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Journal of Vertebrate Paleontology 30(1):109–138, January 2010
©2010 by the Society of Vertebrate Paleontology
ARTICLE
A LATE CRETACEOUS (MAASTRICHTIAN) SNAKE ASSEMBLAGE FROM THE MAEVARANO
FORMATION, MAHAJANGA BASIN, MADAGASCAR
THOMAS C. LADUKE,1DAVID W. KRAUSE,*,2 JOHN D. SCANLON,3and NATHAN J. KLEY2
1Department of Biological Sciences, East Stroudsburg University, East Stroudsburg, Pennsylvania 18301, U.S.A.,
tcladuke@po-box.esu.edu;
2Department of Anatomical Sciences, Stony Brook University, Stony Brook, New York 11794-8081, U.S.A.,
David.Krause@stonybrook.edu, Nathan.Kley@stonybrook.edu;
3School of Biological, Earth and Environmental Sciences, University of New South Wales, UNSW Sydney 2052; and Riversleigh
Fossil Centre, Outback at Isa, Mount Isa Queensland 4825, Australia, riversleigh@outbackatisa.com.au
ABSTRACT—A Late Cretaceous (Maastrichtian) assemblage of snakes from the Maevarano Formation of the Mahajanga
Basin, northwestern Madagascar, constitutes the only fossil record of snakes from the island. The assemblage, which lived
in a highly seasonal, semi-arid climate, includes only archaic forms belonging to the Madtsoiidae and Nigerophiidae, and
therefore no representatives of extant Malagasy clades. A large sample of exquisitely preserved vertebrae and several ribs
are assigned to Madtsoia madagascariensis, a long (almost 8 m), heavy-bodied ambush predator inferred to have subdued its
prey via constriction. A new madtsoiid genus and species, Menarana nosymena, is represented by several associated vertebrae
and rib fragments, and part of the basicranium. It was approximately 2.4 m long and appears to have been a powerful, head-
first burrower, or at least to have had a burrowing ancestry. Kelyophis hechti, by far the smallest snake in the assemblage
(<1 m long), is a new genus and species of primitive nigerophiid based on six isolated vertebral specimens. It was not as
specialized for the aquatic lifestyle inferred for other nigerophiids. Although recent molecular phylogeographic studies suggest
an early colonization of Madagascar by snakes ancestral to modern Malagasy boids, with subsequent vicariant evolution, the
Maevarano Formation assemblage offers no support for this hypothesis. The repeated pattern of extinct archaic lineages being
replaced on Madagascar by basal stocks of extant clades (e.g., Anura, Crocodyliformes, Avialae, Mammalia) after the Late
Cretaceous is also a plausible scenario for the origin of the extant Malagasy snake fauna.
INTRODUCTION
The early evolution of snakes is poorly documented in the
fossil record, with no known occurrences prior to the Cre-
taceous. With the important exception of a remarkably di-
verse assemblage (at least nine species representing at least
seven families) from the early Late Cretaceous (Cenomanian) of
Sudan (Werner and Rage, 1994; Rage and Werner, 1999),
multi-species assemblages (i.e., more than one species from
a single locality or rock unit) of Cretaceous (and even Pa-
leocene) snakes are uncommon. Rare also are occurrences
of associated or articulated specimens of early non-marine
snakes (a notable exception being Dinilysia; Estes et al., 1970;
Caldwell and Albino, 2002; Caldwell and Calvo, 2008). The vast
majority of Cretaceous non-marine snake species are represented
by isolated vertebrae. Interestingly, Late Cretaceous snakes are
far less abundant and speciose on Laurasian than on Gondwanan
landmasses, whereas the reverse is true for non-ophidian squa-
mates (i.e., ‘lizards’) (Krause et al., 2003).
This report describes an assemblage of Late Cretaceous
(Maastrichtian) snakes from Madagascar that includes at least
three species: (1) the previously reported madtsoiid Madtsoia
madagascariensis Hoffstetter 1961a; (2) a new genus and species
of madtsoiid represented by an associated skeleton including a
braincase fragment and a partial atlas; and (3) a new genus and
species of nigerophiid. This constitutes the first report of the
family Nigerophiidae from Madagascar. In addition, owing to the
vastly increased sample size since Hoffstetter’s (1961a) original
*Corresponding author.
description of the species, the morphology of the vertebrae and
the first-known ribs of Madtsoia madagascariensis are described
in detail for the first time.
HISTORY OF STUDY AND GEOLOGICAL CONTEXT
Over 75 years ago, Piveteau (1933) described an isolated,
nearly complete vertebra of a large snake discovered by botanist
J. Perrier de la Bˆ
athie in Upper Cretaceous strata of what was
then known as the Marovoay region of northwestern Madagas-
car. Owing to the limited material, Piveteau did not name a new
taxon but made several relevant comparisons and opined that the
specimen represented a member of the Boidae (=Pythonidae
of Piveteau), which, at the time, included the genus Madtsoia
(then represented only by Madtsoia bai from the Eocene of
Argentina; Simpson, 1933). Unfortunately, no precise locality or
stratigraphic information was provided and the specimen could
not be relocated after being moved from the MNHN in Paris
during World War II (Hoffstetter, 1961a; confirmed by J.-C.
Rage, pers. comm., Feb. 29, 2008). Twenty-eight years later,
Hoffstetter (1961a) described and illustrated five additional
snake vertebrae and a very large zygosphene, all collected by R.
Lavocat in 1954 from three areas southeast of the port city of
Mahajanga (=Majunga). Hoffstetter concluded that the fossils
had been collected from the same general region as Piveteau’s
specimen, regarded them as all belonging to the same taxon,
and referred them to a new species, Madtsoia madagascariensis.
He also concurred with Piveteau’s conclusions concerning mem-
bership of this large snake in the Boidae but assigned Madtsoia
to a new subfamily, the Madtsoinae, to which he also allocated
109
110 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
FIGURE 1. Late Cretaceous and Paleocene
strata of the Mahajanga Basin, northwest-
ern Madagascar. The Berivotra and Masi-
akakoho study areas are indicated by rectan-
gular outlines.
Gigantophis from the Paleogene of Egypt (Andrews, 1901, 1906).
Examination of both Hoffstetter’s (1961a:fig. 1) and Lavocat’s
(1955:fig. 2) maps (see also Krause et al., 2007:fig. 6B) suggests
that Perrier de la Bˆ
athie’s and Lavocat’s specimens of snake
vertebrae were all recovered from the Maevarano Formation,
even though the rock unit had not yet been formally delimited
and named (see Rogers et al., 2000).
The Mahajanga Basin Project, conducted jointly by Stony
Brook University and the University of Antananarivo, was ini-
tiated in 1993, 60 years after Piveteau’s (1933) description of the
first fossil snake specimen from Madagascar. The reconnaissance
expedition and eight field campaigns since (1995, 1996, 1998,
1999, 2001, 2003, 2005, 2007) have focused primarily on the col-
lection of fossil vertebrates and associated contextual data from
the Maevarano Formation in the Berivotra Study Area, which
lies some 35 km southeast of Mahajanga, but recent reconnais-
sance (2003, 2005, 2007) has established two additional study ar-
eas, the Masiakakoho and Lac Kinkony study areas, west of the
Betsiboka River and southwest of Mahajanga (Fig. 1). The Mae-
varano Formation, which crops out in all three study areas, was
named and described by Rogers et al. (2000). It has been ascer-
tained to be of Maastrichtian age and to have been deposited in
a highly seasonal, semi-arid climate (Rogers et al., 2000, 2007;
Rogers and Krause, 2007). The majority of the contained fossils
were entombed in massive debris flows (Rogers, 2005) as sedi-
ments were washed from the crystalline highlands that run down
the north-south axis of the island northwestward toward the
Mozambique Channel. The vertebrate fauna of the Maevarano
Formation includes ray-finned fishes, frogs, turtles, snakes, non-
ophidian squamates, crocodyliforms, birds, non-avian dinosaurs,
and mammals (most recently reviewed in Krause et al., 2006).
The snake specimens described in this report were recovered
from the Berivotra and Masiakakoho study areas; none have yet
been found in the Lac Kinkony Study Area. Snakes are repre-
sented by over 125 specimens, most of them isolated vertebrae
and vertebral and rib fragments. One specimen, the holotype of
a new genus and species of madtsoiid, consists of associated ele-
ments: a sizable braincase fragment, a partial atlas, several com-
plete vertebrae from the mid-trunk and posterior trunk regions,
and many vertebral and rib fragments.
METHODS
The specimens described in this report were collected by field
crew members of the Mahajanga Basin Project through nine field
seasons from 1993 to 2007 via surface collecting, quarrying, and
both dry- and wet-screening methods. All specimens were recov-
ered from the Maevarano Formation in the Berivotra and Masi-
akakoho study areas, Mahajanga Basin, northwestern Madagas-
car, and prepared in the Stony Brook University Fossil Prepara-
tion Laboratory.
Comparisons were made with skeletal material in the col-
lections of the AMNH (including direct comparison with the
holotype of Madtsoia bai), CMNH, and MVZ, as well as those of
the authors. Other fossils were compared through descriptions
and figures in the literature. Vertebral anatomical terminology
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 111
follows LaDuke (1991), except as modified by Head (2005).
However, we continue to follow LaDuke in referring to vertebral
regions as divisions of the column (e.g., anterior, mid-, and
posterior trunk; cloacal; postcloacal). It must be emphasized,
however, that because intracolumnar variation is continuous, a
vertebra from, for instance, a posterior position in the anterior
trunk region will be difficult to differentiate from one in an
anterior position in the mid-trunk region.
The partial basicranium of Menarana nosymena, gen. et sp.
nov., (UA 9684-3) was scanned at the High-Resolution X-ray CT
(HRXCT) Facility at The University of Texas at Austin and the
dataset was rendered in three dimensions using VGStudio MAX
1.2 (Volume Graphics, Heidelberg, Germany). An interactive,
Web-deliverable version of the HRXCT data set, as well as
animations of 3-D reconstructions and technical information
concerning the scans and image processing, can be viewed at
http://www.digimorph.org/specimens/Menarana nosymena; the
original full-resolution HRXCT data are available from the
authors.
Measurements and Anatomical Abbreviations—All measure-
ments were made with hand-held calipers (Helios) or, in the case
of small specimens, with an ocular micrometer in a dissecting mi-
croscope. The following measurements (in order of presentation
in the tables) were made where possible, following abbreviations
of LaDuke (1991): CL =centrum length; NAW =neural arch
width; PRW =width across the prezygapophyses; POW =width
across the postzygapophyses; PR-PO =length from the ante-
rior edge of one prezygapophyseal facet to the posterior edge
of the ipsilateral postzygapophyseal facet; COW =width of the
cotyle measured from the outside of the cotylar rim; CNW =
condyle width; NSH =vertical height of the neural spine mea-
sured from the top of the zygosphene to the highest extremity
of the spine; and ZSW =zygosphene width. In addition; ATV =
anterior trunk vertebra; MTV =mid-trunk vertebra; PTV =pos-
terior trunk vertebra; CV =cloacal vertebra; and PCV =post-
cloacal vertebra.
Institutional Abbreviations—AMNH, American Mu-
seum of Natural History, New York; CMNH, Carnegie
Museum of Natural History, Pittsburgh; FMNH,The
Field Museum, Chicago; MVZ, Museum of Vertebrate
Zoology, University of California at Berkeley; MNHN,
Mus´
eum national d’Histoire naturelle, Paris; QM, Queens-
land Museum, Brisbane; SAMP, South Australian Museum
(Adelaide) Palaeontology; UA, Universit´
e d’Antananarivo,
Antananarivo, Madagascar.
Taxonomic Abbreviations—In relevant places throughout the
text, Madtsoia is abbreviated to Ma.andMenarana is abbreviated
to Me. to save space but also to facilitate differentiation between
species of the two genera.
SYSTEMATIC PALEONTOLOGY
SQUAMATA Oppel, 1811
SERPENTES Linnaeus, 1758
MADTSOIIDAE (Hoffstetter, 1961a) McDowell, 1987
MADTSOIA Simpson, 1933
Type Species—Madtsoia bai Simpson, 1933.
Referred Species—Madtsoia madagascariensis Hoffstetter,
1961a and Ma. camposi Rage, 1998.
Revised Diagnosis—Distinguished from Alamitophis,Heren-
sugea,Menarana (below), Nanowana,andPatagoniophis by large
size and relatively short, broad mid-trunk vertebrae (CL approx-
imately half of PRW). Vertebrae further differ from those of
Menarana in having taller neural spines and less depressed neu-
ral arches, from those of Gigantophis and Rionegrophis in hav-
ing less distinct hemal keels, and from those of Wonambi and
Yurlunggur in having a single parazygantral foramen on each
side. Ribs differ from those of Wonambi and Yurlunggur,which
have multiple small foramina in dorsal groove, in having a single
large foramen in that position (but a much smaller accessory fora-
men can be present). They differ from those of Menarana in hav-
ing a less strongly recessed dorsal facet, in not having the tuber
costae drawn out into a crest, and in possessing fewer foramina
on anteroventral and posterior surfaces.
Comparisons and Discussion
At the time Madtsoia was named, diagnosed, and described
by Simpson in 1933, and then even 28 years later when it
was reassessed by Hoffstetter (1961a), only one other genus
(Gigantophis) of the clade now identified as Madtsoiidae was
known. Since 1961, seven additional genera (Alamitophis,Heren-
sugea, Nanowana,Patagoniophis,Rionegrophis,Wonambi,and
Yurlunggur) have been named and assigned to the Madtsoiidae
and at least two others (Najash [see Apestegu´
ıa and Zaher, 2006]
and Helagras [see Head and Holroyd, 2008]) are questionably al-
lied. Yet, no formal rediagnosis of Madtsoia has been published
since that time. As such, and because of the removal of “Madt-
soia”laurasiae from the genus (see below) and the considerable
addition to knowledge of Ma. madagascariensis based on the new
specimens described here, reassessment of vertebral and rib fea-
tures relative to those of other madtsoiid genera and revision of
the diagnosis of Madtsoia are in order, especially because it serves
as the type genus of the Madtsoiidae.
The genus Madtsoia, as here defined, consists of three large
species: Ma. bai, Ma. camposi,andMa. madagascariensis, with
maximum centrum lengths (CL) of 18–25 mm, and maximum
widths across the prezygapophyses (PRW) of 35–65 mm. Three
madtsoiid genera (Gigantophis, Wonambi,andYurlunggur)in-
clude species of comparable size. Species of Menarana (defined
below) appear to have maximum sizes about one-half to two-
thirds those of the large genera (CL =11–13 mm; PRW =
20–22 mm). Several madtsoiid genera (Alamitophis, Herensugea,
Nanowana,andPatagoniophis) have maximum sizes that are
much smaller (CL <8 mm, PRW <10 mm). Thus, the madt-
soiid genera segregate into three distinct size classes. Members
of each size class can be distinguished further by differences in
vertebral shape: the smaller madtsoiids tend to have relatively
elongate vertebrae (length nearly as great as width); Menarana
has vertebrae that are depressed overall with extremely low neu-
ral spines; and the larger genera have vertebrae that are broader
than they are long, and that are never depressed to the degree
seen in Menarana.
Vertebrae of the larger madtsoiid genera can be distinguished
from one another on the basis of more detailed comparisons.
Madtsoia madagascariensis and Wonambi naracoortensis were
briefly compared by Smith (1976:43), who stated that, “There is
a striking resemblance between Wonambi vertebrae and those
of Madstoia [sic] bai...and M.madagascariensis.” However, she
did not make detailed comparisons of the two species that would
allow differentiation, stating that, “the relationship of Wonambi
to Madstoia [sic] or any other boid will remain obscure until the
skull [of Madtsoia] is known.” Nevertheless, most paleontologists
who work extensively with snakes use vertebrae to differenti-
ate genera and even species. Comparison of vertebrae of Ma.
madagascariensis and W. naracoortensis does indeed reveal a
strong resemblance in shape. However, the large Australian
madtsoiids (Wonambi and Yurlunggur) have a series of small
parazygantral foramina, whereas Madtsoia (indeed, most madt-
soiids) usually have a single, large foramen recessed in a dis-
tinct fossa. Posterior trunk vertebrae of Ma. bai bear paired
posterior tubercles on an otherwise broad, low hemal keel that
were referred to as ‘paired hypapophyses’ (Simpson, 1933:3, 8);
similar structures are seen in Ma. madagascariensis (Hoffstetter
112 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
1961a) and species of Yurlunggur (Scanlon, 1992, 1995), but not
Ma. camposi, which has a more typical rhombic termination of
the hemal keel (Rage, 1998). Posterior bifurcation of the keel
also occurs in a different form (mostly narrower keels) in Won-
ambi (Smith, 1976) and other, smaller Australian taxa (Scanlon,
1997, 2005b). Gigantophis vertebrae have distinctively shaped
neural arches (Andrews, 1906:pl. XXVI, figs. 1–3). The laminae
are thickened and strongly arched in posterior view (slightly an-
gled in Madtsoia,Wonambi,andYurlunggur). Anteriorly, the zy-
gosphene also appears hypertrophied, being much broader than
the opening of the neural canal. The hypapophysis is low and
blunt. Andrews makes no mention of paired tubercles or hypa-
pophyses, and his illustrations do not appear to show any.
The vertebrae of Najash rionegrina are similar to those of
madtsoiids in possessing parazygantral foramina, a shallow in-
terzygapophyseal constriction, and large, broad synapophyses
that exceed the prezygapophyseal facets laterally, and in lack-
ing accessory processes of the prezygapophyses (Apestegu´
ıa and
Zaher, 2006). Najash is distinct from madtsoiids, but similar to
various fossil “anilioids,” in that it lacks a posterior neural arch
notch and has hemal keels that are ‘shallow and thin.’ This mo-
saic of vertebral characters makes Najash vertebrae identifiable,
but provides little support for assignment to a higher level taxon.
MADTSOIA MADAGASCARIENSIS Hoffstetter, 1961a
(Figs. 2–4; Table 1)
Holotype Specimen—MNHN MAJ 5, posterior trunk vertebra
(Hoffstetter, 1961a:fig. 2A).
Type Locality—‘“Gite du Guide,’ North of Berivotra, Mada-
gascar” (Rage, 1984:30).
Referred Specimens—Anterior trunk vertebrae: FMNH PR
2545–FMNH PR 2549, FMNH PR 2558, FMNH PR 2569, FMNH
PR 2702, UA 9688–UA 9693, UA 9703, UA 9728. Mid-trunk
vertebrae: FMNH PR 2550–FMNH PR 2553, MNHN MAJ
9 (Hoffstetter, 1961a:fig. 3E), MNHN MAJ 10 (Hoffstetter,
1961a:fig. 3F), UA 9695, UA 9697, UA 9698, UA 9745. Poste-
rior trunk vertebrae: FMNH PR 2554, FMNH PR 2555, MNHN
MAJ 7 (Hoffstetter, 1961a:fig. 2C), UA 9700. Cloacal vertebra:
FMNH PR 2556. Postcloacal vertebrae: FMNH PR 2557, UA
9701. Fragmentary vertebrae not assigned to region: FMNH PR
2559–FMNH PR 2568, FMNH PR 2570, FMNH PR 2584, FMNH
PR 2585, MNHN MAJ 6 (Hoffstetter, 1961a:fig. 2B), MNHN
MAJ 8 (Hoffstetter, 1961a:fig. 3D), UA 9694, UA 9696, UA 9699,
UA 9702, UA 9704–UA 9712, UA 9715–UA 9718, UA 9721, UA
9726, UA 9727, UA 9729–UA 9731, UA 9735, UA 9736, UA
9738–UA 9744, UA 9747, UA 9765, UA 9766, UA 9768, UA
9772. Nearly complete ribs: UA 9746, UA 9763, UA 9764, UA
9775. Proximal rib fragments: FMNH PR 2571, FMNH PR 2582,
FMNH PR 2583, UA 9714.
