DINOWEB - dinosaurs web-site  

Complete Data Base of Paleozoic and Mesozoic Tetrapods.
Paleo-News and illustrations. Big electronic PDF-library.

line decor
line decor

Download PDF Paleolibrary


?????????? ?????????
сайт о динозаврах
??????? ?????????

рейтинг сайтов
Free Hit Counters

Free Counter
hit counter javascript

myspace hit counter
Powered by counter.bloke.com

Locations of visitors to this page




Genus: Majungasaurus Lavocat, 1955

Classification: Dinosauria - Saurischia - Theropoda - Ceratosauria - Abelisauroidea - Abelisauridae - Carnotaurinae

Etymology: From Majunga, in reference to the province of Mahajanga (formerly Majunga), and saurus, New Latin, “lizard”, from the Greek sauros.

Synonyms: = Majungatholus Sues and Taquet, 1979

Type species: M. crenatissimus (Deperet, 1896) Lavocat, 1955

Other Species: none

Diagnosis: as for type species

Species: Majungasaurus crenatissimus (Deperet, 1896) Lavocat, 1955

Etymology: From crenatus, Latin, “notched or toothed”, and issimus, “most or very much”; in reference to “the serrations which are extended along the entire length of the two trenchant ridges of the teeth” (Deperet, 1896).

Synonyms: = Megalosaurus crenatissimus Daperet, 1896; = Dryptosaurus crenatissimus Deperet and Savornin;, 1928= Majungatholus atopus Sues and Taquet, 1979.

Holotype: MNHN.MAJ 1, fragmentary right dentary of a subadult individual (Lavocat, 1955).

Referred Specimens:
MNHN.MAJ 4 (holotype of Majungatholus atopus) lacrimal fragment, frontals, parietals, mesethmoid, laterosphenoids.
FMNH PR 2008, right premaxilla. This specimen is provisionally assigned to M. crenatissimus on the following grounds: 1) serration morphology on the premaxillary teeth is indistinguishable from that present on the two teeth present in the original collection described by Deperet (1896), as well as on hundreds of isolated teeth found in Upper Cretaceous deposits (Maevarano Formation) of the Mahajanga Basin in 1993 and 1995; 2) among the hundreds of isolated teeth collected in the field area, there is no evidence for more than one large theropod taxon. Exact locality data are unknown for the M. crenatissimus specimens described by Deperet (1896) and Lavocat (1955), though all were found in the Mahajanga Basin, northwestern Madagascar, southeast of Mahajanga. The premaxilla described below (FMNH PR 2008) was recovered from the same field area, at a locality designated MAD93-33. The geographic coordinates of MAD93-33, established with a satellite Global Positioning System (GPS), are: latitude 15°, 54", 28.31' S and longitude 46°, 34", 56.38' E.
FMNH PR 2008–right premaxilla; F
MNH PR 2099–partial skull roof including partially fused frontals with small median cornual process, or ‘horncore,’ of immature individual ;
FMNH PR 2100–nearly complete, exquisitely preserved, disarticulated skull (missing only left premaxilla, right pterygoid, right ectopterygoid, both epipterygoids, both vomers, and both columellae), with 26 associated caudal vertebrae and 18 haemal arches;
FMNH PR 2278–associated cranial (both premaxillae, both maxillae, left jugal, left quadratojugal, left ectopterygoid, left quadrate, left surangular, left angular, left prearticular, and left articular), and postcranial (two fragmentary cervical neural arches, three fragmentary dorsal vertebrae, one fragmentary caudal vertebra, left scapulocoracoid, partial left ilium, left femur, left and fragmentary right tibiae, left and partial right fibulae, left astragalocalcaneum, left metatarsals II-IV, right pedal phalanges II-1 and IV-2, and left pedal phalanges IV-2 and IV-3) elements of large near-adult;
FMNH PR 2293–axis (C2) vertebra;
FMNH PR 2294–five articulated caudal vertebrae (the last three fused pathologically) with two haemal arches;
FMNH PR 2295–3rd cervical vertebra (C3);
FMNH PR 2423–right humerus;
FMNH PR 2424–left tibia;
FMNH PR 2425–left astragalocalcaneum;
FMNH PR 2426–right pedal phalanx II-1;
FMNH PR 2427–right pedal phalanx II-2;
FMNH PR 2428–left pedal phalanges II-3 and III-2 and the distal end of right pedal phalanx II-1;
FMNH PR 2429–left pedal phalanx III-1;
FMNH PR 2430–right pedal phalanx IV-1;
FMNH PR 2431–left pedal phalanx IV-3;
FMNH PR 2432–left pedal phalanx IV-4;
FMNH PR 2433–right pedal phalanx IV-4;
FMNH PR 2434–left pedal phalanx IV-5;
FSL 92.290–pedal ungual phalanx;
MNHN.MAJ 4–partial skull roof with portions of partially fused frontals (with rounded median cornual process), parietals, caudal process of right lacrimal, sphenethmoid, and laterosphenoids;
UA 8678–incomplete and disarticulated skull (including left splenial, left prearticular, right surangular, and right squamosal) of subadult individual associated with 23 presacral vertebrae, 13 cervical and 14 dorsal ribs, a partial sacrum, five proximal caudal vertebrae, one middle caudal vertebra, the first haemal arch, and both ilia;
UA 8709–nearly complete, articulated, but poorly preserved skull (including maxillae, nasals, frontals, jugals, lacrimals, right postorbital and squamosal, pterygoids, ectopterygoids, right palatine, and partial braincase) and both lower jaws;
UA 8716–right premaxilla;
UA 8717–right and left premaxillae;
UA 8718–partial left lacrimal;
UA 8719–partial skull roof;
UA 8782–distal portion of left quadrate;
UA 9031–left humerus;
UA 9032–left tibia;
UA 9033–right astragalocalcaneum;
UA 9034–left metatarsal II;
UA 9035–left metatarsal IV;
UA 9036–left pedal phalanx II-1;
UA 9037–right pedal phalanx II-2;
UA 9038–left pedal phalanx II-3;
UA 9039–right pedal phalanx III-1;
UA 9040– right pedal phalanx IV-1;
UA 9041–right pedal phalanx IV-2;
UA 9042–left pedal phalanx III-2;
UA 9043–pedal phalanx IV-5;
UA 9077–left tibia and fibula;
UA 9078– right fibula;
UA 9079–left metatarsal III;
UA 9081–right pedal phalanx III-1 or III-2;
UA 9082–astragalus;
UA 9089– four proximal caudal vertebrae;
UA Bv 532–left pedal phalanx I-2;
UA Bv 1658–left pedal phalanx I-2;
UA Bv 1260–right pedal phalanx II-1;
UA Bv 1265–left pedal phalanx III-1;
plus literally thousands of isolated teeth (including FMNH PR 2198 and 2228, FSL 92.306a-b, MNHN 1911a-d, MNHN.MAJ 242, MNHN.MAJ 249) from numerous localities in the Berivotra Study Area.
MSNM V5255, MSNM V5256, MSNM V5267, MSNM V5276, MSNM V5509, MSNM V5510, MSNM V6418, MSNM V6419, MSNM V6420, MSNM V6421, pedal elements.

