-
manctus longipes (UF 66061). E, F, Corytophanes hernandesii (UF 72492). First row, Lateral view. Second row,
Medial view. Abbreviations: cn.rec., coronoid recess; ec.fac., ectopterygoid facet; mx.fac., maxillary facet; po.fac.,
postorbital facet; qj.pr., quadratojugal process; so.ra., suborbital ramus; tm.ra., temporal ramus.
passes posteriorly beyond the main body of the bone onto the
lateral surface of a prominent, bluntly terminating posterior
projection.
Comparisons:
The convex dorsal margin of the posterior ramus
of the postorbital is an apomorphy that Orithyia oaklandi shares
with Corytophaninae (Figure 62A, D), as well as Anolis and a
few other scattered iguanids (Lang 1989; Smith 2009a). The gen-
eral form of the postorbital of O. oaklandi is very similar to that
of Laemanctus longipes (Figure 62D). The postorbital of Cory-
tophanes is dorsoventrally elongate, with short anterior and pos-
terior rami (Figure 62G). The postorbital of Basiliscus has a
particularly long posterior ramus (Figure 62A).
A prominent ventral keel on the anterior ramus of the pos-
torbital is absent in Suzanniwana patriciana (Smith 2009b, fig.
3G) and scarcely developed in Basiliscus. In B. basiliscus, there
is a comparatively broad ventral ridge that would have inserted
in a shallow groove on the temporal ramus of the jugal, and it
Late Eocene Lizards of the Medicine Pole Hills • Smith
73
Figure 61. Left postorbital of Orithyia oaklandi (PTRM 19005). A, Lateral view. B, Anterior view. C, Medial view.
Abbreviations: an.ra., anterior ramus; do.ra., dorsal ramus; j.fac., jugal facet; po.ra., posterior ramus; sq.fac.,
squamosal facet.
Figure 62. Left postorbital of selected members of Corytophaninae. A–C, Basiliscus basiliscus (UF 99655). D–F,
Laemanctus longipes (UF 66061). G–H, Corytophanes hernandesii (UF 72492). First row, Lateral view. Second
row, Anterior view (anterior view of C. hernandesii not useful, because the process extending under frontopari-
etal corner is broken). Third row, Medial view. Abbreviations: an.ra., anterior ramus; do.ra., dorsal ramus; j.fac.,
jugal facet; po.ra., posterior ramus; pof.fac., postfrontal facet; sq.fac., squamosal facet.
diminishes rapidly in prominence posteriorly; the ridge is even
more poorly developed in B. plumifrons. Disarticulated speci-
mens of other species of Basiliscus were not available, nor was
an isolated postorbital of Polychrus, although the articulation
facet on the jugal in P. gutturosus suggests the anterior ramus of
the postorbital in that taxon resembled that of Basiliscus. In
Corytophanes hernandesii there is a deep, mediolaterally thin
keel beneath the anterior and dorsal rami, which inserts in a
groove on the postorbital. This keel is obscured in lateral view
by a strong lateral ridge, but it is exposed in medial view (Figure
62G, H). (Posteriorly, the ventral edge of the lateral ridge curves
ventrally, instead of dorsally, merging with the prominent ven-
tral inflection marking the squamosal articulation.) In Laemanc-
tus longipes the keel is only slightly overlapped laterally by the
jugal (Figure 62D, F) and the resulting groove on the jugal is
shallow. The strong, mediolaterally thin keel of Orithyia oak-
landi unites it exclusively with Laemanctus and Corytophanes,
although it is expressed somewhat differently in those two taxa.
Like Corytophanes, O. oaklandi also has an (incompletely devel-
oped) lateral ridge that partly obscures the keel in lateral view.
The ventral margin of the postorbital of both Laemanctus
longipes (Figure 62D) and Corytophanes hernandesii (Figure
62G) shows a distinct inflection toward the ventral at the ante-
rior end of the squamosal facet. The inflection is stronger in
Corytophanes and begins relatively more anteriorly; it is stronger
in both Laemanctus and Corytophanes than in Orithyia oak-
landi. The inflection contributes to a laterally directed facet for
the squamosal. There is no such inflection in Basiliscus (Figure
62A), nor was one observed in disarticulated Anolis or in other
polychrotine outgroups, so its presence is considered derived.
The inflection and associated squamosal facet unite O. oaklandi
exclusively with Laemanctus and Corytophanes, although the
relatively weak development of the inflection suggests that it is
outside the crown clade formed by those two genera.
The strong posterior projection of the posterior ramus in
Orithyia oaklandi, which served solely for articulation of the
squamosal, is not observed in living corytophanines and is con-
sidered autapomorphic.
On the whole the postorbital of Orithyia oaklandi is more
similar to that of Laemanctus longipes in the length of the pos-
terior ramus and the degree of ventral inflection of its ventral
margin, and more similar to Corytophanes hernandesii in the
degree of development of the ventral keel of the anterior ramus.
PARIETAL
The central portion of a single parietal, PTRM 19000, is associ-
ated here on the basis of size, iguanid morphology and similar-
ity of dermal sculpture.
Description:
All margins of the bone are broken (Figure 63).
The lateral margins of the parietal table—the adductor crests
(Figure 63A, add.cr.)—converge posteriorly to form a median
crest; the apex of the V lies posterior to the transverse level of the
recessus processi ascendentis (Figure 63B, rec.pr.asc.), but ante-
rior to the posterior margin of the bone. The table’s lateral mar-
gins are upturned (Figure 63A), giving it a slightly concave
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
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Figure 63. Partial parietal of Orithyia oaklandi (PTRM 19000). A, Dorsal view. B, Lateral view. C, Posterior
view. D, Ventral view. Abbreviations: add.cr., adductor crest; desc. p., descensus parietalis; pin.fos., pineal fossa;
rec.pr.asc., recessus processi ascendentis; st.fos., supratemporal fossa.
dorsal surface. This surface is covered by well-defined but irreg-
ularly shaped polygonal rugosities. Some are broad and low,
others broad and tall, and some even narrow and tall. These
rugosities are almost absent from the posterior portion of the
parietal table. Like those on the frontal, they presumably corre-
spond to epidermal scales. The left margin of the parietal table,
and possibly also the right, does not extend in a straight line pos-
teromedially; rather, it shows a posterolateral bulge at mid-
length. The margins of the table overhang the supratemporal
fossa (Figure 63C, st.fos.), especially anteriorly. The descensi
parietalis (desc.p.), which form the floor of the supratemporal
fossa, extend steeply ventrolaterally.
At the posterior break, the bone is roughly triangular in
transverse cross section, one apex directed dorsally (Figure
63D). The edges of the triangle are all slightly concave. The left
dorsolateral edge does not curve uniformly medially, but
diverges slightly from the mid-line near the dorsal apex, creat-
ing a thickening with a flat top. (Abrasion to the right side has
erased this feature.) This dorsal thickening indicates that the
median crest might have extended posteriorly as a parietal blade.
The recessus processi ascendentis (Figure 63D, rec.pr.asc.)
is a somewhat dorsoventrally flattened in transverse cross
section and extends to a deep but inexactly known extent into
the body of the parietal. Anterior to the opening of the recess,
the ventral surface of the parietal forms a broad, flat, anterodor-
sally sloping surface that curves into the horizontally oriented
roof of the cerebral hemispheres (Figure 63B). The surface of
this cerebral vault evinces weak irregularities; on the left side it
is pierced by a small foramen not far from the broken anterior
margin. The vault is very weakly divided into two halves by a
broad, low ridge, which is punctuated on the mid-line by a small
pineal fossa (pin.fos.).
Comparisons:
The adductor crests are better developed in
Orithyia oaklandi than in most iguanids, including Basiliscus
(Figure 64A), Suzanniwana patriciana (Smith 2009b) and
Geiseltaliellus (Augé 2005; Smith 2009a). They are slightly
stronger than those of Laemanctus (Figure 64D), but not so
strong as in L. serratus. These crests are greatly enhanced in
Corytophanes (Lang 1989; Figure 64G) and some Anolis and
Polychrus (see above), forming a strong shield or casque. Less
well-developed adductor crests are also seen in some phrynoso-
matines (Petrosaurus, some Sceloporus, Phrynosoma; Smith
2009a).
In Basiliscus (Lang 1989; Figure 64A), Suzanniwana patri-
ciana (Smith 2009b) and Geiseltaliellus (Augé 2005; Smith
2009a) the parietal table is Y-shaped, as it is in Laemanctus and
Corytophanes (Figure 64D, G; Frost and Etheridge 1989). How-
ever, in the stem taxa and Basiliscus, the triangular portion of the
table is highly restricted anteriorly, with the margins of the pari-
etal table meeting one another well anterior of the transverse
level of the recessus processi ascendentis. In the latter two gen-
era, the triangular table is more posteriorly extensive, its margins
converging on a median crest at or posterior to the level of the
recess. This is taken to be a derived character, given the basal
position of Basiliscus in Corytophaninae and the inferred posi-
tion of the aforementioned outgroups. It may also be a paedo-
morphic one, given the development of the parietal in Basiliscus
(Lang 1989) and Geiseltaliellus maarius (Smith 2009a). Orithyia
oaklandi shares this character with Laemanctus and Coryto-
phanes.
As noted in the description, the preserved portion of the
parietal in Orithyia oaklandi suggests it may have had a median
parietal blade, as seen in all living corytophanines (Figure 64C,
F, I). This supposition is founded on the morphology of the
median crest at the posterior end of the fossil, but draws some
support from consideration of living taxa (particularly Lae-
manctus and Corytophanes), which show the diversity of living
morphologies and the range of variation that presently is pos-
sible. Yet, it should not be taken as unambiguously demon-
strated. Estes (1983:25) noted a “newly discovered” specimen
of a species close to “Aciprion” that, he suggested, had a median
parietal blade. That specimen, from an unidentified locality
(possibly in the White River Group), was not identified by num-
ber or repository and it has not been located.
The cerebral hemispheres are strongly divided in Basiliscus
basiliscus (Figure 64B), as they also are in Suzanniwana patri-
ciana (Smith 2009b). The median dividing ridge, however, is
weaker in Laemanctus (Figure 64E) and Corytophanes hernan-
desii (Figure 64H), just as in Orithyia oaklandi. This is poten-
tially a synapomorphy of the previous three taxa.
A pineal fossa seems to be absent in Suzanniwana patri-
ciana (Smith 2009b; it is possible, but unlikely, that it was merely
broken away in the single known parietal of that taxon). The
fossa is weak and with indistinct margins in Laemanctus
longipes (Figure 64E) and nonexistent in Corytophanes hernan-
desii
(Figure 64H) and L. serratus. However, it is deep and
anteroposteriorly elongate in Basiliscus basiliscus (Figure 64B).
The small depression interpreted as the pineal fossa in Orithyia
oaklandi is anteroposteriorly shorter than the fossa in either
Basiliscus or Laemanctus.
SQUAMOSAL
A single squamosal is tentatively associated here on the basis of
iguanid morphology and size. Additionally, it lacks an apomor-
phy seen in most Iguaninae, the reduction of the ventral process
(de Queiroz 1987). This element is not considered in the diag-
nosis of the new taxon.
Description: PTRM 19334 is a right element preserving part of
the main rod of the bone as well as its posterior portion (Figure
65). Both dorsal and ventral processes are present at the poste-
rior end of the bone (do.pr. and vn.pr., respectively), but nei-
ther is particularly strongly developed. They are about equal in
size. The posterior margin of the bone is convex. The posterior
edge of the dorsal process is flattened for the parietal articulation
(Figure 65B, p.fac.), that of the ventral process for the quadrate
articulation (q.fac.). Both facets are directed slightly medially
(cf. Figure 65A and B). The main rod of the bone is straight, so
long as it is preserved, showing in particular no medial curva-
ture at its posterior end.
Comparisons:
In the degree of development of the dorsal and
ventral processes, the squamosal associated with Orithyia
oaklandi is similar to that associated with Suzanniwana patri-
ciana (Smith 2009b). The processes are also similarly devel-
oped in Basiliscus (Figure 66A, B). In contrast, the dorsal
process in Geiseltaliellus maarius is distinctly elongated (Smith
2009a). The dorsal process is also elongated in Laemanctus
(Figure 66D–F) and Corytophanes (Figure 66H). It is difficult
to draw conclusions on the evolution of the dorsal process in
Corytophaninae at present. The best one can say is that the
Late Eocene Lizards of the Medicine Pole Hills • Smith
75
squamosal associated with O. oaklandi is not like that of Lae-
manctus and Corytophanes.
Corytophanes shows additional highly autapomorphic fea-
tures, which are lacking in the squamosal associated with
Orithyia oaklandi: the presence of a laterally directed spine (Fig-
ure 66H) and the (near) loss of the ventral process (Figure 66G).
The lack of medial curvature of the posterior end of the
squamosal associated with Orithyia oaklandi is unlike what is
clearly seen in Basiliscus (Figure 66C) and Laemanctus (Figure
66F) and is probably present in Corytophanes (Figure 66H).
If the referral is correct, this is an autapomorphy of O. oak-
landi.
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76
Figure 64. Parietal of selected members of Corytophaninae. A–C, Basiliscus basiliscus (UF 99655). D–F, Lae-
manctus longipes (UF 66061). G–I, Corytophanes hernandesii (UF 72492). First column, Dorsal view. Second
column, Ventral view. Third column, Left lateral view. Abbreviations: desc.p., descensus parietalis; pin.fos.,
pineal fossa; rec.pr.asc., recessus processi ascendentis; st.fos., supratemporal fossa.
DENTARY
Specimens are associated here on the basis of size, relative abun-
dance and dental similarity to the holotype, which was described
by Smith (2006a).
Description:
The holotype comprises the anterior two-thirds
of a right dentary (Smith 2006a, fig. 8). The highlights of its
morphology are as follows: 23 tooth spaces preserved; weak
subdental shelf and gutter present a significant distance pos-
teriorly (two-thirds of preserved length); Meckelian groove
open, but restricted from tooth spaces 11 to 13; intramandibu-
lar septum extending to level of boundary between the 19th
and 20th teeth; accessory cusps well developed, but tooth
crowns parallel-sided.