Localities—The first-known specimen of Madtsoia madagas-
cariensis, described by Piveteau (1933), was listed as com-
ing from the region of Marovoay, southeast of Mahajanga
(=Majunga). The specimens described by Hoffstetter (1961a:fig.
1) were recovered from three areas listed as: (1) north of
Berivotra (the holotype, MNHN MAJ 5), (2) south of Beriv-
otra (MNHN MAJ 8–MNHN MAJ 10), and (3) north of the
Mahajanga-Ambalab´
e road, between km 20 and 25 (MNHN
MAJ 6, MNHN MAJ 7). The Mahajanga Basin Project, initiated
in 1993, has discovered specimens of Ma. madagascariensis in two
major areas (Fig. 1): (1) Berivotra Study Area localities MAD93-
01, 93-09, 93-14, 93-16, 93-17, 93-18, 93-25, 93-28, 93-30, 93-33,
93-34, 93-35, 93-36, 93-38, 93-73, 93-81, 95-14, 96-01, 96-04, 96-32,
98-08, 98-31, 99-15, 99-39, 01-03, 03-03, 03-04, 03-05, 03-09, 05-64;
and (2) Masiakakoho Study Area locality MAD03-23 (Fig. 1).
Age and Distribution—Known only from the Upper Cre-
taceous (Maastrichtian) Maevarano Formation, Berivotra and
Masiakakoho study areas, Mahajanga Basin, northwestern
Madagascar.
Revised Diagnosis—Neural spines differ from those of Madt-
soia bai and Ma. camposi in being taller and more posteriorly
canted. Zygosphenes relatively narrower than in Ma. camposi.
Zygapophyses broad and rectangular, similar to those of Ma. bai
but broader than those of Ma. camposi. Synapophyses project lat-
erally beyond prezygapophyseal facets, as in Ma. camposi, but
not as in Ma. bai, in which synapophyses project far beyond zy-
gapophyses. Ribs differ from those of Ma. bai in lacking a strong
anterodorsal process and from those of Ma. camposi in not hav-
ing the ventral articular facet projecting strongly anteriorly.
Description
An isolated vertebra of this species was described briefly
by Piveteau (1933), but no name was applied at that time.
Hoffstetter (1961a) described six additional specimens (five ver-
tebrae and one zygosphene) and, in addition to naming the
species Madtsoia madagascariensis, listed three differences be-
tween it and Ma. bai, the only other species of Madtsoia then
recognized: (1) the neural spine is taller and its distal portion
is inclined posteriorly; (2) in the posterior trunk vertebrae, the
hemal keel is more clearly delimited by more marked lateral de-
pressions; and (3) the condyle is more circular in outline and less
depressed dorsoventrally. He also described diagnostic charac-
teristics of his new subfamily Madtsoiinae. However, Hoffstet-
ter (1961a) provided only a cursory description of the vertebral
morphology of Ma. madagascariensis, and the only regions of
the vertebral column known to him were the mid- and poste-
rior trunk regions. Based on the specimens recovered as part of
the Mahajanga Basin Project, detailed descriptions of vertebrae
from the anterior trunk, mid-trunk, posterior trunk, cloacal, and
postcloacal regions, as well as parts of seven ribs are provided
here.
Table 1 provides measurements for the specimens of Madtsoia
madagascariensis collected by Mahajanga Basin Project teams
and allows comparisons of the proportions of vertebrae from dif-
ferent regions of the column. Such comparisons reveal, for ex-
ample, that the largest complete vertebrae were not the largest
specimens in the assemblage, as some fragments (e.g., isolated
zygosphenes) were larger than those present on any of the more
complete vertebrae. Furthermore, the zygosphene described and
illustrated by Hoffstetter (1961a:fig. 3D, MNHN MAJ 8) is listed
as being 22 mm wide and is therefore larger than the largest of the
zygosphenes (FMNH PR 2564; ca. 19.4 mm wide) in the samples
collected as part of the Mahajanga Basin Project.
Anterior Trunk Vertebrae—At least 16 specimens repre-
sent this vertebral region, previously undescribed in Madt-
soia madagascariensis. Several specimens are very well pre-
served and essentially complete. One of these (FMNH PR 2546;
Fig. 2A), from the anterior portion of the anterior trunk
region of a large individual, bears a strong hypapophysis.
Another specimen (FMNH PR 2548), representing a more
posterior segment of the anterior trunk region, has a much re-
duced hypapophysis and three specimens that are particularly
complete and well preserved (FMNH PR 2545, FMNH PR 2547,
FMNH PR 2549; Fig. 2B) are from the far posterior portion of
this region, resembling mid-trunk vertebrae except for the pres-
ence of slightly developed hypapophyses, just anterior to the ven-
tral lip of the condyle. The following description is based primar-
ily on these five specimens.
The centra of anterior trunk vertebrae are narrower than those
of mid-trunk vertebrae and the subcentral fossae are less pro-
nounced, especially anteriorly in the region (e.g., FMNH PR
2546). Subcentral foramina are on the sloping portion of the
keel in FMNH PR 2546 or in shallow subcentral fossae in more
posterior vertebrae. The hypapophysis is robust, elongate, and
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 113
FIGURE 2. Trunk vertebrae of Madtsoia madagascariensis from the Late Cretaceous of Madagascar in l, lateral; a,anterior;p, posterior; d, dorsal;
and v, ventral views. A, vertebra from anterior part of anterior trunk region with well-developed hypapophysis, FMNH PR 2546; B, vertebra from
posterior part of anterior trunk region, FMNH PR 2549; C, mid-trunk vertebra, FMNH PR 2551; D, vertebra from anterior part of posterior trunk
region, FMNH PR 2554; E, vertebra from middle part of posterior trunk region, FMNH PR 2555.
114 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
FIGURE 3. Cloacal and postcloacal vertebrae of Madtsoia madagascariensis from the Late Cretaceous of Madagascar in l, lateral; a,anterior;p,
posterior; d, dorsal; and v, ventral views. A, cloacal vertebra, FMNH PR 2556; B, postcloacal vertebra, FMNH PR 2557. Articular facets on ventral
aspect of postcloacal vertebra for chevron bone enlarged at bottom right.
FIGURE 4. Ribs and rib fragments of Madtsoia madagascariensis from the Late Cretaceous of Madagascar. A, anterior; and B, posterior views of
UA 9764, nearly complete left rib exhibiting a pathological lesion (indicated by arrows). C,anterior;D, posterior; and I, stereophotographic proximal
views of UA 9746, proximal half of right rib (reversed to facilitate comparison). E,anterior;F, posterior; and J, stereophotographic proximal views of
FMNH PR 2571, proximal fragment of left rib. G, anterior; and H, posterior views of UA 9763, nearly complete left rib.
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 115
laterally compressed in FMNH PR 2546, much shorter in FMNH
PR 2548, and reduced to a nubbin in FMNH PR 2545, FMNH
PR 2547, and FMNH PR 2549. The elongated hypapophysis on
FMNH PR 2546, which is paddle-like in lateral view, exhibits a
swelling at approximately mid-length of the hypapophysis. This
irregular, asymmetrical swelling resembles a bone callus, and may
indicate a healed break in the bone. The tip of the hypapoph-
ysis is bent slightly toward the left beyond the callus. However,
we note that in some madtsoiids, such as Yurlunggur camfielden-
sis and Riversleigh Yurlunggur spp., bilateral expansions of the
hypapophyses are present that may represent serial homologs of
‘paired hypapophyses’ (Simpson, 1933:3, 8) in the mid- and pos-
terior trunk regions and presumably served as sites for muscle
attachment. The subcentral ridges are not as distinct as those
present on mid-trunk vertebrae, especially anteriorly in the an-
terior trunk region.
The cotyle and condyle are depressed, especially anteri-
orly in the region, with a slightly recessed ventral cotylar
lip, but they are not emarginated ventrally; they differ from
the mid-trunk vertebrae in these respects. The neural canal
is strongly trifoliate in shape and highly depressed, approx-
imately twice as broad ventrally as high. Paracotylar fossae
are present and usually contain one large foramen each, but
the number can vary from zero (e.g., FMNH PR 2546—right
side, FMNH PR 2548—left side) to two (e.g., UA 9727—both
sides).
The zygosphene, although thick, is not massive, but gently con-
vex to flat dorsally. Its lateral margins are not elevated as they
are in the mid-trunk region. Its anterior margin is incised by a
broad, shallow notch. Zygosphenes from more posterior verte-
brae of the anterior trunk approach the massiveness of those of
mid-trunk vertebrae. The zygantrum is very large, and similar to
those of the mid-trunk vertebrae with two notable exceptions.
First, fine subvertical ridges that descend from the laminae in the
mid-trunk vertebrae are absent in the more anterior vertebrae of
the anterior trunk region (e.g., FMNH PR 2546) and only faintly
discernible in the more posterior vertebrae of the region. Second,
the roof of the zygantral cavity is distinctly peaked in the vertebra
from a far anterior position (FMNH PR 2546), though flattened
in the posterior portion of the anterior trunk and all mid-trunk
vertebrae.
In FMNH PR 2546, the neural spine is very tall and robust.
Its height is slightly greater than twice the height of the laminae
above the centrum. Anteriorly, the spine is laterally compressed,
but posteriorly it is thickened, creating a triangular section. The
spine is canted, extending posteriorly well beyond the level of
the postzygapophyses. Postzygosphenal fossae are present, but
do not contain foramina. More posterior vertebrae in the ante-
rior trunk series have shorter and anteroposteriorly longer neural
spines and can contain up to three small foramina in the postzy-
gosphenal fossae, though the foramina are not all necessarily re-
stricted to the bottom of these fossae (FMNH PR 2545).
The zygapophyseal facets are small, approximately as broad
as long. The zygapophyses are not markedly divergent from the
centrum, producing a relatively narrow aspect for the vertebra.
The synapophyses are large, and well preserved in FMNH PR
2546, in which the diapophyseal portion is separated from the
parapophysis by a distinct constriction as a result of a posterior
indentation. This indentation becomes more prominent in more
posterior vertebrae in the series and is particularly prominent in
FMNH PR 2549. The diapophyseal facet is bulbous whereas the
parapophysis is relatively flat. The latter extends ventrally well
below the lower lip of the cotyle in FMNH PR 2546, the most an-
terior vertebra in the series, but this disparity is less extreme or
even absent (FMNH PR 2545) in more posterior vertebrae of the
anterior trunk region.
Mid-trunk Vertebrae—Several complete and nearly complete
mid-trunk vertebrae are represented in the Mahajanga Basin
Project collection, significantly augmenting the sample available
to Hoffstetter (1961a). The following description is derived pri-
marily from a typical larger specimen, FMNH PR 2551 (Fig. 2C).
The centrum is roughly triangular in ventral view, much
broader anteriorly than long. A transversely convex anterior por-
tion is flanked by lateral depressions that contain distinct, paired
foramina. The hemal keel is poorly defined anteriorly, but nar-
rows abruptly in its posterior third into a much better defined keel
that bears a pair of small, blunt processes posteriorly. The lateral
margins of the centrum form prominent subcentral ridges that ex-
tend posteromedially from the posteroventral border of the para-
pophysis, almost to the condyle. The postzygapophyses are trans-
versely broad and elliptical, almost subrectangular in outline.
In anterior view, the cotyle is almost round (very slightly wider
than high) and deep, but its ventral lip is recessed posteriorly
and emarginated ventrolaterally. The neural canal is relatively
small, slightly broader than tall, and roughly triangular; inden-
tations formed by internal ridges along the floor and each of the
lateral walls produce a trifoliate outline. Well-developed para-
cotylar fossae typically contain one or two foramina. Two speci-
mens (FMNH PR 2550 and FMNH PR 2551) have two paracoty-
lar foramina on each side, one larger than the other. Another
(FMNH PR 2552) has paired foramina on the left, but a single
foramen on the right. Other specimens in which the paracotylar
fossae are visible (FMNH PR 2553, UA 9695) have a single fora-
men on each side. The neural arch laminae rise sharply from front
to back and from lateral to medial. The zygosphene is massive
and wedge-shaped in anterior view and its facets are angled at
approximately 30◦from the midline axis. The dorsolateral mar-
gins of the zygosphene project upward, due to the large facets,
creating a dorsal concavity on each side of the anterior margin of
the neural spine.
In posterior view, the condyle is almost round in outline but
slightly flattened ventrally; it is directed strongly posterodorsally.
The zygantrum is spacious and deep, with substantial zygantral
facets that project posteriorly, slightly beyond the margins of the
laminae. A deep, broad, V-shaped notch in the posterior margin
of the neural arch laminae exposes the zygantrum from above.
The anterior face of the zygantral cavity is smooth. A thin, deli-
cate ridge descends ventromedially from the neural arch lamina
approximately 30% of the distance to the ventral edge of the cav-
ity on either side of the midline. Directly below these ridges, deep
ventral fossae penetrate anteroventrally from the vicinity of the
ventral edge of the zygantral facet. The ventrolateral edges of
these fossae contain the endozygantral foramina. Parazygantral
foramina (one on each side) are also present in well-marked fos-
sae on the posterior face of the neural arch, between the zygantral
and postzygapophyseal facets.
In lateral view, the neural spine is prominent, projecting high
above the laminae. It is laterally compressed, and elongate, ex-
tending from the base of the zygosphene to the posterior edge
of the neural arch. The neural spine has a posteriorly curved an-
terior margin and an overhanging posterior end that gives it a
‘swept-back’ appearance. It overhangs the deeply incised neu-
ral arch notch to a considerable degree. At the base of the neu-
ral spine, on either side, a pronounced fossa is excavated into
the lamina of the neural arch posterior to the zygosphene. One
to three small parazygosphenal foramina (Head, 2005) may be
found at or near the base of these fossae. Although these fossae
and foramina appear to be present in at least one other madtsoiid
(Alamitophis argentinus; Albino, 2000:fig. 2C), they are described
specifically here for the first time in Madtsoia madagascariensis.
Posteriorly, the neural spine is buttressed by the neural arch
laminae, which rise to meet the spine at about three-fourths of
its height and about two-thirds of the distance back from the
anterior tip. The dorsal edge of the neural spine is laterally
compressed. The synapophyses are reniform in shape and mas-
sive, their articular surfaces largely eroded, leaving a roughened
116 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
TABLE 1. Measurements of vertebral specimens of Madtsoia madagascariensis. See text for list of abbreviations. ? =vertebral fragment not
assigned to region.
Specimen Position CL NAW PRW POW ZSW COW CNW NSH PR-PO
FMNH PR 2545 ATV 12.920.627.628.111.612.211.312.016.2
FMNH PR 2546 ATV 17.119.2 24 25.512.611.810.823.019.6
FMNH PR 2547 ATV 17.023.831.931.414.311.810.919.321.1
FMNH PR 2548 ATV 19.825 31.832.615.712.811.8—22.5
FMNH PR 2549 ATV 18 26 35.435.716.113.212.119.720.5
FMNH PR 2558 ATV — —————10.6∗——
FMNH PR 2702 ATV 16.421.7—30.0∗—12.811.319.419.6
UA 9688 ATV — —————9.8∗——
UA 9689 ATV 15.7∗———14.7∗14.3∗12.2∗—18.4∗
UA 9690 ATV — —————10.4— —
UA 9691 ATV 13.8∗————11.710.4— —
UA 9692 ATV 16.1∗—————11.1∗——
UA 9693 ATV — —————9.7——
UA 9703 ATV — —————12.0— —
UA 9728 ATV — —————11.7∗——
FMNH PR 2550 MTV 17.8∗27.2—36.0—15.5∗14.0—23.3
FMNH PR 2551 MTV 17.728.139.539.214.414.914.116.222.5
FMNH PR 2552 MTV 16.8∗25.938.7— —14.313.614.622.7
FMNH PR 2553 MTV 18.629.241.241.615.315.414.6∗17.722.6
UA 9695 MTV — 28.1— —15.5∗————
UA 9697 MTV — — — 33.2—12.1— — —
UA 9698 MTV — — — — 12.4———22.0
UA 9745 MTV 16.4∗—35.8—13.4∗14.913.3—21.1
FMNH PR 2554 PTV 15.6∗24.434.233.712.814.212.210.420.1
FMNH PR 2555 PTV 14.319.6—26.7—10.59.7∗10.118.2
UA 9700 PTV — —————14.0—23.8
FMNH PR 2556 CV 7.7∗13.519.4∗18.8∗8.1∗6.0∗5.2∗—11.8∗
FMNH PR 2557 PCV — 9.9— — 5.2∗4.7— ——
FMNH PR 2560 ? 11.015.2———8.6∗7.7∗——
FMNH PR 2561a ? — — — — 17.1————
FMNH PR 2561b ? — — — — 15.1————
FMNH PR 2561c ? — — — — 15.9————
FMNH PR 2562 ? — —————17.8— —
FMNH PR 2564 ? — — — — 19.4∗————
FMNH PR 2565 ? — —————15.7∗——
FMNH PR 2566 ? — —————18.2— —
FMNH PR 2567 ? — — — 27.6∗11.7∗————
FMNH PR 2584 ? — — — — 16.3————
FMNH PR 2585 ? — — — — 10.8————
UA 9694 ? — 19.428.2— —10.8— —17.4
UA 9696 ? 11.6∗18.7— —10.0∗11.0∗10.3∗9.9∗—
UA 9705 ? — —————12.2— —
UA 9706 ? — —————12.3— —
UA 9707 ? — — — — 11.3— —13.2—
UA 9709 ? — —————12.1— —
UA 9710 ? — —————15.7∗——
UA 9712 ? — —————14.9∗——
UA 9715 ? 13.1∗———9.5—7.0∗——
UA 9717 ? 11.4∗—————8.0∗——
UA 9718 ? 14.6∗—————10.1— —
UA 9726 ? 15.8∗—————14.4∗——
UA 9727 ? — — — — 12.0∗——12.7—
UA 9730 ? — ————15.6∗———
UA 9731 ? — ————12.1— — —
UA 9735 ? 16.1—————10.9— —
UA 9736 ? — — — — 19.3— —16.5—
UA 9738 ? 20.7—————15.3— —
UA 9739 ? — —————9.9— —
UA 9740 ? — ———————14.5
UA 9741 ? 15.4∗—————10.0——
UA 9743 ? — —————9.7— —
∗Estimated because of slight breakage or erosion.
surface. Indentation of the posterior border of these structures
demonstrates that they were each at least partially constricted
into a dorsal diapophysis and ventral parapophysis. The para-
pophysis does not extend below the ventral lip of the cotyle. A
single foramen pierces the lateral face of the pedicle.
In dorsal view, the prezygapophyses have large, subrectangular
facets whose main axes are oriented laterally. No trace of acces-
sory processes is present. Pre- and postzygapophyses, which con-
tribute greatly to the overall width of the vertebra, are connected
by a broad, thick, interzygapophyseal ridge. The zygosphene is
broad, but not unusually so, and its anterior margin is shallowly
concave (nearly flat).