Time: Late Cretaceous (Maastrichtian)

Horizon: Maevarano Formation

Location: Mahajanga Basin, northwestern Madagascar, in the small field area surrounding the village of Berivotra, southeast of the port city of Mahajanga.

Total length: 7-9 m.

Mass: 1-2 tonns.

Diagnosis: Abelisaurid theropod with: (1) dorsoventrally deep, fused nasals that are strongly pneumatized via large, bilateral foramina; (2) nasal processes of left and right premaxillae separated by a thin lamina of nasal; (3) maxilla bearing 17 alveoli; (4) frontals rounded rostrally rather than forming a double notch; (5) frontals with a sculptured, median cornual process in adults that is variably pneumatic; (6) pronounced median fossa on sagittal (frontoparietal) crest; (7) dentary bearing 17 alveoli, virtually no extension caudal to last alveolus, and ventral position of lateral sulcus; (8) teeth bearing weakly developed
interdenticular sulci; (9) long, falciform atlantal epipophysis; (10) vertebral centra in cranial dorsal series with dorsoventrally elongate articular surfaces; (11) cranial and caudal borders of midcervical
transverse processes parallel in lateral view; (12) dorsal and caudal vertebral neural spines dorsally expanded (transversely and craniocaudally); and (13) cervical ribs pneumatized via multiple, enlarged foramina on medial surface of shaft, and accessory foramina on cranial and caudal surfaces of capitulotubercular web (Krause, Sampson, Carrano and O'Connor, 2007).

First description Megalosaurus crenatissimus, by Deperet:
Descriptions. — I attribute the following elements to a megalosaurid of moderate size:
1st. Two teeth, of which one is nearly complete up to the base of the crown, and the other is larger but incomplete below. These teeth show the typical characters of megalosaurid teeth: a transversely compressed shape with two sharp ridges anteriorly and posteriorly, the latter more trenchant than the anterior: a recurved posterior profile in the shape of a saber blade; fine transverse serrations on the trenchant ridges: these serrations extend along the entire length of the anterior edge. The enamel is finely striated lengthwise.
2nd. An ungual phalanx in the shape of a recurved claw, unfortunately broken near the point. A blunt ridge that runs over the convex or superior edge along its entire length separates two oblique lateral faces, of which one – doubtless located on the external side – is more developed than the other: this asymmetry of the phalanx makes it possible to think that it is the claw of a lateral digit. Each of the two faces is covered near the base by a wide, curved vascular groove that leaves the inferior edge and moves while rising towards the terminal point of the claw. The posterior or articular face shows indications of two shallow articular excavations, the external being wider, separated by a slightly vertical ridge.
3rd. Two sacral vertebrae are compressed in the middle of the centrum, according to the ordinary type of megalosaurids.
4th. A very elongated caudal vertebra, clearly amphicoelous, whose centrum shows a quadrangular cross-section, higher than wide. A slight median longitudinal crest is visible below, bordered by two weakly marked grooves. The neural arch is inserted along nearly the entire length of the centrum, only a centimeter of which is free posteriorly. A median longitudinal ridge represents the only indication of a spinous process. No surface for the chevrons is seen, which permits attributing this element to the post-median region of the tail. There is an extremely straight neural canal, of elliptical shape. The anterior and posterior zygapophyses are broken.
Relationships and differences. — The characters drawn together from the teeth, the ungual phalanx, and the amphicoelous caudal vertebra described above do not allow any doubt regarding the existence of a predatory dinosaur in Madagascar close to Megalosaurus Buckland from the Jurassic and Cretaceous of Europe, and of a genus near Dryptosaurus Marsh (Laelaps Cope) from the Cretaceous of the United States.
If the elements from Madagascar are compared with those of the type species, Megalosaurus bucklandi Meyer from the Lower Jurassic of England and France, important differences are recognized: the mandibular teeth (1) are higher, but straighter, with much coarser serrations on the posterior edge, and above all on the anterior edge where they exist only on the superior part of the crown; this character is important to note, because the teeth from Madagascar, that of Fig. 4 in particular whose crown is less nearly complete, show serrations along the entire visible part of the anterior edge. The upper teeth of M. bucklandi (2) are similar to the lowers; the serrations only appear less marked. The sacral vertebrae of this species (3) clearly have the short, compressed shape in the middle of the centrum shown by the Malagasy vertebrae; these are only much smaller. The caudal vertebrae from Madagascar entirely resemble the caudal vertebrae of M. bucklandi (4) in their general shape and details; it is only still of more elongate proportions and smaller dimensions by about a quarter. Finally, the ungual phalanx is less transversely compressed and more flattened dorsoventrally than in M. bucklandi (5); it differs further because the lateral groove ends behind the inferior edge of the bone much earlier than in the European species, where this short groove parallels the inferior edge nearly up to the proximal end of the phalanx.
Megalosaurus insignis Desl. from the Upper Jurassic of England and France (1) is a very large species whose teeth have the same straight, elongated form as those of M. bucklandi; they are less strongly recurved posteriorly than in the Malagasy species, the serrations of the trenchant anterior edge are weaker and cease on the inferior third of the length of the crown.
In M. dunkeri Koken (2) from the Wealden of England and Germany, the form of the teeth is likewise straighter and more elongated than in the Malagasy species; but the serrations are already finer and more closely resemble those of this latter type; however they disappear near the middle of the anterior ridge, as in the other European species, and are attenuated fairly easily by use along the entire length of this edge. The ungual phalanges of M. dunkeri (3) are more slender and more transversely compressed than those of the Malagasy species, and the lateral groove remains parallel to the inferior edge instead of recurving below near the posterior third.
Mr. Seeley has described (4) two teeth from the Upper Cretaceous beds of Neue Welt, near Vienna, under the name Megalosaurus pannoniensis that are much closer to the Malagasy teeth in the shape of the crown, which is shorter and wider at the base, and more finely serrated anteroposteriorly than in the other European species. However the posterior curvature is weaker than in the Malagasy species and the serrations cease on the inferior third of the anterior ridge instead of continuing along the entire length of this edge. I do not think that they could be attributed to the same species.
Above all, it is the species from the Arrialoor Group of Trichinopoly (British India), figured by Mr. Lydekker (5) without specific designation, that the Malagasy teeth resemble entirely in shape, which is short, wide at the base, and strongly posteriorly recurved, and in the fineness of the serrations, which are likewise extended along the entire length of the anterior edge. Except for the much greater dimensions of the Indian type, no appreciable difference can be found with the Malagasy form, and this difference of size can be due either to the age of the subject or to the positional order of the tooth in the jaws. Therefore I think that I can join these two types together, and I will give the name Megalosaurus crenatissimus n. sp. to the species because of the serrations which are extended along the entire length of the two trenchant ridges of the teeth.
Some genera from the Jurassic and Cretaceous of America show great affinities with Megalosaurus. The best known is Dryptosaurus Marsh (= Laelaps Cope) (1) from the Upper Cretaceous of New Jersey. The type species D. aquilunguis Cope is very large, attaining the size of M. bucklandi; the teeth differ entirely from those of Megalosaurus in the serrations of the anterior edge, which are extended along the entire length of this edge to near the root, instead of being limited to the upper part of the crown. It is interesting to note that this character is found exactly in the Malagasy and Indian form, therefore the attribution to the genus Dryptosaurus is shown as entirely probable. It is true to add that Leidy expressed the opinion that the American genus was close enough to Megalosaurus of Europe not to be distinguished from it, and this opinion is all the more probable because that the known parts of the skeleton of Dryptosaurus are extremely similar to those of Megalosaurus. Therefore I will attribute the Malagasy species to the large genus Megalosaurus, while emphasizing its affinities with the species from the Upper Cretaceous of America distinguished under the name Dryptosaurus.
Megalosaurus crenatissimus, n. sp. — A predatory dinosaur is represented by two small, compressed teeth, anteroposteriorly recurved in the shape of a saber blade, of the typical form of Megalosaurus but shorter and wider than in all the European species of this genus and characterized above all by fine serrations that ornament the two trenchant ridges anterior and posterior to the crown, extended along the entire length of the anterior edge instead of only occupying part or two thirds of this trenchant edge. The name Megalosaurus crenatissimus, n. sp., is intended to emphasize this character, which
is found in a Megalosaurus sp. noted by Mr. Lydekker in the Upper Cretaceous of India, and also in Dryptosaurus Marsh (Laelaps Cope) from the Upper Cretaceous of the United States. I am thus brought to refer the type from Madagascar to the genus Dryptosaurus, which it is doubtless better to consider as a simple section of the large genus Megalosaurus.
The other elements of M. crenatissimus are: a sacral vertebra, a caudal of more elongate form than M. bucklandi, and finally an ungual phalanx in the shape of a recurved claw, less transversely compressed than in other Megalosaurus, and furnished with a lateral groove that is less prolonged posteriorly than in the described species (Deperet, 1896).
4-8. — "Megalosaurus" crenatissimus, n. sp.
4. Tooth whose crown is a little near complete, from the side. The figure is enlarged by a quarter.
4a. Same tooth; cross-section at the base.
5. Another tooth, incomplete at the base of the crown, from the side. Enlarged by a quarter.
5a. Same tooth; cross-section at the base.
6. Centrum of one of the sacral vertebrae. 2/3 natural size.
7. Amphicoelous caudal vertebra, from the side. 2/3 natural size.
8. Ungual phalanx of a lateral digit, side view. 2/3 natural size.
8a. Same phalanx, proximal articular view (modified from Deperet, 1896).

