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New adapiform primate of Old World affinities from the Devil’sGraveyard
Formation of Texas
E. Christopher Kirk
a
,
*
, Blythe A. Williams
b
a
Department of Anthropology, University of Texas at Austin, 1 University Station C3200, Austin, TX 78712, USA
b
Department of Evolutionary Anthropology, Duke University, Box 90383, Durham, NC 27708, USA
article info
Article history:
Received 15 December 2010
Accepted 18 February 2011
Keywords:
Adapidae
Caenopithecinae
Cercamoniinae
Asiadapinae
Notharctinae
Eocene
Uintan
Mescalerolemur
Mahgarita
abstract
Most adapiform primates from North America are members of an endemic radiation of notharctines.
North American notharctines flourished during the Early and early Middle Eocene, with only two genera
persisting into the late Middle Eocene. Here we describe a new genus of adapiform primate from the
Devil’s Graveyard Formation of Texas. Mescalerolemur horneri, gen. et sp. nov., is known only from the late
Middle Eocene (Uintan) Purple Bench locality. Phylogenetic analyses reveal that Mescalerolemur is more
closely related to Eurasian and African adapiforms than to North American notharctines. In this respect,
M. horneri is similar to its sister taxon Mahgarita stevensi from the late Duchesnean of the Devil’s
Graveyard Formation. The presence of both genera in the Big Bend region of Texas after notharctines had
become locally extinct provides further evidence of faunal interchange between North America and East
Asia during the middle Eocene. The fact that Mescalerolemur and Mahgarita are both unknown outside of
Texas also supports prior hypotheses that low-latitude faunal assemblages in North America demon-
strate increased endemism by the late middle Eocene.
Ó2011 Elsevier Ltd. All rights reserved.
Introduction
The evolution of adapiform primates in North America has been
particularly well studied at Wasatchian (early Eocene) and Bridge-
rian (early middle Eocene) localities in the western interior of the
United States (Matthew, 1915; Gazin, 1958; Gingerich and Simons,
1977; Gingerich, 1979, 1995; Covert, 1985; Krishtalka et al., 1990;
Gunnell, 1995, 2002; O’Leary, 1996). The earliest adapiform species
known from North America, the notharctine Cantius torresi, appears
at the beginning of the Wasatchian during the carbon isotope
excursion that marks the PaleoceneeEocene boundary (Gingerich,
2003). C. torresi is almost certainly an immigrant from Eurasia, due
to its abrupt appearance in the North American fossil record and the
presence of two additional species of Cantius in Europe (Cantius eppsi
and Cantius savagei)(Gingerich, 1986, 2003; Godinot, 1998; Beard
and Dawson, 1999; Bowen et al., 2002). Furthermore, Cantius is
probably ancestral to all subsequent North American notharctine
genera (Copelemur,Hesperolemur,Notharctus,Pelycodus, and Smilo-
dectes)(Gingerich and Simons, 1977; Gingerich, 1986; Godinot,
1998). The diversification of notharctines in North America
primarily occurredin the Wasatchian, and most genera do not persist
beyond the Bridgerian. Indeed, Hesperolemur and Notharctus are the
only notharctine genera currently known from the Uintan (late
middle Eocene) of North America (Gunnell, 1995; Godinot, 1998;
Robinson et al., 2004).
Much less is known about adapiform evolution in southwest
Texas, where numerous Eocene vertebrate localities have been
discovered in the Big Bend region, the Sierra Vieja, and the Gulf
Coastal Plain (Wilson,1986; Runkel,1988; Westgate, 1990; Robinson
et al., 2004; Williams and Kirk, 2008). In the Devil’sGraveyard
Formation of the Big Bend region (Stevens et al., 1984; Wilson,1986),
notharctine adapiforms are represented by a single genus
(Notharctus) known locally only from early Uintan (Ui1) localities at
the base of the stratigraphic section (West, 1982; Williams and Kirk,
2008). Despite intensive collecting at late Uintan (Ui3) localities in
the Devil’s Graveyard Formation since 2005, notharctines have not
been recovered from higher in the stratigraphic column and are
presumed to have become locally extinct after the early Uintan.
Nonetheless, adapiforms were again present in the Devil’sGraveyard
Formation by the early Duchesnean, as documented by the appear-
ance of the adapiform Mahgarita stevensi (Wilson and Szalay, 1976;
Wilson, 1986; Williams and Kirk, 2008).
M. stevensi is of particular significance to understanding Eocene
holarctic primate evolution because for many years it has remained
the only adapiform known from North America that is not
a notharctine (Wilson and Szalay, 1976; Godinot, 1998). Mahgarita
*Corresponding author.
E-mail addresses: eckirk@mail.utexas.edu (E.C. Kirk), blythe.williams@duke.edu
(B.A. Williams).
Contents lists available at ScienceDirect
Journal of Human Evolution
journal homepage: www.elsevier.com/locate/jhevol
0047-2484/$ esee front matter Ó2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jhevol.2011.02.014
Journal of Human Evolution 61 (2011) 156e168
Author's personal copy
was initially described on the basis of a crushed cranium and
mandible recovered in 1973 from the early Duchesnean Teepee
Canyon locality of the Devil’s Graveyard Formation (Wilson and
Szalay, 1976). Since that time, two additional specimens of Mah-
garita have been recovered from the early Duchesnean of the
Devil’s Graveyard Formation ea second crushed cranium and
a partial basicranium (Rasmussen, 1990). Additionally, Westgate
et al. (2010) have reported the presence of Mahgarita at the late
Uintan Lake Casa Blanca locality near Laredo on the basis of an
isolated upper molar.
1
Most cladistic analyses have supported the
hypothesis that Mahgarita is an immigrant from the Old World that
is most closely related to Eurasian or African adapiforms (Kay et al.,
1997; Ross et al., 1998; Seiffert et al., 2009, 2010; Boyer et al., 2010;
but see Rasmussen, 1990).
Here we report the discovery of a new Texas adapiform with Old
World phylogenetic affinities, Mescalerolemur horneri. This new
genus and species is known only from the Purple Bench locality of
the Devil’s Graveyard Formation (Wilson, 1986; Williams and Kirk,
2008). The vertebrate fauna from Purple Bench is late Uintan,
dating either to Chrons C20R or C18R with an absolute age of
approximately 44e41 Ma (Williams and Kirk, 2008). In the Devil’s
Graveyard Formation, the Purple Bench locality underlies the early
Duchesnean localities that have produced the only definitive
specimens of M. stevensi (Wilson, 1986; Williams and Kirk, 2008).
Mescalerolemur shares a number of derived dental features with
Mahgarita, and is only the second non-notharctine adapiform
genus to be described from North America. Mescalerolemur thus
provides additional evidence of faunal exchange between Eurasia
and North America in the Middle Eocene, and reinforces the
conclusion that primate faunas from Texas displayed increased
endemism by the late Uintan (Simpson, 1947; Black and Dawson,
1966; Beard and Wang, 1991; Beard et al., 1994; Williams and
Kirk, 2008).
Materials and methods
The fossils of Mescalerolemur and Mahgarita described here are
housed in the collections of the Texas Memorial Museum at the
University of Texas (Austin, Texas, United States). The comparisons
made in this paper are based primarily on the study of epoxy resin
casts of fossils from other localities. Additionally, published scanning
electron micrographs, photographs, and drawings were used to
supplement our comparisons (Simons, 1962,1997; Russell et al., 1967;
Szalay,1971,1974;Gingerich,1975,1977; Gingerich andSahni,1979,
1984; Szalay and Delson, 1979; Schwartz and Tattersall,1983; Russell
and Gingerich, 1987; Godinot, 1988, 1998; Thalmann et al., 1989;
Hartenberger and Marandat, 1992; Thalmann, 1994; Ducrocq et al.,
1995; Qi and Beard, 1998; Gebo, 2002; Franzen, 2004; Beard et al.,
2007; Rose et al., 2007, 2009; Chaimanee et al., 2008; Gunnell et al.,
2008; Franzen et al., 2009; Seiffert et al., 2009; Marigó et al., 2010).