Posterior Trunk Vertebrae—In addition to the holotype ver-
tebra (MNHN MAJ 5) and MNHN MAJ 7, three vertebrae re-
covered by Mahajanga Basin Project field crews can be allocated
to this region on the basis of their broad and flattened hemal
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 117
keels, more widely spaced posterior hemal keel tubercles, and
the presence of deeper subcentral fossae and paracotylar notches.
One of these specimens represents the anterior part of the se-
ries (FMNH PR 2554; Fig. 2D), another in the middle of the se-
ries (FMNH PR 2555; Fig. 2E), and another, fragmentary spec-
imen (UA 9700), a relatively posterior vertebra in the series.
These intra-regional differences are revealed primarily by the
increasing depth and distinctness of the subcentral fossae, the
related separation of the parapophyses from the cotyle (para-
cotylar notches), and the increasing breadth of the hemal keel.
In general, these vertebrae have narrower zygosphenes, smaller
neural canals, and slightly more depressed cotyles and condyles
than mid-trunk vertebrae. Where intact, the neural spines are
lower, and slightly expanded dorsally with rugose distal sculptur-
ing, which is particularly marked in FMNH PR 2554.
Cloacal Vertebra—FMNH PR 2556 (Fig. 3A) is assigned to
the cloacal region. This is a worn specimen whose extremities
are rounded and eroded. The proportions of the vertebra, includ-
ing its anteroposteriorly shortened aspect and small cotyle and
condyle, the presence of strongly arched neural laminae, and re-
duced zygapophyseal facets would be most unusual for any verte-
bra other than one from the cloacal region (see LaDuke, 1991). It
is assigned to Madtsoia madagascariensis on the basis of its large
size and a general correspondence in shape of various morpho-
logical attributes (e.g., massive zygosphene that is slightly con-
cave anteriorly, high neural arch) to other material assigned to
the species.
The specimen is short anteroposteriorly, giving it a broad as-
pect when viewed from above or below. The zygapophyses are
not very divergent from the centrum. The prezygapophyses are
particularly short mediolaterally relative to those on the trunk
vertebrae. They also lie in a nearly horizontal plane, and are thus
much less inclined than in more anterior regions. The centrum is
reduced in size, with a strongly projecting, but ventrally rounded
hemal keel occupying most of its ventral face. A true hypapoph-
ysis is absent. The condyle is eroded, but its base suggests a small
overall size, which also can be inferred from the cotyle. Even
though the edges of the cotyle are either broken or heavily worn,
it is clear that the size of the cotyle relative to the neural canal is
much less than in the trunk vertebrae. The zygosphene is massive
and its facets are not as vertically oriented as in more anterior
vertebrae. The neural spine, broken off near the base, is posi-
tioned posteriorly and is triangular in section. Parazygosphenal
fossae are present and there is a foramen in the bottom of at least
the right fossa. The paradiapophyseal region is too badly worn
to distinguish what type of processes may have been present,
though based on other features typical of cloacal vertebrae, it is
assumed that they supported lymphapophyses. The neural arch
laminae are strongly convex dorsally and thickened in posterior
view, and the parazygantral foramina (one on each side) are very
large.
Postcloacal Vertebrae—Two postcloacal vertebrae are as-
signed to Madtsoia madagascariensis. One of these (FMNH PR
2557; Fig. 3B), although exhibiting some damage to its extremi-
ties, is clearly from the anterior portion of the postcloacal region.
It is distinctive in possessing a transversely narrowed, dorsoven-
trally thickened zygosphene, and the broken base of a neural
spine that would have been moderately tall, based on its section
and the angle of ascent of its sides from the base. Beside the neu-
ral spine are distinct left and right parazygosphenal fossae, each
pierced by a large foramen. The neural arch is vaulted and the
intact right postzygapophysis has a large parazygantral foramen
(one is also seen in section on the left side). All of these features
of FMNH PR 2557, coupled with its size, support assignment to
Ma. madagascariensis. Assignment to the postcloacal region is
based on the general proportions of the vertebra, and the pres-
ence of transverse processes, broken laterally near the base, that
are the remnants of postcloacal pleurapophyses.
In addition to the above features, this specimen is particularly
noteworthy in having two distinct, rounded articular surfaces on
the ventral face of the centrum. The raised edges of the articular
surfaces (‘pedicels’ of Scanlon and Lee, 2000; Lee and Scanlon,
2002; Scanlon, 2005a) are produced into a distinct, smooth, circu-
lar rim, whereas the centers are rough and pitted, resembling syn-
chondroses. Based on comparisons with non-ophidian squamates
(i.e.,’lizards’), and with other madtsoiids known to exhibit similar
features (e.g., Wonambi naracoortensis,Alamitophis tingamarra;
Scanlon and Lee, 2000; Scanlon, 1993, 2005b), we interpret these
well-defined structures as representing articular surfaces for an
independent chevron bone. However, in contrast to the far pos-
terior position of the articular pedicels in W. naracoortensis and
A. tingamarra, these structures in Madtsoia madagascariensis ap-
pear to lie slightly nearer to the middle of the centrum than to
its posterior edge (though this is difficult to determine with exact
precision because the condyle is eroded away; Fig. 3B).
A second postcloacal vertebra (UA 9701) is missing both
postzygapophyses and has a worn condyle and other extremi-
ties, but the bases of its pleurapophyses are present. It is assigned
to Madtsoia madagascariensis on the basis of its relatively high,
laterally compressed neural spine, vaulted neural arch, and rela-
tively large size. The proportions of this vertebra suggest that it
is from near the posterior extremity of the postcloacal region.
Ribs—Four nearly complete ribs (missing less than half their
shafts) and four proximal rib fragments are assigned to Madtsoia
madagascariensis, primarily on the basis of their large size; six of
these preserve the entire head, whereas two (FMNH PR 2583,
UA 9775) have the ventral articular facet broken away.
Typical of large madtsoiids (e.g., Wonambi naracoortensis;
see Scanlon and Lee, 2000:fig. 2h), the rib heads have a
strong, low, blunt tuber costae, a large, concave, dorsal (di-
apophyseal) articular facet that is slightly recessed from the
relatively flat ventral (parapophyseal) articular facet, and a
modest, obtusely pointed anteroventral process. Although the
dorsal facet is concave on all specimens, the ventral facet
ranges from slightly convex (FMNH PR 2571, UA 9714,
UA 9746, UA 9764) to slightly concave (FMNH PR 2582,
UA 9763). The dorsal and ventral rib facets are separated
from one another by a low, rounded, oblique (oriented from
posterodorsal to anteroventral) ridge and, anteriorly, by a gen-
tle notch that gives the proximal view a slightly ‘waisted’ outline.
This waisting is particularly noticeable on FMNH PR 2582 and
UA 9714, in which the posterior border is also slightly indented.
A prominent dorsal tubercle, with accessory tubercles that de-
scend onto the anterior surface, just distal to the tuber costae, is
present on FMNH PR 2571 and UA 9746, but is less distinct on
UA 9714, UA 9763, UA 9764, and UA 9775 (this area is at least
partially broken away on FMNH PR 2582 and FMNH PR 2583).
In addition, UA 9714 has a distinctive crest accentuating its ven-
tral surface in a posterior position, distal to the location of the
anteroventral process. This crest rises to form a tubercle near its
proximal end, then decreases in height as it runs distally to the
broken surface of the neck. This posteroventral crest is absent or
poorly developed in FMNH PR 2571, FMNH PR 2582, UA 9746,
UA 9763, UA 9764, and UA 9775. In those specimens preserving
the dorsal region distal to the head, a prominent foramen, in a
shallow depression posterior to the tuber costae, pierces the dor-
sal surface of the rib; in FMNH PR 2582, UA 9746, and UA 9763,
a smaller, accessory foramen lies immediately proximal to this
prominent foramen (in FMNH PR 2583 only the smaller fora-
men is partially preserved, the remainder of the rib being broken
away). Two (UA 9763, UA 9764), three (FMNH PR 2571, UA
9714, UA 9747), or even four (FMNH PR 2582) foramina, of vari-
able size and position, are present on the shallowly concave lower
anterior face, distal to the ventral facet. Finally, on those spec-
imens preserving this region well enough for observation, one
(FMNH PR 2582, UA 9714), two (FMNH PR 2571, UA 9746,
118 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
UA 9775), or three (UA 9763) foramina are present on the pos-
terior surface, ventral to the midline, in the area near where the
head narrows to form the neck. Differences among the eight spec-
imens are likely attributable to differential preservation, individ-
ual variation, variability along the length of the vertebral column,
and/or even age/size of the individual at death. Size ranges from
9.9 mm (UA 9763) to 16.6 mm (UA 9764) along the longest axis
of the rib head (posterodorsal to anteroventral).
The most complete specimen, UA 9764, is of additional inter-
est because it presents an apparent pathological lesion, likely a
healed fracture. This specimen has an abrupt swelling just beyond
the apparent midpoint of the shaft (i.e., the straightest part of the
shaft, distal to the angle, and proximal to a slightly more curved
distal region). The swelling has the appearance of a bony callus,
but its posterior face is rough and pitted, as though incompletely
healed.
Comparisons
Vertebrae—In light of the vast expansion of the known sam-
ple of vertebrae of Madtsoia madagascariensis, it is relevant to
underscore that this species is clearly a madtsoiid in its large
size and the following vertebral features: (1) presence of parazy-
gantral foramina in fossae lateral to each zygantral facet; (2) pres-
ence of paracotylar foramina; (3) wide diapophyses; (4) absence
of prezygapophyseal processes; (5) hypapophyses limited to an-
terior trunk region; and (6) hemal keels moderately to well de-
veloped on mid- and posterior trunk vertebrae. In addition, as
in several other madtsoiids (but not other snakes), the mid- and
posterior trunk vertebrae bear short, laterally paired projections
on the posterior extremity of the hemal keel.
Hoffstetter (1961a) pointed out that the vertebrae of Madt-
soia bai differ from those of Ma. madagascariensis in the shape
of their neural spines. Those of Ma. bai are more or less
vertical in orientation, whereas those of Ma. madagascarien-
sis lean posteriorly. Hoffstetter also stated that, in posterior
trunk vertebrae of Ma. madagascariensis, the hemal keel is
better defined and the cotyle and condyle are more rounded.
Comparisons of serially homologous portions of the present
material with the holotype of Ma. bai (which includes only mid-
and posterior trunk vertebrae) reveal a host of differences in
shape. These include (condition of Ma. bai in parentheses): (1)
Madtsoia madagascariensis vertebrae have a high, anteropos-
teriorly short aspect, with rounded condyles and cotyles and
high neural canals (depressed, broad aspect with relatively de-
pressed condyles, cotyles, and neural canals); (2) the zygosphene
is massive and wedge-shaped (broad, but not massive, gently
convex dorsally); (3) the synapophyses are large and extend lat-
erally, slightly beyond the lateral margin of the prezygapophy-
ses (synapophyses with similar-sized articular surface areas, but
much larger because they project far beyond the margin of the
prezygapophyses by approximately half the width of the prezy-
gapophyses); (4) posterior margins of the neural arch laminae
ascend to approximately three-fourths the height of the neural
spine and end about two-thirds of its length back from its ante-
rior edge (the posterior margins of the laminae ascend all the way
to the dorsal margin of the neural spine, joining it approximately
midway between anterior and posterior edges, giving the extrem-
ity of the neural spine a diamond shape from above); and (5)
the postzygosphenal fossae are deeply incised and contain small
foramina (shallow, no foramina observed).
Vertebrae of Madtsoia madagascariensis differ from those
of Ma. camposi Rage 1998 in having a higher, anteroposteri-
orly shorter neural spine, and in lacking a strong, dorsoven-
trally oriented ridge on the anterior face of the prezygapophy-
seal buttress (Rage, 1998). Rage also indicated that Ma.
camposi has a relatively broader and less wedge-like zygosphene
than Ma. madagascariensis. Finally, Ma. camposi appears to have
much less broadened zygapophyseal facets (Rage, 1998:fig. 2).
Both Ma. madagascariensis and Ma. bai have distinctly rectangu-
lar facets, much broader (mediolaterally) than long (anteropos-
teriorly), whereas those of Ma. camposi (holotype similar in size
to FMNH PR 2551) are roughly square.
A few specimens of snake vertebrae from the Senonian of
Niger were mentioned by de Broin et al. (1974) and were il-
lustrated by Rage (1981:fig. 2), who assigned them to Madt-
soia aff. madagascariensis. Comparisons of Rage’s illustrations
to the available material of Ma. madagascariensis reveal that, al-
though there are some general similarities, the Niger specimens
have a more depressed neural arch, with a broader, lower neu-
ral canal; the centrum is more depressed with a broad, more
strongly emarginated cotyle; and the hemal keel appears to be
better defined and ends in a distinctly angular posterior margin
(in Ma. madagascariensis, the posterior margin is more rounded
in shape and bears two distinct tubercles). Differences between
the specimens from Niger and those of Ma. madagascariensis ap-
pear to be at least at the level of species and we therefore rec-
ommend that the former be referred to as ?Madtsoia sp. until ad-
ditional, more diagnostic material can be found, described, and
compared.
Scanlon and Lee (2000:fig. 2f, g) demonstrated that postcloa-
cal vertebrae of Wonambi naracoortensis possess ‘true’ chevron
bones, which are not present in any modern snakes (Hoffstet-
ter and Gasc, 1969). Chevron bones are present in non-ophidian
lepidosaurs, but are represented in modern and most fossil
snakes by the hemapophyses of postcloacal vertebrae, which
are fused to the centrum and nearly always paired, but not
fused distally. Articular surfaces that suggest the presence of
chevron bones in FMNH PR 2557, an anterior postcloacal ver-
tebra of Madtsoia madagascariensis,aswellasinAlamitophis
tingamarra (Scanlon, 1993:fig. 2B; 2005b:fig. 6D), support the
idea that these structures may be characteristic of Madtsoiidae.
If this is true, and if madtsoiids lie outside of ‘crown group
snakes’ (Alethinophidia +Scolecophidia; Serpentes sensu Lee
and Caldwell, 1998), then the presence of paired postcloacal
hemapophyses may represent a synapomorphy of Alethinophidia
(Lee and Scanlon, 2002; Scanlon, 2005a; but see Rieppel et al.,
2002), given that all scolecophidians lack both chevron bones
and hemapophyses (List, 1966; Hoffstetter and Gasc, 1969). The
presence of chevron bones in the pachyophiid Eupodophis de-
scouensi (Rage and Escuilli´
e, 2000) may offer further corrobo-
ration of this hypothesis, as pachyophiids, like madtsoiids, are
often recovered in phylogenetic analyses as basal snakes, ly-
ing outside of Scolecophidia +Alethinophidia (e.g., Lee et al.,
1999; Scanlon and Lee, 2000; Lee and Scanlon, 2002). How-
ever, other analyses have placed these snakes as basal macros-
tomatans, nested deeply within Alethinophidia (e.g., Tcher-
nov et al., 2000; Rieppel et al., 2002; Apestegu´
ıa and Zaher,
2006). Moreover, the structure, position, and relations of the
chevron bones in Eupodophis are rather different from those
seen in Madtsoia,Wonambi,andAlamitophis, suggesting that
these structures in Eupodophis might be autapomorphic rather
than plesiomorphic (Rieppel and Head, 2004). Thus, the evolu-
tion of chevron bones and hemapophyses within snakes remains
incompletely understood given the evidence that is currently
available.
Ribs—The ribs of Madtsoia madagascariensis share the later-
ally recessed dorsal articular facet with Ma. bai and Ma. camposi
(Simpson, 1933; Rage, 1998). Madtsoia madagascariensis differs
from Ma. bai in that it lacks a strong anterodorsal process. Madt-
soia camposi is distinctive in that the ventral articular facet is
thrust anteriorly relative to its position in other madtsoiids (in-
deed most snakes). Madtsoia camposi apparently shares with Ma.
madagascariensis the presence of a ventral crest just distal to the
rib head and slightly posterior in position. This crest is preserved
in only a few specimens of each species, and appears to be most
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 119
pronounced in smaller individuals. Although the distribution of
foramina has not been reported for Ma. camposi,Ma. bai pos-
sesses a large dorsal foramen that is comparable to that of Ma.
madagascariensis.
The ribs of Madtsoia madagascariensis resemble those of Won-
ambi and Yurlunggur in general proportions (Scanlon, 1992).
However, a large dorsal foramen in Ma. madagascariensis is con-
tained within a fossa, whereas variable numbers of smaller foram-
ina are found in a dorsal groove in Wonambi and Yurlunggur
(Scanlon, 1992). Although Nanowana,Alamitophis,andPatag-
oniophis are much smaller than Madtsoia,Nanowana and Alami-
tophis share the general proportions of the rib head of Ma. mada-
gascariensis (Scanlon, 1993). Patagoniophis is more similar to
Ma. bai in possessing an expanded anterodorsal process. Madt-
soia madagascariensis ribs differ in a number of features from
those of Menarana nosymena, described below. Most prominent
among these differences is the less strongly recessed dorsal facet.
Also, the tuber costae is not drawn out into a crest as it is in
Me. nosymena, thus there is a dorsal fossa containing a foramen,
rather than a sulcus or groove as in Me. nosymena. Finally, ribs
of Menarana possess fewer foramina on their anteroventral and
posterior surfaces.
MENARANA, gen. nov.
Type Species—Menarana nosymena, sp. nov.
Referred Species—Madtsoia laurasiae Rage, 1996.
Diagnosis (modified in part from diagnosis of Madtsoia
laurasiae by Rage, 1996a)—Vertebrae differ from those of other
large madtsoiids in having lower to obsolete neural spines and
more depressed neural arches, particularly in the posterior trunk
series, and, with the possible exception of Gigantophis, in hav-
ing anteroposteriorly expanded prezygapophyseal facets. Fur-
ther differs from Madtsoia in possessing relatively narrow zy-
gosphenes, diapophyses that do not extend laterally beyond
prezygapophyseal facets, hemal keel in posterior trunk undercut
laterally by subcentral grooves, keel approaching or exceeding
width of condyle and cotyle, and the latter both subtriangular
(flattened ventrally and narrowing dorsally). Most comparable to
Patagoniophis in possessing low neural spine, depressed and shal-
lowly emarginated neural arch, and hemal keel, defined laterally
by grooves, not bifurcated posteriorly but with elongate lateral
ridges on its posterior half; distinguished from Patagoniophis by
much larger size and proportional differences, such as less elon-
gate centrum. Ribs (based only on Me.nosymena) differ from
those of all other madtsoiids in having a strongly recessed dor-
sal articular facet, leaving a medial pillar that supports the tuber
costae posteriorly, and a dorsal crest that encloses a longitudinal
sulcus containing a single, prominent foramen.
Etymology—From menarana (Malagasy, meaning ‘snake’).
Pronounced may-na-RAH-na.
MENARANA NOSYMENA, gen. et sp. nov.