New specimens clarify the morphology of the posterior
portion of the bone, although none provides a complete tooth
series. A facet for an anterolateral process of the coronoid is
absent (Figure 67A). The coronoid facet is a horizontally
floored space posterior to the tooth row (Figure 67B, cn.fac.).
Anteriorly, the floor of the facet curves ventrally and becomes
a moderately developed intramandibular lamella (im.l.) that
extends at least eight tooth spaces anteriorly (Figure 67C). Pos-
teriorly the anteromedial process of the coronoid would have
inserted between lamella and supra-Meckelian lip (sM.l.), but
Late Eocene Lizards of the Medicine Pole Hills • Smith
77
Figure 65. Partial right squamosal of Orithyia oaklandi (PTRM 19334). A, Lateral view. B, Medial view.
Abbreviations: do.pr., dorsal process; p.fac., parietal facet; q.fac., quadrate facet; vn.pr., ventral process.
Figure 66. Right squamosal of selected members of Corytophaninae. A–C, Basiliscus basiliscus (UF 99655).
D–F, Laemanctus longipes (UF 66061). G, H, Corytophanes hernandesii (UF 72492). First column, Lateral view.
Second column, Medial view. Third column, Dorsal view. Abbreviations: do.pr., dorsal process; p.fac., parietal
facet; q.fac., quadrate facet; sq.fac., squamosal facet; vn.pr., ventral process.
anteriorly the dorsal margin of splenial would have occupied
this position.
PTRM 19462 is an exceedingly small specimen (Figure
67D) and could represent a hatchling. The specimen preserves
teeth of two distinct heights. The shorter teeth invariably have
less well-developed accessory cusps than taller teeth anterior to
them, strongly suggesting an increase in the degree of develop-
ment of these cusps in early ontogeny. The taller teeth, how-
ever, have cusps that are as well developed as in large specimens
(cf. Figure 67B and D). Tooth spacing is irregular.
Tooth crowns of some specimens are slightly flared, as in
the teeth of Iguanid MPH-3.
Comparisons: Smith (2009b) argued that fusion of the Mecke-
lian groove may have proceeded independently in Basiliscus and
in Corytophanes + Laemanctus, because basal species of Basilis-
cus (B. galeritus) have a Meckelian groove that is merely closed,
not fused. He failed to note that the Meckelian groove is also
scarcely closed in Laemanctus serratus (Lang 1989, fig. 30; pers.
obs.), and briefly at that, suggesting that fusion of the groove
might even have occurred independently in Corytophanes and
Laemanctus longipes. Orithyia oaklandi is primitive with respect
to both Laemanctus and Corytophanes in having an open
(if restricted) Meckelian groove. This character, however, is
ambiguous at present (open in stem corytophanines: Smith
2009a, 2009b; at least closed, if not fused, in all living coryto-
phanines). Stem representatives of the extant genera will be nec-
essary to answer definitively the question of the evolution of this
character.
The form of the coronoid facet and development of the
intramandibular lamella are similar to what is seen in Suzanni-
wana patriciana (Smith 2009b). These features are probably ple-
siomorphic in Orithyia oaklandi. The subdental shelf and gutter
are also fairly common in stem and crown representatives of
Corytophaninae (Smith 2009b) and are thus probably ple-
siomorphic in O. oaklandi.
Tooth count is said to increase ontogenetically in iguanid
lizards by the addition of teeth posteriorly (de Queiroz 1987).
This does not mean that particular tooth positions (say, the 10th
tooth) are homologous throughout ontogeny. Not only is tooth
count smaller in juveniles, but also tooth size. Teeth of later
replacement waves are necessarily larger than those of earlier
waves; the difference is probably most marked early in
ontogeny, as illustrated by PTRM 19462. Tooth spacing is irreg-
ular because smaller teeth must be replaced in alternating fash-
ion with larger teeth.
CORONOID
A single coronoid is associated here on the basis of complemen-
tarity with the dentary and because coronoids are already asso-
ciated with the two other common iguanids.
Description:
PTRM 19082 is stream-worn and lacks most of the
anteromedial and posteromedial processes. The coronoid
process is tall and slightly posteriorly inclined, with a convex
anterior margin and a straight or possibly concave posterior
margin (Figure 68A, C, cn.pr.), depending on the extent of wear
to the lateral crest. The medial crest had a distinct posterior
expansion in its upper preserved half, which has been worn
away. In coronal cross section the coronoid process has the form
of a very deep crescent, with a strongly convex anterior edge
and a concave posterior edge. The posterior surface is simple
and smooth (Figure 68B). The dentary facet on the anterolateral
portion of the bone is consistent with the presence of a coro-
noid facet on the dentary, bounded by a lateral wall and con-
tinued ventromedially by an intramandibular lamella. At its
ventral termination the lateral crest is abraded, exposing small
intraosseous lacunae that suggest the presence of a small pos-
terolateral projection.
Comparisons:
In general, the shape, delicacy and orientation of
the coronoid process in Orithyia oaklandi is reminiscent of
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78
Figure 67. Dentary of Orithyia oaklandi. A-C, PTRM 19400 (posterior fragment of left element) in medial, lat-
eral and ventral views, respectively. D, PTRM 19462 (partial right element) in medial view. Abbreviations: cn.fac.,
coronoid facet; im.l., intramandibular lamella; sM.l., supra-Meckelian lip. Note that scale bar represents differ-
ent lengths: 5 mm for A–C, 2.5 mm for D.
Laemanctus (Figure 69C, D) and Corytophanes (Figure 69E, F).
The process in Basiliscus is more anteroposteriorly extended
(Figure 69A, B).
The posterior expansion in the dorsal half of the medial
crest in Orithyia oaklandi was also observed in Corytophanes
hernandesii UF 72492 (Figure 69E; uncertain in other speci-
mens because of adhering soft tissue) and Laemanctus serratus
UMMZ 149101. It was absent in C. percarinatus, but seems to
be present in C. cristatus FMNH 69227 (Digimorph.org
2002–2005). It was absent in L. longipes UF 66061 (Figure 69C)
and Basiliscus spp. (Figure 69A). Additional data on inter- and
intraspecific variation are necessary before its evolutionary
implications can be determined.
The relative strength, sharpness and posterior orientation
of the lateral crest in Orithyia oaklandi was not matched in any
examined corytophanine and may constitute an autapomor-
phy. In general, however, the concave posterior face of the coro-
noid process is more posteriorly and less laterally directed in
Corytophanes (Figure 69F) and Laemanctus (Figure 69D) than
in Basiliscus (Figure 69B), except B. galeritus. Polychrotine out-
groups are variable in this regard. Thus, polarity is uncertain,
and while the restricted lateral exposure of the posterior face in
O. oaklandi is consistent with a relationship to Corytophanes
and Laemanctus, it is not necessarily indicative of one.
The presence of a short posterolateral projection of the lat-
eral crest, but not a strong process, is expected given the pres-
ence of such a structure in living corytophanines (Figure 69B, D,
F). The single known coronoid of Orithyia oaklandi is sugges-
tive of such a structure, but the specimen is too worn to permit
certainty on this point.
COMPOUND BONE
Association of this morphotype is made on the basis of iguanid
morphology, size and relative abundance.
Description: The most complete specimen is PTRM 19325,
which lacks the anterior tip of the surangular, the tip of the
angular process and the prearticular anterior to the articular
surface. Notably, all components of this specimen are fully
fused (Figure 70), indicating a mature animal. A facet is devel-
oped on the medial side of the surangular at its anteriormost
preserved end (Figure 70A, cn.fac.); this facet indicates the
presence in the species of a rounded flange of the coronoid
extending posteriorly from the dorsal portion of the postero-
medial process. On the dorsal margin of the surangular just
medial to the facet is a small rugose area of uncertain signifi-
cance. The lateral surface of the surangular is smooth and con-
vex in cross section (Figure 70B) except ventrally, where an
elongate facet for the angular is developed (an.fac.). The blunt
apex of the angular facet lies on the suture between the suran-
gular (sa.) and prearticular (par.). A small ventral projection of
the surangular marks the anterior end of the Meckelian fossa
(Figure 70A, M.fos.). A large foramen opens into the fossa near
the anterior end; there is also a small foramen anterior to mid-
length and a larger foramen opening into the posterior end of
the fossa. An elongate facet on the ventromedial margin of the
surangular marks the articulation of the prearticular (par.fac.),
most of which has been broken away. A strong tubercle proj-
ects dorsally at the posterior end of the Meckelian fossa. This
tubercle is connected by a flange of bone with the remaining
dorsal margin of the surangular. The posterior surangular fora-
men is located just anterior to the transverse level of this tuber-
cle (Figure 70B, p.sa.f.). A ridge begins just lateral to the angular
facet at about the anteroposterior midpoint of its preserved
length and runs posterodorsally, growing in prominence until
it reaches the posterior surangular foramen, at which point it
veers posteriorly.
The articular is saddle-shaped, clearly divided for the medial
and lateral portions of the articular condyle of the quadrate (Fig-
ure 70C, ar.). The retroarticular process (ra.pr.) is long and tri-
angular. It is bounded by strong medial and tympanic crests
(me.cr. and ty.cr., respectively) and has a deeply concave dorsal
surface. The foramen chorda tympani (f.c.t.) pierces it at the
transverse level of the medial half of the articular surface. The
retroarticular process curves dorsally and terminates bluntly
(Figure 70A). The angular process is a small structure (Figure
70D, an.pr.), extending ventromedially from below the articular
surface and curling anteriorly at its tip. Only a very weak flange
Late Eocene Lizards of the Medicine Pole Hills • Smith
79
Figure 68. Partial right coronoid of Orithyia oaklandi (PTRM 19082). A, Medial view. B, Posterior view. C,
Lateral view. Abbreviations: am.pr., anteromedial process; cn.pr., coronoid process; d.fac., dentary facet; pm.pr.,
posteromedial process; sa.fac., surangular facet.
connects it with the retroarticular process (Figure 70A, D). The
ventral surface of the retroarticular process has a relatively long
ridge that decays anteriorly, but extends as far as the level of the
tubercle anterior to the articular bone (Figure 70B).
Comparisons:
The rugosity on the surangular lateral to the pos-
terior end of the coronoid facet was not encountered in any
other surveyed taxon and is taken to be autapomorphic of
Orithyia oaklandi. What it signifies is unclear. The crest run-
ning anterolaterally from the tubercle anterior to the articular is
stronger and sharper in O. oaklandi than in examined coryto-
phanines (although Corytophanes percarinatus comes close).
This may also be autapomorphic.
The medial crest of the Orithyia oaklandi is comparable in
sharpness and degree of development to Basiliscus (Figure 71A,
B) and Corytophanes, but not Laemanctus (Figure 71C, D). This
is plesiomorphy.
In Corytophanes and Laemanctus (Figure 71D), the bone
is somewhat depressed at the articulation with the quadrate, an
attribute that does not occur in Orithyia oaklandi. This is
plesiomorphy as well and excludes the fossil species from
Corytophanes + Laemanctus.
The angular process is reduced in Orithyia oaklandi as
compared with Basiliscus (Figure 71B) and Geiseltaliellus maar-
ius (Smith 2009a). Reduction of this process is also seen in adult
Laemanctus (Figure 71D) and Corytophanes (Lang 1989) and
supports a relationship between O. oaklandi and the clade
formed by those genera. The angular process, however, retains
a ventral component to its orientation, a feature apparently lost
in Laemanctus + Corytophanes and one that would exclude O.
oaklandi from that clade. Possibly this feature is related to the
relative depression of the compound bone at the articular sur-
face, which is seen in both Laemanctus and Corytophanes but
not O. oaklandi. Moreover, the anterior margin of the angular
process has an anterior orientation that is not seen in any living
corytophanine, nor seemingly in Geiseltaliellus maarius (Smith
2009a, fig. 3). This orientation is thus considered autapomor-
phic of O. oaklandi.
The flange connecting the angular and retroarticular
processes is much better developed in all living corytophanines
(Figure 71B, D) as well as in Geiseltaliellus maarius (Smith
2009a). The reduction of this flange is taken to be an autapo-
morphy of Orithyia oaklandi.
The angular seems to be slightly less posteriorly exten-
sive in Orithyia oaklandi than in living corytophanines, but in
this respect it may be like Geiseltaliellus maarius (Smith 2009a,
figs. 2, 4). Additionally, the ridge running posterodorsally
from just above the angular facet toward the posterior suran-
gular foramen in O. oaklandi was not observed in living cory-
tophanines. Finally, the dorsal curvature of the retroarticular
process was greater than that observed in living corytopha-
nines or in G. maarius. The last two features are considered
autapomorphic.
Remarks
The most variable known portions of cranial skeleton of
Orithyia oaklandi are the maxilla (implicating also the anterior
ramus of the jugal), the dentition and the dermal sculpture.
With respect to the maxilla, a jugal buttress (Smith 2009b) is
absent in a few specimens along the entire length of the jugal
articulation, such that the jugal groove is relatively broad and
has a medial border oblique to the vertical; in most specimens
a jugal buttress is present along the entire length, contributing
to a very narrow jugal groove. Moreover, tooth height varies
considerably, as do the degree of flaring of the crowns, tooth
spacing, and the position of first occurrence of accessory cusps
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
80
Figure 69. Right coronoid of selected members of Corytophaninae. A, B, Basiliscus basiliscus (UF 99655).
C, D, Laemanctus longipes (UF 66061). E, F, Corytophanes hernandesii (UF 72492). First row, Medial view.
Second row, Lateral view. Abbreviations: am.pr., anteromedial process; cn.pr., coronoid process; pm.pr., postero-
medial process.
on the crowns. Notably, tooth spacing and degree of crown
flaring were used by Smith (2006a) to distinguish two species:
Iguanid MPH-3 and cf. Aciprion sp. Yet, there is no correlation
between variation in the jugal articulation and dentition. Addi-
tionally, a couple of specimens partially bridge the morpholog-
ical gap between the two jugal morphologies (see above).
Finally, there is no clear indication from another element that a
distinct and otherwise unrecognized iguanid species is present.