Dr. Decorse has sent to the Museum a megalosaur tooth found at Maevarano. It is larger than the type figured by Deperet; but it probably belongs to the same species, because it is finely crenulated along the entire length of the anterior edge, though also on the posterior edge. Analogous teeth are known from the Cretaceous of India (1) and Austria (2). They show some similarity to the teeth of Laelaps (Dryptosaurus) from the Cretaceous of North America (3).
The same explorer collected fragments of thin hollow bones probably belonging to the same animal, but all poorly preserved. Mr. Bastard has found, in the same locality, biplanar or gently amphicoelous vertebrae with the body is strongly narrowed in the middle; these vertebrae can be attributed to the same bipedal carnivorous dinosaur as the preceding teeth (Thevenin, 1907).
17, 17a. - MEGALOSAURUS CRENATISSIMUS Deperet. - Tooth; profile, lateral face and section. - Same locality.
18. - Ibid. - Caudal vertebra; profile. - Same locality (modified from Lavocat, 1955).
A considerable number of teeth recovered in the Upper Cretaceous of Berivotro and Ambalakidy indicate the presence of a theropod of moderate size to which DEPERET gave the name of Megalosaurus. I possess a portion of mandible from this theropod, in the form of a nearly complete right dentary. This bone was found complete one month before our trip by an inhabitant of the countryside looking for yams, and unfortunately broken by him. Questioned by chance on whether he knew if it had teeth such as those that I showed him, he signaled to me at once as having found some “with the bone.” A visit to the place fortunately permitted collecting most of the pieces and several teeth. It seems that this is the first dentary of a theropod known from Madagascar. According to the Europeans in Marovoay, a mandible was found at another time in the vicinity of this village, but until now it had been impossible to find a trace of it. Without being able yet to give a definitive study of this bone here, I can now note its thin and rather long form (length: around 25 cm) and indicate that the form of the dentary in its posterior region seems to differ markedly from that of Megalosaurus from England, such as it is described by English authors (Lavocat, 1955).