All observations of dental anatomy are our own and are readily
observable in casts or published figures unless otherwise noted.Dental
measurements (Table 1) were made using either digital calipers or
a stereomicroscope fitted with a calibrated reticle.
Abbreviations: BNM ¼Basel Natural History Museum;
MNM ¼Mainz Natural History Museum; TMM ¼Texas Memorial
Museum; c ¼mandibular canine; p ¼mandibular premolar;
m¼mandibular molar; C ¼maxillary canine; P ¼maxillary
premolar; M ¼maxillary molar.
Systematic paleontology
Order Primates Linnaeus, 1758
Semiorder Strepsirrhini Pocock, 1918
Suborder Adapiformes Hoffstetter, 1977
Mescalerolemur, gen. nov.
Type species: M. horneri, sp. nov.
Generic diagnosis
Adapiform primate that differs from omomyiforms in having
a very small m1 paraconid and in lacking an m1 trigonid basin.
Differs from notharctines
2
in having a cingular hypocone on upper
molars. Differs from sivaladapids in having a diminutive m1
hypoconulid that is not twinned with the entoconid. Differs from all
other adapiforms except Mahgarita in having a simple p4 with the
following characteristics: occlusal profile oval and buccolingually
compressed; lacks talonid basin; lacks paraconid, metaconid,
entoconid, and hypoconulid; hypoconid located directly distal to
protoconid
3
; hypoconid connected to protoconid by a centrally
placed (midline) cristid obliqua. Further differs from other adapi-
forms except Mahgarita in having a P3 with a lingual root located
directly lingual to the distobuccal root, a flat mesiolingual crown
face that is oriented strongly obliquely relative to the buccolingual
axis, and an occlusal profile that approximates a right triangle.
Differs from notharctines, adapines, sivaladapids, asiadapines,
Donrussellia,Anchomomys,
4
Periconodon,Pronycticebus,Djebele-
mur,
5
Afradapis,Aframonius, and most species of Protoadapis and
Europolemur in having extremely reduced, single-rooted p2/P2
located mesiolingual to the mesial root of p3/P3. Differs from
adapines, notharctines, Donrussellia,Protoadapis,
6
Pronycticebus,
Marcgodinotius,Anchomomys,
7
and Periconodon
8
in lacking a p1/P1.
Differs from Adapoides in having buccolingually broader lower
molars, in having an m3 with a shorter mesial shelf, a broader less
heel-like hypoconulid, and a smaller more crestiform entoconid,
and in having upper molars with broader lingual and distal cingula
and a larger hypocone. Differs from Barnesia in having a more
mesially positioned P4 protocone, in having larger hypocones and
a broader distal cingulum on M1e2, and in having a smaller M2
pericone. Differs from Buxella in having larger M1e2 hypocones
and metaconules, in having complete lingual cingula on M1e3, in
lacking an M3 pericone, and in having a shorter, less shelf-like m1
paracristid. Differs from Mahgarita in being substantially smaller
and in exhibiting the following dento-gnathic features: mandibular
symphysis unfused; maxilla with a less prominent rugosity for the
1
Having examined this specimen, we agree with Westgate et al. (2010) that his
molar is clearly that of an adapiform similar to M. stevensi. However, the Lake Casa
Blanca specimen differs from definitive M. stevensi from the Devil’s Graveyard
Formation in a number of key dental features (e.g., it has a reduced stylar region)
and thus probably represents a new, more primitive species of Mahgarita.
2
The adapiform families and subfamilies used here follow Godinot (1998) and
Rose et al. (2009).
3
Details of the hypoconid and cristid obliqua are obscured by wear in the only
known p4 of Mahgarita (TMM 41578-8).
4
Following Godinot (1998) and Gebo (2002), we herein treat Hürzeleris (Szalay,
1974) and Fendantia þLaurasia (Schwartz and Tattersall, 1983) as junior synonyms
of Anchomomys. Furthermore, Seiffert et al. (2005a) have shown that “Anchomomys”
milleri (Simons, 1997) is not closely related to definitive European members of the
genus Anchomomys. The type specimen of “Anchomomys”milleri lacks a p1 but
retains a large p2 (Simons, 1997). Assessments of p2/P2 size in definitive
Anchomomys are based on alveolus size.
5
We follow the interpretation of Hartenberger and Marandat (1992) based on
alveolar morphology that Djebelemur probably lacked a p1 but retained a two-
rooted p2.
6
In Protoadapis curvicuspidens and P. angustidens, p1 is variably present or absent
(Russell et al., 1967).
7
Preserved alveoli strongly suggest that Anchomomys retained a p1 (e.g.,
A. pygmaeus; BNM Eh 748) and P1 (e.g., A. quercyi; BMN QH 470).
8
This assessment is based on the presence of a p1 alveolus in MNM PW-1995/
8-LS (Franzen, 2004).
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168 157
Author's personal copy
anterior masseter on the zygomatic process and lacking a well-
developed fossa supero-lateral to M2; p4 lacking a continuous
lingual cingulid and lacking a lateral protocristid; m3 with a more
lingually positioned hypoconulid, a cristid obliqua that meets the
protoconid more buccally, and a paracristid that meets the pre-
metacristid to form a complete mesial crest connecting the proto-
conid and metaconid; P3 lacking a distinct protocone and having
a smaller distolingual basin with a deeper invagination of the distal
margin; P4 with a more waisted and trapezoidal occlusal profile,
a mesiodistally narrower lingual half, lacking a lingual cingulum,
with a protocone situated more mesially than the paracone, and
with a trenchant and elevated preprotocrista; M1e2 with a less
rectangular and more trapezoidal occlusal profile, a narrower stylar
region, and lacking mesostyles; M1e3 lacking enamel crenulation;
M3 buccolingually narrower than M1 and lacking a hypocone. Also
lacks the “twinned”M2 hypocone and accessory cuspules in the
M1eM2trigon basins that are variably found in Mahgarita (see
below).
Etymology
The generic name derives from the Mescalero Apache, in
combination with lemur to acknowledge the strepsirrhine
affinities of adapiform primates. The Mescalero Apache are
a Southern Athabaskan Native American group who occupied the
Big Bend region of Texas and adjacent lands in the 18th and 19th
centuries.
Mescalolemur horneri, sp. nov. (Figs. 1e5,Table 1)
Holotype
TMM 41672-232, associated left and right maxillae with partial
left P3-P4 crowns, complete left M1-M3, right C root, complete
right P2-M1, and partial right M2 crown.
Hypodigm
TMM 41672-230, right mandibular fragment with complete m3;
TMM 41672-233, right partial mandible with partial c alveolus,
complete p2 alveolus, and complete p3em1;TMM 41672-236, right
mandibular fragment with complete p4em1.
Horizon
Locality TMM 41672 (Purple Bench) of the Devil’sGraveyard
Formation, Midwestern State University Dalquest Research Site,
Brewster County, Texas.
Specific diagnosis
As for genus.
Etymology
In honor of Dr. Norman Horner, Entomologist and Professor of
Biology at Midwestern State University, for the many years he has
spent undertaking and facilitating scientific research in the Big
Bend region of Texas.