Thus, maxillary morphology and dentition are considered sim-
ply to be variable features (with the maxillary–jugal articulation
Late Eocene Lizards of the Medicine Pole Hills • Smith
81
Figure 70. Compound bone of Orithyia oaklandi. A–C, PTRM 19325 (partial right element) in medial, lateral
and dorsal views, respectively. D, PTRM 19080 (fragment of left element) in dorsomedial view. Abbreviations:
an.fac., angular facet; an.pr., angular process; ar., articular; cn.fac., coronoid facet; f.c.t., foramen chorda tympani;
me.cr., medial crest; M.fos., Meckelian fossa; par., prearticular; par.fac., prearticular facet; p.sa.f., posterior suran-
gular foramen; ra.pr., retroarticular process; sa., surangular; ty.cr., tympanic crest.
Figure 71. Compound bone of selected members of Corytophaninae. A, B, Basiliscus basiliscus (UF 99655). C,
D, Laemanctus longipes (UF 66061). First column, Dorsal view. Second column, Medial view. Abbreviations:
an.pr., angular process; ar., articular; cn.fac., coronoid facet; f.c.t., foramen chorda tympani; me.cr., medial crest;
M.fos., Meckelian fossa; ra.pr., retroarticular process; ty.cr., tympanic crest.
showing two quasidistinct states). The differences observed in
dermal sculpture probably primarily reflect ontogenetic stage.
Orithyia oaklandi is united with Corytophaninae by the
continuous jugal buttress of the maxilla, the convex dorsal
edge of the posterior ramus of the postorbital, the Y-shaped
parietal table, the deep and horizontally floored coronoid facet
behind the tooth row, and the moderately developed intra-
mandibular lamella. It is furthermore united with the clade
Corytophanes + Laemanctus by 10 synapomorphies: medial
folding of facial process occurs low on maxilla; slightly more
oblique angle of neck of ectopterygoid to lateral margin; (pos-
sibly) poor development of periorbital scale row; angulation in
ventral margin of frontal process of prefrontal; prominent
ventral keel on anterior ramus of postorbital; distinct ventral
inflection along posterior ramus of postorbital for squamosal
articulation; strong adductor crests of parietal; junction of
adductor crests shifted posteriorly; poor division of cerebral
hemispheres; and reduction of angular process of prearticular
in mature animals.
The following eight plesiomorphies exclude Orithyia oak-
landi from the clade Corytophanes + Laemanctus: gutter on
maxilla relatively short; more gradual posterior decay of facial
process; extremely weak palatine process of maxilla; median
ridge on ventral surface of frontal between grooves for solium
supraseptale well developed; quadratojugal process of jugal
absent; ventral inflection along posterior ramus of postorbital
weak; compound bone not depressed at articular; and angular
process with anteroventral orientation.
The following nine features are autapomorphies of
Orithyia oaklandi: fossa on orbital surface of antorbital flange of
prefrontal; incision of medial palatine nerve into medial edge
of antorbital flange; ridge beneath prefrontal boss bladelike;
(variably) deep longitudinal fossae laterally along cristae cranii;
dual foramina below postorbital facet on jugal; rugosity on lat-
eral surface of surangular opposite posterior end of coronoid;
reduction of flange connecting angular with retroarticular
process; ridge running posterodorsally from just above angular
facet toward posterior surangular foramen; and distinct dorsal
curvature of retroarticular process.
Orithyia oaklandi suggests that the most recent common
ancestor of Corytophanes and Laemanctus looked a great deal
like the latter. In particular, the parietal, postorbital and dermal
sculpturing of the fossil species are very reminiscent of Lae-
manctus.
Iguanidae, incertae sedis
Tuberculacerta Smith, 2006a
Tuberculacerta pearsoni Smith, 2006a
Figures 72, 73
Holotype. PTRM 5296 (left dentary; Smith 2006a, fig. 7.1).
Paratypes
. See Smith (2006a).
Newly referred specimens
. PTRM 19020 (partial right maxilla),
19021 (partial right maxilla; Figure 72D–F), 19022 (premaxilla;
Figure 72A–C), 19023 (partial left postorbital; Figure 73I–J),
19051 (left maxilla fragment), 19052 (maxilla fragment), 19116
(partial frontal; Figure 73E, F), 19135 (partial right ectoptery-
goid; Figure 73A–D), 19145 (maxilla fragment), 19146 (left
maxilla fragment), 19263 (partial right dentary), 19292 (partial
right dentary), 19293 (partial left maxilla), 19294 (left maxilla
fragment), 19295 (right maxilla fragment), 19335 (partial right
jugal), 19411 (right dentary fragment), 19412 (partial right max-
illa), 19450 (partial left maxilla; Figure 72G, H), 19532 (partial
right maxilla), 19538 (right jugal fragment; Figure 73G, H),
19539 (partial left maxilla), 19555 (left maxilla fragment), 19588
(partial right dentary).
Emended diagnosis. Small iguanid similar to most members
of Crotaphytinae, Hoplocercinae, Polychrotinae* and Coryto-
phaninae in having a sharp ventral keel between the nasal facets
on the nasal process of the premaxilla (plesiomorphy?). Simi-
lar to Hoplocercinae, Iguaninae, Polychrotinae* and Coryto-
phaninae in having a weak palatine process of the maxilla.
Uniquely similar to Hoplocercinae in that the nasal process of
the premaxilla is rhomboidal, with strongly projecting lateral
corners at mid-height. Similar to Polychrotinae* and Coryto-
phaninae in having supraorbital flanges on the frontal. Similar
to many polychrotines in having rugosites on dermal skull
bones, extending as far as the nasal process of premaxilla. Dif-
fers from most polychrotines in having (multiple) anterior pre-
maxillary foramina. Similar to Anolis in having a strongly
medially folded facial process of the maxilla, with a projection
at its anterior end that bounds a depression on the premaxillary
process. Differs from Anolis in that the angle of folding is
greater. Differs from all living polychrotines in having an open
Meckelian groove. Differs from all other iguanids in having
only four premaxillary teeth.
Description
PREMAXILLA
A single premaxilla, PTRM 19022, is associated on the basis of
size, relative abundance and the tuberculation of the nasal
process, which is similar to that on other dermal skull bones.
Description: The specimen is nearly complete, lacking only part
of the left side of the nasal process (Figure 72). It measures only
2.1 mm in width at its base and 3.1 mm in length from the base
of the parapet to the tip of the nasal process. The anteroventral
portion of the bone forms a bulge that overhangs the tooth row
(Figure 72A); the bulge is most prominent on the mid-line and
diminishes laterally. The exterior surface in this portion is
smooth. On each side of the mid-line is a set of anterior pre-
maxillary foramina (a.pm.f.), which form a row parallel to the
parapet. The nasal process (n.pr.) is a broad, rhombic structure
that increases in width for the first half of its height and then
decreases again, giving rise to strong lateral corners. These cor-
ners are anteriorly deflected (Figure 72B), so that the anterior
surface, exclusive of the rugosities, is concave between them in
coronal cross section.
The nasal process dorsal to the anterior premaxillary
foramina is beset with rugosities separated by deep grooves (Fig-
ure 72A). The ventralmost rugosity is small and conical, located
only slightly to the right of the mid-line. The largest rugosities
are located on the dorsal half of the nasal process. The distal tip
of the nasal process appears smooth, but it is possible that a
small portion of the dorsal surface (with any rugosity) has been
broken away here. The rugosities are deeply incised by irregu-
lar grooves, which probably contain tiny foramina.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
82
Each short lateral process bears a dorsal articulation surface
(Figure 72B, mx.fac.) partly divided by a low ridge that indicates
that the premaxillary process of the maxilla was slightly anteri-
orly bifurcated. The ridge rises medially and then forms a blunt
projection overhanging the articulation facet (Figure 72A, C).
Posterior premaxillary foramina (Figure 72B, p.pm.f.), extend-
ing anteroventrally into the body of the premaxilla, are sur-
rounded by a thick, semicircular ridge that separates them from
the palatal shelf and the maxillary articulation. The edge of the
palatal shelf is highly worn (Figure 72C, pl.sh.); on the mid-line
it projects downward in what seems to have been a unitary inci-
sive process (in.pr.).
The posterior surface of the nasal process bears a strong,
blunt median keel that becomes weaker and more acute dis-
tally (Figure 72C). Along the distalmost 1.0 mm of the nasal
process are the triangular nasal facets (n.fac.). One base of the
triangle parallels the medial keel, another extends dorsolater-
ally toward the lateral corners of the nasal process. The nasal
facets incise the undersurface of the nasal process to increas-
ing depth ventrally.
Four pleurodont teeth are present (Figure 72C). Tooth mor-
phology in the specimens, however, is mostly effaced by abrasion.
Comparisons: Tooth counts for various iguanid clades are given
in de Queiroz (1987), Smith (2009b) and above (under Sauro-
pithecoides charisticus). The tooth count in Tuberculacerta pear-
soni is very low for Iguanidae and, so far as I know, is only
equalled or exceeded in this respect by Leiosaurus paronae,
which has three (Smith 2009b).
The form of the rugosities on the nasal process of the pre-
maxilla in Tuberculacerta pearsoni is very reminiscent of those
on the premaxilla in many polychrotines, particularly in
Anisolepini and Anolis. The nasal process of most other
members of Clade A is smooth.
The form of the nasal process in Tuberculacerta pearsoni—
rhomboidal, with strongly projecting lateral corners at
Late Eocene Lizards of the Medicine Pole Hills • Smith
83
Figure 72. Cranial elements of Tuberculacerta pearsoni. A–C, Partial premaxilla (PTRM 19022) in anterior,
right lateral, and posterior views, respectively. D–F, Partial right maxilla (PTRM 19021) in lateral, dorsal and
medial views, respectively. G, H, Posterior half of left maxilla (PTRM 19450) in lateral and dorsal views, respec-
tively. Abbreviations: a.pm.f., anterior premaxillary foramina; cr.tv., crista transversalis; ec.fac., ectopterygoid
facet; fa.pr., facial process; in.pr., incisive process; j.fac., jugal facet; mx.fac., maxillary facet; n.fac., nasal facet; n.pr.,
nasal process; pl.fac., palatine facet; pl.pr., palatine process; pl.sh., palatal shelf; p.pm.f., posterior premaxillary
foramina; s.a.f., superior alveolar foramen; sn.a.f., subnarial arterial foramen; v.fac., vomerine facet.
mid-height—shows virtually unique derived similarity to many
members of Hoplocercinae.
Anterior premaxillary foramina, as discussed above under
the previous three species, are found in several parts of Clade
A. Only in Polychrus, Hoplocercinae and Iguaninae can they be
multiple, as in Tuberculacerta pearsoni, and only in Polychrus
are they colinearly arrayed above jaw parapet. In this respect, T.
pearsoni is uniquely similar to Polychrus.
The triangular nasal facets that run along the posterior
mid-line of the bone, creating a sharp, elongate median keel, are
common to iguanids of Clade A exclusive of Crotaphytinae
(with a primitively narrow nasal process), Iguaninae and cer-
tain taxa in which the breadth of the nasal process has been
reduced (e.g., Laemanctus longipes, many Anolis). Thus, a broad
nasal process is probably necessary for having broad triangular
facets. It is not sufficient, however. In Sphenodon punctatus, the
nasal spines of the paired premaxillae together form a relatively
broad dorsal process, but the ventral corners of the nasals are
not restricted to the medial portion of the process, and a trian-
gular facet as seen in Clade A is not formed.
A strong ventral keel between the nasal facets has a broad
distribution in Iguania. It is found in Leiolepis belliana, but
not Uromastyx (which is more like Iguaninae). A strong keel
is formed in almost all members of Clade A (except Iguani-
nae and Gambelia wislizenii), but also in several members of
Clade B (e.g., Microlophus occipitalis). This feature is unre-
lated to the breadth of the nasal process and is instead partly
controlled by the degree to which the anteromedial process of
the nasal follows the lateral margin of the nasal process or runs
deep to it.
In summary, the broad, triangular nasal facet and strong
ventral keel on the nasal process in Tuberculacerta pearsoni
matches the morphology of many members of Clade A, but
these features are either dependent on other changes (increase
in breadth of nasal process) or of uncertain polarity (develop-
ment of keel).
MAXILLA
Specimens are associated on the basis of similarity to paratypes,
similarity of tooth form to dentaries, size and relative abun-
dance.
Description:
Smith (2006a) described a decent maxilla of this
species. The highlights of the description are dorsal surface of
premaxillary process basinlike, bounded by lateral ridge; ante-
rior inferior alveolar and subnarial arterial foramina separate;
facial process covered in largish rugosities; facial process
strongly folded medially to create an anterodorsally facing sur-
face; angle of fold to horizontal relatively high; and superior
alveolar foramen highly restricted (no gutter).
Additional specimens provide new information. The
depression on the dorsal surface of the premaxillary process
can be fairly shallow when the lateral ridge is weak. The crista
transversalis extends first anteromedially (the usual orienta-
tion), but then makes a distinct bend anteriorly, following the
medial margin of the bone (Figure 72E, cr.tv.). The vomerine
facet is tall, flat and vertical (Figure 72F, v.fac.); in PTRM
19020, unlike in PTRM 19021 (Figure 72F) and 19051, it
diminishes in height anteriorly. There is always a dorsal pro-
jection at the anterior end of the facial process (fa.pr.) which
enhances the basinlike character of the premaxillary process
(Figure 72D); it is possible but not demonstrable that the
anterolateral corner of the nasal articulated here. This projec-
tion, in combination with the anterodorsal projection of the
lateral corners of the nasal process of the premaxilla, suggests
that the nostrils were protrusive. In some specimens the sub-
narial arterial foramen (sn.a.f.) occurs more anteriorly (PTRM
19020) than in others. A posterior projection of the premax-
illa along the lingual border of the premaxillary process is
absent (PTRM 19020) or rounded and extremely weak
(PTRM 19021). The anterior margin of the premaxillary
process is simply concave.
The palatine process (Figure 72E, H, pl.pr.) is extremely
weak in all specimens and the palatine articulates on top of it
(pl.fac.). The superior alveolar foramen (s.a.f.) is very short,
about one-and-a-half tooth spaces in length. Posteriorly the
jugal groove is completely open laterally (Figure 72G, j.fac.). It
rises step-wise anteriorly, reaching the level of the dorsal sur-
face of the palatal shelf at the level of the anterior margin of the
superior alveolar foramen (Figure 72H). The ectopterygoid facet
(ec.fac.) is relatively wide posteriorly, but is abruptly restricted
anteriorly. Posteriorly the facet faces dorsomedially, but anteri-
orly it is directed dorsolaterally.
