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examples from southwest and northeast Japan. Science 286, 937±939 (1999).
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29. Hochstaedter, A. G., Kepezhinskas, P., Defant, M., Drummond, M. & Koloskov, A. Insights into the
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Acknowledgements
We thank P. Kelemen and K. Furlong for discussions; J. Morris and M. Defant for
comments on the manuscript; and A. Bellousov, M. Bellousova, M. Ejzak, A. Koloskov,
G. Ponomarov and V. Ponomareva for assistance in the ®eld. This work was supported by
the US NSF (G.M.Y. and J.M.L.), the German Science Foundation, the Volkswagen
Foundation and the European Union (INTAS) (to G.W. and T.C.), the Russian Founda-
tion for Basic Research (O.V. and T.C.), and by a grant from the Whitaker Foundation to
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Correspondence and requests for materials should be addressed to G.M.Y.
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.................................................................
A bizarre predatory dinosaur from the
Late Cretaceous of Madagascar
Scott D. Sampson*, Matthew T. Carrano
²
& Catherine A. Forster
²
* Utah Museum of Natural History and Department of Geology and Geophysics,
University of Utah, 1390 East Presidents Circle, Salt Lake City, Utah 84112-0050,
USA
²
Department of Anatomical Sciences, Health Sciences Center,
State University of New York, Stony Brook, New York 11794-8081, USA
..............................................................................................................................................
Here we report the discovery of a small-bodied (,1.8 m) pre-
datory dinosaur from the Late Cretaceous (Maastrichtian) of
Madagascar. Masiakasaurus knop¯eri, gen. et sp. nov., repre-
sented by several skull elements and much of the postcranial
skeleton, is unique in being the only known theropod with a
highly procumbent and distinctly heterodont lower dentition.
Such a derived dental morphology is otherwise unknown among
dinosaurs. Numerous skeletal characteristics indicate that
Masiakasaurus is a member of Abelisauroidea, an enigmatic
clade of Gondwanan theropods. Previously, small-bodied abeli-
sauroids were known only from Argentina
1±3
. The occurrence of
Masiakasaurus on Madagascar suggests that small-bodied abeli-
sauroids, like their larger-bodied counterparts, were more cos-
mopolitan, radiating throughout much of Gondwana and
paralleling the diversi®cation of small coelurosaur theropods in
Laurasia.
Several expeditions
4±7
have recovered abundant, well-preserved
skeletal remains of dinosaurs and other vertebrates from the Upper
Cretaceous (Maastrichtian) Maevarano Formation of northwestern
Madagascar. The non-avian dinosaur fauna includes a large abeli-
saurid theropod, Majungatholus atopus
5
, and at least two titano-
saurian sauropods. Remains of at least ®ve species of birds have also
been recovered, including the basal avian Rahonavis ostromi
7
. Our
study describes a previously unknown small-bodied form recovered
from the same deposits.
Saurischia Seeley 1888
Theropoda Marsh 1881
Abelisauroidea Bonaparte 1991
Masiakasaurus knop¯eri gen. et sp. nov.
Etymology. From masiaka (Malagasy, meaning vicious), sauros
(Greek, meaning lizard) and knop¯eri (after singer/songwriter
Mark Knop¯er, whose music inspired expedition crews).
Holotype. Universite
Â
d'Antananarivo (UA) 8680, well-preserved
right dentary with several teeth (Fig. 1).
Referred specimens. Field Museum of Natural History (FMNH PR
2108±2182): maxilla; dentaries; splenial; cervical, dorsal, sacral and
caudal vertebrae; dorsal rib; humeri; manual phalanges and ungual;
pubes; femora; tibiae; tibia/®bula/astragalocalcaneum; metatarsals
II and III; pedal phalanges and unguals. UA 8681±8696: dentary;
cervical, dorsal, and caudal vertebrae; femora; tibia/astragalocalca-
neum; pedal phalanges; and unguals.
Localities and horizon. All specimens are from the Anembalemba
Member of the Upper Cretaceous (Maastrichtian) Maevarano
Formation, Mahajanga Basin, near the village of Berivotra, north-
western Madagascar
8
. With few exceptions, elements attributable to
Masiakasaurus, including the holotype dentary (UA 8680), were
recovered as isolated specimens from a 3-m
2
area in one strati-
graphic horizon of a single locality, MAD 93-18.