Description
Mescalolemur horneri is a relatively small adapiform primate,
with teeth broadly similar in size to those of Cantius torresi from the
early Eocene of North America and Cantius eppsi from the early
Eocene of Europe. The areas of the maxillary and mandibular first
molars of Mescalerolemur are approximately 63% of the size of those
in the related genus Mahgarita (Table 1). Using Conroy’s (1987) all-
primate regression for m1 area, the body mass of Mescalerolemur is
estimated to be 371 g (range: 136e1013 g). Although most known
adapiform species are estimated to have been considerably larger
than 371 g (Fleagle, 1999), several taxa (notably Donrussellia,
Anchomomys,Periconodon,Marcgodinotius, and Panobius)were
clearly smaller than Mescalerolemur based on dental dimensions
(Szalay and Delson, 1979; Godinot, 1988, 1998, Franzen, 2004;
Gunnell et al., 2008; Rose et al., 2009).
Corpus depth relative to crown height cannot be assessed in any
of the three known mandibular specimens due to damage of the
inferior margin of the corpus. Nonetheless, it is clear that corpus
depth was more than twice that of m1 crown height (Fig. 2). The
number of mental foramina on the external surface of the
mandibular corpus is variable. TMM 41672-233 has two oval
mental foramina: one larger foramen inferior to the lamina of bone
separating the canine and p2 alveoli, and one smaller foramen
inferior to the distal root of p3. By comparison, TMM 41672-236
exhibits only a single oval foramen inferior tothe position of the p2
Table 1
Dental dimensions of all known specimens of Mescalerolemur horneri and Mahgarita stevensi.* ¼measurement based on root or alveolus; ** ¼estimated from damaged tooth.
Upper dentition
Taxon Catalogue
number
C
Length
C
Width
P2
Length
P2
Width
P3
Length
P3
Width
P4
Length
P4
Width
M1
Length
M1
Width
M2
Length
M2
Width
M3
Length
M3
Width
Mescalerolemur
horneri
41672-232
(holotype)
3.23* 2.37* 0.78* 0.68* 2.93 2.50 2.64 3.30 3.13 3.80 3.13 4.10 2.45 3.35
Mahgarita stevensi 41578-9
(holotype)
3.62 2.26 0.98 0.86 3.23 3.10 2.74 3.74 3.62 4.40 3.62 4.89** 3.03 4.41
Mahgarita stevensi 41578-20 4.32 3.15 3.13 3.06 2.84 3.96 3.82 4.96 3.62 5.31 3.23 4.89
Lower dentition
Taxon Catalogue
number
c
Length
c
Width
p2
Length
p2
Width
p3
Length
p3
Width
p4
Length
p4
Width
m1
Length
m1
Width
m2
Length
m2
Width
m3
Length
m3
Width
Mescalerolemur
horneri
41672-230 3.42 2.05
Mescalerolemur
horneri
41672-233 2.15* 0.80* 1.20* 3.13 1.96 3.03 1.96 3.23 2.25
Mescalerolemur
horneri
41672-236 3.13 1.86 2.93 2.05
Mahgarita stevensi 41578-8 2.93 1.96 1.20* 1.10* 3.23 1.86 3.33 2.11 3.67 2.53 3.67 2.65 4.21 2.40
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168158
Author's personal copy
(which is not preserved). TMM 41672-233 preserves two additional
features worthy of comment. First, a portion of the inferior
mandibular symphysis is preserved in the specimen, revealing that
the reciprocal symphyseal surfaces in the left and right dentaries
were rugose but not fused (Fig. 2). There is no evidence of a superior
transverse torus at the symphysis, but the presence or absence of
this feature is difficult to ascertain with certainty because the
inferior margin of the symphyseal region is not preserved. Second,
there is a slight depression of the external surface of the mandib-
ular corpus lateral to the canine and p2 alveoli and superior to the
larger mental foramen. The fossa would presumably have accom-
modated a projecting maxillary canine. The presence of such
a canine fossa, combined with the large size of the lower canine
alveolus, suggests that both the maxillary and mandibular canines
were relatively large in Mescalerolemur.
Incisors have not been recovered for Mescalerolemur.The
mandibularcanine and p2 of Mescalerolemur are also not preserved in
the four knownspecimens, but the alveoli for both teeth are present
in TMM 41672-233 (Figs.1 and 2). The partial canine alveolus is oval in
horizontal cross-section, with its long axis oriented w40 degrees
from the plane of the mandibular symphysis. The canine alveolus is
also relatively large and deep, extending at its base to within a milli-
meter of the surface of the mandibular symphysis. Judging from the
size of the alveolus, the root of the mandibular canine was evidently
larger at the level of the alveolar process than the roots of any other
preserved teeth in this specimen. By comparison, the p2 alveolus is
much smaller thanthe adjacent alveoli for the canine and the p3. The
p2 alveolus is elliptical in horizontal cross-section, mesiodistally
compressed, and is located mesiolingual to the mesial root of the p3.
Figure 2. Lingual view of partial mandible with p3-m1 (TMM 41672-233) of Mesca-
lerolemur horneri. Scale bar equals 2 mm.
Figure 1. Occlusal views of partial palate (TMM 41672-232 holotype, at left in two parts) and mandible (TMM 41672-233) of Mescalerolemur horneri. TMM 41672-232 includes the
right C root, right P2-M1, right partial M2, and left P3-M3. TMM 41672-233 includes the c and p2 alveoli and p3-m1. The two specimens are not shown at the same scale. Scale bars
for both specimens equal 2 mm.
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168 159
Author's personal copy
There is no evidencefor diastemata between the canine and p2, or the
p2 and p3. The p2 of Mescalerolemur was evidently a diminutive
single-rooted tooth that was lingually displaced and closely
appressed between the much larger canine and p3.
The p3 of Mescalerolemur is a simple tooth dominated by a large
protoconid (Figs. 2 and 3). It is oval in occlusal profile and bucco-
lingually compressed. The p3 has two roots and the mesial root is
displaced buccally. As a result, the mesiodistal (long) axis of the p3
crown is oriented obliquely relative to the mesiodistal axis of the
mandibular corpus. The p3 crown lacks any trace of a paraconid,
metaconid, entoconid, or hypoconulid. The only p3 cusp other than
the protoconid is a tiny hypoconid, located distobuccally on a very
short talonid shelf. Weakly developed crests (the paracristid and
protocristid) run directly mesially and distally from the apex of the
protoconid. Buccal and lingual cingulids are present but weakly
developed.
The p4 of Mescalerolemur is a simple but distinctive pre-
molariform tooth (Figs. 2 and 3). Like the p3, the p4 is oval in
occlusal profile, buccolingually compressed, has weakly developed
Figure 4. Occlusal view of the maxillary premolars (P2eP4) of Mescalerolemur horneri
(top row) and Mahgarita stevensi (bottom row). Top row: TMM 41672-232 (holotype,
right side); Bottom row: TMM 41578-9 (holotype, right side). Scale bar equals 1 mm.
Figure 5. Occlusal view of the maxillary molars (M1eM3) of Mescalerolemur horneri
(top row) and Mahgarita stevensi (bottom row). Top row: TMM 41672-232 (holotype,
left side reversed); Bottom row: TMM 41578-20 (right side). Scale bar equals 1 mm.
Figure 3. Occlusal view of the mandibular dentitions of Mescalerolemur horneri (top two rows) and Mahgarita stevensi (bottom row). Top row: TMM 41672-236 (p4em1); Middle
row: TMM 41672-233 (p3em1) and TMM 41672-230 (m3); Bottom row: TMM 41578-8(p3em3); Scale bar equals 1 mm.
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168160
Author's personal copy
buccal and lingual cingulids, and lacks any evidence of a paraconid,
metaconid, entoconid, or hypoconulid. The p4 crown thus retains
only two cusps: a tall protoconid and a smaller hypoconid. These
two cusps are located along the central mesiodistal axis of the p4
and are connected by a centrally positioned cristid obliqua that
runs to the apices of both cusps. The p4 protoconid is slightly
shorter than the p3 protoconid, but slightly taller than the m1
protoconid. A weakly developed paracristid runs directly mesially
from the apex of the p4 protoconid. The sizes of the p4 hypoconid
and cristid obliqua are variable. In TMM 41672-233, the hypoconid
is diminutive and does not stand out above the cristid obliqua. In
TMM 41672-236, the hypoconid is cuspate and taller than in TMM
41672-233, and the cristid obliqua is more trenchant. In TMM
41672-236 there is also a shallow cleft between the hypoconid and
distolingual cingulid that is not present in TMM 41672-233.