(Figs. 5–9; Table 2)
Holotype Specimen—UA 9684, partial skeleton consisting
of a large number of articulated or associated complete,
nearly complete, and fragmentary vertebrae (including a par-
tial atlas), several fragmentary ribs, and a sizable fragment of
the braincase, all presumed to have been derived from the
same individual because they share comparable morphology
and similar preservational characteristics, represent the same-
sized snake, and were collected from the same small area
(∼2m
2) at Locality MAD93-14. For descriptive purposes and for
tabulation of measurements in Table 2, suffixes were added to
the specimen number for several individual elements. As such, in
the description below, UA 9684-1 is a mid-trunk vertebra, UA
9684-2 is a posterior trunk vertebra, UA 9684-3 is the basicranial
fragment, UA 9684-4 is the atlas, and UA 9684-5 is the proximal
fragment of a right rib.
Diagnosis—Vertebrae differ from those of Menarana laurasiae
in lacking ridge extending dorsomedially from posterodorsal part
of diapophysis (interrupting interzygapophyseal ridge and ex-
tending to near anterior limit of neural spine), and in possess-
ing shallower neural arch notch into which posterior portion
of thicker neural spine projects, mediolaterally narrower zy-
gapophyseal facets, and extremely broad and flat hemal keel on
mid- and posterior trunk vertebrae (expanding to width of cotyle
anteriorly and with margins drawn out into elongate lateral ridges
in posterior half), in which both anterior and posterior ends are
undercut laterally by subcentral grooves.
Etymology—From nosy (Malagasy, meaning ‘island’) and
mena (Malagasy, meaning ‘red’), in reference to the commonly
used nickname for Madagascar, the Red Island. Pronounced
know-see-MAY-na.
Type Locality—MAD93-14, Berivotra Study Area, Mahajanga
Basin, northwestern Madagascar.
Referred Specimens—Anterior trunk vertebrae: UA 9687
(two associated specimens, designated UA 9687-1 and UA 9687-2
for descriptive purposes). Mid-trunk vertebrae: FMNH PR 2543,
FMNH PR 2544, FMNH PR 2703, UA 9686 (juvenile). Posterior
trunk vertebra: FMNH PR 2542. Fragmentary vertebrae not as-
signed to region: UA 9685, UA 9713, UA 9733.
Localities—Berivotra Study Area localities MAD93-14, 93-16,
93-35, 99-31, 05-14; Masiakakoho Study Area localities MAD05-
59, 07-37 (Fig. 1).
Age and Distribution—Known only from the Upper Cre-
taceous (Maastrichtian) Maevarano Formation, Berivotra and
Masiakakoho study areas, Mahajanga Basin, northwestern
Madagascar.
Description
Braincase Fragment—A single cranial fragment was found in
association with the vertebrae and ribs of UA 9684. For descrip-
tive purposes, it is designated UA 9684-3. It is considered to com-
prise most of the basioccipital and adjacent parts of the paired
prootics and opisthotic-exoccipital complexes, as well as the me-
dian parabasisphenoid, fused together so that few traces of su-
tures are retained (Fig. 5). Such fusion of braincase elements, al-
though apparently restricted among extant snakes to small fosso-
rial forms (e.g., Scolecophidia, Uropeltidae; List, 1966; Rieppel
et al., 2009; Rieppel and Zaher, 2002; Cundall and Irish, 2008), is
known in a large adult (but not in several smaller specimens) of
Yurlunggur sp. (Scanlon 2006), and is thus consistent with refer-
ral of UA9684-3 to Madtsoiidae.
Remnants of sutural margins can be identified on the ventral
(external) surface, but more distinctly on the dorsal (en-
docranial) surface. Postmortem cracks are also present in this
specimen. In some instances it is difficult to differentiate between
sutures and cracks, and the sutures are not perfectly symmetrical
bilaterally; it is assumed here that some of the cracks were
propagated along lines of weakness resulting from sutures or
sutural remnants. The dorsal surface reveals an ‘H-shaped’
sutural pattern; the transverse suture across the midline appears
to be the contact between basioccipital and parabasisphenoid,
and it meets longitudinal sutures (approximately symmetrical,
but indistinct posteriorly on the right side, where fusion may be
more complete) interpreted as the junctions between the lateral
margins of the basioccipital and parabasisphenoid and the medial
margins of the prootics. Ventrally, there are deep transverse
fissures approaching the midline between ridges representing
the posterior margin of the parabasisphenoid and anterolateral
crests of the basioccipital (the prootics are presumably exposed
120 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
FIGURE 5. Braincase fragment, UA 9684-3 (part of holotype), of Menarana nosymena, gen. et sp. nov., from the Late Cretaceous of Madagascar.
Stereophotographs (left and center) and interpretive drawings (right) of A, dorsal; B, ventral; C, left lateral; and D, right lateral views. Abbreviations:
bbs, basisphenoid-basioccipital suture; ci, crista interfenestralis; ct, crista tuberalis; ds, dorsum sellae; eap, exoccipital ascending process; lr, lagenar
recess; pbs, prootic-basisphenoid suture; pip, inferior process of prootic; rst, recessus scalae tympani; sot, spheno-occipital (basal) tubercle; vc,Vid-
ian canal; VII, facial canal; VII h, foramen for hyomandibular branch of facial nerve; VII p, foramen for palatine branch of facial nerve; and XII,
hypoglossal canal.
ventrally in the lateral part of these fissures, but recessed
relative to the other bones), and a thin and interrupted suture
across the midline where the sagittal crests of basioccipital and
parabasisphenoid meet. No trace of sutures has been detected
where the opisthotic-exoccipitals meet either the basioccipital or
prootics, but the approximate locations of these boundaries can
be inferred by comparison with Yurlunggur,Wonambi, and other
squamates.
Posteriorly, the occipital condyle is broken off at an oblique
fracture through its neck; this is nearly round in posterior
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 121
FIGURE 6. Braincase fragment, UA 9684-3 (part of holotype), of
Menarana nosymena, gen. et sp. nov., from the Late Cretaceous of Mada-
gascar in dorsolateral view (image obtained from HRXCT dataset). Ab-
breviations:bbs, basisphenoid-basioccipital suture; ci, crista interfenes-
tralis; ds, dorsum sellae; eap, exoccipital ascending process; lc, lagenar
crest; lr, lagenar recess; rst, recessus scalae tympani; VII, facial canal; and
XII, hypoglossal canal.
view (slightly flattened dorsally) and no trace of exoccipital-
basioccipital sutures is visible on the broken face, so it is un-
clear whether the exoccipitals met broadly on the dorsal surface
of the condyle and neck. Robust ventral tubercles form a ‘collar’
on the neck, separated by a distinct median notch containing a
prominent foramen and continuous laterally with the crista tu-
beralis of the exoccipital (nearly complete on the left side, dam-
aged on the right), the combined crest being strongly concave
ventrally. The specimen is broken horizontally just dorsal to the
condylar neck, so that only a small ventral segment of the margin
of the foramen magnum is preserved.
Nearly symmetrical, roughly triangular areas of breakage
are seen in dorsal view immediately anterior to the condy-
lar neck on either side of the foramen magnum. Between
them is the anteriorly widening posterior part of the brain-
case floor, where sutures between exoccipitals and basioccip-
ital would be expected (here regarded as fully fused, as in
Yurlunggur sp. QMF45111; Scanlon, 2006). Six small foramina
are present in this area, three on each side of the midline [cf.
two and four foramina in Wonambi naracoortensis and Yurlung-
gur sp., respectively]. The preserved part of the braincase floor
forms an elongate, bowl-shaped depression surrounded by bro-
ken surfaces, canals, and recesses of the ear region on either
side.
The triangular broken areas (sections through ascending
arches of exoccipitals) are bounded anterolaterally by canals
that extend in a horizontal plane from the endocranial surface to
emerge posterolaterally in a concavity dorsal to the crista
tuberalis; these are interpreted as foramina for branches of
the hypoglossal nerve (XII). (The only other identification to
be considered, that of jugular foramina, is suggested by their
relatively large size, but ruled out by their ventral position.)
Anteriorly adjacent to these openings are a second pair of
canals (fully exposed by breakage on the left side, but still
partly roofed by bone on the right) that are impressed more
deeply (ventrally) into the bone and open more widely in a
more lateral position, as a dorsal trough extending (on the
left side) to the most lateral part of the crista tuberalis. These
canals are identified as the recessus scalae tympani (and thus as
being bordered by the basioccipital, exoccipital, and opisthotic,
where the latter two elements remain separated by the metotic
fissure), and are discussed further below where comparisons
are made with other taxa. The recess is overhung anteriorly by
the narrow broken end of a bridge-like structure, expanding
anteriorly into smoothly concave dorsolateral and dorsome-
dial surfaces separated by a dorsal ridge; this is the crista
interfenestralis (anteroventral, opisthotic part of the
opisthotic-exoccipital), bearing the ventral part of the crest
defining the fenestra ovalis (occupied in life by the stapedial
footplate) and thus separating the (lateral) juxtastapedial re-
cess from the cavum vestibuli. In the floor of the latter is the
deep, rounded lagenar recess, and these recesses, each mostly
surrounded by vertical crests, are among the most conspicuous
features of the specimen in dorsal view. The crista interfenestralis
is less conspicuous on the right side as its lateral part is broken
away. On the left, it apparently extended to the lateral surface
of the braincase as part of the spheno-occipital (basal) tuber,
but no distinct traces of sutures are visible between the crista
interfenestralis, crista tuberalis, and prootic (in either dorsal or
lateral view). Medial to the crista interfenestralis, the anterior
wall of the recessus scalae tympani is smoothly continuous with
the medially convex wall of the tympanic bulla (sensu Oelrich,
1956). Each lagenar recess is partly encircled by a dorsally open
groove narrowest posteromedially, then widening anteriorly and
ultimately curving back laterally around the medial edge of the
recess, and sharply defined from it by an overhanging ridge of
bone, the lagenar crest. Anterior to each recess is a transverse
parapet of broken bone bordered anteriorly by the floor of a
transverse canal, apparently quite unconnected to the cavum
vestibuli, and identified here as the canal for the facial nerve
(VII), distal to its divergence from the vestibulocochlear nerve
(VIII) intracranially. The facial nerve canal is partly preserved
FIGURE 7. Atlas, UA 9684-4 (part of holo-
type), of Menarana nosymena, gen. et sp.
nov., from the Late Cretaceous of Madagas-
car. Stereophotographs of A, anterior; and B,
posterior views.
122 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
FIGURE 8. Trunk vertebrae of Menarana nosymena, gen. et sp. nov., from the Late Cretaceous of Madagascar in l, lateral; a,anterior;p, posterior;
d, dorsal; and v, ventral views. A, anterior trunk vertebra, UA 9687-1 (lateral view reversed); B, mid-trunk vertebra, UA 9684-1 (part of holotype); C,
posterior trunk vertebra, UA 9684-2 (part of holotype).
for its full width on the left, but somewhat worn, and connects
the cranial cavity to the external braincase wall. On the right,
the medial part of the canal is broken away but the lateral part
is more extensively preserved, including a ventral expansion
deep within the bone, which is inferred to be where the palatine
and hyomandibular branches of the nerve diverge toward their
separate external foramina. The floor of the braincase slopes
upward toward the anterior margin of the fragment, representing
the posterior slope of the dorsum sellae. HRXCT reveals that a
longitudinal groove in the braincase floor, crossing the transverse
sutural remnant to the left of the midline, contains a single
foramen (transverse slice number 168) that joins a transverse
canal within the bone (mainly slice numbers 138–148); however,
there is no trace of paired foramina or canals for the abducens
TABLE 2. Measurements of vertebral specimens of Menarana nosymena, gen. et sp. nov. See text for list of abbreviations. ? =vertebral
fragment not assigned to region.
Specimen Position CL NAW PRW POW ZSW COW CNW NSH PR-PO
UA 9687-1 ATV 8.17.511.0—4.54.34.1—9.8
UA 9687-2 ATV 8.5∗————4.4∗———
FMNH PR 2543 MTV 8.7∗12.217.6—6.77.16.63.111.7
UA 9686 MTV 7.4∗7.411.1— —4.74.0∗2.48.8
UA 9684-1 MTV 11.514.8∗—18.96.98.37.63.215.1
UA 9684-7 MTV 10.4—————5.1——
UA 9694-8 MTV 12.614.521.2—7.48.47.93.316.0∗
UA 9694-9 MTV — 14.8∗20.9—7.2∗7.6—3.515.8
UA 9694-10 MTV 11.412.017.4—5.87.66.93.113.7
UA 9694-11 MTV 11.7—20.7— —8.67.6——
UA 9694-12 MTV 10.4—————5.2——
UA 9694-13 MTV 10.4—————5.0——
FMNH PR 2544 MTV 7.411.8—17.26.4∗—5.23.5—
FMNH PR 2703 MTV 8.29.814.2—5.56.25.32.59.8
UA 9684-2 PTV 11.312.417.8— —8.07.23.514.1
UA 9684-5 PTV — 11.517.6— —7.0—3.3—
FMNH PR 2542 PTV 11.4—————7.7——
UA 9684-6 ? — — — — 7.0 ————
UA 9685 ? — — — — 8.0——3.8—
UA 9733 ? 9.0—————6.4——
∗Estimated because of slight breakage or erosion.
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 123
FIGURE 9. Proximal fragment of right rib, UA 9684-5 (part of holo-
type), of Menarana nosymena, gen. et sp. nov., from the Late Cretaceous
of Madagascar in A,anterior;B, posterior, and C, stereophotographic
proximal views.
(VI) nerves, so the crista sellaris must have been somewhat
anterior to the broken edge.
In ventral view the specimen is marked by a distinct but smooth
sagittal crest, and several more rugose and sculptured transverse
crests. The sagittal crest is narrow anteriorly (the boundary of
concave ventrolateral areas on the anterior one-third of the frag-
ment) and disappears posteriorly just anterior to the paired ven-
tral tubercles on the condylar neck, but is deepest where it forms
a smooth-surfaced, kite-shaped expansion in the middle of the
ventral surface; this lies directly between the deep ventrolateral
troughs and is crossed by a narrow, sinuous groove that appears
to be a remnant of the suture between the parabasisphenoid and
basioccipital (as revealed by HRXCT scans, this groove is present
only externally, supporting its identification as a fused suture).
Extending laterally and somewhat anteriorly from this central
‘boss’ are somewhat sculptured crests formed by the posterior
margin of the basisphenoid. More strongly sculptured, thicker,
and more sinuous crests also extend posterolaterally from the
boss, representing the anterolateral margins of the basioccipi-
tal, which are continuous laterally with the basal tubera (com-
plete on left, broken off on right). Posterior to these crests,
there is no clear distinction between the basioccipital and ex-
occipitals, and the paired tubera on the condylar neck are con-
tinuous laterally with the crista tuberalis, together extending al-
most directly laterally to meet the other crests at the basal tu-
ber. The prootics are recessed in ventral view between the crests
of the basisphenoid and basioccipital, forming deep transverse
troughs as noted above, and these form deep, overhung de-
pressions, pierced by several foramina, at their medial extremi-
ties where the three bones are interpreted to have met on each
side.
A direct lateral view of the element is difficult to interpret, but
3-D HRXCT renderings at several angles, from ventrolateral to
dorsolateral, assist with identification of internal as well as exter-
nal structures. The fragment is more complete posteriorly on the
left side, but anteriorly on the right. The ear region is seen best
in left dorsolateral view (Fig. 6), with the deep trough of the re-
cessus scalae tympani diverging from the hypoglossal canal, over-
hung by the crista interfenestralis, and extending to near the lat-
eral edge of the basal tuber. As far as preserved, there is no sign
that the apertura lateralis (occipital recess) was subdivided by a
dorsolateral contact between the crista tuberalis and crista inter-
fenestralis (as it is in Wonambi,Yurlunggur, and most modern
snakes). However, as in these snakes, and unlike the condition ex-
hibited by Dinilysia and Najash, the fenestra ovalis (as marked by
the crest on the crista interfenestralis) was deeply recessed from
the lateral skull wall.
Fusion of the elements contributing to the basal tubera
appears to be practically complete, so that the margins of
the crista tuberalis, crista interfenestralis, basioccipital, and
prootic are not discernible laterally; however, the dorsally bro-
ken crest forming the anterolateral part of the tuber and
bounding the juxtastapedial recess (on both sides) can be
identified as part of the crista prootica (forming the anterior
part of the crista circumfenestralis). At the dorsolateral mar-
gin on each side, a notch represents the foramen for the hy-
omandibular branch of the facial nerve (as described in dorsal
view above), and extending anteriorly from directly below it is
a laterally open trough (partly preserved on left, more complete
on right) identified as the parabasal (Vidian) canal. The canal is
open posteriorly but defined by distinct dorsal and ventral mar-
gins that become deeper anteriorly, tending to close laterally (as
preserved on right), but both margins are broken; although no
suture is preserved, the dorsal and ventral margins of the canal
represent parts of the prootic and basisphenoid. Under the over-
hanging prootic crest on each side (clearly visible ventrolater-
ally) is a foramen presumably for the palatine branch of the fa-
cial nerve, considerably smaller than the hyomandibular foramen
posterodorsal to it. The right side preserves a considerable part of
the lower anterior process of the prootic, but its anterior and dor-
sal surfaces are broken and no part of the trigeminal foramen is
preserved.
A dorsolateral view of the specimen (Fig. 6) allows observa-
tion of the medial aspect of the inner braincase wall, including
the partly preserved hypoglossal foramen on each side (which
would have been entirely within the exoccipital), medial aper-
ture of the recessus scalae tympani (still roofed by bone on right
side; at the boundary of the exoccipital and opisthotic with—in
most squamates—the basioccipital, all three elements being fused
here), and internal foramen of the facial nerve (partly preserved
on left). No part of the acoustic foramen is preserved on either
side, as the thin wall of the tympanic bulla is broken at too low a
level.
The lagenar recess is normally connected to the recessus
scalae tympani by the perilymphatic foramen, passing below the
posteromedial part of the crista interfenestralis. It was initially
unclear whether such passages were obscured by matrix within
the recesses, but further preparation and HRXCT scanning
shows that this is not the case. The broken posterodorsal margin
of the lagenar crest is interrupted on each side (transverse
slices 530–540), just medial to the crista interfenestralis, by a
semicircular notch that is interpreted as the lower part of the
perilymphatic foramen, in a similar position to that of Wonambi
(illustrated but not named in Scanlon 2005a:fig. 11). There
is no indication in micro-CT slices that there was a contact
between the crista interfenestralis and crista tuberalis dividing
the occipital recess into two lateral openings (i.e., the ‘fenestra
pseudorotunda’ appears to be absent).
Atlas—A fragment associated with the skeleton of UA 9684,
designated UA 9684-4 (Fig. 7), represents the intercentrum of
the atlas and associated lower portions of the two neural arch
124 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
halves. The size of this element also serves to confirm the associ-
ation of the basicranial fragment described above with the trunk
vertebrae of Menarana nosymena.
The entire structure is a very short, biconcave disc from which
the upper parts of the two halves of the neural arch have been
broken away. What is interpreted to be the anterior cotyle is
evenly concave, narrower, and deeper than what is interpreted to
be the posterior cotyle (these relative shapes are consistent with
those in comparative specimens of extant snakes). The wall be-
tween the two cotyles is complete ventrally but incomplete dor-
sally, and is marked by a small, ventrally projecting, V-shaped
notch. Two symmetrically positioned grooves on the anterior
edge appear to mark the anterior portion of the now fused su-
ture between the intercentrum and the neural arch halves. Poste-
riorly, the intercentrum bears a large articular surface to receive
the dens/odontoid process of the axis. The hemal keel is thick and
I-shaped, with the top horizontal part of the I situated posteriorly
and longer than the bottom horizontal part of the I, which is sit-
uated anteriorly. In living snakes, the atlas remains tripartite (or
bipartite, as in some uropeltids) throughout ontogeny, without
fusion of sutures (Hoffstetter and Gasc, 1969).