Comparisons: Smith (2006a), noting the folded facial process,
the open Meckelian groove and the rugosities, suggested a rela-
tionship of Tuberculacerta pearsoni to Phrynosomatinae, pos-
sibly to Phrynosoma, predicting that, if this is correct, the
palatine process would be large and triangular. The new speci-
mens show that the palatine process was evidently not broken
in the type material. The process is weak in all specimens. This
was found to be an autapomorphy of Smith (2009a)’s Clade A
exclusive of Crotaphytinae.
The length of the superior alveolar foramen seems to be
similar to that in Anolis and Polychrus marmoratus FMNH
42501 (Digimorph.org 2002–2005, slices xy157 ff.). In P. gut-
turosus, there is an additional, much-smaller foramen posteri-
orly (Figure 5C), but it is unknown how common this condition
is in Polychrus; such a condition is otherwise unknown to me in
Iguanidae. In the leiosaur Pristidactylus torquatus, the foramen
is slightly longer, a little more than two tooth spaces, and in
Leiosaurus catamarcensis it is longer still, about three tooth
spaces (Digimorph.org 2002–2005, slices xy91 ff.).
The medial folding of the facial process in Tuberculacerta
pearsoni is also found in Anolis, Phrynosomatinae (exclusive of
Phrynosoma) and Tropidurini (Smith 2006a). The angle of the
lateral ridge created by the fold is greater than in examined Ano-
lis and also Anolbanolis geminus from the early Eocene (Smith,
in press). It is less than generally seen in Phrynosomatinae or
Tropidurinae*.
The anterior projection of the facial process in Tubercu-
lacerta pearsoni is similar to that seen in many Anolis (e.g., see
Figure 5D) and constitutes a potential synapomorphy of the two
taxa. It is never seen in Phrynosomatinae or Tropidurinae*,
even when the strong folding is present. The depression on the
dorsal surface of the premaxillary process is also similar to what
is seen in many Anolis.
ECTOPTERYGOID
A single ectopterygoid is tentatively associated with this species
on the basis of size, iguanid morphology and complimentarity
of articulation with the maxilla.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
84
Description: PTRM 19135 is a partial right element. The antero-
lateral process experiences an abrupt reduction in width just
beyond its base (Figure 73A, al.pr.). The slender remaining part
was broken, as indicated by the lacuna exposed at its anterior
end (Figure 73B). The pterygoid process extends ventromedially
at a relatively shallow angle (Figure 73B, C, pt.pr.). The ptery-
goid facet (pt.fac.) is very deep and overhung dorsally by a
strong (and incompletely preserved) corner (Figure 73C, D).
The posterolateral process (pl.pr.) is broken at its base. The max-
illary facet is relatively broad and, although it becomes laterally
restricted posteriorly, it is unknown whether a flange was pres-
ent that would have braced the posterior end of the maxilla.
There is a small foramen within the facet.
Comparisons:
The strong corner overhanging the pterygoid
facet is reminiscent of the one seen in some Anolis (e.g., A.
garmani; Figure 9G), as is the great depth of the pterygoid
facet. The angle formed between the neck of the bone and
the lateral margin is intermediate between what is seen in
many Anolis and the perpendicular, the presumed primitive
condition.
FRONTAL
A partial frontal is associated here on the basis of iguanian mor-
phology, size and the occurrence of dermal rugosities similar to
those of the facial process of the maxilla.
Description: The specimen preserves only the central portion
of the bone (Figure 73E, F). It is tiny, measuring 1.25 mm across
at midorbit. The dorsal surface is covered by low, rounded
rugosities with smooth apical surfaces (Figure 73E). At the ante-
rior end, the dorsal surface may have been flat in transverse
cross section, but at midorbit the bone is depressed along the
mid-line, and the surface is concave. The central portion of the
bone is very thin posteriorly. On the right side, the posterior-
most portion of the prefrontal facet is preserved (but the cavity
is a sediment-filled fracture, not part of the facet).
The cristae cranii are distinct for the entire preserved por-
tion of the bone (Figure 73F, cr.cr.). The grooves for the planum
or solium supraseptale (so.ss.) extend to midorbit and termi-
nate in slightly expanded and deepened pits. Anteriorly, the
descending portion of the crista cranii is preserved on the right
side. Well-developed supraorbital flanges (so.fl.) are present and
Late Eocene Lizards of the Medicine Pole Hills • Smith
85
Figure 73. Additional cranial elements of Tuberculacerta pearsoni. A–D, Partial right ectopterygoid (PTRM
19135) in dorsal, anterior, posterior and lateral views, respectively. E, F, Frontal fragment (PTRM 19116) in
dorsal and ventral views, respectively. G, H, Right jugal fragment (PTRM 19538) in lateral and medial views,
respectively. I–K, Partial left postorbital (PTRM 19023) in lateral, anterior and medial views, respectively. Abbre-
viations: al.pr., anterolateral process; an.ra., anterior ramus; cr.cr., crista cranii; do.ra., dorsal ramus; j.fac., jugal
facet; pl.pr., posterolateral process; po.fac., postorbital facet; po.ra., posterior ramus; pof.fac., postfrontal facet;
pt.fac., pterygoid facet; pt.pr., pterygoid process; so.fl, supraorbital flange; sso.ss., groove for attachment of solium
supraseptale; tm.ra., temporal ramus.
on both sides the crista cranii is longitudinally impressed. A
foramen is present on the supraorbital flange on the right side
only.
Comparisons:
Supraorbital flanges are common in Polychroti-
nae* and Corytophaninae (Smith 2009a). The concave trans-
verse cross section is seen in Polychrus, Anolis and Coryto-
phaninae (Smith 2009a, b) and also Enyalius iheringii (pers.
obs.), but not in Anisolepis undulatus or Urostrophus vautieri, or
generally in Leiosaurini. Dermal rugosities may be primitive for
polychrotines but are also seen on the frontal in the stem cory-
tophanine Suzanniwana patriciana (Smith 2009b) and some
members of the crown (see above). However, the great extent of
the rugosities is only found in Polychrotinae*. The cristae cranii
are widely separated (the primitive condition), unlike in Poly-
chrus, Anolis, Laemanctus and Corytophanes.
JUGAL
A jugal morphotype is tentatively associated here on the basis of
iguanian morphology, small size and the occurrence of dermal
rugosities not too different from those seen on the facial process
of the maxilla.
Description:
PTRM 19538 consists of much of the temporal
ramus of the bone (Figure 73G, tm.ra.). It ceases to taper distally,
as far as it is preserved. The lateral surface is covered by rugosi-
ties. A quadratojugal process is lacking. In medial view, the pos-
torbital facet is a deep incision into the orbital face of the bone
(Figure 73H, po.fac.). A single foramen pierces this face just
anterior to the facet.
Comparisons:
The jugal provides little data on the affinities of
Tuberculacerta pearsoni.
POSTORBITAL
A postorbital is tentatively associated here on the basis of iguan-
ian morphology and diminutive size. It is not considered in the
diagnosis. For further discussion of its attribution, see Compar-
isons below.
Description: The specimen, PTRM 19023, is less than 2.5 mm
in height. The orbital margin is rounded (Figure 73J), that is,
there is no orbital rim. The anterior ramus (an.ra.) is delicate
but seems to be nearly complete. At its distal end the jugal facet
is located mostly ventrally, but proximally the facet shifts to a
ventrolateral position (Figure 73I, j.fac.). The posterior portion
of the jugal facet and the squamosal facet are not clearly defined.
A low, circular, apically rounded eminence is found at mid-
height on the postorbital (Figure 73I, J). On the anterior face of
the distal end of the dorsal ramus (do.ra.) is a facet, presumably
for articulation with the postfrontal (pof.fac.). The dorsal ramus
lacks a process that would extend underneath the frontopari-
etal corner. The posterior ramus (po.ra.) is not as delicate as the
anterior ramus, and its anterior edge is somewhat sharper. It is
incomplete.
Comparisons: The lack of rugosities on the lateral surface of the
bone stands in marked contrast to the other dermal skull bones
described above. On the other hand, the bone is relatively small,
so the lack of rugosities might be a juvenile feature. The mor-
phology of the postorbital facet on the jugal is not very helpful
in this regard. If this element does not belong to Tuberculacerta
pearsoni, the next best candidate would be Cypressaurus sp.
MPH (described below), where it would certainly represent a
juvenile animal.
This postorbital provides relatively little phylogenetic
information. Articulation of this bone only on the posterior face
of the postfrontal is a derived feature common to Iguaninae and
Hoplocercinae, as well as rare members of Clade B. However,
the anterior ramus is short by comparison with hoplocercines.
The broad, low eminence at mid-height on the bone distin-
guishes it from H. spinosus MCZ 20679. Such a protuberance
was considered characteristic of Clade A (Smith 2009a).
DENTARY
New dentary specimens are poorly preserved and offer no new
information on the morphology of this species.
Remarks
Smith’s (2006a) hypothesis of phrynosomatine affinities for
Tuberculacerta pearsoni is probably wrong. The maxilla evinces
several features that occur in polychrotines and especially Anolis.
The angle of folding of the facial process is greater than in living
Anolis (Smith, in press), but this might just be plesiomorphy
(related to a shorter snout). The frontal has derived features that
are consistent with polychrotine or corytophanine affinities. The
premaxilla is very autapomorphic but has rugosities like those in
polychrotines. In summary, the best present hypothesis for the
relationship of T. pearsoni is that it is a stem Anolis.
Speaking against this hypothesis is the open Meckelian
groove. There is some indication that a shift from closure to
fusion occurred multiple times in Polychrotinae*, including
the mere closure of the Meckelian groove in Anolbanolis gemi-
nus (Smith, in press) and Anisolepis grilli (pers. obs.). However,
I am unaware of any putative polychrotine with an open Meck-
elian groove. If the hypothesis is correct— and more evidence
must first accumulate for it to be convincing—then it possibly
represents a long-surviving, early diverging branch of the Ano-
lis stem, or the open Meckelian groove here is a reversal, a rare
but not unknown transformation in Iguanidae (Pregill 1992).
Cypressaurus Holman, 1972
Cypressaurus sp. MPH
Figure 74
Iguanid MPH-2 Smith, 2006a:11.
Iguanid MPH-4 Smith, 2006a:17.
Cypressaurus sp. Smith, 2006a:18.
Newly referred specimens. PTRM 19063 (maxilla fragment),
19085 (partial left jugal; Figure 74G–I), 19215 (partial right
dentary), 19235 (left maxilla fragment; Figure 74E, F), 19267
(right maxilla fragment; Figure 74A–D), 19296 (jaw fragment),
19297, 19298 (right dentary fragments), 19299 (left dentary
fragment), 19300 (jaw fragment), 19301 (right maxilla frag-
ment), 19409 (right maxilla fragment), 19468 (left jugal frag-
ment), 19494 (right jugal fragment), 19502 (left maxilla
fragment), 19509 (partial left dentary), 19550 (partial right den-
tary), 19556 (right dentary fragment), 19582 (partial right den-
tary; Figure 74J, K), 19589 (right dentary fragment), 19590
(partial left dentary).
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
86
Description
MAXILLA
A maxillary morphotype is associated on the basis of dental sim-
ilarity to the dentaries. Smith (2006a) described some specimens
of this species.
Description: The premaxillary process is best preserved in
PTRM 19267. The dorsal surface is flat but slopes strongly
laterally (Figure 74A, C). No lateral crest or ridge is present (Fig-
ure 74A). The crista transversalis (Figure 74B, cr.tv.) is tall by
comparison with the palatal shelf (pl.sh.) and mediolaterally
very thick (Figure 74C). The subnarial arterial foramen (sn.a.f.)
opens just lateral to its apex, and a groove runs from it to the
anterior margin of the bone. Broadly speaking, the anterior
margin is concave, with a strong medial process and a delicate
lateral one. However, in between there is a tiny anterior projec-
tion; between that and the medial process runs the groove for
the subnarial artery. Posteriorly, where it joins the facial process,
the crista transversalis is indistinct. Ventrally is an extensive
Late Eocene Lizards of the Medicine Pole Hills • Smith
87
Figure 74. Cranial elements of Cypressaurus sp. MPH. A–D, Anterior fragment of right maxilla (PTRM 19267)
in lateral, medial, dorsal and ventral views, respectively. E, F, Partial left maxilla (PTRM 19235) in lateral and
medial views, respectively. G–I, Partial left jugal (PTRM 19085) in lateral, medial and dorsal views, respectively.
J, K, Partial right dentary (PTRM 19582) in medial and lateral views, respectively. Abbreviations: a.i.a.f.,
anterior inferior alveolar foramen; cr.tv., crista transversalis; ec.fac., ectopterygoid facet; fa.pr, facial process;
M.gr., Meckelian groove; pl.pr., palatine process; pl.sh., palatal shelf; pm.fac., premaxillary facet; sM.l., supra-
Meckelian lip; sn.a.f., subnarial arterial foramen; so.ra., suborbital ramus; tm.ra., temporal ramus.
surface where the maxilla overlapped the premaxilla (Figure
74D, pm.fac.); this surface implies the presence of a posterior
spine of the premaxilla along the lingual margin.
PTRM 19235 retains the most complete facial process of
any specimen (Figure 74E, fa.pr.). The anterior margin of the
process rises steeply, and the anterior inferior alveolar foramen
(a.i.a.f.) is located on its edge a little above the presumed level
of the dorsal surface of the premaxillary process. The lateral
surface of the facial process is flat. There is a small foramen at
the same transverse level as the anterior inferior alveolar fora-
men, which opens on the palatal shelf in PTRM 19235 (Figure
74F), but this foramen is absent in PTRM 19409. The shelf as
a whole slopes slightly medially and rises posteriorly. The snout
of the animal may have been foreshortened, for the palatine
process (pl.pr.) begins already above the seventh tooth behind
the premaxillary process. The process is extremely weak (see
also Smith 2006a, fig. 11); the palatine articulates wholly dor-
sally on the maxilla, so far as its articulation is preserved in
PTRM 19267, and posteriorly the facet slopes slightly laterally,
that is, toward the gutter (described in Smith 2006a).This gut-
ter begins above the fifth tooth behind the premaxillary process
and is five tooth-spaces long. The main portion of the facial
process—to which the prefrontal was applied—was probably
tall but extremely anteroposteriorly short (Figure 74E). The
posterior margin of the main portion curves posteriorly and
then runs nearly horizontally. This posterior remnant is
extremely tall. A distinct facet for the lacrimal on the posterior
remnant is not in evidence (Figure 74F). Laterally is a row of six
labial foramina distributed irregularly over a space of nine teeth
(Figure 74E).