However, both specimens lack any significant basin in the talonid
region. As a result, the p4 talonid of Mescalerolemur consists of
a centrally placed wedge formed by the hypoconid and cristid
obliqua. During Phase I of occlusion, this wedge would have
sheared against the trenchant preprotocrista of the P4 (see below).
The m1 trigonid has two principal cusps: a protoconid and
a slightly shorter metaconid (Figs. 2 and 3). The metaconid is
located distolingual to the protoconid. The paraconid is tiny and
located in the midline at the most mesial point of the m1 crown,
mesiolingual to the protoconid. The paracristid is weakly developed
and the trigonid is completely open mesiolingually. There is no
basin in the trigonid region. The m1 trigonid is only moderately
taller than the talonid. The m1 talonid also has two principal cusps:
a hypoconid and a slightly shorter entoconid. The preentocristid
and postmetacristid are moderately well developed, so that the
talonid basin is lingually enclosed. The hypoconulid is very small
and slightly buccal to the midline of the m1. The medial and lateral
postcristids slope down toward the midline of the tooth and are
oriented roughly buccolingually. The m1 hypoflexid is deep,
reaching nearly to the midline of the tooth. The medial and lateral
protocristids are weakly developed, and the postvallid is deeply
notched where they meet. The m1 cristid obliqua runs mesiolin-
gually from the hypoconid to meet the base of the postvallid dis-
tolingual to the protoconid. There the cristid obliqua turns lingually
to run up to the apex of the metaconid. The m1 enamel surface is
smooth, and buccal and lingual cingulids are absent.
The m2 of Mescalerolemur is unknown. The m3 trigonid has
a protoconid and metaconid of approximately equal height, and
lacks any trace of a paraconid (Fig. 3). The metaconid is distolingual
to the protoconid. The paracristid runs mesially from the apex of the
protoconid for a short distance, and then turns to run lingually.
Similarly, the premetacristid runs mesially from the apex of the
metaconid for a short distance, and then turns buccally to meet the
paracristid. Accordingly,the paracristid and premetacristid together
form a short, low shelf on the mesial face of the m3 that is unbroken
except for a shallow cleft where the two crests meet. These two
crests thus enclose a narrow and shallow trigonid basin that is
approximately twice the height of the talonid basin. The postvallid is
tall, flat, and only slightly notched at the junction of the medial and
lateral protocristids. The m3 talonid basin is broad with slightly
crenulated enamel. The hypoconid and hypoconulidare large, broad
and approximately equal in height, while the entoconid is small and
crestiform. The m3 hypoflexid is very shallow, and the cristid obli-
qua runs mesially from the hypoconid to the apex of the protoconid.
The hypoconulid is located far lingual to the midline of the m3, and is
separated from the hypoconid by a notch in the lateral postcristid.
The medial postcristid, entoconid, preentocristid, and post-
metacristid form an unbroken crest that runs mesiodistally along
the lingual margin of the talonid, so that the talonid basin is fully
enclosed lingually.
The upper dentition of Mescalerolemur is known only from the
type specimen (TMM 41672-232; Figs. 1, 4 and 5). The upper inci-
sors are not preserved, and the upper canines are represented only
by a root that retains a fragment of the dentine from the distal
margin of the right canine crown. The canine root is oval in cross-
section, with its long axis oriented mesiodistally. The canine root
extends superiorly to more than twice the height of the adjacent
premolar and molar roots. Based on the preserved anatomy, it is
clear that the canine crown of this specimen would have been quite
large, projecting well beyond the postcanine occlusal plane and
extending presumably to the region of the shallow canine fossa
infero-lateral to p2.
The P2 is a tiny, peg-shaped single-rooted tooth located
mesiolingual to the mesiobuccal root of P3 (Figs. 1 and 4). The P2 is
located immediately adjacent to the P3 crown, but is separated
from the top of the canine root by a small gap (w1mm). Although
the tip of the P2 crown is damaged, it is clear that P2 did notextend
to the level of the occlusal plane formed by the much larger P3eM3.
Nonetheless, it appears that the P2 crown would have contacted the
mesial edge of the tall p3 protoconid at centric occlusion.
The P3 of Mescalerolemur is a very distinctive tooth with three
roots (Figs. 1 and 4). The lingual root of P3 is displaced so far distally
that it is situated directly lingual to the distobuccal root. As a result,
the flat mesial face of the P3 crown is oriented strongly obliquely
rather than buccolingually. The occlusal profile of the P3 crown
thus approximates a right triangle, with the oblique mesiolingual
crown face forming the hypotenuse. Furthermore, between the
lingual and distobuccal roots, the distal margin of the P3 crown is
incised by a marked flexus. The P3 crown is dominated by a single
large cusp ethe paracone. It is not possible to assess the presence
or absence of a P3 parastyle due to damage, but the postparacrista is
well developed. A buccal cingulum is present but weakly devel-
oped. There is no distinct P3 protocone. In its place, there is
a shallow basin situated over the lingual root of the P3. Because of
the distal position of the lingual P3 root and the existence of a distal
flexus, the P3 crown has a small, circumscribed basin projecting
distolingual to the large paracone. This distolingual P3 basin
evidently contacted the large p4 protoconid during centric occlu-
sion. Running along the mesiolingual margin of the P3 crown is
a low crest that is presumably homologous with the preprotocrista.
However, due to the unusual configuration of this tooth, this crest
effectively forms a tall mesiolingual cingulum along the base of the
paracone.
The P4 is less derived than the P3 and exhibits a more typical
premolariform morphology (Figs. 1 and 4). In its occlusal profile,
the P4 crown is moderately waisted and has a more trapezoidal
shape than the P3. The P4 has three roots, and the lingual root is
located directly lingual to the paracone. The paracone is large and
centrally placed on the mesiodistal axis of the crown’s buccal half.
Although the details are partly obscured by damage, the paracone is
flanked by well developed pre- and postparacristae, a large para-
style, and a complete buccal cingulum. The paraconule is very small
and poorly developed. The protocone is distinct and cuspate but
shorter than the large paracone. The protocone is located mesial to
the buccolingual axis of the P4 crown, and is thus situated more
mesially than the paracone. Running mesiobuccally from the pro-
tocone is a tall and trenchant preparacrista that forms the mesio-
lingual margin of the P4 crown. This crest and the P4 protocone
appear to have occluded with the trenchant complex formed by the
cristid obliqua and hypoconid of p4. The holotype palate exhibits
a slight left/right asymmetry in the anatomy of the postprotocrista.
In both the left and right P4 crowns, the postprotocrista is lower
and less trenchant than the preprotocrista. In the left P4, the
postprotocrista meets the base of the protocone, where it forms
aflexure. However, in the right P4, a small fovea is present at the
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168 161
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juncture of the postprotocrista and protocone. In both P4s, this site
where the postprotocrista meets the base of the protocone would
have accommodated the tiny m1 paraconid at centric occlusion.
The M1 of Mescalerolemur has a tall paracone and metacone of
similar height (Figs. 1 and 5). The parastyle and metastyle are small.