Anterior Trunk Vertebrae—The only two definitive anterior
trunk vertebrae, UA 9687-1 and UA 9687-2, are damaged. UA
9687-1 (Fig. 8A) is the most complete specimen and forms the
primary basis for the following description; it is missing the neu-
ral spine and hypapophysis, and the posterior portion of the neu-
ral arch is damaged, though the right postzygapophysis is intact.
UA 9687-2 is comprised of the centrum as well as the left prezy-
gapophysis.
In ventral view, the centrum is short and broad, with strong
subcentral ridges that converge toward the posterior end. The
hypapophysis is broken off near its base, which is triangular in
shape, with the sharp apex being directed anteriorly. The postzy-
gapophyseal facet, preserved only on the right side, is rounded.
In anterior view, the cotyle is round and the neural canal trian-
gular. The zygosphene is wedge-shaped with gently convex dor-
sal and slightly concave anterior borders. The zygapophyses do
not extend very far lateral to the neural arch, and have nearly
horizontal facets. Two paracotylar foramina are present on the
right (one much larger than the other), and three small foramina
are present on the left. The prezygapophyseal buttress is massive.
There is no indication of any type of accessory processes.
From above, the zygosphene is narrow and the prezygapophy-
ses are rounded. The posterior part of the neural arch is broken
away, except for the right postzygapophysis. The interzygapophy-
seal ridge is well developed.
In lateral view, there is a single lateral foramen on each side.
The synapophyses are heavily eroded, but their outline shows
that they were large and rounded. The neural spine is missing.
In posterior view, the condyle is rounded and the neural canal
is triangular and vaulted. There is a large parazygantral fora-
men above the intact right postzygapophysis, beside the zygantral
facet. In general, the vertebra is taller, relative to its width, than
those in the mid-trunk and posterior trunk regions.
Mid-trunk Vertebrae—A single mid-trunk vertebra, UA 9684-
1 (part of holotype), was selected to serve as the primary spec-
imen on which to base this description of mid-trunk vertebral
morphology (Fig. 8B).
In ventral view, the vertebra is broad with a wide, flattened
hemal keel that occupies most of the ventral surface. The lateral
edge of this keel region is pierced by a single subcentral foramen
on each side. These foramina are closer to the anterior than to the
posterior end. Lateral to the keel region, there are raised shelves
that represent the lateral portion of the ventral face of the cen-
trum. These raised areas are confluent with paracotylar notches
and correspond to weakly developed subcentral paralymphatic
fossae, indicating a position in the posterior portion of the mid-
trunk region.
The anterior face is depressed, with a broad, low neural canal
(though some dorsoventral crushing exaggerates the lowness)
and a cotyle that is wider than high. The cotyle is also recessed
and relatively emarginate below. The paracotylar fossae are dis-
tinct and each is flanked by a more or less vertically oriented
keel that protrudes slightly forward from the prezygapophyseal
buttress. On the anterior face of the prezygapophyseal buttress,
just below the facet and lateral to the keel, there is a minute
tubercle that points anteriorly. This tubercle differs in size, po-
sition, and orientation from typical prezyapophyseal accessory
processes seen in most alethinophidian snakes. There is no obvi-
ous sign of a foramen in the paracotylar fossa on the right side
and the fossa is damaged on the left. The zygosphene is nar-
row (just slightly wider than the neural canal) and wedge-shaped
with a concave dorsal surface along its most anterior border.
Its facets are oriented approximately 20◦from the vertical. The
prezygapophyses project laterally to a modest extent. Their facets
are oriented at a low angle (approximately 20◦) to the horizontal
plane.
In posterior view, the condyle is subspherical (wider than high)
and directed posterodorsally. The zygantrum is deep but not
wide. Its anterior face is convex and bears endozygantral foram-
ina (visible on at least the left side) within laterally positioned
fossae. The neural arch pedicles are low, bringing the postzy-
gapophyses into close proximity with the condyle. The posterior
edge of the neural arch has a narrow, shallow notch that is occu-
pied largely by the posterior edge of the neural spine. The poste-
rior surface of the postzygapophysis bears a single foramen at the
bottom of a shallow fossa.
In lateral view, the neural spine is barely raised above the level
of the posterior margin of the neural arch laminae. The anterior
end of the spine drops abruptly to the base of the zygosphene.
Breakage in the interzygapophyseal ridge area of this specimen
may obscure some detail. The subcentral ridges are strong and
sharply angular anteriorly, just behind the synapophyses, but they
curve medially and merge with the body of the centrum before
reaching the condyle. The synapophyses of UA 9684-1 are eroded
and their features cannot be determined.
From above, the vertebra appears broad and flattened. The
neural spine, rugose along its dorsal aspect, is narrowly pointed
anteriorly, but broadens into a lozenge-shaped structure, widest
where the neural arch joins it near its posterior end. The poste-
rior tip of the neural spine is blunt and wide and occupies most
of the small posterior neural arch notch. Beside the base of the
neural spine are distinct parazygosphenal fossae. These are de-
limited laterally by low ridges that proceed posteriorly from the
lateral margins of the zygosphene. No parazygosphenal foramina
were detected within or near the parazygosphenal fossae. The in-
terzygapophyseal ridges are broad and thick. The zygosphene is
narrow from above and concave anteriorly. The prezygapophyses
are reniform in shape from above and project anterolaterally.
Most of the vertebrae identified as from the mid-trunk region
of this species are similar to UA 9684-1. These include several ad-
ditional complete and fragmentary specimens from UA 9684, as
well as FMNH PR 2703 and FMNH PR 2543 (both nearly com-
plete and well-preserved specimens), UA 9686 (a nearly com-
plete immature vertebra), and FMNH PR 2544 (parts of two
vertebrae, one a centrum and the other a neural arch). The
width of the hemal keel and its distinctness from the ventral
face of the centrum vary such that some specimens bear broad-
ened, more flattened keels, similar to those in vertebrae identi-
fied as being from the posterior trunk region. These specimens
are instead assigned to the mid-trunk region because their sub-
central paralymphatic fossae and paracotylar notches are not
as strongly developed as those of posterior trunk specimens. In
some fragmentary vertebral centra of UA 9684, the synapophy-
ses are well preserved. They include a rounded diapophyseal
facet that projects laterally and slightly posteriorly, which is
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 125
distinct from a ventral parapophyseal facet that is laterally flat-
tened and projects slightly below the adjacent edge of the cen-
trum (but not lower than the hemal keel). Although parazy-
gosphenal foramina were not found in the parazygosphenal fos-
sae of any specimens of Menarana nosymena, several vertebrae
possess foramina on the base of the neural spine just above
the fossa. These are interpreted as homologous to the parazy-
gosphenal foramina identified in Madtsoia madagascariensis, but
occupying a slightly different position. The foramina in the para-
cotylar fossae can be present on both sides (FMNH PR 2543,
FMNH PR 2544), present on only one side (FMNH PR 2703),
or absent on both sides (UA 9684-1, UA 9686). Similarly, dis-
tinct endozygantral foramina can be observed deep within the
lateral fossae of the zygantra on some specimens, but not on
others.
One vertebra, UA 9686, is assigned to this species on the ba-
sis of similar overall morphology with differences as would be
expected in an immature specimen. Specific characters that sup-
port this assignment include the broad, depressed neural arch,
broad hemal keel, low neural spine, and interzygapophyseal
ridges that are broad and sharp. Features that support identifi-
cation as a juvenile include the fact that the cotyle and condyle
are largely composed of rough, unfinished endochondral bone
surfaces. Also, the edge of the cotyle is particularly thin and is
damaged in several places. Unusual features of this specimen in-
clude a zygosphene that is very narrow, less than the width of the
cotyle. The neural spine is slightly taller than in other observed
specimens, suggesting an anterior position within the mid-trunk
series. The latter two features could also be due to its young age.
Posterior Trunk Vertebrae—Vertebrae from this region, rep-
resented by several specimens of UA 9684, but also FMNH PR
2542, are not noticeably more depressed, but are slightly nar-
rower in aspect than the mid-trunk vertebrae. In addition, the
zygapophyses do not extend as far from the neural arch and the
hemal keels are broader and particularly flattened ventrally, and
are more strongly differentiated from the centrum by deeply in-
cised subcentral paralymphatic fossae. In the best-preserved pos-
terior trunk vertebra of UA 9684, designated UA 9684-2 (Fig.
8C), these fossae are incised so deeply as to undercut the lateral
edge of the hemal keel, producing a distinctive lateral lip, espe-
cially on the left side. The paracotylar notches are deeper on this
specimen as well. The neural spine, however, is not lower than is
typical in other vertebrae examined; indeed, it is almost identical
in size and shape as on the mid-trunk vertebra described above
(UA 9684-1).
Ribs—Roughly 100 rib fragments, including approximately 20
rib heads (most of them poorly preserved), were recovered in as-
sociation with the partial skeleton of UA 9684 (one of these is
designated as UA 9684-5 and illustrated in Fig. 9). The heads of
these ribs have distinct dorsal (diapophyseal) and ventral (para-
pophyseal) facets of approximately equal size. Thus, the articular
surfaces are about twice as high as they are wide. They also have
well-developed tubera costae that are oriented approximately
parallel to the long axes of the articular surfaces. These are pro-
duced into strong ridges that run distally along the posterodorsal
border of the shaft for a considerable distance until they finally
merge onto the rib shafts. The dorsal surface of each rib just distal
to the dorsal articular facet is marked by a strong groove or sulcus
that contains a prominent foramen. The ridge of the tuber costae
forms the posterior border of this sulcus. The anterior aspect of
the diapophyseal articular facet is strongly recessed distally from
the level of the parapophyseal facet. However, the tuber costae is
supported by a strong column of bone that extends dorsally from
the more proximal parapophyseal facet. The diapophyseal articu-
lar surface extends onto the anterior surface of this column, pro-
ducing a concave shape anteriorly, while maintaining a dorsoven-
trally convex aspect. The ventral articular facet is relatively flat
and featureless, but is bounded by both anteroventral and pos-
teroventral processes, the former more robust than the latter. The
anterior face of the rib head has a ventrally situated fossa distal to
the ventral facet and below the cylindrical extension of the shaft.
This contains one or two foramina. The posteroventral process
may be extended as a crest along the posteroventral border of
the head and neck. A large foramen is present on the posterior
surface at the point where the head narrows to form the neck of
the rib on all specimens where this region is preserved.
Comparisons
Braincase—Relevant taxa for comparison include not only
Wonambi and Yurlunggur (madtsoiids in which the basioccip-
ital and adjacent elements are known—Barrie, 1990; Scanlon
and Lee, 2000; Rieppel et al., 2002; Scanlon 2003, 2005a, 2006),
but also Najash (a braincase referred to N. rionegrina lacking
the basioccipital but retaining adjacent bones—Apestegu´
ıa and
Zaher, 2006), Dinilysia (a close outgroup to madtsoiids, the
braincase of which is known by several specimens and closely re-
sembles that of Najash as well as Australian forms—Caldwell and
Albino, 2002; Apestegu´
ıa and Zaher, 2006; Scanlon, 2006; Cald-
well and Calvo, 2008), basal modern snakes, and varanoid and
mosasauroid ‘lizards’.
As noted already, the fusion of the basioccipital with all ad-
jacent elements (parabasisphenoid, exoccipital-opisthotics, and
prootics) is highly unusual, but a similar condition is known in
one large specimen of Yurlunggur sp. (Scanlon 2006). This can
be interpreted as a shared derived character of Madtsoiidae and
can be predicted to occur in other members of the group, if only
in late stages of ontogeny (near maximum adult size). Late on-
togenetic fusions occur in some colubroid snakes, but this seems
always to involve superficial overgrowth of sutures by discrete ex-
ostoses. Fractured surfaces that cross suture lines in the Yurlung-
gur specimen and in HRXCT slices in Menarana reveal that in
both, the fusion of bones (indicated by uniform bone texture)
is complete internally before the external and intracranial su-
ture lines begin to disappear. On the other hand, whereas there
is no positive sign of fusion of braincase elements in the com-
parably large Wonambi (Scanlon, 2005a), we note that only the
basioccipital-parabasisphenoid suture was not disarticulated ei-
ther before burial or during preparation, and might be co-ossified
in SAMP30178. This suture remains unfused in the Yurlunggur
specimen, but the order of fusions might vary between taxa.
Yurlunggur,Wonambi,andMenarana all exhibit mid-ventral
keels on the basioccipital and parabasisphenoid, a common con-
dition in Macrostomata (possibly convergently), whereas there
are only paired crests, and the bones are concave across the mid-
line in Dinilysia and the skull referred to Najash, as in ‘lizards.’
In both Wonambi and (most distinctly) Menarana, but not in
Yurlunggur, the crests expand into a kite-shaped boss at the
suture.
Menarana resembles Dinilysia in having the basal tubera ex-
tending far posteriorly, whereas in Wonambi they project mainly
laterally, and in Yurlunggur they are oriented similarly to those
of Menarana but are relatively shorter. Menarana also has an ex-
tremely thick ‘collar’ on the condylar process of the basioccipi-
tal, formed by large paired tubercles flanking a midline groove
containing a foramen posterior to the sagittal keel, and continu-
ous laterally with the almost transverse crista tuberalis. A simi-
lar ‘collar’ is present in various extant booid taxa (e.g., Python,
Antaresia,Boa, and Eunectes), all of which bear distinct tu-
bercles similar to those of Me. nosymena. This feature seems
to be more frequently expressed in large individuals, hence it
may be more an allometric function of size than a character
indicating phylogenetic affinity. Dissection of a large Epicrates
cenchria (unnumbered specimen in collection of first author)
revealed that this ‘collar’ provides an attachment site for the
atlanto-occipital ligament. In Yurlunggur there are also distinct
126 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
but flatter tubercles posterior to the keel, and a midline fora-
men, but the ‘collar’ extends along the margins of the ba-
sioccipital toward the furthest anterolateral part of the crista
tuberalis. Wonambi has weakly developed paired tubercles and
a small foramen at the posterior end of the keel, and thin crests
extending along the sides of the keel and diverging anterolat-
erally to intersect the thick anterolateral crests on the basioc-
cipital. Dinilysia is most similar to Menarana in the orientation
of these structures but crests are less prominent ventrally. Sim-
ilar features and variation occur within macrostomatan groups,
and the very strong development of these crests in Menarana
implies relatively high loads at the craniovertebral joint, consis-
tent with head-first burrowing behavior (see “Paleobiology and
Paleoecology”).
The more posterior transverse ridges near the condylar process
in the basicranial fragment of Menarana are absent in Wonambi,
but are well developed in several examined specimens of Python,
Antaresia,Boa, and Eunectes, all of which also bear distinct tu-
bercles similar to those of Me. nosymena. In most alethinophid-
ian snakes, a single basioccipital crest provides insertion points
for the M. rectus capitis anterior, pars ventralis (medially), and
the medial head of the M. rectus capitis anterior, pars dorsalis
(lateral extremity) (Pregill, 1977).
Vertebrae—The morphology of these specimens agrees closely
with that detailed by Rage (1996a, 1999) in his diagnosis of Madt-
soia laurasiae, a species known only from vertebral specimens.
The following diagnostic characters are shared between these
two taxa: (1) neural spine very low, barely exceeding height of
posterior border of neural arch; (2) neural arch depressed com-
pared to that of other large madtsoiids; (3) zygosphene not as
thick as in other large madtsoiids; and (4) diapophyses do not
extend laterally beyond prezygapophyses. These similarities be-
tween Menarana nosymena and Me. laurasiae suggest a strong
taxonomic affinity and that the two species may tentatively be
regarded as sister taxa. However, vertebral morphology is noto-
riously labile among snakes and the possibility of a convergent
adaptive response under similar selective regimes cannot be ex-
cluded. Nonetheless, in the absence of contradictory evidence,
Madtsoia laurasiae is here transferred to the genus Menarana.
Despite their close similarities, vertebrae of Menarana nosy-
mena differ from those of Me. laurasiae (see Rage, 1996a:fig. 1;
1999:fig. 10) in a number of features: (1) Me. nosymena lacks the
raised process that extends posterodorsally from the diapophy-
ses, described as diagnostic of Me. laurasiae (Rage, 1996a, 1999);
(2) the zygapophyses are not as broad as those in Me. laurasiae;
(3) the posterior neural arch notch is very shallow in Me. nosy-
mena and largely filled by the posterior end of the neural spine,
whereas the notch is deeply incised in the holotype of Me.
laurasiae; and (4) the neural spines are very thick in Me. nosy-
mena, especially posteriorly, and they project into the posterior
neural arch notch, whereas in Me. laurasiae the spine appears
thinner and has no posterior projection. Some of the Malagasy
specimens have well-defined, narrow hemal keels, as described by
Rage (1996a, 1999) for Me. laurasiae, but most have low, broad,
flat hemal keels. In this respect, they agree with Rage’s (1999)
description of posterior trunk vertebrae. The posterior trunk ver-
tebrae are marked by strongly developed subcentral fossae and
paracotylar notches, which reinforces their assignment to this re-
gion of the column.
Finally, the following features of the Malagasy specimens
are not mentioned by Rage (1996a, 1999) in his description
of Menarana laurasiae and are not determinable from his il-
lustrations: (1) parazygosphenal fossae are present, though not
as deeply incised as those of Madtsoia madagascariensis,de-
scribed above; and (2) the prezygapophyses have a minute,
but distinct tubercle on the anterior face, near the lateral ex-
tremity, just below the facet, and facing directly anteriorly.
The latter character appears to be a barely formed ‘acces-
sory process,’ but its homology to that of other alethinophid-
ians is doubtful. It does not agree in position with the acces-
sory processes of boas and pythons, caenophidians, or other ex-
amined macrostomatans, in which the process is placed at the
anterolateral corner of the prezygapophyses and is more later-
ally than anteriorly oriented. The absence of accessory processes
is otherwise characteristic of the Madtsoiidae.
Ribs—The ribs of Menarana nosymena differ from those of
Madtsoia madagascariensis in several features. The diapophyseal
articular facet is much more strongly recessed distally than that of
Ma. madagascariensis,producing a more strongly concave articu-
lar surface that is obliquely oriented in a cranial direction, and ap-
pears less prominent overall. The tuber costae of Me. nosymena is
relatively larger than that of Ma. madagascariensis, and its size is
accentuated by the recession of the diapophyseal surface from the
posterior column that links it to the parapophyseal facet. The dor-
sal surface of the rib head of Me. nosymena lacks the pronounced
tubercle seen in specimens of Ma. madagascariensis, and has in
its place a strong crest. This crest encloses a distinct longitudi-
nal sulcus that contains the dorsal rib foramen in Me. nosymena.
The dorsal foramen is not found within a sulcus in Ma. madagas-
cariensis. The anteroventral and posteroventral crests are not as
distinct as those of Ma. madagascariensis (as seen in UA 9714),
and the ventral anterior fossa usually includes only one foramen,
occasionally two, whereas in Ma. madagascariensis, the known
specimens exhibit three such foramina.