Comparisons:
The maxilla of Cypressaurus sp. MPH is in many
ways divergent. I have not encountered such a strongly laterally
sloping dorsal surface of the premaxillary process in any other
iguanid, and this is probably autapomorphic of the fossil line-
age. The middle projection at the anterior end of the premaxil-
lary process was absent in examined iguanids. If this feature is
constant in the species, it would also be an autapomorphy.
The anteroposteriorly extremely short facial process is to
my knowledge not seen in any iguanid group except Hoplo-
cercinae, particularly (among examined taxa) in Hoplocercus
spinosus, Morunasaurus annularis and Enyalioides laticeps. In
Enyalioides oshaughnessyi the process is distinctly longer,
although the extremely steep anterior and posterior margins
remain. A further similarity between Cypressaurus sp. MPH and
some hoplocercines—in particular with Morunasaurus annu-
laris and Enyalioides oshaughnessyi—is the tallness and nearly
horizontal course of the posterior remnant of the facial process.
Even in species in which the remnant decreases in height, the
decrease is very gradual. The consequence of this is that the jugal
attains only extremely restricted exposure laterally below the
orbit, and the remnant leaves a very convex facet on the jugal,
where it does eventually (abruptly) decrease in height. Both fea-
tures are highly unusual in Iguanidae.
On the other hand the premaxillary process in Cypressaurus
sp. MPH is unlike that of any hoplocercine I have examined,
lacking three features common to that clade: elongate nature;
presence of a strong lateral ridge, which makes the premaxillary
process dorsally concave; and crista transversalis strong where
it joins the facial process. For this reason, Cypressaurus sp. MPH
can reasonably be excluded from the hoplocercine crown.
JUGAL
A jugal morphotype is associated here on the basis of size and
relative abundance.
Description: The most complete specimen is PTRM 19085, a
partial left element preserving the base of the suborbital ramus
and perhaps half of the temporal ramus. The lateral surface of
the bone is smooth (Figure 74G). The suborbital ramus (so.ra.)
is dorsoventrally tall. The ridge along its dorsal margin does not
exactly follow the orbital margin posteriorly; rather, it deviates
from it distally on the temporal ramus (tm.ra.), extending out
onto the lateral face of that ramus. The temporal ramus extends
posterodorsally at a high angle to the horizontal. A curvilinear
row of small foramina pierces the lateral face of the bone.
Medially the ectopterygoid facet is strongly marked (Fig-
ure 74H, ec.fac.), indicating a strong dorsal corner of the pos-
terolateral process of the ectopterygoid. The posteroventral
angle of the jugal is very subtly flattened (Figure 74G), possibly
indicating where the ventral corner of the posterolateral process
of the ectopterygoid rested. There was probably only a single
foramen on the orbital face of the temporal ramus below the
postorbital suture (Figure 74H). The orbital face of the subor-
bital ramus does not expand anteriorly (Figure 74I).
Comparisons:
This morphotype is distinguished from the jugal
of Queironius praelapsus by several features: high angle of tem-
poral ramus, extension of dorsal ridge of suborbital ramus onto
lateral face of temporal ramus, lack of expansion of orbital face
anteriorly and (probably) only a single foramen on orbital face
of temporal ramus. Yet these features are either plesiomorphic
or autapomorphic and so do little to constrain the relationships
of Cypressaurus sp. MPH.
DENTARY
Dentary specimens are associated here on the basis of size and
tooth morphology. For more detailed comments on the equiv-
alence of Iguanid MPH-2 and MPH-4 and Cypressaurus sp.
MPH, see Remarks below.
Description: PTRM 19582, a partial right dentary, is smaller
than the first-recognized specimen of Iguanid MPH-2 but oste-
ologically similar to it in the location of closure of the Meckelian
groove and the abrupt upturn of the anterior end (Figure 74J,
K). The Meckelian groove (M.gr.) does not open as abruptly
posteriorly, and the supra-Meckelian lip (sM.l.) is not as deep in
the region of closure, but these minor differences are attributed
to variation. The teeth of PTRM 19582 are like those of Cypres-
saurus sp. in being extremely tall and with tapering crowns.
PTRM 19215 is more poorly preserved than PTRM 2602 but
nearly osteologically identical. Closure of the Meckelian groove
in PTRM 19509 is intermediate between PTRM 2602 and
19582. PTRM 19556 is osteologically just like PTRM 2041, the
illustrated specimen of Iguanid MPH-4 (Smith 2006a).
Comparisons:
The dentary of Cypressaurus sp. MPH does not
provide new data on the phylogenetic position of the species.
Remarks
Smith (2006a) concluded that Iguanid MPH-4 was distinct from
Cypressaurus sp. MPH because tooth crown height was much
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
88
lower in the former taxon. Either corrosion or abrasion must be
responsible for preferentially reducing crown height in PTRM
2041, the illustrated specimen of Iguanid MPH-4 (Smith 2006a,
fig. 10), because specimens otherwise osteologically identical to
that specimen now show the tall teeth characteristic of Cypres-
saurus. Smith (2006a) also concluded that Iguanid MPH-2 was
distinct from Iguanid MPH-4, because the Meckelian groove
closed gently in the latter, abruptly in the former; additionally,
intermediate sizes did not exist (although admittedly sample size
was low). A larger sample size and better-preserved specimens
show that (1) Iguanid MPH-2 has tooth morphology essentially
identical to that of Cypressaurus sp. MPH and (2) the largest
specimens of Cypressaurus sp. MPH are similar in size to the
largest specimens like Iguanid MPH-2. Thus, Iguanid MPH-2,
Iguanid MPH-4 and Cypressaurus sp. MPH are all considered to
represent the same species.
The maxilla of Cypressaurus sp. MPH presents a set of very
curious features—the anteroposterior shortness of the tall main
portion of the facial process and the great height and horizon-
tality of the posterior extension of the facial process—otherwise
only found in Hoplocercinae. However, the maxilla lacks several
features of the premaxillary process of living hoplocercines.
Whatever the relation between the two taxa, it is clear that
Cypressaurus is outside (crown) Hoplocercinae.
Scincomorpha Camp, 1923
Amphisbaenia Gray, 1844
Rhineuridae Berman, 1972
cf. Rhineura sp. MPH (after Smith, 2006a)
Newly referred specimens. PTRM 19128 (precaudal vertebra),
19147 (partial right dentary), 19147, 19148 (partial right den-
taries), 19149 (right dentary fragment), 19163 (nearly complete
left dentary), 19164 (partial left dentary), 19165 (partial right
dentary), 19166 (partial left dentary), 19167 (right dentary frag-
ment), 19168 (left dentary fragment), 19169 (jaw fragment),
19170 (left maxilla fragment), 19421 (partial right maxilla),
19424 (nearly complete left dentary), 19425, 19489 (partial right
dentaries), 19490, 19491 (left dentary fragments), 19492 (jaw
fragment), 19527 (partial right maxilla), 19546, 19547 (precau-
dal vertebrae), 19566 (partial left dentary), 19567 (right dentary
fragment), 19568 (left maxilla fragment).
cf. Spathorhynchus sp. MPH
(after Smith, 2006a)
Newly referred specimens. PTRM 19160 (partial left dentary),
19161, 19162 (partial right dentaries), 19216 (partial right max-
illa), 19420 (partial left dentary), 19422? (right maxilla frag-
ment), 19423 (jaw fragment), 19524–19526 (partial vertebrae).
Xantusiidae Baird, 1858
Palaeoxantusia Hecht, 1956
Palaeoxantusia borealis Holman, 1972
Figure 75
Newly referred specimens. PTRM 19024 (partial right frontal;
Figure 75J, K), 19026 (partial left mandible; Figure 75L), 19150
(right dentary fragment), 19171, 19172 (partial left maxillae),
19173 (left maxilla fragment), 19174–19179 (right maxilla frag-
ments), 19180 (partial premaxilla; Figure 75A), 19181 (premax-
illa fragment), 19182 (partial premaxilla), 19183–19187 (partial
left dentaries), 19188, 19189 (left dentary fragments),
19190–19195 (partial right dentaries), 19196–19200 (right den-
tary fragments), 19201, 19202 (jaw fragments), 19413 (left den-
tary fragment), 19414 (right dentary fragment), 19415, 19416
(left maxilla fragments), 19417 (right maxilla fragment), 19418
(partial premaxilla), 19439 (left dentary fragment), 19440, 19441
(partial right maxillae), 19442 (right maxilla fragment), 19443
(left maxilla fragment), 19469 (nearly complete left pterygoid;
Figure 75G–I), 19477 (partial right dentary), 19478 (right den-
tary fragment), 19479, 19480 (partial left dentaries), 19481 (par-
tial right maxilla), 19482 (left maxilla fragment), 19483, 19484
(partial left maxillae), 19485, 19486 (left maxilla fragments),
19487 (partial premaxilla), 19488 (premaxilla fragment), 19511
(partial right dentary), 19512, 19513 (right dentary fragments),
19517 (left dentary fragment), 19523 (left frontal fragment),
19528 (partial left dentary), 19529 (partial left maxilla), 19540,
19541 (partial right dentaries), 19542 (nearly complete right
maxilla), 19543 (nearly complete right maxilla; Figure 75B–D),
19544 (partial right maxilla; Figure 75E, F), 19557, 19558 (par-
tial left dentaries), 19559 (left dentary fragment), 19560 (partial
right dentary), 19561 (right dentary fragment), 19562, 19563
(left maxilla fragments), 19564, 19565 (right maxilla fragments).
Description
PREMAXILLA
Premaxillae are referred here on the basis of xantusiid morphol-
ogy, size and relative abundance.
Description:
The most complete specimen is PTRM 19180 (Fig-
ure 75A), which indicates that there were seven tooth spaces
(confirmed by PTRM 19182). The nasal process is narrow and,
for the proximal 40% of its length, parallel-sided. It then tapers
abruptly where the nasal facets (n.fac.) become visible in ante-
rior view. These poorly defined facets are developed primarily
on the lateral side of the nasal process (n.pr.). A lateral ridge
bisects each facet, extending about two-thirds of the way down
from its dorsal end and diminishing in size. The ridge is visible
in anterior view. At its distalmost end the nasal process is fully
overlapped anteriorly by the nasals. The nasal process is deeper
than wide and its depth gradually increases proximally until
near its base it becomes rapidly deeper, defining a brace for the
palatal shelf. There is a well-developed circular depression on
the dorsal surface of the lateral process, creating a small anterior
rim. The posterior premaxillary foramina (p.pm.f.) are small
and hidden behind the nasal process.
Comparisons:
This element is similar to the premaxilla of
Palaeoxantusia sp. CG from the early Eocene (Smith 2009b).
The two differ in the following ways: (1) P. borealis the nasal
process is less deep and (2) the brace for the palatal shelf less
strong.
The depression on the dorsal surface of the lateral process
is found in Xantusia but not in Lepidophyma. Possibly it is an
autapomorphy of Xantusia, but the osteology of Cricosaura typ-
ica is not yet well enough known to draw a conclusion.
Late Eocene Lizards of the Medicine Pole Hills • Smith
89
MAXILLA
A maxillary morphotype is associated here on the basis of xan-
tusiid morphology, size and relative abundance.
Description: Two of the best-preserved maxillae are PTRM
19542 and 19543 (Figure 75B–D). The premaxillary process is
short, even accounting for the wear to the lateral and medial
projections. It is poorly distinguished from the facial process
(Figure 75B, fa.pr.). The anterior margin of the latter rises
steeply at first, but then has a posterior deflection that (com-
pared with modern taxa) indicates the farthest extent of the
nasal articulation. From its apex the facial process then dimin-
ishes gradually in height, curving slightly posteriorly as it reaches
the posterior process. The lateral surface of the facial process
bears rugosities cut by deep grooves, which indicate the mar-
gins of epidermal scales. These consist of two scales immedi-
ately above the labial foramina (lab.f.)—the large posterior and
smaller anterior loreal scales (lo.sc.p. and lo.sc.a., respectively),
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
90
Figure 75. Cranial elements of Palaeoxantusia borealis. A, Premaxilla (PTRM 19180) in left lateral view. B–D,
Right maxilla (PTRM 19543) in lateral, medial and dorsal views, respectively. E, F, Partial right maxilla (PTRM
19544) in medial and dorsal views, respectively. G–I, Nearly complete left pterygoid (PTRM 19469) in ventral,
dorsal and medial views, respectively. J, K, Partial right frontal (PTRM 19024) in dorsal and ventral views, respec-
tively. L, Partial left mandible (PTRM 19026) in medial view. Abbreviations: acc.f., accessory foramen; a.i.a.f.,
anterior inferior alveolar foramen; a.mh.f., anterior mylohyoid foramen; bpt.fac., basipterygoid facet; cm., com-
pound bone; cn.fac., coronoid facet; cr.cr., crista cranii; ec.pr., ectopterygoid process; ep.fac., epipterygoid facet;
fa.pr., facial process; j.fac., jugal facet; lab.f., labial foramina; lo.sc.a., loreal scale (anterior); lo.sc.p., loreal scale
(posterior); n.fac., nasal facet; n.pr., nasal process; p.pm.f., posterior premaxillary foramen; pl.pr., palatine process;
pl.sh., palatal shelf; prf.fac., prefrontal facet; prf.sc., prefrontal scale; q.ra., quadrate ramus; s.a.f., superior alveo-
lar foramen; spl., splenial.
which are separated by a nearly vertical boundary—and the ven-
tralmost corner of the prefrontal scale (prf.sc.; on nomencla-
ture, see Gauthier et al. 2008). The rugosities are stronger in
PTRM 19543 than in PTRM 19542 (not figured), although the
latter is distinctly larger than the former (heights of facial process
1.8 mm and 1.5 mm, respectively). In PTRM 19543 alone there
is a nonartifactual notch developed on the dorsal margin of the
facial process between the prefrontal and posterior loreal scales.