The buccal cingulum is continuous but narrow and weakly devel-
oped. There is a shallow M1 ectoflexus, and there is no evidence of
a mesostyle. The trigon basin is deep and cone-shaped, reaching its
greatest depth at a single point. Although the trigon basin is fully
enclosed by crests on all sides, the postparacrista and premetacrista
meet at an acute angle and deeply incise thebuccal side of the basin
at the midpoint between the paracone and metacone. Although not
as tall as the paracone and metacone, the protocone is a large cusp
with well developed pre- and postprotocristae. The preprotocrista
ends at the parastyle, while the terminus of the postprotocrista is at
the base of the metacone. The paraconule is large and cuspate, and is
located along the preprotocrista at the midpoint between the pro-
tocone and parastyle. The paraconule is also situated centrally at the
mesial margin of the M1, and is thus more mesially positioned than
the paracone. The metaconule is slightly smallerand more crestiform
than the paraconule. The metaconule is located along the post-
protocrista near its terminus lingual to the metacone. The M1
hypocone is cingular, distolingual to the protocone, and about half
the height of the protocone.The hypocone is connected to the base of
the protocone bya short but well-developed prehypoconecrista that
runs mesiodistally. Mesiolingual and distal cingula are very
pronounced on the M1. The mesiolingual cingulum runs from the
base of the paraconule to the hypocone. It is narrow mesially, and
broad lingually. The distal cingulum, between the hypocone and
metastyle, is particularly broad and encloses a shallow basin distal to
the postprotocrista and metaconule. Although there is a slight
swelling of the cingulum lingual to the protocone and a very small
crest running a short distance up the base of the protocone from this
swelling, there is no distinct pericone.
The M2 is slightly buccolingually broader than M1, but is very
similar in its overall occlusal morphology (Figs. 1 and 5). Differences
that distinguish the M2 from the M1 are as follows: The paracone is
slightly taller than the metacone; the paraconule is larger; the
parastyle and metastyle are less well developed; the distal
cingulum is narrower; the prehypocone crista is taller, arcuate, and
meets the postprotocrista rather than the base of the protocone. In
addition to these differences, M2 also has a tiny but distinct peri-
cone located on the lingual cingulum directly lingual to the
protocone.
The single left M3 of the Mescalerolemur holotype is cracked and
missing the base of the paracone, but many details of its
morphology are preserved (Figs. 1 and 5). The M3 has three roots,
the tips of which are exposed on the infero-lateral floor of the orbit.
The M3 crown is smaller in area and has a more triangular occlusal
profile than the M1e2 crowns. Also unlike M1e2, the buccal face of
the M3 crown is oriented oblique to the mesiodistal axis of the
tooth row. The M3 paracone is substantially taller than the meta-
cone, which in turn is substantially taller than the protocone.
A hypocone, pericone, and distinct parastyles and metastyles are all
absent. The trigon basin of M3 is shallower than in M1e2, but still
reaches its greatest depth at a single point rather than being
smoothly curved across its floor. The pre- and postprotocristae of
the M3 are shorter and less trenchant than those of M1e2. Lingual
and distal cingula are present and continuous, but they are narrow
and poorly developed. A tiny metaconule is present on the post-
protocrista near its terminus at the base of the metacone. The
presence or absence of a paraconule and buccal cingulum cannot be
assessed due to damage.
Several features of the cranial anatomy of Mescalerolemur are
preserved in the type specimen, which includes a partial left
maxilla and a fragment of the left palatine (Fig. 1). The palatine
bone is separated from the maxilla by a suture running obliquely in
the narrow trough (w1.5 mm wide) between the M3 and the
pyramidal process of the palatine. The pyramidal process is well
developed and projects approximately 1 mm inferior to the level of
the hard palate at the infero-lateral angle of the choana, medial to
M3. The sphenopalatine canal, connecting the infero-medial orbital
fossa with the postero-lateral nasal fossa, is w1.5 mm long, ellip-
tical in cross section, and about 1 mm in maximum diameter. The
sphenopalatine canal is located medial to the M3 and is enclosed
entirely within the base of the vertical process of the palatine bone.
The root of the zygomatic process of the maxilla is located supero-
lateral to M2. There is a weakly developed rugosity at the base of
the zygomatic process that marks the site of origin of the anterior
masseter, but this rugosity is not projecting. The inferior margin of
the orbital aperture is damaged, but it is clear that the maxilla was
supero-inferiorly shallow. This conclusion is reinforced by the fact
that the lingual roots of M2 and M3 were exposed on the maxillary
floor of the orbit. The postero-lateral margin of the orbital floor is
thin (approx 1.5 mm thick) and rounded along its free edge
between the zygomatic process and M3. The damaged inferior
orbital margin has a very shallow curvature, suggesting that the
orbital apertures were relatively large in Mescalerolemur. This
conclusion is also supported by the very shallow maxilla below the
orbit and the exposure of molar roots in the orbital floor, but it is
not possible to quantify orbital aperture size in existing specimens.
Discussion
In a number of its key dental features (e.g., lack of a pseudohy-
pocone on upper molars, absence of p1/P1, extreme reduction of
the p2/P2, and simplified p4 crown morphology), Mescalerolemur
clearly differs from endemic North American notharctines. By
contrast, Mescalerolemur shares many derived dental features with
Mahgarita, a North American genus with presumed Eurasian
affinities (Wilson and Szalay, 1976;Figs. 4 and 5). Among Eurasian
taxa, Mescalerolemur and Mahgarita clearly differ from adapines
and pronycticebines in lacking a p1/P1, in having a highly reduced
p2/P2, and in lacking a molariform or more complex p4/P4. Mes-
calerolemur and Mahgarita also lack the more complex p4 and
derived twinning of the lower molar entoconid and hypoconulid
shared by sivaladapids (Qi and Beard, 1998; Beard et al., 2007;
Chaimanee et al., 2008). Accordingly, the adapiform taxa with the
greatest dental similarity to both Mescalerolemur and Mahgarita
include various members of the Cercamoniinae, Caenopithecinae,
and Asiadapinae.
The absence of a p1 and the presence of a diminutive, single-
rooted p2 located between a much larger canine and two-rooted p3
is a derived similarity shared by Mescalerolemur horneri,Mahgar-
ita stevensi,Caenopithecus lemuroides,Cercamonius brachyrhynchus,
Europolemur dunaifi,
9
Protoadapis weigelti,
10
Godinotia neglecta,
Darwinius masillae,
11
and Aframonius diedes. By contrast, the p2 is
completely lacking in Afradapis longicristatus (Seiffert et al., 2009).
In Asiadapis cambayensis, the p2 was evidently single-rooted and
relatively small (based on the p2 alveolus of the Asiadapis type
specimen GU/RSR/VAS-6), but was still considerably larger than
9
Here we follow Godinot (1988), who attributed a partial mandible with a small,
single-rooted p2 from Bouxwiller to Europolemur dunaifi. Unlike E. dunaifi, the p2 of
E. klatti,E. koenigswaldi, and E. kelleri has two roots (Franzen et al., 2009).
10
Unlike Protoadapis weigelti, the p2 of P. angustidens,P. curvicuspidens,P. igno-
ratus and P. meuchelnensis has two roots (Russell et al., 1967; Thalmann, 1994;
Franzen et al., 2009).
11
Here we follow the interpretation of Franzen et al. (2009), who state that the
juvenile type specimen of Darwinius possessed a very small, single-rooted adult p2.
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that of Mescalerolemur. Similarly, in Asiadapis,Aframonius,God-
inotia, and Protoadapis weigelti, the p2 root was not closely
appressed between the canine root and mesial p3 root as it was in
Mescalerolemur,Mahgarita,Caenopithecus, and Cercamonius. In the
latter four genera, crowding of the anterior dentition results in an
oblique orientation of the p3 relative to the mesiodistal axis of the
mandibular corpus, with the mesial p3 root located more buccally
than the distal root. As a result, in Mescalerolemur,Mahgarita,
Caenopithecus, and Cercamonius the much smaller p2 is located
mesiolingual (i.e., rather than directly mesial) to the mesial p3 root.