Lavocats description dentery of Majungasaurus crenatissimus:
The presence of theropods in the Upper Cretaceous of Madagascar was noted around 1896 by DEPERET, based on teeth that he likened to similar teeth from India, making from the group a new spceies, Megalosaurus crenatissimus. Some other remains, notably an ungual phalanx and vertebrae, were attributed to the same animal. No bones belonging to the head have been published until now, and the portion of mandible that will be described is the first for Madagascar. It is a right dentary. I will recall briefly here the circumstances of its discovery. Found, while excavating the sandstones to collect yams,
by a native of the country who was naturally entirely unaware of its importance, this dentary, complete and intact in the locality, was broken and fractured by this man. Happily, at the time of my paleontological survey carried a month later, supported with teeth, he saw these teeth and understood at once the interest of his lucky find. A visit to the place, along with subsequent excavation of the spoil, permitted recovering not all, alas, but at least the most essential fragments. The discovery site is three meters above the bed of a river in a box ravine, two or three kilometers north of the Berivotro hotel, this village being located on the route to Majunga near kilometer 527. The bed could be very slightly inferior to that of the strict Berivotro horizon; it is in any case within the continental Upper Cretaceous.
The postero-superior and antero-inferior regions of this dentary, each complete, are assembled in perfect connection. The superior part of the symphyseal region also exists, but does not show any point of contact, so that a small margin of uncertainty remains as to its exact position, and it has not been figured for this first description. The length taken from the postero-superior edge to the edge of the symphysis is 23 cm (fig. 1,A)2. The elongate bone is hardly elevated, and it appears to be so even in the posterior region, although it is raised towards the rear. The ratio of height (in the posterior region)
to total length seems to be markedly less than in Tyrannosaurus, and much closer to that which characterized Megalosaurus bradleyi described by A. S. WOODWARD. The inferior part is wide, massive and robust. There are 17 dentary alveoli, a considerable number for a Cretaceous genus. The functional teeth are either lost or broken; some germ teeth are visible, of which some are in the process of eruption, and others are in their very young position against the lingual wall of the dentary alveoli; several teeth were recovered in the spoil and certainly belong to this dentary. If the alveolar proportions are believed, all the teeth would have been of very similar dimensions. They were small, like nearly all the isolated teeth found in this horizon, and of the same form described by Deperet, which
besides were found essentially in the same region and the same beds.
On the external side, a series of nutrient foramina, of which the anterior ones are small and the posterior ones are large and elongate, spread out along a line separating the bone in two very distinct regions, the superior part vertical and flat, while the inferior is convex and reinflated exteriorly, particularly under alveoli 8 to 15. This feature does not exist in Tyrannosaurus, where the external wall of the bone is appreciably flat from top to bottom.
Judging by the figures and descriptions given, this character does not exist either in the European Megalosaurus. The posterior external region of the bone bears a large notch (fig. 1, A) bounded by two straight and fairly long processes, one above and the other below. In the internal plane, the superior process is extended below by a bony lamina having a surface slightly weaker than that of the notch, and descends nearly up to the level of the inferior process, from which it is separated by another long and anteriorly rounded horizontal notch. The shape of this region seems to be fairly close to that of Tyrannosaurus; in contrast, there does not seem to be a similar structure in Megalosaurus.
On the internal face, the most remarkable character is that of the dentary alveolar wall. In most described theropods, and in any case in Megalosaurus and Tyrannosaurus, the authors insist on the fact that the alveolar partitions of the internal face are formed from rough bones, of triangular shape depending on the transverse partitions, and well separated from one another. Here, in contrast, a continuous longitudinal wall is observed, entirely symmetrical with the external wall, which is distinguished only by the fact that on the one hand the bone forming it is extremely thin – a simple lamina –, and that on the other hand the notch curving from the superior border which corresponds to each tooth is a little less marked on this internal face. But ultimately complete alveoli are found here, closed on the four sides and perfectly individualized. One finds on the other hand, a very distinct bony dental sac is found for each, whose wall is completely separated on the external face from the external wall of the dentary. The data on this last point are lacking for Megalosaurus. What renders indisputible the homology of this continuous partition with the simply bony triangles of other theropods, is the presence of the nutrient groove that runs the entire length of the bone, even at the foot of this partition, as it runs at the foot of the bony triangles (fig. 1, C). A very large, very elongate (the part around the total length of the alveoli) nutrient foramen opens into the inferior part of this groove at the level of each dentary alveolus; at the same time it notches the base of the internal wall laterally. Nothing permits knowing whether a supradentary existed, as for example in Tyrannosaurus.
On its internal face, the dentary bears a vast triangular lodging (fig. 1, B) that was certainly at least partly filled by the splenial. Meckel’s groove is difficult to locate. In Tyrannosaurus it is considered to be a longitundinal groove situated at the mid-height of the dentary. There is a groove here in about the same topographic location; but this is less marked and the attribution remains uncertain. In transverse section the dentary is observed to be formed from two distinct parts: a wide, low, robust bony body that is convex on the external side, and a straight alveolar superior part with tall vertical walls, situated on the median longitudinal axis (fig. 1, D).
As brief as the preceding description is, it nonetheless clearly reveals that this animal cannot be attributed to the genus Megalosaurus. The teeth, taken as the basis for this assignment, cannot provide any serious systematic argument in theropods. The teeth of our specimen being identical to those described by DEPERET, it is impossible to prove that they did not belong to the same species. As they are specimens recovered in the same stage of the same locality, the specific identity is more than probable; it is very probable. Under these conditions, it seems preferable to conserve the species name given by DEPERET, but by specifying that this name is recognized under the following diagnosis. However, it seems necessary to create a new genus, which we name Majungasaurus, the type mandible coming from the province of Majunga. This mandible will therefore be the type of Majungasaurus crenatissimus Dep. sp. emend. with the following diagnosis:
Fairly low dentary, with inferior part strongly convex externally. Continuous alveolar partition of the lingual face. Of moderate size (Lavocat, 1955).

FIG. 1. — Right dentary of Majungasaurus crenatissimus, type x 1/2. — A. External view. — B. Internal
view. — C. Occlusal view. — D. Transverse section at the level of the posterior external nutrient foramen (modified from Lavocat, 1955).
Right dentary of Majungasaurus crenatissimus, type
Majungatholus atopus:
Etymology: The generic name is derived from the name of the region where the specimen was found and the Latin tholus, 'dome'.The specific epithet is derived from the Greek atopos, 'strange' (or, in its original derivation, 'out of place' — a perhaps more appropriate meaning in the present context).

Diagnosis: A single dome-like thickening of the frontal region; frontal dome thick, with highly irregular, rugose dorsal surface. Parietal without significant thickening, participating in a well developed parieto-squamosal shelf. Very large supratem-poral fenestrae. Olfactory portion of the braincase long; olfac­tory lobes ventrally enclosed by bone (Sues and Taquet, 1979).
Medium-sized pachycephalo-saurid with single well-developed dome formed by fused and thickened frontals. Dor­sal surface of dome with highly irregular ornament of nodes and furrows; median depres sion on parietals without significant thickening, participating in formation of parietosquamosal shelf. Supratemporal fenestrae large. Olfac­tory stalks very long; olfactory lobes almost completely enclosed by bone ventrally (Sues, 1980).
Diagnostic characters for Majungatholus atopus: thickened, fused, highly pneumatic nasals with large, bilateral foramina; frontals with median hornlike projection; cervical ribs bifurcate distally; cervical ribs
with multiple enlarged pneumatic foraminae proximally (diameter . 10 mm) (Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998).

Holotype: Partial skull, consisting of the frontals and parietals (the latter being some­what damaged posteriorly) and the anterior part of the braincase. Formerly in the collec­tions of the Ecole des Mines, Paris (uncata-logued), now in the collections of the Museum National d'Histoire Naturelle, Paris, MNHN.MAJ 4. (formerly in the collections of the Ecole des Mines, Paris).