Other authors have identified several differences among the
ribs of madtsoiid snakes. These include the prominence of the
dorsal (diapophyseal) articular facet, its position relative to the
ventral (parapophyseal) facet, and whether it bears an anterodor-
sal process; the size and orientation of the tuber costae; and the
presence of a dorsal groove and the number of foramina that it
contains. The ribs of Madtsoia bai differ significantly from those
of either Malagasy species in that they possess a marked an-
terodorsal process and the tuber costae is strongly tilted poste-
riorly. Madtsoia bai does possess a dorsal groove.
NIGEROPHIIDAE Rage, 1975
KELYOPHIS, gen. nov.
Type Species—Kelyophis hechti, gen. et. sp. nov.
Diagnosis—As for the type and only species.
Etymology—From kely (Malagasy), meaning ‘small,’ and
ophis (Greek), meaning ‘serpent’; in reference to the small size
of this snake. Pronounced kay-lee-O-phis.
KELYOPHIS HECHTI, gen. et sp. nov.
(Fig. 10; Table 3)
Holotype Specimen—UA 9682, a single, nearly complete mid-
trunk vertebra from a juvenile individual.
Diagnosis—Nigerophiid with synapophyses positioned ven-
trally, but less so than in Nigerophis and Indophis.Centrum
downswept posteriorly, as in former two genera, but also dis-
tinctly narrowed posteriorly, unlike Nigerophis and Indophis.
Postzygapophyses elevated above level of condyle, but not as
strongly as in Nigerophis and Indophis. Neural spines lower
than those of Indophis, but of comparable height to those of
Nigerophis. Further differs from other nigerophiid genera in
having more robust vertebrae with stronger interzygapophyseal
ridges, subcentral ridges, and prezygapophyseal buttresses.
Etymology—Named for the late Dr. Max K. Hecht, graduate
advisor of the senior author, for his contributions to knowledge
of reptilian evolution and for suggesting this study to the senior
author.
Type Locality—MAD93-01, Berivotra Study Area, Mahajanga
Basin, northwestern Madagascar.
Referred Specimens—Anterior trunk vertebrae: FMNH PR
2539 (juvenile), FMNH PR 2540, UA 9683. Mid-trunk vertebra:
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 127
FIGURE 10. Trunk vertebrae of Kelyophis hechti, gen. et sp. nov., from the Late Cretaceous of Madagascar in l, lateral; a,anterior;p, posterior; d,
dorsal; and v, ventral views. A, anterior trunk vertebra, FMNH PR 2539 (lateral view reversed); B, mid-trunk vertebra, UA 9682 (holotype).
FMNH PR 2541 (juvenile). Fragmentary vertebra not assigned to
region: UA 9725.
Localities—Berivotra Study Area localities MAD93-01, 93-35,
and 93-37; Masiakakoho Study Area localities MAD03-15 and
05-59 (Fig. 1).
Age and Distribution—Known only from the Upper Cre-
taceous (Maastrichtian) Maevarano Formation, Berivotra and
Masiakakoho study areas, Mahajanga Basin, northwestern
Madagascar.
Description
Six vertebral specimens are assigned to this new taxon, three of
which (FMNH PR 2539 and FMNH PR 2540, both from the an-
terior trunk region, and UA 9682, from the mid-trunk region) are
relatively complete and well preserved; they serve as the primary
basis for the following description. The other three specimens,
UA 9683 (partial centrum from anterior trunk series), FMNH
PR 2541 (fragmentary and poorly preserved mid-trunk centrum
and partial neural arch), and UA 9725 (centrum not assigned to
vertebral region) contribute little, other than the fact that UA
9683 is the largest known specimen of Kelyophis hechti (Table
3). UA 9682, as well as FMNH PR 2539 and FMNH PR 2541,
are identified as representing juvenile individuals based on their
small size as well as by preservation characteristics employed by
LaDuke (1991). Specifically, the perichondral walls of the ver-
tebra are thin, but opaque. This is particularly notable near the
edges of damaged surfaces. Furthermore, a remnant of the early
endochondral ossification center of the centrum is clearly visible
(much lighter color) in the center of the cotyle.
Anterior Trunk Vertebrae—Two specimens clearly belong to
the anterior trunk series and form the basis for the follow-
ing description. FMNH PR 2540 represents an adult individual,
whereas FMNH PR 2539 (Fig. 10A) is much smaller and repre-
sents a juvenile (Table 3).
In ventral view, the centrum is elongate, narrow, and has
strong subcentral ridges. The hemal keel is broken posteriorly
on FMNH PR 2540, but clearly did not contact the condyle; this
is less clearly the case in FMNH PR 2539, which, although more
complete, exhibits some effects of postmortem erosion. Anteri-
orly, the hemal keel gives rise to a broad, flattened, triangular
plate that merges into the lower lip of the cotyle. This flattened
platform bears a slight mid-ventral ridge. The eroded parapophy-
ses project ventrally to (FMNH PR 2539) or beyond (FMNH PR
2540) the ventral border of the centrum.
In anterior view, the cotyle is circular in outline. Deep para-
cotylar fossae possess a single foramen on each side. The
synapophyses are eroded, but are located in a relatively ventral
TABLE 3. Measurements of vertebral specimens of Kelyophis hechti, gen. et sp. nov. See text for list of abbreviations.
Specimen Position CL NAW PRW POW ZSW COW CNW NSH PR-PO
FMNH PR 2540 ATV 5.7 4.16.7— —2.82.4 — 6.6
UA 9683 ATV 7.6 — — — — — 3.4 — —
FMNH PR 2539 MTV 3.6 2.23.73.31.61.7— —3.8
FMNH PR 2541 MTV 3.4∗—————1.9
∗——
UA 9682 MTV 3.0 2.13.53.51.51.51.3 0.33.7
UA 9725 ? 7.0∗—————3.2
∗——
∗Estimated because of slight breakage or erosion.
128 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
position. The prezygapophyseal buttress above the diapophysis is
strong, but does not produce an anterolateral keel, as it does in
Nigerophis. The prezygapophyseal facets are somewhat elevated,
and tilted dorsally at their lateral ends. Their distal tips are bro-
ken away on both specimens. The neural canal is roughly trian-
gular in shape, broader ventrally than dorsally. The zygosphene
(broken off on the left side of FMNH PR 2540 but complete in
FMNH PR 2539) is moderately thin and convex dorsally; as for
vertebrae in the mid-trunk region, it is roughly the same width as
the cotyle.
In posterior view, the condyle is small and round. The posterior
end of the neural arch is largely broken away in FMNH PR 2540,
including the zygantrum, but enough of the left postzygapophysis
is present to see a parazygantral foramen in a shallow fossa. The
neural arch is complete and well preserved in FMNH PR 2539
and the parazygantral foramina are clearly present.
In dorsal view, the neural arch is relatively long and narrow.
The laminae meet at a slightly peaked mid-sagittal ridge (less
pronounced in FMNH PR 2539 than in FMNH PR 2540). The
posterior portion of the neural arch is broken away in FMNH PR
2540, but the relatively complete neural arch of FMNH PR 2539
demonstrates that the neural spine was, at most, poorly devel-
oped and strongly restricted to the posteriormost end of the neu-
ral arch. The prezygapophyseal facets are teardrop-shaped and
directed anterolaterally. The zygosphene is narrow and, as best
seen in FMNH PR 2539, its anterior margin is shallowly concave.
The relatively shallow interzygapophyseal constriction is narrow-
est anterior to mid-vertebra.
In lateral view, the neural arch laminae and pedicles meet at
a sharp angle, producing a strong interzygapophyseal ridge. The
body of the centrum is downswept posteriorly, whereas the neu-
ral arch is slightly upswept. There is a distinct lateral foramen
on the pedicle, just above the subcentral ridge on each side of
FMNH PR 2540. One or more smaller, much less distinct foram-
ina lie between this primary foramen and the interzygapophyseal
ridge. Two or more lateral foramina also occur on the laminae
of FMNH PR 2539. The parapophysis apparently had the same
posterior connection to the subcentral ridges seen in the holo-
type. The prezygapophyseal buttress and synapophysis are more
robustly developed in FMNH PR 2540 than in the juvenile spec-
imens. The hemal keel of FMNH PR 2540 is broken off poste-
riorly and that of FMNH PR 2539 is eroded but, in both cases,
the remnants suggest that it was produced into a low hypapoph-
ysis, in which case these specimens are derived from the posterior
portion of the anterior trunk series.
Mid-trunk Vertebrae—UA 9682, the holotype, is a nearly com-
plete vertebra from the posterior portion of the mid-trunk re-
gion (Fig. 10B). It is small, with a centrum length (lower lip of
cotyle to extremity of condyle) of 3.0 mm and a width across
the postzygapophyses of 3.5 mm. We regard this specimen to
represent a juvenile individual but proportions of various parts
of the vertebra suggest that it was approaching an adult shape.
For example, the neural canal, although relatively large, is nar-
row. Furthermore, the zygosphene is relatively narrow, the zy-
gapophyses are relatively large, and the centrum is elongate and
narrow in ventral view, as in adult snakes. The specimen is identi-
fied as a mid-trunk vertebra because it lacks a hypapophysis and
its subcentral paralymphatic notches and fossae are only weakly
developed.
The centrum of the vertebra is elongate and narrow in ven-
tral view, widening moderately at the synapophyses. The lat-
eral border of the centrum is smoothly rounded posteriorly, but
gives rise to a moderately developed subcentral ridge anteri-
orly. This ridge is confluent with a posterior extension of the
parapophysis. The hemal keel is distinct, and strongly project-
ing ventrally from the centrum, especially at its posterior ex-
tremity. Although there is a chip of bone missing from the mid-
dle of the hemal keel, the posterior end is intact and indicates
the absence of a hypapophysis. The hemal keel widens anteri-
orly to produce a triangular platform that forms the ventral lip
of the cotyle. The ventral surface of the centrum is slightly in-
dented adjacent to the margin of the hemal keel, and there is a
single, small foramen on each side, at the deepest part of the in-
dentation. A slight notch occurs between the parapophyses and
the lower lip of the cotyle. Following the positioning criteria of
LaDuke (1991), this vertebra is from the posterior portion of
the mid-trunk region. The postzygapophyseal facets are slightly
elongate ovals (slightly truncated on the right by breakage) that
are directed obliquely posterolaterally (more posteriorly than
laterally).
In anterior view, the cotyle is depressed with only faint evi-
dence of ventrolateral emargination of the lip. Dorsally, the edge
of the lip is broken away. Distinct paracotylar fossae on each
side contain a single, large foramen. The neural canal is high,
narrow, arched dorsally, and surmounted by a thin, narrow zy-
gosphene. The anterior border of the zygosphene is concave in
dorsal view, with anteriorly directed lateral extensions produced
by the zygosphenal facets. The zygosphene is subequal in width
to the cotyle. The synapophyses are divided into parapophyseal
and diapophyseal regions by a weak posterior indentation (only
the left synapophysis has an intact articular surface).
In dorsal view, the prezygapophyseal facets are elon-
gate, oval surfaces that are directed obliquely anterolaterally
(more anteriorly than laterally). They bear no trace of ac-
cessory processes, and the diapophyses extend further later-
ally than the prezygapophyses. The interzygapophyseal ridge
is distinct, and moderately developed. The relatively shallow
interzygapophyseal constriction is narrowest anterior to mid-
vertebra. The neural arch has a smoothly rounded dorsolateral
surface. The neural spine, though eroded dorsally, is a very low,
short, posteriorly restricted tubercle. The base of the neural spine
is roughly triangular in section, the apex being directed anteri-
orly. The posterior neural arch notch is very shallow.
In posterior view, the neural arch is depressed, but dorsally
positioned, leaving a larger-than-typical gap between the postzy-
gapophyses and the condyle. The zygantral facets extend slightly
beyond the posterior margin of the neural arch laminae. Lateral
to the zygantral facets are shallow fossae with distinct parazy-
gantral foramina. The condyle is relatively small and depressed.
A significant portion of its surface (mostly on the left side) is bro-
ken away, but the overall shape is clear.
In lateral view, the neural spine is restricted to the posterior
part of the neural arch. Although the top of the spine is slightly
eroded, it does not appear to have been more than a low tubercle.
The diapophysis is larger than the parapophysis and bulbously
convex. The parapophysis lacks a parapophyseal process, but has
a distinct posterior extension that is connected to the anterior ex-
tremity of the subcentral ridge. The interzygapophyseal ridge is
distinct, but only moderately developed. There is a minute fora-
men in the middle of the pedicle of the neural arch.
Comparisons
In addition to its small size, Kelyophis is assigned to the
Nigerophiidae on the basis of its elongate vertebral centrum, tu-
bercular shape of the neural spine and its restriction to the pos-
terior portion of the neural arch, reduced notch of the neural
arch, absence of true accessory processes on the prezygapophy-
ses, ventral deflection of the posterior portion of the centrum,
elevation of the zygapophyseal facets above the centrum, and
the somewhat ventrally positioned and ventrolaterally directed
synapophyses (Rage and Werner, 1999). Parazygantral and para-
cotylar foramina are absent in most nigerophiids (Nessovophis,
Nigerophis,Nubianophis,andWoutersophis) but are present in
Kelyophis and some specimens of Indophis sahnii. As for many
basal snakes, members (including questionable members) of the
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 129
family Nigerophiidae are characterized by the absence of hy-
papophyses in mid- and posterior trunk vertebrae (Rage, 1975,
1980; Rage and Prasad, 1992; Werner and Rage, 1994; Prasad and
Rage, 1995; Averianov, 1997; Rage and Werner, 1999; Rage et al.,
2003, 2004). Rage and Werner (1999) refined the diagnosis of the
Nigerophiidae and underscored the tentativeness of the assign-
ment of Indophis to this family. Yet, as currently defined, it is the
clade to which Kelyophis should be assigned.
Kelyophis hechti differs from Nigerophis and Nubianophis in
possessing stronger subcentral and interzygapophyseal ridges,
and centra that are broader anteriorly than posteriorly. In these
regards, the Malagasy specimens more closely resemble those of
Indophis sahnii. In addition, Indophis and Kelyophis both possess
parazygantral foramina, a characteristic generally associated with
Madtsoiidae. Indophis,Nessovophis,andNigerophis all possess
prominent vertical ridges on the anterolateral aspect of the prezy-
gapophyseal buttresses that project beyond the prezygapophy-
seal facet. These are lacking in Kelyophis (condition not known
in Nubianophis). Nessovophis is unusual in possessing a centrum
that is triangular in cross section, but a similar section of the
centrum of Nigerophis is subtriangular (Rage, 1975). Published
figures of I.sahnii (Rage and Prasad, 1992:figs. 1–5; Prasad and
Rage, 1995:fig. 15; Rage et al., 2004:fig. 3F–H) indicate that it dif-
fers from Kelyophis in that it has a higher neural spine, more dor-
sally deflected posterior neural arch, more ventrally positioned
synapophyses, and a narrower, higher aspect overall. Thus the
two forms are different enough to warrant distinction at the
generic level. Moreover, both FMNH PR 2540 and UA 9683, ver-
tebrae of mature K. hechti, are considerably larger than any In-
dophis specimens. Some of the differences noted, such as the ro-
bustness of the prezygapophyseal buttress and synapophyses in
the present material, may thus be due to allometric changes with
increased size. Based on their overall similarity, if Indophis is ul-
timately removed from the Nigerophiidae, then Kelyophis will
probably be removed as well.
INDETERMINATE SPECIMENS
There are a number of specimens that cannot be assigned, pri-
marily owing to their incompleteness, to any of the species listed
above, even though they may, indeed, pertain to them.
The following specimens, listed by locality, possess one or
more features of the Madtsoiidae and are referable to that
family: Locality MAD93-35: FMNH PR 2572—nearly com-
plete but eroded vertebra. Locality MAD93-38: FMNH PR
2573—fragmentary vertebra. Locality MAD93-73: FMNH PR
2577—complete vertebra.
The following specimens are clearly parts of snake verte-
brae but cannot be assigned confidently even to familial level:
Locality MAD93-01: FMNH PR 2574—vertebral centrum.
Locality MAD93-06: UA 9719—vertebral fragment. Local-
ity MAD93-19: UA 9720—zygosphene. Locality MAD93-27:
FMNH PR 2575—vertebral centrum. Locality MAD93-35:
FMNH PR 2579—vertebral centrum. Locality MAD93-40:
FMNH PR 2576—vertebral fragment. Locality MAD93-
44: UA 9722—vertebral fragment. Locality MAD93-81:
UA 9723—zygosphene, UA 9724—vertebral centrum, UA
9732—vertebral condyle. Locality MAD93-86: FMNH PR
2578—vertebral centrum. Locality MAD05-59: FMNH PR
2580—neural arch.
DISCUSSION
Diversity and Abundance
New species of extant non-marine Malagasy snakes are being
discovered and described at a rapid rate (an average of more than
one species per year for the last 25 years [Cadle, 2003]). There
are now over 85 extant non-marine species of snakes known
from Madagascar (and the nearby islands of the Comoros and
La R´
eunion) (Raxworthy, 2003). Of these, three are boids, 74
are colubrids, and 11 are typhlopids. All except one species of
typhlopid (Ramphotyphlops braminus) are considered endemic.
Not surprisingly, the assemblage of snakes recovered as a re-
sult of the Mahajanga Basin Project reveals a much lower di-
versity on Madagascar during the Late Cretaceous. This most
likely reflects reality, owing to a lack of diversification, but is
also undoubtedly influenced strongly by relatively poor sampling.
Nonetheless, the Mahajanga Basin Project collections demon-
strate that Late Cretaceous snake species diversity on the island
was greater than previously reported (Piveteau, 1933; Hoffstet-
ter, 1961a; Rage, 1984), with the addition of a new genus and
species of madtsoiid, Menarana nosymena, and a new genus and
species of nigerophiid, Kelyophis hechti. Furthermore, relatively
abundant and well-preserved new material of a previously known
form, Madtsoia madagascariensis, provides a vastly improved as-
sessment of variability in vertebral anatomy and the first informa-
tion on rib anatomy. Based on numbers of specimens (94 from
over 30 localities), Ma. madagascariensis appears to be much
more abundant in the assemblage than the other two species but,
again, this could well represent a sampling artifact in that Ma.
madagascariensis was much larger (and thus fossils of it are eas-
ier to find) than either Me. nosymena (nine specimens from six
localities) or K. hechti (six specimens from five localities).
Phylogeny
The primary objective of this report is to identify and describe
the two madtsoiid taxa and the one nigerophiid taxon that oc-
cur in the Maevarano Formation assemblage. Comprehensive
and robust phylogenetic assessment of generic or species-level
relationships within the families Madtsoiidae and Nigerophiidae
have not been published but are beyond the scope of this pa-
per; as such, phylogenetic placement of Madtsoia madagascarien-
sis and Menarana nosymena within Madtsoiidae and Kelyophis
hechti within Nigerophiidae is not rigorously evaluated. A par-
ticular hindrance for assessing madtsoiid relationships relates to
the currently very poor knowledge of serial variation in the ver-
tebrae of madtsoiid taxa that are reasonably well represented by
fossil material. Scanlon (in prep.) is currently conducting such an
assessment for the Australian madtsoiid Yurlunggur, now rep-
resented by several skeletons, and will employ those data, cou-
pled with the character states gleaned from the Malagasy madt-
soiids detailed in this paper, in a more comprehensive analysis of
madtsoiid relationships. Assessment of the phylogenetic relation-
ships of Nigerophiidae is plagued by a more severe problem: the
fact that the contained taxa are each represented by only a few
vertebrae. The wisdom of attempting a phylogenetic assessment,
such as that conducted by Averianov (1997) for nigerophiids (and
palaeophiids), by employing characters derived strictly from iso-
lated vertebrae has been questioned by Rage et al. (2003:699).