On the medial surface of the facial process is a ventrally
and slightly posteriorly trending rounded ridge, which extends
from mid-height to the palatal shelf (covered by irremovable
sediment in Figure 75C). Behind the ridge is a deep impression
that encompasses the palatal shelf (pl.sh.) and part of the facial
process. The superior alveolar foramen (s.a.f.) is located at the
level of the boundary between the eighth and ninth teeth. Pos-
terior to it, the palatal shelf curves ventrally, but not strongly so
(Figure 75C, E). In many specimens there is an accessory fora-
men (acc.f.) lateral to the superior alveolar foramen, slightly ele-
vated from the palatal shelf on the facial process. In PTRM
19544 alone, the palatal shelf experiences an abrupt narrowing
posterior to the palatine process and superior alveolar foramen
(Figure 75F). The jugal groove is restricted to the edentulous
posterior process of the maxilla (Figure 75D, j.fac.), which in
some specimens (e.g., PTRM 19529) is highly developed. Gen-
erally there is one or more tiny foramina associated with the
anterior end of the jugal groove. In the divergent PTRM 19544,
the jugal groove is not distinct (Figure 75F).
There are 10 tooth spaces each in PTRM 19542 and 19543
(Figure 75C).
Comparisons: Smith (in press) homologized the ridge on the
medial surface of the facial process with the “oblique ridge” of
Meszoely (1970) and noted that its orientation in Xantusia and
Lepidophyma differentiated them from the rest of Scleroglossa.
PTERYGOID
A single pterygoid (PTRM 19469) is referred to this species on
the basis of size and the presence of apomorphies of Xantusiidae
and of Xantusia.
Description: The specimen, a right element 4.0 mm long, is
largely complete. The posterior half of the quadrate ramus is
broken (Figure 75G, q.ra.) and the rounded terminus of the
palatine process (pl.pr.) of the anterior part suggests it has been
abraded. The quadrate ramus is a thin blade whose preserved
portion curves slightly posterolaterally. The blade has a dorso-
medial concavity that grows in prominence posteriorly. The
quadrate ramus grows in width posteriorly. The ventral surface
of the quadrate ramus bears a shallow, longitudinal groove (Fig-
ure 75H), which seems to narrow slightly anteriorly and is oblit-
erated well posterior of the level of the epipterygoid facet. The
epipterygoid facet (ep.fac.) is set in an eminence that forms the
dorsoventrally tallest part of the bone (Figure 75I). The fossa is
nearly circular (Figure 75H). Just anterior to the fossa, a nar-
row, shallow groove develops on the dorsal surface of the bone,
extending anterolaterally toward the flange found along the pos-
terolateral edge of the anterior part of the bone; the groove is
confined, however, to the neck between the epipterygoid fossa
and the anterior part, being obliterated before it reaches the
flange. Anteriorly on the dorsal surface, there is a strong, trian-
gular impression. Near the medial margin of this impression is
a narrow, shallow, sinuous groove that extends at least partway
up the posterolateral surface of the palatine process, possibly
marking the boundary of the palatine articulation. The medial
surface of the palatine process bears a small facet that might also
represent the remnants of the bifurcation that clasps the poste-
rior tip of the palatine in xantusiid lizards. The ventral surface
of the anterior part of the pterygoid is essentially flat (Figure
75G). The finger-like ectopterygoid process (ec.pr.) is slightly
anteriorly deflected. The facet for the basipterygoid articulation
is a very shallow, circular impression on the medial surface of
the bone (Figure 75I, bpt.fac.), slightly anterior to the midpoint
of the epipterygoid fossa.
Comparisons: An isolated pterygoid has been described thus
far in only one fossil xantusiid, Palaeoxantusia sp. CG (Smith
2009b). Comparisons below rely heavily on CT scans (see Digi-
morph.org 2002–2005).
The impression on the ventral surface of the quadrate
ramus in Palaeoxantusia borealis is also seen in Xantusia river-
siana, X. sonorae, X. henshawi and X. vigilis. It is moreover pres-
ent in Lepidophyma, in which it is much deeper and has sharper
margins. The impression is absent, however, in Cricosaura
typica, which, by comparison with potential scincomorph
outgroups (Plestiodon fasciatus, Kentropyx borckianus,
Dicrodon guttulatum and Takydromus takydromoides, but not
Novoeumeces algieriensis) is probably an autapomorphy.
Palaeoxantusia borealis is like most Xantusia and Lepido-
phyma in that the impression on the ventral surface of the
quadrate ramus does not approach the level of the epipterygoid
fossa. In Xantusia riversiana, in contrast, the impression contin-
ues anteriorly as a small groove that reaches the level of the fossa.
The absence of the impression in Cricosaura typica does not help
to polarize this feature. However, in the potential scincomorph
outgroups listed above, the impression, when present, generally
extends as far as the epipterygoid fossa, suggesting that this is the
primitive condition. Restriction of the anterior extent of the
impression could be a synapomorphy of Xantusia and Lepido-
phyma, but the evolution of this feature might also be ambigu-
ous, depending on the position of X. riversiana (Vicario et al.
2003). The condition in P. borealis could be plesiomorphic.
The epipterygoid fossa in Palaeoxantusia borealis, as noted,
sits atop an eminence that forms the tallest part of the ptery-
goid. The eminence appears to be a consequence of a decrease
in the dorsoventral height of the quadrate ramus and—the
ramus being tall in Lepidophyma and Cricosaura—must be an
autapomorphy of Xantusia (Smith 2009b). The presence of this
apomorphy unites P. borealis with Xantusia. The quadrate
ramus is not reduced in earliest Eocene Palaeoxantusia sp. CG
(Smith 2009b), implying that P. borealis lies more crownward.
In P. borealis, as in Xantusia, the highest point of the eminence
is just anterior to the epipterygoid fossa.
Smith (2009b) also described the narrow, arcuate groove
on the dorsal surface of the anterior part of the pterygoid as a
xantusiid synapomorphy. In Palaeoxantusia sp. CG, Xantusia
riversiana, X. vigilis, X. henshawi and X. sonorae, the groove is
continuous with the apex of the triangular impression on the
dorsal surface of the anterior part (though there is often a kink
at their junction) and extends as far posteriorly as the epiptery-
goid fossa, typically (but not always) interrupting the anterior
wall of the fossa. In at least some X. sonorae, there is a foramen
at the posterior end of the groove, just anterior to the epiptery-
Late Eocene Lizards of the Medicine Pole Hills • Smith
91
goid fossa, which opens into the interior of the bone. In P. bore-
alis the groove appears to be autapomorphically reduced,
restricted to the neck between the quadrate ramus and anterior
part and failing to reach either the epipterygoid fossa or the
anterior impression.
The sinuous groove at the medial edge of the dorsal
impression on the anterior part is much better developed in
Xantusia riversiana than in X. sonorae or Palaeoxantusia bore-
alis, but the phylogenetic distribution of this feature is poorly
constrained by available material.
FRONTAL
Two frontals are tentatively associated here on the basis of size,
relative abundance and the absence of anguimorph or iguan-
ian morphology.
Description: The most complete specimen is PTRM 19024, a
right element. It is broken and abraded, lacking the anterior and
posteromedial portions. The dorsal surface is smooth in most
places (Figure 75J), which could be attributed to stream-wear.
Only the posteromedial portion of the element preserves rugosi-
ties, which are marked by coarse grooves and foramina. No dis-
tinct boundaries between epidermal scales are apparent.
However, a shallow, possibly linear depression runs anterolat-
erally from the mid-line toward the point of greatest constric-
tion of the frontal. This groove could mark the boundary
between the frontoparietal and more anteriorly situated frontal
scales (for nomenclature, see Gauthier et al. 2008). A curvilin-
ear row of foramina runs parallel to the orbital margin.
The postorbitofrontal and prefrontal (prf.fac.) facets are
very subtle due to stream-wear (an arrow marks the extent of
the postorbitofrontal facet in Figure 75K). The crista cranii
(cr.cr.) is rounded in cross section. Supraorbital flanges are
absent. The frontal is thicker at midorbit, thinning anteriorly
and posteriorly.
Comparisons: The frontals attributed to Palaeoxantusia borealis
differ from those of living Xantusia and Lepidophyma, and
known stem representatives of these clades (Smith 2006b), in
lacking sharp supraorbital flanges. The well-developed grooves
marking the anterior portion of the distinctively xantusiid
rhomboidal interparietal scale are also absent, but this owes pre-
sumably to stream-wear and the breakage of the posteromedial
portion of the bone.
MANDIBLE
Many dentaries are referred to this species, but few of them pre-
serve the posterior portion of the bone.
Description:
The most complete specimen discovered so far,
and the only one preserving postdentary bones, is PTRM 19026,
a partial left mandible retaining nearly all the spleniodentary
and the anterior portion of the compound bone (Figure 75L).
The splenial (spl.) is fused dorsally to the dentary and also ven-
trally from the anterior inferior alveolar foramen (a.i.a.f.) to the
anterior mylohyoid foramen (a.mh.f.). Posterior to the latter
foramen, however, the dentary and splenial are discrete. The
dentary depth at the ultimate tooth is 1.2 mm.
Posterior to the tooth row is the facet for the anteromedial
process of the coronoid (Figure 75L, cn.fac.). It has a rounded
anterior margin, but it is very poorly marked. This process
wrapped around the posterior edge of the dentary and con-
tacted the compound bone (cm.). Posterior to this facet is a
deep depression in the compound bone that would have been
situated between the anteromedial and posteromedial
processes of the coronoid. Opposite this depression on the lat-
eral surface of the mandible is a second well-developed depres-
sion, with an arcuate anterior margin, for the adductor
musculature. Its apex is located slightly anterior to the anterior
end of the first depression.
There are spaces for 13 teeth in the dentary, but the teeth
are poorly preserved, if preserved at all (Figure 75L).
Comparisons:
PTRM 19026 is the first specimen to document
fusion of the splenial and dentary in Palaeoxantusia borealis
from the Medicine Pole Hills. It is smaller than the specimen
from Calf Creek, Saskatchewan, Canada, showing fusion of
these elements, which has a dentary depth at the ultimate tooth
of 1.5 mm (Smith 2006a).
Remarks
Smith (2006a) referred small xantusiid remains from the Medi-
cine Pole Hills to Palaeoxantusia borealis Holman. The more
complete material presented here should allow for more careful
comparisons with the type material from the Cypress Hills For-
mation of Saskatchewan, should such material be discovered.
No further evidence of a scincoid has been discovered in the
Medicine Pole Hills (i.e., Scincoid MPH-1 of Smith 2006a). Many
of the new specimens initially considered to represent a scincoid
in fact are referable to Palaeoxantusia borealis, and the remainder
to the gerrhonotine described below. It thus seems likely that
Smith’s (2006a) identification of a scincoid was in error.
Anguimorpha Fürbringer, 1900
Anguimorph MPH (after Smith, 2006a)
Newly referred specimens. PTRM 19212–19214, 19461 (jaw
fragments).
Remarks. The new specimens are considerably more fragmen-
tary than the one illustrated by Smith (2006a, fig. 16).
Anguidae Gray, 1825
Annielline MPH
Figure 76
Referred specimens. PTRM 19129 (dorsal vertebra; Figure 76),
19548 (dorsal vertebra).
Description. PTRM 19129 is the better preserved of the two ver-
tebrae. It is elongate (Figure 76). The prezygapophyseal (prz.)
and postzygapophyseal (poz.) surfaces are elongate and inclined
(Figure 76A). The cotyle (cot.) and condyle (con.) are depressed
(Figure 76B, C). The neural spine is low but well developed on
the posterior half of the neural arch (Figure 76A, B). Its dorsal
end is well formed, suggesting an ontogenetically advanced indi-
vidual. The synapophyses (syn.) are poorly preserved. The cen-
trum is parallel-sided in ventral view and its ventral surface is
flat, with sharp lateral margins (Figure 76C). A single subcentral
foramen is present on the left side.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
92
Remarks
The flat morphology of the ventral surface of the vertebral cen-
trum is found, among anguid lizards, only in the fossorial clades
Anguinae and Anniellinae (Gauthier 1980). In Anguinae, the
vertebrae are typically more square and have (primitively) taller
neural spines.
California legless lizards, genus Anniella, are restricted to
the western coast of California and Baja California today. How-
ever, Gauthier (1982) first recognized that a tiny anguid species
from the early Eocene of Wyoming, which he called Apo-
dosauriscus minutus, pertains to this lineage. Its first occurrence
in central North America has since been extended to the earli-
est Eocene (Smith 2009b). Otherwise, the Anniella lineage is
known only from the Miocene to Pleistocene (Gauthier 1980;
Bell and Whistler 1996) of California. Annielline MPH is thus
the last known record of the lineage in central North America.
Whether it looked more like Apodosauriscus or Anniella cannot
be determined on the basis of present material.
Diploglossine MPH
(after Smith, 2006a:26)
Figure 77
Newly referred specimens. PTRM 19207 (right maxilla frag-
ment), 19208 (left maxilla fragment), 19209 (right maxilla frag-
ment), 19346 (frontal fragment), 19358 (left quadrate; Figure
77B–D), 19428 (left dentary fragment), 19474 (right maxilla
fragment; Figure 77A), 19591? (partial left dentary), 19784 (par-
tial osteoderm; Figure 77E).
Description
MAXILLA
This maxilla is associated with Diploglossine MPH on the basis
of anguid morphology, the relatively stout teeth and the strong
oblique ridge (see below).
Description: All specimens are poorly preserved. PTRM 19474
preserves the anterior base of the facial process and five com-
plete tooth spaces (Figure 77A). The first tooth is very short and
seems to have been unicuspid. The second and third are
markedly taller and appear to have borne mesial accessory
cusps. The fifth tooth is not taller than the third, but it is more
robust. The medial surface of the facial process (fa.pr.) bore a
strong oblique ridge that extends anteroventrally onto the dor-
sal surface of the palatal shelf (pl.sh.).
Comparisons:
The oblique ridge on the medial surface of the
facial process is highly reduced in Gerrhonotinae and does not
cross the palatal shelf, unlike in Diploglossinae. For this reason,
the maxillary specimens are associated with Diploglossine MPH
rather than Gerrhonotine MPH.