The specimen, a detailed anatomical description of which will be presented elsewhere, evidently represents a dome-headed dinosaur referable to the Pachycephalosauridae. Like other pachycephalosaurids, it differs from the Ankylosauria in show­ing very long olfactory stalks and thickening of the cranial roof bones by upgrowth of the bones rather than by fusion of dermal ectopic elements. Furthermore, in ankylosaurs the upper temporal fenestrae are always closed.
Majungatholus represents a distinctive type of the dome-headed ornithischians; its single frontal dome and its very large upper temporal fenestrae are unique features. The earliest known pachycephalosaurid, Yaverlandia bitholus, from the Lower Cretaceous (Wealden) of the Isle of Wight 1 , shows some resemblance in having large supratemporal fenestrae and thickening restricted to the frontal region; it differs, however, in having a small dome on each frontal and in being much smaller. The only Upper Cretaceous pachycephalosaurid species show­ing a certain similarity is a flat-headed form referred to Stegoceras from the Campanian of Alberta, Canada . In this species the supratemporal fenestrae are large and a parieto-squamosal shelf is well developed; the frontals, however, are but slightly thickened and the species is smaller than Majungatholus atopus. A peculiar feature only present in Majungatholus and the two Laurasian species mentioned above is a median circular depres­sion on the postero-dorsal surface of the frontals.
Majungatholus can be derived from a Yaverlandia-\ike form and probably represents a lineage evolving in geographical separation from Northern Hemisphere pachycephalosaurids.
The presence of a pachycephalosaurid in Madagascar and of other 'Laurasian' dinosaur families in the Southern Hemisphere during the Late Cretaceous can be explained in two different ways. First, dispersal from Laurasia could be assumed as all these families have their greatest diversity and most primitive species in the Northern Hemisphere. The Tethyan sea belt separated the two super-continents during the Cretaceous but it was at least in part a fairly shallow epicontinental sea and passage routes may have become available on several occasions. The exact locations of some of these connections may never be known as many potential areas have subsequently been affected by Cretaceous and Tertiary orogeneses. Cox has suggested the existence of a filter route in the Central American or Carribean region to account for the presence of a hadrosaur in Argentina . But it can also be argued that the existence of similar dinosaurs in both hemispheres is the result of vicariance events (the breakup of Pangea). The evidence presently available does not permit a choice between the two hypotheses. It is clear that faunal exchange by land connections between Laurasia and Gondwanaland was possible at least during the first half of the Cretaceous, possibly even at a later date (Sues and Taquet, 1979).

Majungatholus atopus,MNHN.MAJ 4. Partial skull in dorsal (a) and lateral (b) view (modified from Sues and Taquet, 1979).
Majungatholus atopus,MNHN.MAJ 4. Partial skull

About a century ago, French paleontologist Charles Deperet received a shipment of vertebrate fossils recovered from Upper Cretaceous strata near the town of Mahajanga (=Majunga), northwestern Madagascar. He recognized six specimens as the remains of a large theropod, and placed them in a new species of Megalosaurus, M. crenatissimus (Deperet, 1896). Lavocat (1955) later assigned an incomplete dentary, also recovered from the Mahajanga Basin, to this species, but erected a new genus, Majungasaurus. Russell et al. (1976) reported the discovery of a partial skeleton of M. crenatissimus from the Mahajanga Basin, but this specimen remains unprepared and unstudied in the Service de Paleontologic, Universite d' Antananarivo. Additional Late Cretaceous theropod remains purported to resemble those of M. crenatissimus include isolated teeth and terminal phalanges from Egypt (Gemellaro, 1921; Stromer and Weiler, 1930), isolated teeth from Argentina (Bonaparte and Powell, 1980), and an incomplete tooth from India (Mathur and Srivastava, 1987).
While some workers have considered Majungasaurus a "megalosaurid" (e.g., Molnar, 1980), others have suggested tyrannosaurid affinities (e.g., Charig, 1973; Sues, 1980). Sues (1980: 959) concluded with regard to M. crenatissimus that the "scanty remains ... are too fragmentary to allow assessment of the affinities of the species." Bonaparte (1986, 1991) referred Majungasaurus "with doubts" to Abelisauridae. Molnar (1990) tentatively supported the abelisaurid designation, noting that Carnotaurus sastrei from the Middle Cretaceous of Argentina possesses a similarly curved dentary (Bonaparte et al., 1990), yet relegated Majungasaurus to Theropoda incertae sedis.
In the austral winter of 1993, a joint SUNY-Stony Brook! Universite d' Antananarivo expedition recovered numerous specimens of fossil vertebrates from Upper Cretaceous terrestrial deposits in the Mahajanga Basin, northwestern Madagascar (Fig. 1; Krause and Hartman, 1996). Among these was a nearly complete, exquisitely preserved premaxilla of the poorly known large theropod, Majungasaurus crenatissimus.
This element, the first known cranial remains of M. crenatissimus, possesses derived morphology supporting placement of the taxon within the ceratosaurian clade Abelisauridae. It also shares several synapomorphies with the premaxilla of Indosuchus raptorius, a large theropod from the Late Cretaceous of India. Other than overall size, there are no significant differences in the premaxillae of these two taxa, supporting contentions that: 1) Majungasaurus and Indosuchus are sister taxa within Abelisauridae; and 2) Madagascar and the Indian subcontinent remained part of the same biogeographic
province into the Late Cretaceous (Sampson, Krause, Dodson and Forster, 1996).

Premaxilla of Majungasaurus crenatissimus in lateral (A) and medial (B) views (modified from Sampson, Krause, Dodson and Forster, 1996).
Premaxilla of Majungasaurus crenatissimus
Recent discoveries of fossil vertebrates from the Late Cretaceous of Madagascar include several specimens of a large theropod dinosaur. One specimen includes a nearly complete and exquisitely preserved skull with thickened pneumatic nasals, a median frontal horn, and a dorsal projection on the parietals. The new materials are assigned to the enigmatic theropod group Abelisauridae on the basis of a number of unique features. Fossil remains attributable to abelisaurids are restricted to three Gondwanan landmasses: South America, Madagascar, and the Indian subcontinent. This distribution is consistent with a revised paleogeographic reconstruction that posits prolonged links between these landmasses (via Antarctica), perhaps until late in the Late Cretaceous (Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998).
One of the theropod specimens (FMNH PR 2100) includes a nearly complete skull —among the best preserved and most complete dinosaur skulls known—and most of the tail. The skull is disarticulated and individual bones are virtually undistorted, allowing comprehensive and detailed study of all elements. The external surface of many elements is covered in rugose sculpturing, and the skull roof is adorned with three median ornamentations: thickened, fused nasals; a low frontal horn; and a parietal eminence. The total skull length is 57 cm, and comparisons with a closely related taxon, Carnotaurus sastrei from Argentina, suggest a total adult body length of about 7 to 9 m. A second specimen (UA 8678) of the same taxon includes an incomplete and disarticulated skull, most of the precaudal axial column, and the left ilium. Several of the vertebrae and ribs, particularly in the cervical region, were recovered in articulation. The small size of the skull elements relative to those of FMNH PR 2100, combined with the lack of fusion between several vertebral centra and corresponding neural arches, indicates that this animal was immature at the time of death.
Although large theropod materials from the Maevarano Formation have generally been referred to Majungasaurus crenatissimus, the inadequacy of the holotype and neotype specimens requires that
this taxon be regarded as a nomen dubium. Comparison of the recently collected materials with the fragmentary holotype specimen of the putative Malagasy pachycephalosaur, Majungatholus atopus, demonstrates that Majungatholus is not a pachycephalosaur but rather a “domed” theropod. This finding has biogeographic significance in that it removes the only report of a pachycephalosaur from a Gondwanan landmass, thereby restricting occurrences of this dome-headed ornithischian clade to Laurasia. Thus, the materials described herein are referred to Majungatholus atopus and placed within the enigmatic theropod group Abelisauridae (Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998).