Biogeography
Madtsoiidae—Madtsoiids were widespread on Gondwana dur-
ing the Late Cretaceous and Paleogene, known from all major
landmasses except Antarctica (Table 4; Fig. 11). They disappear
from the fossil record in the mid-Paleogene except in Australia,
where they survived into the Pleistocene. Removal of Menarana
laurasiae from the genus Madtsoia leaves only three valid species
in the genus: Ma. bai from the early Eocene (and possibly late Pa-
leocene) of Argentina, Ma. camposi from the middle Paleocene
of Brazil, and Ma. madagascariensis from the Late Cretaceous of
Madagascar. Phylogenetic and therefore biogeographic ties be-
tween various clades of latest Cretaceous vertebrates of Mada-
gascar with those of South America (and the Indian subconti-
nent) are now well documented (e.g., see Krause et al. [2006]
for review of evidence from crocodyliforms, non-avian dinosaurs,
130 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
FIGURE 11. Temporal and geographic distribution of madtsoiid (localities indicated by solid symbols, numbers) and nigerophiid (open symbols,
letters) snakes. See Tables 4 and 5 for more detailed information.
and mammals; and Evans et al. [2008] for evidence from frogs).
It is tempting to suggest that the genus Madtsoia provides yet
another line of independent evidence of such a special connec-
tion (i.e., to the exclusion of others). However, the fact that there
are many other snake fossils assigned to Madtsoia (or ?Madtsoia)
or to the Madtsoiidae (or ?Madtsoiidae) from the Late Creta-
ceous of Argentina, Niger, Sudan, Romania, France, and India,
as well as from the Paleogene of Argentina, Bolivia, Morocco,
India, and Australia (see Table 4; Fig. 11), reveals a potentially
much broader distribution and more complicated pattern. This
underscores the need for a comprehensive taxonomic review and
phylogenetic assessment of the Madtsoiidae before any firm bio-
geographic conclusions can be drawn.
Nonetheless, the disjunct distribution of the two known species
of Menarana,Me.laurasiae from the Campanian of Spain (Rage,
1996a, 1999) and Me.nosymena from the Maastrichtian of Mada-
gascar, invites consideration. Specimens of madtsoiids, or ques-
tionable madtsoiids, have also been reported from the Cam-
panian of France (Sig´
e et al., 1997) and the Maastrichtian
of Romania (Folie and Codrea, 2005). Other typically Gond-
wanan vertebrate taxa are known from these and other Campa-
nian/Maastrichtian localities in southern Europe as well (Pereda-
Superbiola, 2009), but there are no pre-Campanian Late Creta-
ceous records of madtsoiids from Europe. Gheerbrant and Rage
(2006:236) opined that the “European madtsoiids were immi-
grants from Africa that reached Europe probably during the Late
Cretaceous” (see also Rage, 1995, 1996a, 1999; Rage et al., 2008).
When during the Late Cretaceous is, however, a critical question
and Pereda-Superbiola (2009) notes that nothing excludes a dis-
persal event during the Early Cretaceous. In this regard, the com-
position of the snake fauna from the Late Cretaceous of Africa
is obviously relevant. There are no Campanian/Maastrichtian
records of madtsoiids from Africa at all. Late Cretaceous African
madtsoiids are known only from the early Senonian of Niger
(de Broin et al., 1974; Rage, 1981; Madtsoia aff. madagascarien-
sis—re-identified in this paper as ?Madtsoia sp.) and the Ceno-
manian of Sudan (Rage and Werner, 1999; Madtsoiidae indet.).
These two pre-Campanian records, therefore, are too indetermi-
nate to shed light on the issue.
In light of this poor fossil record, there are several possibilities
to explain the presence of Menarana (and other shared faunal
elements) in the Campanian/Maastrichtian of Madagascar and
southern Europe, including the following.
(1) A pan-Gondwanan (including southern Europe) or nearly
pan-Gondwanan (for the issue at hand, Australia is
more or less peripheral to the argument) Early Creta-
ceous distribution of which the Campanian/Maastrichtian
records of Menarana in Madagascar and southern Eu-
rope are relictual. During the Late Cretaceous, Europe
was a complex archipelago (Dercourt et al., 2000) and,
in a recent assessment of the biogeographic affinities of
Late Cretaceous European tetrapods, Pereda-Superbiola
(2009:65) concluded that “isolation from other landmasses
may have facilitated survival of relict taxa in Europe until
Campanian-Maastrichitan times.” This scenario, if it pertains
to Menarana, requires that Menarana evolved before South
America separated from Africa at or near the Early/Late
Cretaceous boundary. This can be confirmed, in part,
through the discovery of Menarana in pre-Late Cretaceous
horizons on any Gondwanan landmass. The absence of such
records, especially from the relatively well-sampled South
American record, is currently the only evidence against this
scenario.
(2) Africa (only) as an intermediate landmass, with connections
to Madagascar via a Late Cretaceous land bridge or via
sweepstakes dispersal across the marine barrier formed by
the Mozambique Channel, with a minimal distance of 430
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 131
TABLE 4. Temporal and geographic distribution of madtsoiid and questionably madtsoiid snakes (arranged alphabetically by genus and species,
and then by more uncertain family-level attributions). Abbreviations:E=Early; M=Middle; L=Late.
Taxon Locality Age Reference
1. Alamitophis argentinus Los Alamitos, Argentina Campanian/Maastrichtian Albino, 1986
2. Alamitophis argentinus La Colonia, Argentina Campanian/Maastrichtian Albino, 2000
3. Alamitophis argentinus Salinas de Trapalc ´
o, Argentina Campanian/Maastrichtian Albino, 1994; Albino, 2007
4. Alamitophis argentinus El Palomar, Argentina Campanian/Maastrichtian Albino, 1994
5. Alamitophis argentinus Salitral de Santa Rosa, Argentina Campanian/Maastrichtian Martinelli and Forasiepi, 2004;
Albino, 2007
6. Alamitophis elongatus Salinas de Trapalc ´
o, Argentina Campanian/Maastrichtian Albino, 1994; Albino, 2007
7. Alamitophis elongatus Los Alamitos, Argentina Campanian/Maastrichtian Albino, 1994
8. Alamitophis tingamarra Tingamarra, Australia E. Eocene Scanlon, 2005b
9. Gigantophis garstini Dor et Talha, Libya L. Eocene Hoffstetter, 1961b
10. Gigantophis garstini Fayum, Egypt L. Eocene∗Andrews, 1901, 1906
11. Herensugea caristiorum La ˜
no, Spain L. Campanian Rage, 1996a, 1999
12. Madtsoia bai Ca ˜
nad ´
on Vaca, Argentina E. Eocene Simpson, 1933
13. Madtsoia cf. M. bai Gaiman, Argentina L. Paleocene Hoffstetter, 1959; Simpson, 1935
14. Madtsoia camposi Itaborai, Brazil M. Paleocene Rage, 1998
15. Madtsoia laurasiae (=Menarana
laurasiae in this paper)
La ˜
no, Spain L. Campanian Rage, 1996a, 1999
16. Madtsoia madagascariensis Mahajanga Basin, Madagascar Maastrichtian Hoffstetter, 1961a; LaDuke et al.,
this paper
17. Madtsoia aff. M. madagascariensis (=
?Madtsoia sp.inthispaper)
In Beceten, Niger E. Senonian de Broin et al., 1974; Rage, 1981
18. ?Madtsoia sp. Ca ˜
nad ´
on Hondo, Argentina L. Paleocene Albino, 1993
19. ?Madtsoia sp. Ca ˜
nad ´
on Vaca, Argentina E. Eocene Albino, 1993
20. ?Madtsoia sp. Gran Barranca, Argentina E. Eocene Albino, 1993
21. Menarana nosymena Mahajanga Basin, Madagascar Maastrichtian LaDuke et al., this paper
22. Najash rionegrina (?Madtsoiidae) La Buitrera, Argentina E. Cenomanian Apestegu´
ıa and Zaher, 2006
23. Nanowana godthelpi Riversleigh, Australia E. Miocene Scanlon, 1997
24. Nanowana schrenki Riversleigh, Australia E. Miocene Scanlon, 1997
25. Patagoniophis australiensis Tingamarra, Australia E. Eocene Scanlon, 2005b
26. Patagoniophis parvus Los Alamitos, Argentina Campanian/Maastrichtian Albino, 1986
27. Patagoniophis parvus Salitral de Santa Rosa, Argentina Campanian/Maastrichtian Martinelli and Forasiepi, 2004;
Albino, 2007
28. Rionegrophis madtsoioides Los Alamitos, Argentina Campanian/Maastrichtian Albino, 1986, 2007
29. Wonambi barriei Riversleigh, Australia L. Oligocene/E. Miocene Scanlon and Lee, 2000
30. Wonambi naracoortensis Naracoorte, Australia Pleistocene Smith, 1976
31. Wonambi naracoortensis Mammoth Cave, Australia Pleistocene Scanlon, 1995
32. Wonambi naracoortensis Koala Cave, Australia Pleistocene Scanlon, 1995
33. Wonambi naracoortensis Wellington Caves, Australia Pleistocene Scanlon, 1995
34. Wonambi naracoortensis Corra-Lynn Cave, Australia E. Pliocene? Scanlon, 1995; 2005a
35. Wonambi naracoortensis Tight Entrance Cave, Australia Pleistocene Scanlon, 2005a
36. Yurlunggur camfieldensis Bullock Creek, Australia M. Miocene Scanlon, 1992
37. Yurlunggur sp. Kanunka, Australia Pliocene Scanlon, 1995; 2004
38. Yurlunggur sp. Tarkarooloo, Australia L. Oligocene Scanlon, 2004
39. Yurlunggur sp. Lake Ngapakaldi, Australia E. or M. Miocene Scanlon, 2004
40. Yurlunggur sp. Chinchilla, Australia E. or M. Pliocene Mackness and Scanlon, 1999;
Scanlon, 2004
41. Yurlunggur sp. Gogolo-Garnpung, Willandra Lakes,
Australia
L. Pleistocene Scanlon, 2004
42. Yurlunggur sp. Kangaroo Well, Australia L. Oligocene Megirian et al., 2004
43. Yurlunggur sp. Wyandotte, Australia L. Pleistocene Scanlon, 1995; 2004
44. Yurlunggur sp. or spp. Riversleigh, Australia L. Oligocene/E. Miocene Scanlon, 2006
45. Madtsoiidae indet. Salinas de Trapalc ´
o, Argentina Campanian/Maastrichtian Gomez and Baez, 2006
46. Madtsoiidae indet. Wadi Abu Hashim, Sudan Cenomanian Rage and Werner, 1999
47. Madtsoiidae indet. Adrar Mgorn, Morocco L. Paleocene Gheerbrant et al., 1993
48. Madtsoiidae indet. Yacimiento Las Flores, Argentina M. Paleocene Albino, 1993
49. Madtsoiidae indet. Hat¸eg Basin, Romania Maastrichtian Folie and Codrea, 2005
50. Madtsoiidae indet. Kelapur, Maharashtra, India Maastrichtian Rage et al., 2004
51. Madtsoiidae indet. Salitral de Santa Rosa, Argentina Campanian/Maastrichtian Martinelli and Forasiepi, 2004;
Albino, 2007
52. ?Madtsoiidae Takli, India Maastrichtian Gayet et al., 1985
53. ?Madtsoiidae Champ-Garimond, France Campanian Sig ´
e et al., 1997
54. ?Madtsoiidae Los Alamitos, Argentina Campanian/Maastrichtian Albino, 2007
55. ?Madtsoiidae La Colonia, Argentina Campanian/Maastrichtian Albino, 2000
56. ?Madtsoiidae Ranquil-C ´
o, Argentina Campanian/Maastrichtian Gonz´
alez Riga, 1999; Albino, 2007
57. ?Madtsoiidae indet. Salitral de Santa Rosa, Argentina Campanian/Maastrichtian Martinelli and Forasiepi, 2004;
Albino, 2007
58. ?Madtsoiidae indet. Vastan Lignite Mine, Gujarat, India E. Eocene Rage et al., 2008
59. ?Madtsoiidae indet cf. Madtsoia sp. Tingamarra, Australia E. Eocene Scanlon, 2005b
60. ?Madtsoiidae or Boidae Tiupampa, Bolivia E. Paleocene Rage, 1991
61. ?Madtsoiidae or Boidae La Colonia, Argentina Campanian/Maastrichtian Albino, 2000
62. ?Madtsoiidae or Boidae Panandhro Mine, Kutch, India E. Eocene Rage et al., 2003
63. ?Madtsoiidae or Boidae Asifabad, India Maastrichtian Rage et al., 2004
64. ?Madtsoiidae or Boidae Pisdura, India Maastrichtian Rage et al., 2004
∗Revised age from Seiffert (2006).
132 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
TABLE 5. Temporal and geographic distribution of nigerophiid and questionably nigerophiid snakes (arranged alphabetically).
Taxon Locality Age Reference
A. Kelyophis hechti Mahajanga Basin, Madagascar Maastrichtian LaDuke et al., this paper
B. Nigerophis mirus Krebb de Sassao & Tillia, Niger Paleocene Rage, 1975
C. Nubianophis afaahus Wadi Abu Hashim, Sudan Cenomanian Rage and Werner, 1999
D. Nubianophis cf. N. afaahus Wadi Abu Hashim, Sudan Cenomanian Rage and Werner, 1999
E. Indophis sahnii (?Nigerophiidae) Naskal, India Maastrichtian Prasad and Rage, 1995
F. Indophis sahnii (?Nigerophiidae) Anjar, Gujarat, India Maastrichtian Rage et al., 2004
G. ?Indophis sahnii (?Nigerophiidae) Kelapur, Maharashtra, India Maastrichtian Rage et al., 2004
H. “Nessovophis”zhylga (?Nigerophiidae) Zhylga, Kazakhstan Early Eocene Averianov, 1997; Rage et al., 2003
I. Woutersophis novus (?Nigerophiidae) Van Pachtenbeke Sand Pit, Belgium Middle Eocene Rage, 1980
km. Discovery of Menarana in the Cretaceous of Africa (and
non-discovery from South America) would at least be consis-
tent with this scenario. Gheerbrant and Rage (2006) argued
that the presence of Madtsoia aff. madagascariensis in the
pre-Campanian Late Cretaceous of Niger and M. madagas-
cariensis in the Maastrichtian of Madagascar indicates that
there was dispersal between the two landmasses, purportedly
along a land bridge formed by the Davie Ridge (Taquet,
1982; Rage, 1988; see also McCall, 1997). Re-identification of
the Niger madtsoiid as ?Madtsoia sp. de-emphasizes the need
to invoke a land bridge. In any case, there is no evidence that
one existed. The Davie Ridge is a north-south linear feature
on the floor of the Mozambique Channel, paralleling the
east coast of Tanzania and Mozambique, that represents the
strike-slip fault along which Madagascar moved southward
some 1000 km until it reached its current position relative to
Africa roughly 120 Ma, when it re-sutured with the African
plate. There is no geological evidence for a continuous,
emergent land bridge along the Davie Ridge during the
Late Cretaceous and Early Tertiary and, indeed, there is
considerable faunal evidence, albeit largely negative, against
it (Krause et al., 1997a, 1999; Rabinowitz and Woods, 2006).
Whether or not Menarana dispersed across the Mozambique
Channel without the aid of a land bridge is impossible to test
in light of the current fossil record.
(3) A northern dispersal route between Madagascar and Eu-
rope that involved the Seychelles Plateau, the Indian sub-
continent, and mainland Asia (Rage, 1996b, 2003). This
seems highly unlikely for several reasons. First, it assumes
that “the absence of numerous taxa in Africa... repre-
sent true absences” and that “the role of Africa as an in-
tervening landmass... is ruled out” (Rage, 2003:661). The
generally very poor record of Late Cretaceous fossil ver-
tebrates from mainland Africa, particularly from Campa-
nian/Maastrichtian horizons, as detailed above, does not per-
mit these assumptions. Second, physical connection between
the passive margin of the Indian subcontinent and the active
margin of Asia likely did not occur until at least 55 Ma (e.g.,
Ali and Aitchison, 2008; Garzanti, 2008). Even if it occurred
at the very end of the Cretaceous, as Rage (2003) suggests,
it is too late to account for the presence of Menarana in the
Campanian of Spain if the dispersal was from the Indian sub-
continent to Eurasia and also too late to have provided a
connection to Madagascar if the dispersal was from Eurasia
to the Indian subcontinent since the India-Seychelles block
separated from Madagascar at roughly 88 Ma (Storey et al.,
1995, 1997). Third, there is not a single record of Menarana
from well-sampled Cretaceous horizons in either the Indian
subcontinent or mainland Asia.
Clearly, a convincing explanation to account for the
disjunct distribution of species of Menarana in Campa-
nian/Maastrichtian horizons of Madagascar and southern
Europe is still lacking but, of the scenarios considered, the first
seems the most likely.
Nigerophiidae—Nigerophiids are much less well known than
madtsoiids in terms of both species diversity and tempo-
ral and geographic distribution (Table 5; Fig. 11). Their
earliest known occurrence is in the Cenomanian of Africa
(Nubianophis, Sudan—Rage and Werner, 1999), where they
survived into at least the Paleocene (Nigerophis, Niger—
Rage, 1975). Referral of taxa recovered from the Maas-
trichtian of the Indian subcontinent (Indophis, India—Rage
and Prasad, 1992; Prasad and Rage, 1995; Rage et al., 2004),
the Eocene of western Asia (“Nessovophis,” Kazakhstan—
Averianov, 1997; Rage et al., 2003), and the Eocene of
Europe (Wouterophis, Belgium—Rage, 1980) to the Nigerophi-
idae is tentative. The addition of Kelyophis from the Maas-
trichtian of Madagascar, especially in the absence of an hypoth-
esis of relationships among nigerophiids, does little to elucidate
the biogeographic history of this poorly known clade other than
to add another element for future consideration when a rigorous
assessment of Nigerophiidae is undertaken; again, such an assess-
ment is beyond the scope of this study.
Origins of the Modern Malagasy Snake Fauna—The occur-
rence of snake remains in the Upper Cretaceous Maevarano
Formation currently provides the only direct fossil evidence
of potential relevance to elucidate the biogeographic history
of the diverse radiation of extant snakes on Madagascar. The
fossil snake assemblage recovered from the Mahajanga Basin
includes only madtsoiids and nigerophiids and is therefore
archaic in aspect; none of the extant Malagasy families (Boidae,
“Colubridae,” Typhlopidae) are represented.