The p4 of Mescalerolemur has a very simple and highly distinc-
tive crown morphology that is most similar to the p4 of Mahgarita,
Marcgodinotius,Asiadapis,Panobius,Anchomomys,Periconodon,
Mazateronodon, and Djebelemur. All nine genera share p4s that are
buccolingually compressed, and all except Panobius and Djebelemur
have a p4 with an oval occlusal profile. Mescalerolemur,Mahgarita,
Mazateronodon,Panobius, and Djebelemur also have p4s that lack
a paraconid and metaconid. By contrast, primitive adapiforms
such as Cantius torresi and Donrussellia gallica have p4 trigonids
with distinct paraconids and metaconids. Larger European adapi-
forms have p4s that either retain metaconids (e.g.,
Cercamonius brachyrhynchus and Protoadapis curvicuspidens)or
retain both metaconids and paraconids (e.g.,
Caenopithecus lemuroides). Very small but distinct p4 paraconids
are retained in Anchomomys (e.g., BNM En-1) and Periconodon (e.g.,
NHB BCHS 495). In Asiadapis and Marcgodinotius, the presence and
size of the p4 paraconid and/or metaconid are variable (Rose et al.,
2009). Some dental specimens that have been identified as p4s of
Asiadapis have comparatively large and distinct paraconids and
metaconids (e.g., GURSR/VAS-745), while others lack a distinct
metaconid and have only a tiny paraconid (e.g., GURSR/VAS-38,
GURSR/VAS-1627). Similarly, some p4s attributed to Marcgodino-
tius lack paraconids but retain a distinct p4 metaconid (e.g., GURSR/
VAS-727), while others lack both paraconid and metaconid (e.g.,
GURSR/VAS-40) and thus bear a striking resemblance to the p4 of
Mescalerolemur. This variability in asiadapine p4 morphology
cautions against making over-generalizations of dental anatomy
based on a limited fossil sample, but it is striking that both known
p4s of Mescalerolemur retain only two cusps (the protoconid and
hypoconid). The p4 of Mescalerolemur is also distinctive in lacking
any evidence of a talonid basin and in lacking a mesiolingual cin-
gulid. Asiadapis,Marcgodinotius,Panobius,Anchomomys,Mazater-
onodon, and Djebelemur all have small but discrete talonid basins
lingual to the p4 hypoconid/cristid obliqua, and these six genera
plus Periconodon and Mahgarita all have a mesiolingual cingulid on
the p4. By the same token, the p4s of Mescalerolemur and Djebele-
mur are distinctive in having a hypoconid located directly distal to
the protoconid as well as a midline cristid obliqua connecting the
apices of the hypoconid and protoconid. As noted above, the p4
cristid obliqua and hypoconid of Mescalerolemur form a wedge that
shears against the elevated preprotocrista of P4 during occlusion.
Mescalerolemur also lacks any trace of a lateral protocristid on p4.
By comparison, Anchomomys,Periconodon, and Asiadapis have p4s
with a distinct lateral protocristid lingual to the cristid obliqua and
a hypoconid located buccal to the midline of the crown. The p4s of
Marcgodinotius and Panobius have a hypoconid located along the
midline of the tooth, but retain a lateral protocristid. In Mazater-
onodon, the cristid obliqua runs distolingually from the protoconid
rather than distally as in Mescalerolemur. The position of the p4
hypoconid in Mahgarita is obscured by wear in the only known
specimen (TMM 41578-8), but a p4 lateral protocristid is visible.
The characteristic morphology of the p4 in Mescalerolemur thus
distinguishes the genus from all other known adapiforms.
As noted above, various details of dento-gnathic anatomy
distinguish Mescalerolemur from Mahgarita (Figs. 3e5). The most
salient of these differences include size (Mescalerolemur is smaller
than Mahgarita), the anatomy of the mandibular symphysis (the
symphysis is unfused in Mescalerolemur and fused in Mahgarita),
and the occlusal anatomy of the maxillary postcanine dentition. For
example, the P3 of Mescalerolemur lacks a protocone and has distal
margin with a comparatively deep flexus. In Mahgarita, the P3 has
a small but distinct protocone and a very shallow distal flexus. The
P4 of Mescalerolemur has a trapezoidal occlusal profile, lacks
a lingual cingulum, and has a protocone that is mesially shifted
relative to the paracone. In Mahgarita, the P4 has a more oval
occlusal profile, has a complete lingual cingulum, and has a proto-
cone that is directly lingual to the paracone. In Mescalerolemur,
M1e2 have trapezoidal occlusal profiles and comparatively narrow
stylar regions, narrow lingual cingula, and small hypocones. In
Mahgarita,M1e2 have rectangular occlusal profiles and compara-
tively broad stylar regions, broad lingual cingula, and large hypo-
cones. Furthermore, in Mahgarita, the two known specimens that
preserve maxillary teeth demonstrate considerable variation in
molar anatomy. In TMM 41572-20, the M2 hypocone is twinned
(i.e., it takes the form of two closely-appressed but distinct cusps)
on both left and right sides, M1e2 have large mesostyles and well-
developed accessory cuspules in the trigon basins, and M1e3have
highly crenulated enamel. By contrast, TMM 51478-9 (holotype)
has a more typical, single-cusped M2 hypocone, lacks accessory
cuspules in the M1e2 trigon basins, has only moderately crenulated
enamel on M1e3, and has a small mesostyle on M1.
12
Mescaler-
olemur resembles the Mahgarita holotype in lacking twinning of the
M2 hypocone and lacks accessory trigon cuspules, but Mescaler-
olemur also lacks significant enamel crenulation and lacks meso-
styles on any molars. Finally, the M3 of Mescalerolemur lacks
a hypocone, while in Mahgarita the M3 has a broad, low hypocone.
Despite these differences, Mescalerolemur and Mahgarita share
a number of derived dental features that collectively distinguish
both genera from other adapiforms. As noted above, in Mescaler-
olemur and Mahgarita the p4 has a very simple crown morphology.
Detailed comparisons are hindered by the advanced state of wear
on the only known mandible of Mahgarita, but only the presence/
absence of a lateral protocristid and mesiolingual cingulid appears
to distinguish the p4s of Mescalerolemur and Mahgarita.
The loss of p1/P1, tiny size of the p2 and P2, and crowding of the
antemolar dentition are additional distinctive synapomorphies
found in both Mescalerolemur and Mahgarita. In the only known
mandible of Mahgarita (TMM 41578-8), the p2 crown is missing
bilaterally and there appears to be variation in both root and alve-
olus size. On the right side of TMM 41578-8, a round p2 alveolus is
preserved, but on the left side there is a much smaller and laterally
compressed p2 root and alveolus. The size of the p2 in Mescaler-
olemur can only be inferred from the size of the alveolus in TMM
41672-233, which is similar in absolute size to the right p2 alveolus
of TMM 41578-8 (Mahgarita). Because Mescalerolemur is absolutely
smaller than Mahgarita based on postcanine tooth dimensions,
these observations suggest that Mescalerolemur may have had
a relatively larger p2 than Mahgarita. Nonetheless, both genera have
a proportionately smaller p2 than in all other adapiforms except
perhaps Caenopithecus lemuroides (e.g., Eh 597) and
Cercamonius brachyrhynchus (e.g., Basel QV 619). The p2 alveoli of
Mescalerolemur and Mahgarita are absolutely much smaller than
that of the larger-bodied Caenopithecus and Cercamonius, but it is
possible that Mescalerolemur,Caenopithecus, and Cercamonius had
p2s that were relatively similar in size compared to the dimensions
of the adjacent canine and p3. Furthermore, the p2 of
12
A small mesostyle may have been present on M2, but the buccal cingulum of
M2 is damaged.