Reconstruction of the skull and lower jaws of Majungatholus atopus, based on preserved elements of FMNH PR 2100 (12). (A) Left lateral view of skull and lower jaws; (B) rostral view of skull; (C) occipital view of skull; (D) dorsal view of skull; (E) palatal view of skull. Numbered features: 1, thickened nasals; 2, pneumatic foramen of nasal; 3, frontal horn; 4, parietal eminence; 5, enlarged antorbital fenestra; 6, lacrimal with suborbital process; 7, postorbital with suborbital process; 8, enlarged laterotemporal fenestra; 9, enlarged external mandibular fenestra; 10, nuchal crest; 11, median depression between
frontal horn and parietal eminence (modified from Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998).
Reconstruction of the skull and lower jaws of Majungatholus atopus
The known distribution of abelisaurids (Argentina, Indian subcontinent, and Madagascar), like that for gondwanathere mammals, is consistent with at least two major biogeographic hypotheses: Abelisaurids originated before the major continental fragmentations of the Early Cretaceous, and spread throughout most of Gondwana and perhaps into Laurasia. In keeping with this scenario, the current absence of documented African abelisaurids is attributable to poor sampling, differential extinction, or both. Abelisaurids originated sometime in the Early Cretaceous after the tectonic isolation of Africa. If so, abelisaurids never existed on Africa but rather dispersed between South America and Indo-Madagascar via Antarctica, making use of the postulated land bridge across the Kerguelen Plateau. Both views are equally probable given the data at hand.
Reconstructions of dinosaur biogeography initially focused on distinctions between Laurasian and Gondwanan faunas. More recently, it has been argued that dinosaur faunas were relatively cosmopolitan until the beginning of the Late Cretaceous, at which time the isolation of continental landmasses by oceanic barriers resulted in an abrupt shift toward marked provincialism. Recent paleogeographic and paleontological data, including those presented here for abelisaurid theropods, suggest an alternative hypothesis: African faunas became increasingly endemic during the Cretaceous after Africa’s isolation
from South America, whereas retention of subaerial connections among the remaining Gondwanan landmasses resulted in relatively extensive cosmopolitanism for the associated terrestrial faunas, perhaps until
late in the Late Cretaceous (Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998).
Synapomorphies of Abelisauridae observable in Majungatholus atopus include Cranial: External sculpturing of craniofacial elements; premaxilla with reduced to absent palatal process; maxilla-jugal contact
elongate; rostral process of lacrimal strongly reduced or absent; lacrimal with pronounced suborbital process; broad lacrimal-postorbital contact; long axis of postorbital oriented rostroventral-caudodorsal;
postorbital with pronounced suborbital process; high, transversely broad nuchal crest with large squamosal contributions; medial alveolar border of premaxilla, maxilla, and dentary bearing fused interdental plates with series of vertical ridges and grooves; hypertrophied external mandibular fenestra and associated weak contacts between dentary and postdentary elements. Postcranial: Postaxial epipophyses elongate (Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998).
Synapomorphies of Majungatholus and Carnotaurus include Cranial: Postorbital rostrocaudally elongate; postorbital with stepped-down ventrolateral fossa; dorsally placed median fossa in saddle-shaped depression overlapping contact of frontals and parietals; enlarged, caudodorsally projecting parietal eminence supported ventrally by stout supraoccipital; laterally directed paroccipital processes with upturned
distal ends; stout, triangular splenial with straight caudal margin) (Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998).

Many lines of evidence have been brought to bear on the question of theropod feeding ecology, including functional and physiological considerations, morphological constraints, taphonomic associations, and telling—although rare—indications of direct ingestion. Tooth marks of theropods, although rarely described and generally left unassigned to a particular taxon, can provide unique clues into predator–prey interaction, and can also yield insights into the extent of carcass utilization. Here we describe a sample of tooth-marked dinosaur bone recovered from three well-documented localities in the Upper Cretaceous Maevarano Formation of Madagascar that provides insights into the feeding ecology of the abelisaurid theropod Majungatholus atopus. Intensely tooth-marked elements from multiple individuals show that Majungatholus defleshed dinosaur carcasses. Furthermore, Majungatholus clearly fed upon the remains of not only sauropods, but also conspecifics, and thus was a cannibal. Cannibalism is a common ecological strategy among extant carnivores, but until now the evidence in relation to carnivorous dinosaurs has been sparse and anecdotal (Rogers, Krause, and Curry Rogers. 2003).