QUADRATE
A single quadrate is associated here on the basis of anguid mor-
phology, size, relative abundance (of other specimens) and the
occurrence of a diploglossine apomorphy.
Description: A detailed description is best presented when
more detailed comparisons can be made. The element,
PTRM 19358, is nearly complete (Figure 77B–D). The pos-
terior crest (po.cr.) is accompanied by a strong, deeply con-
cave lateral concha whose lateral edge forms the tympanic
crest (ty.cr.) and a weak medial crest (me.cr.). Near the ven-
tral end of the medial crest, which does not reach the ven-
tral end of the bone, is a small, broken medial expansion
(Figure 77B, D). The ventral condyle (ve.con.) is weakly sad-
dle-shaped. The posterior crest is strongly concave and ter-
minates dorsally in the flattened cephalic condyle (ce.con.).
The dorsal surface of this condyle curves anterolaterally. It
is not confined to a narrow strip that follows the tympanic
crest, but rather has a strong anteroventral expansion, form-
ing a tuberosity on the anterodorsal margin of the bone,
medial to the dorsal end of the tympanic crest (Figure 77D).
The medial half of the anterior surface of the bone forms a
Late Eocene Lizards of the Medicine Pole Hills • Smith
93
Figure 76. Dorsal vertebra (PTRM 19129) of Annielline MPH. A, Dorsal view. B, Right lateral view. C, Ventral
view. Abbreviations: con., condyle; cot., cotyle; n.sp., neural spine; poz., postzygapophysis; prz., prezygapophysis;
syn., synapophysis.
strong vertical concavity opposite the posterior crest (Figure
77D).
Comparisons: The anteroventral expansion of the distinct dor-
sal margin of the bone onto the anterodorsal surface was
observed only in anguids of the clade Diploglossinae. Structural
homologies in Xenosaurus and Shinisaurus are not in all cases
immediately clear, but in neither taxon does such a strong
expansion occur. Although present comparative material is
insufficient to draw conclusions, this bone offers perhaps the
greatest promise yet for determining the precise phylogenetic
relations of mid-latitude Eocene relatives of Diploglossinae.
OSTEODERMS
Several osteoderms of this species were identified. They are asso-
ciated on the basis of diploglossine morphology and size.
Description: The few osteoderms known are thin and delicate
(Figure 77E). They grow broader posteriorly. The gliding sur-
face shows a distinct posterior projection. The surface sculpture
is abraded and all that remains is a grid of foramina.
Comparisons:
The posterior projection of the gliding surface is
a unique apomorphy of Diploglossine among living anguids
(Strahm and Schwartz 1977; Gauthier 1982). How early along
the stem it arose is uncertain.
Remarks
The new specimens confirm Smith’s (2006a) identification of a
(stem) diploglossine in the Medicine Pole Hills assemblage. The
quadrate may provide the best evidence on the relationships of
this species when more comparative material is drawn into con-
sideration.
Gerrhonotine MPH
Figure 78
Referred specimens. PTRM 19025 (partial left dentary), 19206
(right dentary fragment), 19210 (right dentary fragment),
19419 (left dentary fragment), 19473 (nearly complete left den-
tary; Figure 78), 19514 (left dentary fragment), 19592 (partial
left dentary).
Description. PTRM 19473 is a nearly complete but stream-worn
left dentary, and unless otherwise expressed or implied, the
description is based on it. Twenty-four tooth positions are pres-
ent, but most teeth are poorly preserved in detail (Figure 78). In
some specimens teeth with distinct mesial accessory cusps are
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
94
Figure 77. Skeletal elements of Diploglossine MPH. A, Right maxilla fragment (PTRM 19474) in medial view.
B–D, Left quadrate (PTRM 19358) in posterior, lateral and anterior views, respectively. E, Partial osteoderm
(PTRM 19784) in apical (exterior) view. Abbreviations: ce.con., cephalic condyle; fa.pr., facial process; me.cr.,
medial crest; pl.sh., palatal shelf; po.cr., posterior crest; ty.cr., tympanic crest; ve.con., ventral condyle.
present already by the 9th tooth. A weak subdental gutter is
present along much of the tooth row. The supra-Meckelian lip
(sM.l.) grows in height anteriorly at a nearly constant rate, grow-
ing only slightly more rapidly anterior to the splenial facet
(spl.fac.), whose dorsal termination lies beneath the 11th tooth.
The intramandibular septum (im.s.) extends as far posteriorly
as the boundary between teeth 20 and 21. A short facet for the
anterolateral process of the coronoid is present on the pos-
terodorsal margin of the dentary.
Remarks
Smith (2006a) found only one small anguid in the fauna,
Diploglossine MPH-1. The recognition of another small anguid,
Gerrhonotine MPH, makes the assignment of rare additional
cranial material problematic. These specimens are PTRM 19117
and 19346 (frontal fragments). On the basis of size, these pre-
sumably belong either to the gerrhonotine or the diploglossine.
The discovery of Gerrhonotine MPH also calls into question
the assignment of the osteoderm PTRM 5378 (Smith 2006a, fig.
17-2), which lacks the posterior extension of the gliding surface.
A gerrhonotine was expected in the Medicine Pole Hills
local fauna on stratigraphic grounds (Smith 2006a).
Glyptosaurinae
McDowell et Bogert, 1954
Peltosaurus Cope, 1872
cf. Peltosaurus sp. MPH
(after Smith, 2006a)
Figure 79
Newly referred specimens. PTRM 19211 (jaw fragment), 19364
(parietal fragment; Figure 79A, B), 194267 (partial right max-
illa), 19427 (jaw fragment), 19470 (left dermarticular; Figure
79C, D).
Description
PARIETAL
A single parietal is associated here on the basis of size (in com-
bination with advanced ontogenetic stage) and anguid mor-
phology.
Description:
PTRM 19364 is a heavily stream-worn, right antero-
lateral fragment of the parietal. Osteoderms are fused to the dor-
sal surface of the bone (Figure 79A). The osteoderm sculpture is
nearly completely erased. The boundary between the parietal
and interparietal scutes (p.sc. and ip.sc., respectively) is indicated
by a small groove anteriorly; a groove also marks the lateral
boundary of the parietal scute. The parietal foramen is not pre-
served. The small postfrontal facet is seen ventrally (Figure 79B,
pof.fac.). The descensus parietalis (desc.p.) defines a broad lateral
space for the attachment of the adductor musculature.
DERMARTICULAR
A single dermarticular is associated here on the basis of size,
ontogenetic stage and anguimorph morphology.
Description: PTRM 19470 is a heavily stream-worn posterior
fragment of the left dermarticular. The articular surface, formed
of the articular bone, is directed somewhat posteriorly (Figure
79C, ar.). Posterior to its medial half is the foramen chorda tym-
pani (f.c.t.). The retroarticular process (ra.pr.) is long, and its
distal end expands medially. Its dorsal surface is divided into
two depressions by a longitudinal ridge that grows in promi-
nence posteriorly. Medial to this ridge the retroarticular process
is slightly ventrally deflected. The surangular was not fused to
the dermarticular and left a long facet (Figure 79D, sa.fac.) that
extends posteriorly past the articular surface. On the ventral sur-
face is a longitudinal impression that more or less corresponds
to the ridge on the dorsal surface.
Late Eocene Lizards of the Medicine Pole Hills • Smith
95
Figure 78. Nearly complete left dentary (PTRM 19473) of Gerrhonotine MPH in medial view. Abbreviations:
iM.l., infra-Meckelian lip; im.s., intramandibular septum; M.gr., Meckelian groove; mand.f., mandibular fora-
men; sM.l., supra-Meckelian lip; spl.fac., splenial facet.
Remarks
Peltosaurus granulosus is represented by well-preserved speci-
mens (multiple complete skulls and partial skeletons) from the
White River Oligocene (Estes 1983). The species, however, has
not been described in great detail. The material here will be of
interest given its earlier age (Chadronian).
Helodermoides Douglass, 1903
Helodermoides sp. MPH
(after Smith, 2006a:28)
Figure 80
Newly referred specimens. PTRM 19028 (right jugal fragment),
19549 (partial left jugal; Figure 80).
Description. PTRM 19549 is a large partial left jugal. Its lateral
surface is covered by two curvilinear rows of bulbous osteoderms
(Figure 80A). The osteoderms of the dorsal row are relatively
smaller than those of the ventral row. Space for a third row is pres-
ent on the posteroventral margin of the bone, but these osteo-
derms were not co-ossified. On the posteromedial surface of the
temporal ramus (tm.ra.) is a depression, the coronoid recess,
which is pierced by a large foramen well above its base. The sub-
orbital ramus (so.ra.) is characterized medially by a strong, nearly
horizontal ridge projecting over the maxillary facet.
PTRM 19028 is similar to PTRM 19549 but is smaller and
lacks fused osteoderms.
Remarks
The bulbous osteoderms are characteristic of Helodermoides
tuberculatus (Sullivan 1979). Smith (2006a) noted differences
between the parietal bone of Helodermoides in the Medicine
Pole Hills local fauna and well-preserved Chadronian speci-
mens referred to H. tuberculatus, which are distinguished by
closure of the supratemporal fenestra (Sullivan 1979). However,
the parietal is not preserved in the (Chadronian) type material
from Wyoming.
Varanidae Gray, 1827
Saniwa Leidy, 1870
Saniwa edura Smith, 2006a
Newly referred specimens. PTRM 19036 (8 teeth), 19155 (3
teeth), 19339 (3 teeth), 19360 (1 tooth), 19375 (7 teeth), 19437
(18 teeth), 19472 (2 teeth), 19516 (2 teeth), 19545 (2 teeth),
19552 (1 tooth).
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
96
Figure 79. Cranial elements of cf. Peltosaurus sp. MPH. A, B, Right anterolateral fragment of parietal (PTRM
19364) in dorsal and ventral views, respectively. C, D, Left dermarticular fragment (PTRM 19470) in dorsal and
ventral views, respectively. Abbreviations: ar., articular; desc.p., descensus parietalis; f.c.t., foramen chorda tym-
pani; ip.sc., interparietal scute; p.sc., parietal scute; pof.fac., postfrontal facet; ra.pr., retroarticular process; sa.fac.,
surangular facet.
Discussion
Faunal Composition in the Eocene
Smith (2009b; see also Gauthier 1982 and Smith
2006b) provided the first description of an Eocene
lizard fauna from central North America based on
large microvertebrate collections. This fauna
derives from the earliest Eocene of the Bighorn
Basin, in the middle of the Paleocene–Eocene
Thermal Maximum. By comparison with the fauna
described by Estes (1988) from the Golden Valley
Formation of North Dakota, the Castle Gardens
local fauna is substantially more complete. It indi-
cates a major transition from known Paleocene
lizard faunas, which are dominated by anguimorph
lizards of more or less uncertain relationships.
Known immigrant taxa in the Castle Gardens
fauna are the anguid lizard groups Diploglossinae
and Anniellinae, a stem relative of the xantusiid
genus Lepidophyma, an iguanid on the stem of
Corytophaninae, another iguanid related to Poly-
chrotinae* and possibly to Anolis, and a third
iguanid of uncertain affinities (Smith 2009b). Other
immigrants first appearing later in the early Eocene
are the acrodontan iguanian Tinosaurus and a scin-
coid, Scincoideus, of uncertain affinities (Smith
2006b). These immigrants joined a set of holdovers
from the Paleocene, including glyptosaurine
anguids, possible gerrhonotine anguids, the xan-
tusiid Palaeoxantusia, xenosaurids and possibly a
varanoid (Smith 2006b).
Whereas middle Eocene lizards from central
North America are presently unknown, an excel-
lent opportunity for comparison with the early
Eocene is now provided by the late Eocene Med-
icine Pole Hills local fauna. Below is a revised fau-
nal list for the latter fauna, following this work
and Smith (submitted).
Squamata
Iguania
Acrodonta
Agamidae*
Leiolepidinae (?)
Tinosaurus sp. MPH
Iguanidae
Polychrotinae*
Sauropithecoides charisticus
Iguaninae
Queironius praelapsus
Corytophaninae
Orithyia oaklandi
Tuberculacerta pearsoni
Cypressaurus sp. MPH
Scleroglossa
Scincomorpha
Amphisbaenia
Rhineuridae
cf. Rhineura sp. MPH
cf. Spathorhynchus sp. MPH
Xantusiidae
Palaeoxantusia borealis
Anguimorpha
Anguidae
Annielline MPH
Diploglossine MPH
Gerrhonotine MPH
Glyptosaurinae
cf. Peltosaurus sp. MPH
Helodermoides sp. MPH
Varanidae
Saniwa edura
Late Eocene Lizards of the Medicine Pole Hills • Smith
97
Figure 80. Partial left jugal (PTRM 19549) of Helodermoides sp. MPH. A, Lateral view. B, Medial view. Abbre-
viations: so.ra., suborbital ramus; tm.ra., temporal ramus.
Of these species, Annielline MPH and Ger-
rhonotine MPH have not previously been recog-
nized. (The snakes of the Medicine Pole Hills have
yet to be described.) That iguanid diversity is found
to be lower here reflects two shortcomings of Smith
(2006a): (1) an insufficient appreciation of intra-
specific variation in the case of two species
(Orithyia oaklandi, Cypressaurus sp. MPH) and (2)
a lack of understanding of taphonomic processes
in the case of one (Cypressaurus sp. MPH).
One notable similarity between early and late
Eocene faunas is the great numerical (if not taxo-
nomic) abundance of iguanid lizards. Whether
this reflects a real community dominance or
merely taphonomic processes (Gauthier 1982) is
presently unknown.
Perhaps the most surprising aspect of the
Medicine Pole Hills local fauna is its great taxo-
nomic similarity to early Eocene faunas of central
North America. Most of the immigrant taxa of
early Eocene Wyoming—the acrodontan lizard
Tinosaurus, polychrotine and corytophanine
iguanids, annielline and diploglossine anguids—
are still present, and in similar relative abun-
dances. Two early Eocene immigrants are absent
from the Medicine Pole Hills: a relative of Lepi-
dophyma (Smith 2009b) and the scincoid Scin-
coideus (Smith, in press). Lepidophyma exists
today in Mesoamerica and was possibly extir-
pated from the central Rocky Mountain interior
by the late Eocene (if it ever made it as far north
as North Dakota). Alternatively, it is always a rare
taxon where known (Smith 2006b, 2009b) and its
absence in the Medicine Pole Hills may relate to
sample size. Scincoideus, on the other hand, is
very abundant wherever it occurs in the early
Eocene (Smith 2006b, in press), and sample size is
a poor explanation for its absence in the late
Eocene.