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168 163
Author's personal copy
Mescalerolemur and Mahgarita is located mesiolingual to p3, while
the mesial root of p3 is displaced buccally. This configuration of the
p3 is also shared with Caenopithecus and Cercamonius, so that in all
four genera the p3 is oriented obliquely relative to the mesiodistal
axis of the mandibular corpus.
Although P2 crown morphology is unknown in Mescalerolemur
and Mahgarita, more evidence is available regarding the P2 in these
genera. In Mahgarita, both known crania that preserve maxillary
dentitions have small rounded P2 alveoli on the left side. In TMM
41578-20, the right anterior maxilla is damaged, but in TMM 41578-
9, there is a tiny, peg-shaped P2 on the right side (Fig. 4). This P2 in
Mahgarita is absolutely larger than the only known P2 of Mesca-
lerolemur (TMM 41672-232), but the morphology, position, and
relative size of the two teeth is very similar. The P2s in both spec-
imens lack the crown tip, but it is not clear whether this condition is
due to occlusal wear or damage. Additionally, in both Mescaler-
olemur and Mahgarita the P2 is located mesiolingual to the mesial
root of P3 and is very tightly appressed between the maxillary
canine and P3. Together, these features of the P2 (i.e., very small
size, single root, relatively lingual position, and lack of substantial
Figure 6. Majority-rule cladogram from “expanded”PAU P
*
analysis, which includes Mescalerolemur,Mahgarita, and all adapiforms and crown strepsirrhines analyzed by Boyer et al.
(2010). Character matrix contained 360 characters scored for 43 taxa. Twenty-one most-parsimonious trees were recovered. The number adjacent to each node represents the
percentage of recovered cladograms supporting the node. Tree length¼862.999; consistency index excluding uninformative characters ¼0.3517; retention index ¼0.5692; rescaled
consistency index¼0.2091.
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168164
Author's personal copy
adjacent diastemata) distinguish Mescalerolemur and Mahgarita
from all other known adapiforms.
Although the P3s of Mescalerolemur and Mahgarita exhibit some
discrete differences in crown morphology (e.g., presence or absence
of a protocone), the shape of the P3 crown and configuration of its
roots representadditional dental synapomorphies of the two genera.
In both Mescalerolemur and Mahgarita, the lingual P3 root is shifted
distally so that it is directly lingual to the distobuccal P3 root. As
a result, the P3 crown has an occlusal profile that approximates
a right triangle, with the flat mesiolingual face of the P3 forming the
hypotenuse. The mesiolingual face of the P3 crown thus faces much
more lingually in Mescalerolemur and Mahgarita than in many other
adapiforms (e.g., Cantius,Pronycticebus). By comparison, the lingual
P3 root is also located lingual to the distobuccal P3 root in adapines
but the P3 crown has an oval rather than triangular occlusal profile.
Similarly, the lingual P3 root is shifted somewhat distally in
Anchomomys,Periconodon, and Caenopithecus, but it does not lie
directly lingual to the distobuccal P3 root.
Figure 7. Majority-rule cladogram from “reduced”PAUP
*
analysis, which excludes five taxa with large amounts of missing data (>75%) following Seiffert et al. (2010). Twenty-one
most-parsimonious trees were recovered. The number adjacent to each node represents the percentage of recovered cladograms supporting the node. Tree length ¼837.610;
consistency index excluding uninformative characters ¼0.3617; retention index ¼0.5703; rescaled consistency index ¼0.2153. A bootstrap analysis based on 1200 pseudoreplicates
found greater than 50% support for the following clades (bootstrap percentages in parentheses): Adapis þLeptadapis (85%), AfradapisþCaenopithecus (61%), Hoangho-
nius þRencunius (72%), Mahgarita þMescalerolemur (69%), Asiadapis þMarcgodinotius (66%), Donrussellia gallica þDonrussellia provincialis (69%).
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168 165
Author's personal copy
Phylogenetic analyses
The many derived dental similarities shared by Mescalerolemur
and Mahgarita favor the conclusion that the two genera are sister
taxa. Furthermore, comparisons with other adapiforms reveal that
both Mescalerolemur and Mahgarita generally do not resemble
notharctines in their dental morphology. At the same time, Mesca-
lerolemur and Mahgarita share a number of derived dental features
with some asiadapines (e.g., Marcgodinotius and Asiadapis), caeno-
pithecines (e.g., Caenopithecus), and cercamoniines (e.g., Cercamo-
nius,Anchomomys,Periconodon,Mazateronodon, and Djebelemur). In
particular, all of these genera demonstrate varying degrees of
simplification of the p4 crown and/or reduction and crowding of the
anterior premolars compared to the most primitive adapiforms
Donrussellia and Cantius. While it is possible that these dental
features evolved in parallel in multiple adapiform clades, such
shared derived attributes provide a priori support for a hypothesis of
common ancestry.
In order to more systematically evaluate the phylogenetic rela-
tionships of Mescalerolemur and Mahgarita vis a vis both adapi-
forms and crown strepsirrhines, we conducted a parsimony
analyses using PAUP
*
4.0b10 (Swofford, 1998) software. The anal-
ysis included 360 characters and 43 species of extant strepsirrhine
primates and adapiforms (i.e., Mescalerolemur and all taxa included
in Boyer et al., 2010)inan“expanded”analysis, and 38 species in
a“reduced”analysis that excluded adapiforms with large amounts
of missing data (i.e., taxa included in Seiffert et al., 2010). The
matrix used in this study (see Electronic Appendix) was originally
established by Ross et al. (1998) and has been modified and
supplemented by many authors since then (e.g., Kay et al., 2004;
Seiffert et al. 2005b, 2009). The most recently modified version
upon which our analysis is based is that of Boyer et al. (2010). Some
characters were rescored for Mahgarita because original fossil
materials were available and morphological details that were
obscured in casts could be more clearly observed. These analyses
follow Seiffert et al. (2009) in using a molecular scaffold of extant
strepsirrhines as a “backbone”constraint and in the use of step
matrices to constrain the reacquisition of lost premolars. Some
characters were treated as unordered. Characters treated as
ordered were scaled so that no character contributed more than
one step to tree length. The heuristic search option was employed
with random addition sequence and the tree bisection and recon-
nection branch-swapping algorithm across 1000 replicates. Boot-
strap support based on 1200 pseudoreplicates was only assessed
for the “reduced”analysis because the “expanded”analysis
included large amounts of missing data. Tree statistics are reported
in Figs. 6 and 7.
The majority-rule cladogram from our “expanded”phylogenetic
analysis is shown in Fig. 6. In 100% of the most parsimonious
cladograms that were recovered, Mescalerolemur and Mahgarita are
sister taxa. Both Texas genera comprise the sister group to a larger
clade that includes “Anchomomys”milleri (from the late Eocene of
Egypt), Djebelemur martinezi (from the early Eocene of Tunisia), and
crown strepsirrhines. In turn, all of these taxa are nested within
a group of European (Caenopithecus,Darwinius,Europolemur,God-
inotia)and African (Afradapis,Aframonius) adapiforms.
The majority-rule cladogram from our “reduced”phylogenetic
analysis is shown in Figure 7. As in the “expanded”analysis, 100% of
the most parsimonious cladograms identify Mescalerolemur and
Mahgarita are sister taxa. Furthermore, the sister-taxon relation-
ship of Mescalerolemur and Mahgarita received relatively strong
support in the bootstrap analysis (bootstrap percentage¼69%).
However, unlike the “expanded”cladogram, the “reduced”analysis
places the two Texas adapiforms as the sister group to a clade that
includes crown strepsirrhines and a large assemblage of European
(Caenopithecus,Darwinius,Europolemur,Godinotia), African (Afra-
dapis,Aframonius), and Asian (Hoanghonius,Rencunius) adapiforms.