Majungasaurus crenatissimus has had a complex taxonomic history. The original sample, collected from several localities near the Betsiboka River, was described by Deperet (1896a, b) and included two teeth, an ungual phalanx, two partial sacral vertebrae, and a partial caudal vertebra. Deperet named the new species and assigned it to Megalosaurus, but he did not designate any of the six specimens comprising the type series as the holotype and, in addition, a type locality was not specified. Nor did Deperet indicate whether the specimens had been derived from a single individual or, indeed, even the same locality. Deperet and Savornin (1928) later assigned M. crenatissimus to Dryptosaurus, along with D. superbus (=Erectopus), D. aquilunguis, and D. saharicus (=Carcharodontosaurus). Deperet (1896b:191) had earlier revealed his inclination for this assignment by stating the following: “The type species D. aquilunguis Cope is very large, attaining the size of M. bucklandi; the teeth differ entirely from those of Megalosaurus in
the serrations of the anterior edge, which are extended along the entire length of this edge to near the root, instead of being limited to the upper part of the crown. It is interesting to note that this character is found exactly in the Malagasy and Indian form, therefore the attribution to the genus Dryptosaurus is shown as entirely probable.”
Nearly 60 years after publication on the original sample by Deperet (1896a, b), Lavocat (1955a, b) described a dentary from the same general field area (though several km to the north) and convincingly argued that it represented the same species of theropod as the six specimens described by Deperet. This argument was based primarily on dental morphology because several teeth within and associated with the dentary were regarded as identical to the two teeth described by Deperet. Lavocat, however, recognized that the morphology of the dentary was different from that of other species of Megalosaurus and therefore assigned M. crenatissimus to a new genus, Majungasaurus. Although not explicitly stated, it appears that Lavocat (1955a, b) did not consider any of the specimens in Deperet’s type series to be worthy of designation as the lectotype; instead, he opted to designate the dentary as the neotype of the species. This same specimen, however, was later considered to be nondiagnostic by Sampson and colleagues (1998), and Majungasaurus crenatissimus was thereby regarded as a nomen dubium. In its place, Sampson and colleagues (1998) designated Majungatholus atopus as the valid name for the Maevarano theropod. This followed the 1996 discovery of a theropod skull with lower jaws, which clearly showed that the skull roof (MNHN.MAJ 4) identified by Sues and Taquet (1979) as representing a new genus and
species of pachycephalosaur, Majungatholus atopus, instead belonged to a theropod. Sampson and colleagues (1998) argued that, because Deperet did not explicitly designate a holotype for the mid-sized Malagasy theropod, and because Lavocat’s dentary (MNHN.MAJ 1) was non-diagnostic, Majungatholus atopus must be the valid name assigned to the mid-sized theropod from the Maevarano Formation.
The recovery and analysis of additional dentary material and especially dental morphology, along with detailed comparison to the dentary (MNHN.MAJ 1) and teeth described by Lavocat (1955), compel us to once again reconsider the taxonomic designation of this theropod. The dentary described by Lavocat (1955), MNHN.MAJ 1, is typically abelisaurid in being broad, laterally bowed (in dorsal view), and relatively foreshortened, as well as in possessing a much-enlarged external mandibular fenestra (resulting in a relatively short post-alveolar portion, terminating caudally slightly behind the last alveolus), pronounced
longitudinal sulcus on the lateral surface containing neurovascularm foramina, and rugose subcutaneous texture on its external surfaces (as on the skull). These same features are found in the dentaries of FMNH PR 2100 and UA 8709. As outlined by Sampson and Witmer the adult dentaries of this species can be distinguished from those of other known abelisaurids (e.g., Carnotaurus and the Indian taxon represented by AMNH 1960 [referred to Indosuchus raptorius by Chatterjee, 1978]) by a suite of features, most notably the presence of 17 alveoli, the virtual lack of an extension of the dentary caudal to the last alveolus, and the ventral position of the lateral sulcus. The subadult dentary,MNHN.MAJ 1, possesses these same features and is therefore distinctive among theropods. Indeed, Sampson and Witmer state that “detailed comparisons of MNHN.MAJ 1 with the dentary of FMNH PR 2100 revealed no notable differences other than size (MNHN.MAJ 1 being approximately 25% smaller).”
Furthermore, detailed examination of the teeth preserved in MNHN.MAJ 1 by Smith (this volume) reveals that they fall within the same size and shape parameters as the two isolated teeth (FSL 92.306a-b) described by Deperet (1896a, b), those preserved in the gnathic elements of adult individuals described by Sampson and Witmer ( e.g., FMNH PR 2008, 2100; UA 8709, 8716, and 8717), and the thousands of isolated teeth recovered from the Maevarano Formation by Mahajanga Basin Project personnel and others. The teeth of the Malagasy abelisaurid most closely resemble those of AMNH 1753, 1955, and 1960 from the Late Cretaceous of India (referred to Indosuchus raptorius by Chatterjee, 1978) but, importantly, the Malagasy taxon possesses weakly developed interdenticular sulci whereas the Indian specimens lack them. These sulci can also be seen on the erupting teeth of MNHN.MAJ 1.
The possession of distinctive features in the dentary and teeth described by Lavocat (1955) and their full morphological congruence with other specimens attributed to the mid-sized Malagasy taxon from the Maevarano Formation (not to mention the lack of evidence for any other mid-sized theropod in the Maevarano Formation, despite the recovery of thousands of vertebrate specimens), ineluctably leads to the conclusion that MNHN.MAJ 1 represents a subadult individual of the same taxon represented by other dentaries (FMNH PR 2100, UA 8709) and countless isolated teeth. As such, and according to the Principle of Priority of the International Code of Zoological Nomenclature (1999), MNHN.MAJ 1 must be designated as the valid type specimen and Majungasaurus crenatissimus as the valid name of this theropod (Krause, Sampson, Carrano and O'Connor, 2007).

The abelisaurid theropod Majungasaurus crenatissimus inhabited the plains of northwestern Madagascar during the Late Cretaceous. It lived alongside other nonavian dinosaurs, including a small-bodied noasaurid theropod (Masiakasaurus knopfleri) and a titanosaurian sauropod (Rapetosaurus krausei). Although an inhabitant of the expansive floodplains of the Mahajanga Basin, M. crenatissimus also frequented the broad and sandy channel belts that drained Madagascar’s central highlands. These shallow rivers were populated by a variety of aquatic and semi-aquatic animals, including fish, frogs, turtles, and several species of both large and small crocodyliforms. These animals were likely adapted for seasonal fluctuations in water availability because the sediments that entomb their remains (fine-grained debris flow deposits intercalated with stream flow deposits) indicate a strongly variable discharge regime. Associated oxidized calcareous paleosols with localized accumulations of carbonate nodules suggest that the ambient climate was semiarid. The numerous bonebeds preserved in these same sediments are indicative of localized and recurrent pulses of mortality. M. crenatissimus fed on carcasses preserved in these bonebeds, and there is good indication from a wealth of toothmarked bone derived from two conspecific individuals that it focused on the well-muscled axial skeleton in a fashion similar to that of many modern vertebrate carnivores. This evidence for intraspecific feeding renders M. crenatissimus the only theropod dinosaur with demonstrated cannibalistic tendencies (Rogers, Krause, Curry Rogers, Rasoamiaramanana and Rahanarisoa, 2007).

Recent fieldwork in the Upper Cretaceous (Maastrichtian) Maevarano Formation, northwest Madagascar, has yielded important new skull material of the abelisaurid theropod, Majungasaurus crenatissimus. One of these specimens in particular—a virtually complete, disarticulated, and well preserved skull—greatly elucidates the craniofacial osteology of abelisaurids. Herein we describe the skull and lower jaws of this mid-sized theropod dinosaur. A number of features of the facial skeleton and cranium (as well as the postcranium) appear to result from increased levels of mineralization and ossification, which, at least in some instances, can be related directly to specific soft-tissue structures; examples include lacrimal-postorbital contact dorsal to the orbit, suborbital processes of the lacrimal and postorbital, presence of a mineralized interorbital septum, fused interdental plates, and mineralization of the overlying integument. Autapomorphic features include a highly derived nasal—greatly thickened and fused to its counterpart, with a large
interior pneumatic chamber—and a median, ‘dome'-like thickening of the frontals, which appear to have been variably pneumatized by a paranasal air sac. Majungasaurus also possesses a derived suite of skull morphologies, including: a rostrocaudally abbreviated, dorsoventrally deep, and transversely broad skull; an expanded occiput, likely associated with expanded cervical musculature; short-crowned dentition; and an enlarged external mandibular fenestra consistent with a moderate degree of intramandibular movement or accommodation. A number of characters, present on both the skull and postcranial skeleton, suggest a divergent mode of predation relative to other, non-abelisaurid theropods ( Sampson and Witmer, 2007).