With regard to the iguanids, what is most
salient is the phylogenetic progression of known
lineages. Sauropithecoides charisticus is much
closer to the crown of Polychrus than early Eocene
representatives (Smith, in prep.). Early Eocene
stem corytophanines are replaced by representa-
tives of the crown (Orithyia oaklandi). The most
notable difference is the addition of a crown rep-
resentative of Iguaninae, a clade otherwise undoc-
umented in the Eocene.
The only other common early Eocene taxon
not yet known from the Medicine Pole Hills local
fauna is Xenosauridae. The stems of both
Xenosaurus and Shinisaurus are well documented
from the Cretaceous through early Eocene of cen-
tral North America (Gauthier 1982; Gao and Fox
1996; Conrad 2006; Smith 2006b), and the stem of
Xenosaurus is additionally known from the early
Oligocene (Gauthier 1982; Bhullar 2008, 2010).
The absence of stem Shinisaurus could be attrib-
uted to extirpation—the lineage is only known
from eastern Asia today—but the absence of stem
Xenosaurus requires another explanation.
Oxygen isotope values from planktonic
foraminifera have suggested a long decline in
temperature from the early Eocene (see, e.g.,
Zachos et al. 2001) and estimates of mean annual
temperature from fossil floras have also been
thought to reflect decreasing mean annual tem-
peratures and increasing mean annual range of
temperature through the later Eocene (Wolfe
1978, 1992). The overwhelming continuity
between early and late Eocene lizard faunas, how-
ever, is more consistent with the notion that late
Eocene surface temperatures at middle latitudes
were greater than previously recognized (see also
Pearson et al. 2007; Zanazzi et al. 2007; Schouten
et al. 2008; Liu et al. 2009). At the same time, it
must still be borne in mind that some proxy
estimates may show strong seasonal biases at
higher latitudes and thus may not faithfully
reflect mean annual temperatures (Eberle et al.
2010).
Calibration Points
This study was preceded by a less-detailed paper
on the locality (Smith 2006a), based primarily on
dentigerous elements, vertebrae and osteoderms.
Although dentigerous elements alone sufficed to
establish the presence of a member of the Poly-
chrus lineage, the relationships of all other iguanid
species were more or less uncertain. Most were
given only informal appellations; the species
Tuberculacerta pearsoni was suggested to be a
phrynosomatine, but the evidence was not strong.
This new study provides two new calibration
points for the estimation of lineage divergence
times by techniques drawing on genetic data, as
follows:
1. The iguanid clade Corytophaninae is
thought to have diverged from its sister-clade by
the earliest Eocene (Smith 2009b). The Medicine
Pole Hills local fauna shows that the basal
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
98
divergence in Corytophaninae between Basiliscus
and Corytophanes + Laemanctus had occurred by
the late Eocene, at least 35.2 Ma.
2. Thus far, the earliest known (crown) igua-
nine has been the early middle Miocene taxon
Armandisaurus explorator, a relative of the basal
species Dipsosaurus dorsalis (Norell and de
Queiroz 1991). Queironius praelapsus now pushes
back the age of the basal divergence by some 20
million years.
On the other hand, it can now be said with
some confidence that the species Polychrus charis-
ticus Smith, 2006a, conservatively referred to that
genus for want of more precise data, does not rep-
resent the earliest record of the crown of Poly-
chrus, but rather its stem. Thus, I have removed
the species to a separate genus and emphasize that
it should be used only as a calibration point for
the divergence of Polychrus and its sister-lineage
(as done by Noonan and Sites 2010), whatever
that might be (Frost et al. 2001; Schulte et al. 2003;
Conrad and Norell 2007; Conrad et al. 2007; Con-
rad 2008; Smith 2009a). It can also now be stated
with some confidence that the proposed relation-
ship between Tuberculacerta pearsoni and
Phrynosomatinae (Smith 2006a) was in error.
Biogeography
There has been less attention, as Matthew (1939)
noted, to smaller terrestrial poikilotherms,
although these have presumably since at least the
Cretaceous constituted the bulk of poikilotherm
diversity (and, with about 6000 and about 8500
described amphibian and squamate species,
respectively, at least 40% of terrestrial vertebrate
diversity today). Except for rare Lagerstätten,
remains of such animals are more difficult to
obtain (generally quarrying or screen-washing is
required) and recovered isolated elements are dif-
ficult to study. Yet careful attention to a broader
spectrum of their remains—especially non-
dentigerous elements—enhances understanding
of their morphology and so makes detailed sys-
tematic studies possible. Phylogenetic relation-
ships in turn permit an explicit examination of
their historical biogeography, which may differ
from that indicated by present distributions.
Lang’s (1989) careful phylogenetic study of
the iguanid clade Corytophaninae, for instance,
was based exclusively on living species (no fossils
were known, at least securely so, at the time). He
concluded that the clade Laemanctus + Coryto-
phanes had a center of origin in Yucatán, Mexico.
The discovery of mid-latitude early Eocene stem
representatives of Corytophaninae (Smith 2009a,
2009b) is not inconsistent with Lang’s conclusion,
but the apparent phylogenetic progression
observed over the course of the Eocene makes
that conclusion increasingly less tenable, requir-
ing an increasing number of dispersals from
Central America. A definitive refutation of the
hypothesis that Corytophaninae evolved in the
tropics, however, may require the discovery of
several tropical Eocene faunas that lack coryto-
phanines.
As noted in the introduction, paleontologists
have long recognized that species belonging to
tropical groups, including various squamates,
occurred well outside the tropics in the early Pale-
ogene. Smith (2009b) generalized this observation
for squamates by studying a complete earliest
Eocene assemblage (excluding the snakes, whose
relations were not well understood). Many ecolo-
gists, in turn, have recognized that greenhouse
conditions in the early Paleogene—or rather, the
global cooling that began in the Oligocene—may
have influenced the present slope of the latitudi-
nal diversity gradient (e.g., Ricklefs 2004; Wiens
and Donoghue 2004; Mittelbach et al. 2007).
Thus, the past distribution of groups like Coryto-
phaninae has implications for broader questions
in biology.
Smith (2006a) distinguished two biogeographic
models that incorporate the extratropical fossil
occurrence of presently tropical groups: (1) the
restriction or extirpation model, in which no merid-
ional shifts take place and taxa unable to adapt to
deteriorating conditions at middle latitudes simply
go extinct; and (2) the retreat or concentration
model, in which taxa adapted to warm and frost-
free conditions track climate and move toward the
equator. Subsequently, Smith (2009b, fig. 22) elab-
orated on and presented an explicitly phylogenetic
interpretation of these models. Under the first
model, the middle latitudes have fewer species
because diversity there was decimated when climate
deteriorated, and diversification had to begin anew.
Under the second model, the middle latitudes have
fewer species because they lost many of them to the
tropics; that is, diversity became concentrated into
the tropics. Without coeval fossil assemblages from
the geographic tropics, it is difficult to distinguish
Late Eocene Lizards of the Medicine Pole Hills • Smith
99
between these models using paleontological data.
However, Fine and Ree’s (2006) indirect test sup-
ports the second model. Smith (2009b) furthermore
used a stratigraphic sequence of fossil assemblages
at mid-latitude to document biogeographic shifts
coincident with climate change, also providing
some measure of support for the second model. The
search for tropical Paleogene faunas will continue.
Summary
The inclusion of nondentigerous skull elements
has greatly increased phylogenetic resolution for
the iguanian species of the Medicine Pole Hills
local fauna. In addition to providing more phylo-
genetic data on the relationships of the fossil
Polychrus, these elements have enabled the iden-
tification of the iguanid lineages Corytophanes +
Laemanctus and Dipsosaurus (this study) and
perhaps of the acrodontan lineage Leiolepis
(Smith, submitted). Two other small anguid
taxa—an annielline and a gerrhonotine—have
also been identified in this fauna for the first time.
Taken as a whole, the Medicine Pole Hills
local fauna now shows great similarity to early
Eocene lizard faunas with respect to both taxo-
nomic composition and the relative abundance
spectrum.
As previously recognized (Gauthier 1982;
Smith 2006a, 2009b), mid-latitude Eocene lizard
faunas have a largely tropical character. They not
only document the ancient history of many living
tropical lineages but also show that the history of
these lineages was at least partly extratropical in
the early Paleogene. The retreat or restriction of
these lineages to tropical latitudes after the Eocene
may be a contributing factor to the observed pres-
ent diversity differential between tropical and
middle latitudes (Smith 2009b).
Acknowledgments
Anika Vogel (Senckenberg Research Institute) took
all of the comparative photographs and many of
the photographs of fossils, and also put together the
figures; this monograph owes a great debt to her. I
thank Olaf Vogel (Senckenberg Research Institute)
for specimen preparation. I am grateful to G. Köh-
ler and L. Acker (Senckenberg Research Institute),
K. Krysko (University of Florida Museum of Nat-
ural History), S. Rogers (Carnegie Museum), J.
Losos and J. Rosado (Museum of Comparative
Zoology, Harvard), H. Voris and A. Resetar (Field
Museum), D. Frost and D. Kizirian (American
Museum of Natural History), and G. Schneider
and R. Nussbaum (University of Michigan
Museum of Zoology) for generous access to mod-
ern skeletal material. A. Henrici and K. C. Beard
(Carnegie Museum) kindly permitted access to fos-
sil specimens. A. Kihm, G. Knauss, and D. Pearson
provided assistance in the field; D. Pearson and A.
Kihm are wholly responsible for the collection of
this material. I thank C. J. Bell, B.-A. Bhullar, J. A.
Gauthier, W. G. Joyce, A. Kihm, and D. Pearson
for discussion on various aspects of this paper, and
B.-A. Bhullar, R. Etheridge, W. G. Joyce, and D. R.
Prothero for their helpful reviews. Financial sup-
port for this project came from the Texas Memor-
ial Museum of the University of Texas at Austin
and from the Senckenberg Museum.
Received 20 June 2010; revised and accepted 14
September 2010.
Appendix
Many modern osteological specimens were exam-
ined for this study. The list below focuses on
Smith’s (2009a) Clade A, since most (or more) of
the iguanids described here are referable to it. Note
that because the specimens were available at dif-
ferent times, not all characters described in this
work were evaluated in every specimen.
Polychrotinae*
Anisolepis undulatus (MCZ 59274), Anolis acutus (UF 62414),
A. armouri (UF 99504), A. bimaculatus (UF 11683, 24020), A.
biporcatus (YPM HERR 012131, UF 52563), A. brevirostris
(UF 99349, 99616), A. carolinensis (UF 99671, 99750), A.
chlorocyanus (UF 42494, 99949), A. cristatellus (UF 12048), A.
cybotes (UF 99513, 99927), A. distichus (UF 99621), A.
equestris (YPM HERR 011195), A. extremus (UF 15017,
15019), A. garmani (UF 42404, 48915), A. grahami (UF 48997,
99166), A. marmoratus (UF 11712), A. maynardi (UF 21738,
63862), A. lemurinus (UF 99315), A. lineatopus (UF 48996), A.
lividus (UF 11489, 48327), A. olssoni (UF 99681), A. opalinus
(UF 48917), A. ortonii (UF 68183, 68185), A. princeps (SMF
66729), A. pulchellus (UF 99345), A. richardii (UF 144517), A.
ricordii (UF 64820, 99672), A. sagrei (UF 99521), A. scriptus
(UF 99541, 99565), A. smaragdinus (UF 99357, 99381), A.
wattsi (UF 11488, 24019), A. whitemani (UF 99686), Enyalius
iheringii (MCZ 6316), Polychrus acutirostris (SMF 24870), P.
femoralis (FMNH 81405), P. gutturosus (MCZ 46441, UF
49377), P. marmoratus (MCZ 6101a–b, 74149–74153,
131760–131762, 147437, 173135, YPM HERR 013556), P.
Bulletin of the Peabody Museum of Natural History 52(1) • April 2011
100
Late Eocene Lizards of the Medicine Pole Hills • Smith
101
peruvianus (MCZ 18776), Pristidactylus torquatus (YPM
HERR 011031), Urostrophus vautieri (MCZ 84036).
Corytophaninae
Basiliscus basiliscus (UF 99625, 99655), B. galeritus (UF 61491),
B. plumifrons (UF 61951, 71704, 71725), B. vittatus (UF 44905,
61307, 140835, YPM HERR 011031, YPM HERR 011132),
Corytophanes cristatus (UF 69072, YPM HERR 011183), C. her-
nandesii (CM 57586, 57587, UF 72492), C. percarinatus (CM
43644, 43645), Laemanctus longipes (UF 43115, 62082, 66061,
YPM HERR 011183), L. serratus (UMMZ 149101).
Hoplocercinae
Enyalioides heterolepis (MCZ 28384), E. oshaughnessyi (SMF
67590), E. praestabilis (MCZ 163653), Hoplocercus spinosus
(MCZ 20679).
Iguaninae
Amblyrhynchus cristatus (SMF 57458, UF 54782, YPM HERR
012819), Brachylophus fasciatus (SMF 81134, 81156, UF 37578),
Conolophus subcristatus (SMF 11208, UF 11583), Ctenosaura
clarki (UF 61948), C. hemilopha (UF 11477), C. oedirhina (UF
28530), C. pectinata (UF 62493), C. similis (UF 61966, 67982),
Cyclura cornuta (SMF 33229, 72159, UF 99656), C. ricordi (UF
86762), Dipsosaurus dorsalis (CM 40505, 144937, UF 55334,
YPM HERR 011550, 012811), Iguana iguana (SMF 33227,
82536, YPM HERR 010829), Sauromalus hispidus (UF 38333),
S. obesus (CM 37155, 38491, 145003, UF 45624, YPM HERR
011623–011625), S. varius (UF 62313).
Xantusiidae
Xantusia riversiana (CM 56451, 56454, 56457).
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