The biogeography of the Malagasy herpetofauna has histori-
cally been a subject of considerable interest (e.g., Mertens, 1972;
Rage, 1996b; Vences et al., 2001, 2003; Raxworthy et al., 2002;
Nagy et al., 2003; Noonan and Chippindale, 2006a, 2006b). Based
on molecular phylogenetic evidence, Noonan and Chippindale
(2006a, 2006b) recently suggested that several Malagasy reptil-
ian groups (including boid snakes) originated as vicariant deriva-
tives of more cosmopolitan Gondwanan lineages when Madagas-
car became isolated from the other southern landmasses. This
claim is based on similar estimated timing of divergence of the
Malagasy groups, with Boidae originating approximately 75 Ma,
Pelomedusidae 80 Ma, and Iguanidae 67 Ma, and general con-
gruence of these events with the separation of Madagascar from
the Indian subcontinent (ca. 88 Ma—Storey et al., 1995, 1997) and
Antarctica (as recent as ca. 80 Ma—Hay et al., 1999). The present
study, based on a sample of fossils from an admittedly small
area and a thin time horizon in the Mahajanga Basin of north-
western Madagascar, provides no support for the hypothesis that
boid snakes were present on the island at the time that it rifted
from the other Gondwanan plates. Furthermore, the fossil record
from other parts of Gondwana has yet to yield any boid fos-
sils that antedate the purported time of separation of Madagas-
car from other southern landmasses. At present, the Maevarano
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 133
Formation snake fauna presents a pattern that is congruent with
that shown by many other Malagasy taxa in the fauna (with
the possible exception of the podocnemidid Erymnochelys—see
Gaffney and Forster, 2003): the species present in the latest Cre-
taceous deposits of the Mahajanga Basin belong to archaic Meso-
zoic lineages that were eliminated and replaced by basal stocks
of the modern fauna sometime after the close of the Cretaceous
(Krause et al., 2006; Yoder and Nowak, 2006).
Paleobiology and Paleoecology
Our ability to infer aspects of the paleobiology and paleoe-
cology of the Maevarano Formation snake assemblage is lim-
ited for three principal reasons. First, distributional data do not
provide meaningful insight into differences among the three de-
scribed species, given that two of them have been found at sev-
eral localities (Madtsoia madagascariensis and Menarana nosy-
mena at MAD93-16, Ma. madagascariensis and Kelyophis hechti
at MAD93-01, and Me. nosymena and K. hechti at MAD05-59)
and all three co-occur at MAD93-35. Thus, the single conclu-
sion that can be drawn from these data is that all three species
had the ability to survive in the highly seasonal, semi-arid cli-
mate deduced from sedimentological and taphonomic analyses
of the Maevarano Formation (Rogers et al., 2000, 2007; Rogers
and Krause, 2007).
Second, the phylogenetic placement of these taxa remains
uncertain. Nigerophiids are believed by some to be closely
related to acrochordids (Rage, 1984, 1987; McDowell, 1987),
but they have not been included in any large-scale cladistic
analyses of snake interrelationships, presumably because their
morphology remains known only very incompletely. In con-
trast, madtsoiids have been included in several phylogenetic
analyses, but the results of these studies have varied signifi-
cantly; some have recovered them as basal snakes, lying out-
side of the clade containing Scolecophidia +Alethinophidia
(Scanlon and Lee, 2000; Lee and Scanlon, 2002; Scanlon, 2006),
whereas others have concluded that they are more derived
alethinophidians, nested within Macrostomata (Rieppel et al.,
2002). Collectively, these points of uncertainty effectively pre-
clude rigorous historical analysis of the natural histories of these
three species.
Finally, as is the case for most fossil snakes, especially terres-
trial ones, the Maevarano taxa are known predominantly from
vertebral specimens. Although some studies have attempted to
correlate aspects of snake vertebral morphology with habitat, lo-
comotor mode, diet, or method of prey capture (e.g., Johnson,
1955; Hoffstetter and Gasc, 1969; Ruben, 1977; Lillywhite et al.,
2000), few detailed analyses have been undertaken in this regard.
Moreover, Moon (1999) recently demonstrated that considerable
caution must be exercised when attempting to make functional
inferences about snakes based solely on vertebral morphology.
Consequently, much of what follows should be regarded as some-
what speculative until such time as more rigorous analyses of the
functional morphology of the vertebrae of extant snakes can be
completed.
Madtsoia madagascariensis—Although the detailed de-
scriptions above serve to greatly expand our knowledge of the
anatomy of Madtsoia madagascariensis, they provide frustrat-
ingly few clues about its paleobiology, given our rudimentary
current understanding of the functional morphology of snake
vertebrae. Indeed, in many respects, the vertebrae of Ma.
madagascariensis strongly resemble those of many terrestrial
generalists among extant snakes, including in particular a variety
of boids and pythonids (e.g., Gasc, 1974), which collectively
exhibit a wide range of life history strategies. Many such snakes
exhibit strong arboreal or semi-aquatic tendencies, and the
dietary diversity they exhibit is extraordinarily high, including
a wide array of mammals, birds, crocodilians, and lepidosaurs
(e.g., Shine, 1991; Greene, 1997). However, whereas discrete
anatomical characters may not (yet) provide significant insight
into the paleobiology of Ma.madagascariensis, one more general
feature of its vertebrae—size—may be more informative in this
regard, as it serves as a useful proxy for estimating the overall
body size of this species.
Body size is an extremely important factor in determining a
number of life history traits in snakes, including feeding, locomo-
tion, and habitat usage (e.g., Greene, 1997). However, estimating
snake body size solely from measurements of individual verte-
brae presents a number of potential difficulties, not the least of
which is that vertebral number varies widely, ranging from just
over 100 to more than 550 (e.g., Rochebrune, 1881; Alexander
and Gans, 1966; Polly et al., 2001; upper end of range approxi-
mated indirectly based on scale counts provided by Gow [1977]
and Hahn and Wallach [1998]). Nevertheless, a recent study by
McCartney et al. (2008) demonstrated that nearly all standard
morphometric measurements of snake vertebrae are highly cor-
related with measurements of total length. Furthermore, on the
basis of this somewhat unexpected finding, these authors pro-
posed a method for estimating the size of fossil snakes from iso-
lated vertebrae and provided equations for doing so based on re-
gressions of vertebral size against total length, calculated across
a phylogenetically and morphologically diverse sample of extant
snakes. Using this method, along with morphometric data from
one of the largest and best preserved mid-trunk vertebrae of
Madtsoia madagascariensis (FMNH PR 2553; Table 1), we es-
timate the total length of this species to be approximately 5.1
m. Moreover, the width of such mid-trunk vertebrae and the
length and curvature of the most completely preserved ribs (e.g.,
UA 9764) suggest a mid-body diameter of approximately 15 cm.
Taken together, these two estimates are suggestive of a relatively
heavy-bodied snake, with an overall body mass of at least 50 kg.
However, large adults of Ma.madagascariensis may have reached
significantly greater proportions than this; the largest vertebral
specimen known from this species (MNHN MAJ 8; see Hoff-
stetter, 1961a:fig. 3D) is an isolated zygosphene that is over 50%
wider than that of FMNH PR 2553, suggesting that this species
may have at least occasionally reached lengths of nearly 8 m.
By analogy with modern snakes, the estimated proportions
of Madtsoia madagascariensis indicate a relatively slow-moving
snake that would likely have relied predominantly on a recti-
linear mechanism of locomotion (e.g., Mosauer, 1932; Bogert,
1947; Gray, 1968; Gans, 1974). Consistent with this hypothesis is
the complete absence of accessory prezygapophyseal processes,
which tend to be greatly enlarged anterolaterally in taxa that
rely primarily on a lateral undulatory mechanism of locomotion,
such as most colubroids (excluding viperids) and scolecophidi-
ans (Johnson, 1955). Moreover, the overall shape of the verte-
brae in Ma. madagascariensis differs greatly from that seen in
rapidly moving locomotor specialists, typically characterized by
relatively narrow, elongate vertebrae (Johnson, 1955).
The large size of Madtsoia madagascariensis also suggests
it was a sit-and-wait ambush predator rather than an active
forager. Unfortunately, with no knowledge of its cranial mor-
phology, it is difficult to estimate a size range for prey that
it may have exploited, and thus the type of prey that it may
have consumed. Nevertheless, it can be safely assumed that
this species faced the same fundamental physiological chal-
lenge that all snakes do in feeding: it had to provide ad-
equate nourishment for a very long body while retaining a
relatively small head, a most serious challenge indeed for a gape-
limited predator that must swallow prey whole, and a problem
with a limited number of solutions (Gans, 1961; Greene, 1997).
One such solution is to eat very large numbers of relatively
small prey (microphagy). However, this strategy has evolved only
rarely within Serpentes; it is restricted primarily to blindsnakes
(Scolecophidia), which feed almost exclusively on ant brood and
134 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 30, NO. 1, 2010
termites (e.g., Shine and Webb, 1990; Webb and Shine, 1993;
Webb et al., 2000; Kley, 2003a, 2003b, 2003c). It is significant to
note that few microphagous snakes even approach 1 m in length,
and most are in fact significantly smaller than this. The vast ma-
jority of all other modern snakes—nearly 90% of approximately
3000 recognized species, including all those that approach or ex-
ceed 5 m in length—are macrophagous, feeding infrequently on
relatively large prey. Therefore, it is reasonable to assume that
Ma. madagascariensis was also macrophagous. Furthermore, and
again by analogy with modern giant snakes (e.g., Shine et al.,
1998), it is also likely that this species would have exhibited an
ontogenetic shift in diet, such that relatively small vertebrates
would have been deleted from the diets of large adult individ-
uals (a very common phenomenon among extant snakes and one
fully predicted by optimal foraging theory; Arnold, 1993). Thus,
although juvenile Ma. madagascariensis mayhavefedonarel-
atively wide array of small vertebrates, adults probably preyed
on a narrower range of larger taxa. Possible adult prey among
the known fauna of the Maevarano Formation (see Krause et
al., 2006, for a recent review) would have included medium-sized
crocodyliforms (e.g., adult Simosuchus clarki, subadult Maha-
jungasuchus insignis) as well as small theropod dinosaurs (e.g.,
adult Masiakasaurus knopfleri, subadult Majungasaurus crenatis-
simus). Such large and potentially injurious prey would have al-
most certainly necessitated a highly efficient mechanism of prey
subjugation. Given the lack of any evidence suggesting the pres-
ence of a venom delivery system in madtsoiids (e.g., Scanlon,
2005a, 2006), and the relative inefficiency of some mechanisms
of prey subjugation, such as simple biting and/or pinioning used
by many modern snakes when feeding on relatively harmless
prey (e.g., Loop and Bailey, 1972; Willard, 1977; Greenwald,
1978; de Queiroz, 1984), we consider it most likely that Ma.
madagascariensis was a constrictor. However, we emphasize that
this inference is based entirely on a process of elimination from
the collective constellation of prey subjugation mechanisms ex-
hibited by living snakes (for a recent review, see Cundall and
Greene, 2000); constriction appears to be first and foremost a
behavioral innovation, and osteological correlates of this behav-
ior have yet to be identified conclusively (Greene and Burghardt,
1978).
Menarana nosymena—Although known much less completely
than Madtsoia madagascariensis,Menarana nosymena differs
from the former species in exhibiting a number of clearly adap-
tive morphological traits that collectively offer considerable in-
sight into its paleobiology.
Perhaps the most remarkable aspect of the morphology
of Menarana nosymena is the extensive degree to which
individual elements of the braincase (viz., parabasisphenoid, ba-
sioccipital, exoccipitals, prootics) have become fused together.
Among the more than 25,000 recognized species of extant
tetrapods, such a pattern of extensive basicranial fusion is seen
only among the most highly specialized limb-reduced, head-
first burrowers, such as in the ‘os basale’ of caecilians (e.g.,
Wiedersheim, 1879; Taylor, 1969; Wake and Hanken, 1982), the
‘otic-occipital complex’ of amphisbaenians (e.g., Zangerl, 1944;
Maisano et al., 2006; Montero and Gans, 2008), and the ‘otico-
occipital complex’ of derived uropeltid snakes (Rieppel and
Zaher, 2002; Baumeister, 1908; Cundall and Irish, 2008). The re-
peated convergent evolution of this morphological phenomenon
in these three highly fossorial clades, together with its general
absence among other tetrapods, suggests strongly that either Me.
nosymena was itself a very powerful head-first burrower, or that it
evolved from ancestors that were. Discovery of additional cranial
material, in particular elements of the snout, would likely help
to refine this interpretation. However, it is interesting to note in
this context that adult Yurlunggur also exhibit fusion among sev-
eral elements of the posterior braincase (though fewer than in
Menarana), yet clearly retain a rather unspecialized snout that
would appear to be very poorly suited for head-first burrowing
(Scanlon, 2006). Moreover, the very large size of this taxon alone
(estimated to be approximately 5 m; Scanlon, 2006) would appear
to be enough to make burrowing through compact soils impossi-
ble (see below). Thus, the presence of these basicranial fusions in
large adult Yurlunggur likely represents the retention of an an-
cestral trait, rather than direct evidence of adaptive modifications
within this particular taxon.
The morphology of the trunk vertebrae of Menarana nosymena
is also consistent with the hypothesis of a burrowing lifestyle
or ancestry. Most telling in this respect are the very low neural
spines and the rather depressed overall appearance of the ver-
tebrae, features that are nearly ubiquitous among extant snakes
that exhibit strong fossorial tendencies (e.g., scolecophidians,
Anilius,Cylindrophis, uropeltids, Xenopeltis,Loxocemus) (Hoff-
stetter and Gasc, 1969; Gasc, 1974). Somewhat more difficult
to interpret is the morphology of the atlas, in which the neu-
ral arches are fused completely with the intercentrum. How-
ever, in light of other available evidence, it is tempting to con-
sider this also an adaptation for burrowing, as this might serve
to maintain the integrity of the anterior atlantal cotyle (and thus
the craniovertebral joint as a whole) under the extreme loading
regimes that would be expected during tunnel construction, as
it would prevent the three constituent components of the cotyle
from being forced apart. Indeed, modifications of the atlas-axis
complex are relatively common among head-first limbless bur-
rowers (Gans, 1958; Williams, 1959; Taylor, 1977; Wake, 1980).
However, among the most specialized head-first burrowing squa-
mates, most notably amphisbaenians and uropeltid snakes, mod-
ifications to the atlas most commonly involve reduction rather
than fortification. Specifically, there is a tendency toward reduc-
tion or loss of the atlantal intercentrum, as well as reduction in
size of the articular facets on the pedicles of the atlantal neural
arches, which together greatly reduce the overall contribution of
the atlas to the craniovertebral joint (Zangerl, 1945; Williams,
1959). The result of these modifications is ultimately very simi-
lar to that of atlantal fusion in Menarana: the occipital condyle
is received predominantly by a single (rather than tripartite)
element—the odontoid process in amphisbaenians, and the axial
cotyle in uropeltids (members of the latter clade lack an odontoid
process).
Despite the numerous morphological features discussed above
that Menarana nosymena shares with many extant forms of limb-
reduced, head-first burrowing amphibians and reptiles, it must be
emphasized that few such taxa exceed even 1 m in total length,
and the vast majority are significantly smaller than this. Perhaps
even more significant, most are less than 1 cm in diameter, and
nearly all are less than 2.5 cm in diameter. The latter is particu-
larly important because it has been suggested that the force re-
quired to push an object through a given substrate increases with
the cross-sectional area (and thus the square of the diameter)
of that object (Gans, 1960). That is, it would be predicted that
as the diameter of a burrowing snake’s head increases, the force
that would be required to effectively burrow through compact
soil would increase very rapidly, according to a quadratic func-
tion rather than a linear one. This implies, for example, that if
a snake having a head diameter of 1 cm required 25 N of force
to burrow through a given substrate, one with a head diameter
of 3 cm would have to generate a much greater 225 N of push-
ing force to burrow through the same medium. Given this rela-
tionship, and the inherent physiological and mechanical limita-
tions common to all vertebrate skeletal muscles with respect to
their capacity to generate force, it remains somewhat question-
able whether a head-first burrowing mechanism could have been
effective, or even possible, in a limbless animal of the size of Me.
nosymena, which we estimate to have been approximately 2.4 m
in total length (using the equations of McCartney et al., 2008) and
in excess of 7 cm in mid-body diameter. Nevertheless, available
LADUKE ET AL.—LATE CRETACEOUS SNAKES FROM MADAGASCAR 135
anatomical evidence points strongly toward this species having at
least a burrowing ancestry, if not a burrowing lifestyle itself, as
inferred for some other madtsoiids (e.g., Herensugea caristiorum;
Rage, 1999).
The jaw apparatus of Menarana nosymena, like that of Madt-
soia madagascariensis, remains completely unknown, making in-
ferences about its diet and feeding difficult at best. However,
once again body size provides the most important clues in this
respect, as it significantly narrows the list of potential prey. By
analogy with modern alethinophidian snakes, the estimated pro-
portions of Me.nosymena suggest a maximum prey size for this
species of well under 5 kg, and possibly as small as 1–2 kg. Thus,
we can eliminate from the list of potential prey all of the larger
known fauna of the Maevarano Formation, including adults of
all non-avian dinosaurs and most crocodyliforms (the one known
exception being the very small Araripesuchus tsangatsangana;
Turner, 2006). More likely forms of potential prey include much
smaller ground-dwelling or fossorial vertebrates, possibly includ-
ing other snakes, non-ophidian squamates (‘lizards’) or small
mammals.
Kelyophis hechti—Kelyophis hechti, the Malagasy
nigerophiid, was probably less than 1 m long and thus much
smaller than the madtsoiids, Madtsoia madagascariensis and
Menarana nosymena. It appears to have been more generalized
than other nigerophiids, such as Nigerophis, Nubianophis,
and Indophis, which have been interpreted to have been very
highly specialized aquatic snakes on the basis of their ventrally
positioned synapophyses, their ‘peculiar’ prezygapophyseal
buttresses, and the high, narrow shape of their mid-trunk,
posterior trunk, and postcloacal vertebrae (Rage and Prasad,
1992; Prasad and Rage, 1995; Rage and Werner, 1999). Based
on its somewhat shorter vertebrae with less ventrally shifted
synapophyses, Kelyophis was apparently less well adapted to an
aquatic lifestyle. However, given the extremely limited nature of
the available material representing this species, few additional
inferences can be made about its paleobiology.
ACKNOWLEDGMENTS
We gratefully acknowledge field teams of the Maha-
janga Basin Project for the collection of specimens de-
scribed in this report; A. Rasoamiaramanana of the Univer-
sit´
e d’Antananarivo, B. Andriamihaja and his staff of the
Madagascar Institute pour la Conservation des Environnements
Tropicaux, and the villagers of Berivotra for logistical support
in the field; J. Groenke and V. Heisey for preparation of fos-
sils; M. Colbert for scanning the partial basicranium of the holo-
type of Menarana nosymena; J. Maisano for processing of µCT
images; R. Bonett, M. Norell, and D. Wake for access to com-
parative material; S. Burch, R. Jacobs, J. Sertich, and W. Simp-
son for assistance with curation; M. Stewart for photography; L.
Betti-Nash for drawing or arranging the figures; J.-C. Rage and
M. Godinot for curatorial information concerning MNHN speci-
mens of Madtsoia madagascariensis; and R. Jacobs for assistance
in compiling distributional data. We also thank J. McCartney,
J. Pruetz, and J. Sertich for reviewing early drafts, or parts of
drafts, of the manuscript, and the anonymous JVP reviewers for
their helpful comments on the submitted draft. This research was
funded by grants from the National Science Foundation (DEB-
9224396, EAR-9418816, EAR-9706302, DEB-9904045, EAR-
0106477, EAR-0116517, EAR-0446488) and the National Geo-
graphic Society (1999, 2001, 2004) to DWK.
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Submitted January 5, 2009; accepted April 15, 2009.