Diagnosis. Differs from all known theropods in that the four
dentary teeth most rostral in position are procumbent, with the
®rst tooth set in a large, ventrally expanded alveolus that is almost
horizontal in orientation. Also differs from all known theropods in
that it has a strongly heterodont lower dentition: the ®rst four teeth
are elongate and weakly serrated, with labiolingually positioned
carinae. Each of these four teeth terminates in a pointed apex that
hooks caudally. The teeth become increasingly recurved and trans-
versely compressed with increasing caudal position in the jaw, and
possess more standard, mesiodistally positioned carinae.
Description. Together, the specimens referred to Masiakasaurus
knop¯eri account for about 40% of the skeleton (Fig. 1). The
concentration of isolated Masiakasaurus elements at MAD 93-18
includes remains of at least six individuals. All of these specimens
are assigned to a single species, despite many of the elements (for
example, femora, tibiae and vertebrae) being represented by several
specimens, as none shows evidence of belonging to more than one
taxon of small-bodied non-avian theropod. Two osteological fea-
tures (closure of the vertebral sutures and fusion of the crural and
tarsal elements) indicate that the largest materials represent adult or
near-adult individuals of this small-bodied taxon.
The maxilla, which is represented by a single partial specimen
(Fig. 1; FMNH PR 2183), has a pronounced, raised external rim
forming the perimeter of the extensive antorbital fossa. Although
lacking accessory foramina, a deep accessory fossa occupies the
rostral portion of the antorbital fossa. Seven alveoli are preserved
and, although a small portion of the caudal alveolar margin is
missing, it is unlikely that the maxillary tooth count exceeded ten.
Unerupted teeth, which are preserved in the third and ®fth alveoli, are
transversely compressed, recurved and bear moderate serrations.
Although the ®rst tooth is absentÐand thus the crown orientation
cannot be determined with con®denceÐthe ®rst alveolus is
oriented at about 458 to the horizontal, indicating that the rostrally
positioned teeth in the upper jaw may have been procumbent.
The specialized dentary (Fig. 2), represented by four specimens,
has a greatly emarginated caudal end that indicates an enlarged
intramandibular fenestra, as in Abelisauridae. The number of tooth
positions in the dentary of Masiakasaurus varies from 10 to 12. The
slightly enlarged ®rst alveolus is oriented almost horizontally to
such an extent that the ®rst tooth is directed forward. The ®rst four
teeth are radially arrayed, and become progressively more vertical
and parasagittal with increased caudal position.
The bizarre morphologies of these ®rst four teeth are unique
among theropods. The caudal carina is labial (lateral), whereas the
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rostral carina has migrated to a lingual (medial) position, resulting
in a tooth with a convex rostral face and a slightly concave caudal
face. The carinae of these teeth converge to a sharp, caudolaterally
hooked tip, and a series of longitudinal grooves cover the caudal
surface of the tooth between the carinae. Further back in the
dentary, the teeth gradually assume a more typical theropod
form, being recurved and transversely compressed, as the carinae
migrate into more rostral and caudal positions. Although hetero-
donty has been described for other theropod taxa (for example,
ref. 9), the degree of dental differentiation does not approach that of
Masiakasaurus. Modern mammals with procumbent dentitions,
such as some caenolestid marsupials, are often insectivorous,
using these teeth to assist in procuring prey items. Although the
speci®c diet of Masiakasaurus remains speculative, such a deviation
in dental morphology probably indicates a marked divergence from
the typical theropod diet.
The cervical vertebrae are moderately elongate and lack any
vertical offset of the cranial face over the caudal face. The centra
are broad, rather than tall, with no obvious pneumatic features. In
contrast, the neural arches are heavily pneumatized. The neural
spines are cranially positioned, greatly abbreviated in length, and
are short dorsoventrallyÐexceeded in height by the postzygapo-
physes. The postzygapophyses are elongate and swept back, forming
a deep, V-shaped notch that terminates cranially at the neural spine.