After Mescalerolemur and Mahgarita, the next closest relatives of
this group are Asiadapis and Marcgodinotius. Bootstrap support for
these higher-level phylogenetic relationships was relatively low
(i.e., below 50%; Fig. 7).
These phylogenetic analyses largely support our two main
expectations based on comparative dental morphology. First, both
the “expanded”and “reduced”analyses favor the conclusion that
Mescalerolemur and Mahgarita are sister taxa. Second, both analyses
strongly suggest that Mescalerolemur and Mahgarita are more
closely related to Eurasian and African adapiforms than to North
American notharctines. This latter result provides further support
for the early conclusion of Wilson and Szalay (1976) that Mahgarita
has Old World phylogenetic affinities (see also Kay et al., 1997; Ross
et al., 1998; Seiffert et al., 2009, 2010; Boyer et al., 2010). While we
regard these two findings as fairly robust, we believe that caution is
warranted in drawing more specific conclusions on the basis of the
phylogenetic analyses that we have presented here. Although both
cladograms (Figs. 6 and 7) are similar in several key respects (e.g.,
both suggest that the Cercamoniinae as construed by Godinot (1998)
is paraphyletic and polyphyletic; both favor a monophyletic Ada-
pinae and Asiadapinae; both favor a clade including Afradapis,
Caenopithecus,Aframonius, and Darwinius), there are substantial
differences in tree topology.For instance, the proposed relationships
between Mescalerolemur þMahgarita,Europolemur þGodinotia,
and hoanghoniines are not concordant in the two cladograms, and
yet each analysis found 100% support with regard to the topology of
these clades. Furthermore, both cladograms suggest that a number
of key derived dental features that have been used to reconstruct
adapiform phylogeny (e.g., loss of the p1/P1, extreme reduction in
the size of the p2/P2, reduction in the number of p2 roots, and
simplification of p4 crown morphology) probably appeared in
parallel in multiple adapiform clades. For instance, in both clado-
grams (Figs. 6 and 7), the asiadapines Marcgodinotius and Asiadapis
form a clade to the exclusion of all other taxa. Within this clade,
Asiadapis resembles Mescalerolemur in lacking a p1 while Marcgo-
dinotius retains a p1. Conversely, Marcgodinotius more closely
resembles Mescalerolemur in having a simplified p4 crown
morphology. Accordingly, while we are confident in our conclusion
that Mescalerolemur and Mahgarita are not notharctines like other
known North American adapiforms, we regard the precise sub-
familial affinities of the two Texas genera as unknown based on the
data currently available.
Conclusions
Comparisons of dental anatomy and morphological cladistic
analyses of stem and crown strepsirrhines indicate that M. horneri
and M. stevensi are closely related sister taxa. Furthermore, none of
the craniodental features evident in Mescalerolemur horneri would
exclude the species from being directly ancestral to
Mahgarita stevensi. This possibility of an ancestor-descendant
relationship is bolstered by biogeographic considerations: both
species are known definitively only from the Devil’sGraveyard
Formation of Texas, with Mescalerolemur horneri occurring in the
late Uintan and Mahgarita stevensi occurring in the early Duch-
esnean. Further examination of the hypothesis that Mescalerolemur
and Mahgarita are representatives of a single evolutionary lineage
will require additional fossil material and improved biostrati-
graphic resolution in the Devil’s Graveyard Formation, as well as
clarification of the status of a molar from Lake Casa Blanca that has
been attributed to Mahgarita (Westgate et al., 2010). Nonetheless,
the presence of both Mescalerolemur and Mahgarita in the Devil’s
Graveyard Formation adds additional weight to the conclusion that
E.C. Kirk, B.A. Williams / Journal of Human Evolution 61 (2011) 156e168166
Author's personal copy
primate faunas in Texas demonstrate increased endemism in the
late Uintan and Duchesnean (Williams and Kirk, 2008).
Our analyses further demonstrate that Mescalerolemur and
Mahgarita are more closely related to Eurasian and African adapi-
forms than to the endemic radiation of North American notharc-
tines. It is also noteworthy that both Mescalerolemur and Mahgarita
appear in the North American fossil record after the last known
occurrences of most species. These findings provide additional
evidence of faunal interchange (including primates) between North
America and Asia in the middle Eocene (Simpson, 1947; Black and
Dawson, 1966; Russell and Zhai, 1987; Beard and Wang, 1991;
Beard et al., 1994; Robinson et al., 2004). If Mescalerolemur is
ancestral to Mahgarita, then the earliest representatives of this
lineage must have arrived in North America from northeast Asia no
later than the late Uintan (Ui3). However, our results also raise the
larger question of why Mescalerolemur and Mahgarita persisted in
the Big Bend region of Texas during the late Uintan and early
Duchesnean while notharctines did not. Although it is possible that
Mescalerolemur and Mahgarita were in some way better able than
notharctines to cope with a changing environment during the Uin-
tan and Duchesnean (e.g., Janis, 1993; Prothero, 1998; Wing,
1998;Townsend et al., 2010), there is very little evidence with
which to evaluate this hypothesis. Nonetheless, it is clear that later-
occurring notharctines such as Notharctus tenebrosus,Smilodectes
gracilis, and Hesperolemur actius are uniformly much larger than
both Mescalerolemur and Mahgarita (Table 1;Gunnell,1995; Fleagle,
1999). Because body mass is closely tied to many important
ecological factors such as diet, substrate use, and energetic needs
(Damuth and MacFadden, 1990), these differences in body mass
suggest, at a minimum, that Mescalerolemur and Mahgarita probably
occupied niches that differed from those of the later-occurring
notharctines.
Beyond the evidence that we have presented for a close rela-
tionship between Mescalerolemur,Mahgarita, and various Old World
adapiforms, the precise higher-level phylogenetic affinities of the
two Texas genera are currently unresolved. This consideration
makes the subfamilial taxonomic status of Mescalerolemur and
Mahgarita uncertain. At present, it is easiest to conclude that Mes-
calerolemur and Mahgarita should not be placed in the Sivaladapi-
nae, Adapinae, or Pronycticebinae. Instead, Mescalerolemur and
Mahgarita are probably most closely related to the Asiadapinae,
Cercamoniinae, or Caenopithecinae, although our phylogenetic
analyses suggest that the latter two subfamilies are problematic as
currently construed (Godinot, 1998). It is also worth noting that
a close relationship between Mescalerolemur and Mahgarita
provides additional evidence that adapiforms are not stem anthro-
poids (Ross, 1994; Seiffert et al., 2009; Williams et al., 2010; but see
Franzen et al., 2009; Gingerich et al., 2010).In particular, the unfused
mandibular symphysis of Mescalerolemur indicates that the fully
fused symphysis of Mahgarita represents yet another example of the
parallel evolution of symphyseal fusion in primatesand is therefore
not a good indicator of anthropoid affinities (Rasmussen, 1990;
Williams et al., 2010).
Acknowledgements
This paper would not have been possible without the generous
assistance of Norman Horner, Bill Cook, and the many field crews
that have worked to recover fossils at the Dalquest Research Site.
The Dalquest Research Site is owned and maintained by Mid-
western State University, which has provided invaluable logistical
support for paleontological research at the site since 2004. Excel-
lent curatorial, preparatory, and logistical assistance was provided
by Tim Rowe, Matt Brown, and Lyn Murray at the Texas Memorial
Museum Vertebrate Paleontology Laboratory. Chris Beard, Rachel
Dunn, Gregg Gunnell, Ken Rose, and Bill Sanders kindly provided
casts of fossil specimens for this research. Erik Seiffert generously
provided the character-taxon matrices that we modified for this
analysis. Jim Westgate, Dana Cope, and Chris Beard offered useful
comments on the fossils described in this paper and provided
access to fossil specimens in their care. This paper was also greatly
improved by revisions suggested by Steve Leigh, Erik Seiffert, and
two anonymous reviewers.
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