Figure 1 Skeletal anatomy of Masiakasaurus knop¯eri, based on a composite of isolated
specimens from locality MAD 93-18. a, Partial right maxilla (FMNH PR 2183) in medial
view. Dashed lines indicate reconstructed outline of the element. b, Posterior cervical
vertebra (FMNH PR 2139) in left lateral view. c, Left pubis (FMNH PR 2108) in dorsal view.
d, Left femur (FMNH PR 2117) in cranial view. e, Medial caudal vertebra (FMNH PR 2126)
in left lateral view. f, Partial right humerus (FMNH PR 2143) in medial view. g, Left pubis
(FMNH PR 2108) in lateral view. h, Proximal left tibia (FMNH PR 2118) in lateral view. i,
Left tibia/®bula/astragalocalcaneum (FMNH PR 2112) in cranial view. Dashed lines
emphasize contacts between individual elements. j, Pedal ungual (FMNH PR 2155) in
lateral view. k, Right metatarsals II (FMNH PR 2129) and III (FMNH PR 2151) in cranial
view. Scale bars, 1 cm. am, acetabular margin; aof, antorbital fossa; as, astragalus; bg,
blood groove; ca, calcaneum; cn, cnemial crest; dp, deltopectoral crest; epi, epipophysis;
®, ®bula; hh, humeral head; idp, interdental plates; ip, pit for ilio-pubic articulation; lt,
lesser trochanter; mc, mediodistal crest; mt2, metatarsal II; mt3, metatarsal III; ns, neural
spine; pb, pubic boot; pf, pubic fenestra; poz, postzygapophysis; pop, parapophysis; pp,
palatal process; prz, prezygapophysis; ti, tibia; ts, trochanteric shelf.
Figure 2 Dentary and lower dentition of Masiakasaurus knop¯eri. a, Holotype dentary (UA
8680) in right lateral view. The tooth in position four has been displaced caudally post
mortem. b±d, Scanning electron microscope photographs of isolated dentary teeth
(FMNH uncatalogued). b, Anterior tooth, position 2±4 in lingual view. c, Anterior tooth,
position 1±3, in lingual view. d, Anterior tooth, position 1±3, in lateral view. e,
Reconstructed dentary with full complement of teeth in right lateral view. f, Reconstructed
dentary in dorsal view, showing relative sizes and orientations of alveoli. c, carina; emf,
external mandibular fenestra; lg, longitudinal groove; s, serration. Tooth positions are
numbered sequentially from cranial to caudal positions. Scale bars, 10 mm (a, e±f);
5mm(b±d).
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The humerus has a straight shaft, with a bulbous head that is
separated from a well-developed deltopectoral crest. The femur is
strongly bowed, with a greatly enlarged mediodistal crest. Proxi-
mally, the relatively long, slender tibia has a pronounced cnemial
crest that curves dorsolaterally; distally, this element appears to back
both the astragalus and calcaneum. The astragalus has a plate-like,
rectangular ascending process that is fused with the ®bula along its
lateral margin. Metatarsal II is relatively straight, with the proximal
two-thirds reduced to a thin shaft. The weakly curved pedal unguals
possess a triangular arrangement of vascular grooves on both the
lateral and medial surfaces.
Masiakasaurus can be clearly diagnosed as a theropod dinosaur
on the basis of several shared, derived characters, such as recurved,
serrated, laterally compressed teeth, trenchant manual unguals and
markedly thin-walled skeletal elements
10,11
. Most phylogenetic ana-
lyses of Theropoda
10±13
have recognized two major clades, Cerato-
sauria (Coelophysoidea and Neoceratosauria) and Tetanurae
(Spinosauroidea, Allosauroidea, Coelurosauria). However, a few
studies
14±16
have suggested that Ceratosauria is paraphyletic, with
Coelophysoidea and Neoceratosauria as successive sister taxa to a
monophyletic Tetanurae.
Masiakasaurus possesses a number of synapomorphies that
support its membership in Abelisauroidea (Abelisauridae plus
Noasauridae)
17
(Fig. 3). These include: a specialized caudal dentary
margin with enlarged intramandibular fenestra; straight-shafted
humerus with enlarged, bulbous head; peg-and-socket articulation
of ilium and pubis; mediodistal crest of femur hypertrophied to
form a thin lamina; large, laterally curved and dorsally elevated
cnemial crest of the tibia; and triangular arrangement of grooves on
the pedal unguals. In the Abelisauroidea, abelisaurids are all
relatively large-bodied theropods that are identi®ed by a suite of
derived features, and are currently known from the Late Cretaceous
of India, Madagascar and Argentina
2,3,5,16,17
. In contrast, noasaurids
are small-bodied forms previously represented by one, or possibly
two, fragmentary taxa restricted to the Late Cretaceous of Argen-
tina
1±3
. Given that Masiakasaurus shares derived features with the
noasaurid Noasaurus leali from the Late Cretaceous of Argentina,
such as cranially positioned cervical neural spines and reduced
metatarsal II, it is possible that the new Malagasy taxon represents
a geographical extension of Noasauridae outside of Argentina.
However, Noasaurus, as well as several other small-bodied, Late
Cretaceous Gondwanan theropods from Argentina
18
and India
19
,
are represented by only a handful of elements, and thus the
phylogenetic relationships of these taxa remain obscure.
The placement of Masiakasaurus in the Abelisauroidea indicates
that small-bodied members of this clade, together with larger-
bodied forms, spread throughout much of the southern super-
continent Gondwana by the Late Cretaceous. Thus, it seems that the
Late Cretaceous radiation of North American coelurosaur thero-
pods into small-bodied (ornithomimid, troodontid, dromaeo-
saurid) and large-bodied (tyrannosaurid) forms
12
occurred in
parallel with the diversi®cation of Gondwanan abelisauroid ther-
opods. Furthermore, the peculiar dental and jaw morphology of
Masiakasaurus suggests that we are still far from fully appreciating
the morphological diversity of dinosaurs.
M
Received 5 May; accepted 26 October 2000.
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m. Soc. Ge
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ol.
Fra. 139, 19±28 (1980).
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paleobiogeography. GSA Today 9, 1±7 (1999).
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evidence from the Late Cretaceous of Madagascar. Science 279, 1915±1919 (1998).
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Mahajanga Basin, Madagascar: implications for ancient and modern faunas. J. Geol. 108, 275±301
(2000).
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Argentina and the early evolution of Dinosauria. Nature 361, 64±66 (1993).
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California Academy of Sciences, San Francisco, 1986).
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systematics. J. Paleontol. 68, 1100±1117 (1994).
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theropod dinosaur evolution. J. Vert. Paleontol. 19, 36A (1999).
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Acknowledgements
We thank A. Rasoamiaramanana, B. Rakotosamimanana, P. Wright, B. Andriamihaja and
the staff of the Institute for the Conservation of Tropical Environments for help with
®eldwork in Madagascar; members of the 1993, 1995, 1996, 1998 and 1999 expeditions for
their efforts; F. Novas amd P. Currie for photographs of Noasaurus; D. Krause for
comments on earlier drafts of the manuscript; V. Heisey for preparation; F. Grine for
scanning electron microscope photography; and L. Betti-Nash and J. Higgins for assistance
with the ®gures. This work was funded by grants from the National Science Foundation,
the National Geographic Society, and the Dinosaur Society.
Correspondence and requests for materials should be addressed to S.D.S.
(e-mail: ssampson@umnh.utah.edu).
144
208
65
1
2
3
TRIASSIC JURASSIC CRETACEOUS
Upper UpperLower LowerMidMU
THEROPODA
Eoraptor
Coelophysidae
Herrerasaurus
Dilophosaurus
Ceratosaurus
Majungatholus
Carnotaurus
Abelisaurus
Masiakasaurus
Noasaurus
NEOCERATOSAURIA
TETANURAE
Abelisauridae
Abelisauroidea
Figure 3 Stratigraphically calibrated cladogram of phylogenetic relationships of
Abelisauroidea, including Masiakasaurus. Unambiguous synapomorphies supporting the
nodes are: (1) (Neoceratosauria), lateral temporal fenestra much larger than orbit;
numerous foramina surrounding axial diapophysis; notched posterior iliac margin; peg-
and-socket articulation between ilium and pubis; femoral fourth trochanter reduced to low
ridge; deeply excavated medial surface of proximal ®bula; enlarged ilio®bularis tubercle
on ®bular shaft; (2) (Abelisauroidea): caudal dentary margin with notch for surangular;
enlarged external mandibular foramen; cervical neural spine abbreviated craniocaudally;
seven sacral veretebrae; large rounded coracoid; humerus straight-shafted with bulbous
head; hypertrophied mediodistal crest on femur; large tibial cnemial crest with laterally-
directed hook; distal; cnemial crest curved dorsally; rectangular astragalar ascending
process; triangular set of grooves on lateral and medial pedal unguals; and (3)
(Abelisauridae), craniofacial elements with external sculpturing; long, shelf-like maxilla±
jugal contact; greatly exposed paradental plates bearing a series of vertical ridges and
grooves; dorsal veretebral parapophyses projecting far laterally from centrum; distal ends
of caudal transverse processes expanded craniocaudally; forelimb short relative to other
skeletal elements. M, Middle; U, Upper. Dates are millions of years before present.
© 2001 Macmillan Magazines Ltd