Despite the known diversity of abelisaurid theropod dinosaurs, their dental anatomy remains poorly understood. Discoveries of elements preserving in situ dentition of the Late Cretaceous (Maastrichtian) Malagasy taxon Majungasaurus crenatissimus, coupled with recent progress in morphometric analysis of theropod teeth, provide an opportunity to document dental morphology and quantitatively evaluate positional variation in an abelisaurid dentition. Majungasaurus possesses an unusually static dental formula of 4/17/17 and a relatively even pattern of tooth replacement. The teeth are brachydont, moderately heterodont, and exhibit fairly well-developed interdenticular sulci/caudae. The premaxillary teeth are significantly wider, more elongate, and less curved than those in the maxilla and dentary, whereas the dentary crowns are shorter and more ‘squat’ than those in the upper dentition. Knowledge gained from teeth preserved within jaws demonstrates that isolated crowns recovered from the same deposits in the Maevarano Formation of the Mahajanga Basin, and assigned to Majungasaurus by earlier workers, can be confidently referred to that species. Qualitative and quantitative differences are demonstrated between the teeth of Majungasaurus and those of the only other known non-avian theropod in the Maevarano assemblage, the noasaurid Masiakasaurus knopfleri. Documentation of the intra-individual and intraspecific variation in Majungasaurus tooth anatomy provides a standard against which other abelisaurids can be compared and provides a suite of dental features that potentially can be used to assist in evaluation of the phylogenetic position of Majungasaurus among abelisaurids and Abelisauridae among theropods (Smith, 2007).

Featured among the discoveries is an exquisite specimen (UA 8678) that preserves a virtually complete precaudal vertebral column, numerous costal elements, and portions of the skull and appendicular
skeleton. This contribution represents the first description highlighting the postcranial axial skeleton of Majungasaurus. Owing to the completeness and quality of preservation, this specimen allows an examination of the serial transformation of features along the length of the axial skeleton, including a detailed analysis of postcranial pneumaticity in a nontetanuran theropod. Notable features of Majungasaurus include pneumatic cervical ribs with caudally bifurcate shafts and extensive pneumaticity of all postatlantal, precaudal vertebrae. Several postcranial features exhibited by Majungasaurus—
including a well-developed cervical epipophysis, laterally expanded dorsal parapophysis, and sub-divided infradiapophyseal fossa in middle dorsal series—support previous phylogenetic studies placing it within Abelisauroidea and Abelisauridae. Majungasaurus (and abelisaurids generally) exhibit a robust cervical skeleton that features tightly interlocking cervical ribs, hyperossification of cervical rib shafts, and hypertrophied muscle attachment sites relative to other basal theropods. These features together highlight an axial core constructed to withstand high stresses, likely reflecting feeding adaptations for predation on large-bodied prey (O'Connor, 2007).

The appendicular skeleton of the abelisaurid theropod Majungasaurus crenatissimus (Deperet, 1896) Lavocat, 1955 is described for the first time. The available materials include an incomplete pectoral girdle and forelimb, along with the ilium and a nearly complete hind limb. These materials display a number of ceratosaur, abelisauroid, and abelisaurid synapomorphies, supporting the phylogenetic placement of Majungasaurus based previously on cranial anatomy. As in Ceratosaurus and Carnotaurus, the scapular blade is relatively wide and has a pronounced dorsal lip over the glenoid. The humerus is short and bears a globular head, but is more slender than in Carnotaurus. The ilium has a preacetabular hook, a strong supraacetabular crest, a notched posterior margin, and peg-and-socket articulations with both the pubis and ischium. Hind limb elements are proportionally stocky, as in some other abelisaurids. The femur lacks a trochanteric shelf, the tibia has a greatly enlarged cnemial crest, and the fibula bears a deep, posteriorly facing medial fossa. The abelisaurid astragalocalcaneum is described here in detail for the first time, and is more similar to that of tetanurans than to those of coelophysoids. Taken together, these materials illustrate that the appendicular skeleton of abelisaurids was specialized over the typical condition in basal theropods, particularly through the development of enlarged muscle attachment processes.
The appendicular morphology of the abelisaurid theropod Majungasaurus crenatissimus is described. Abelisaurid appendicular materials have not been well documented, and several relatively complete specimens of this Late Cretaceous Malagasy theropod greatly clarify this region of the skeleton in these theropods. The forelimb of Majungasaurus is similar to those of other abelisaurids and includes a short, highly modified humerus. Numerous abelisaurid and abelisauroid synapomorphies are also found in the pelvis and hind limb. In addition, the pelvis and hind limb display a combination of features that strongly suggest a close affinity between abelisauroids and tetanurans. Functionally, the abelisaurid forelimb remains obscure and its interpretation must await more complete materials. The hind limb appears to show specializations for strong knee extensors, as well as unusual modifications of the metatarsus and pes that may have additional locomotor implications. (Carrano, 2007).

Recent collecting efforts (1993 to present) in the Upper Cretaceous (Maastrichtian) Maevarano Formation of northwestern Madagascar have yielded numerous specimens of the medium-sized abelisauroid theropod Majungasaurus crenatissimus (Deperet, 1896) Lavocat, 1955. Exquisite preservation, coupled with near-complete articulated or associated skeletons, has allowed an assessment of individual skeletal variation in this taxon, including a preliminary analysis of osteopathology in a non-tetanuran theropod. Importantly, Majungasaurus is the first abelisauroid theropod for which comprehensive pathology data are available. In a survey of 181 postcranial skeletal elements from a minimum of 21 individuals, abnormalities were identified in eight elements from a minimum of four individuals. These include a pedal
phalanx with a mediolateral diaphyseal expansion of unknown etiology, a dorsal vertebra with a small exostosis, a caudal vertebra with probable idiopathic ossification of vertebral ligaments, and a pathologically truncated series of distal caudal vertebrae. The latter occurrence represents the first identified caudal truncation in a predatory dinosaur and only the second documented occurrence among non-avian dinosaurs (Farke and O'Connor, 2007).

Majungasaurus crenatissimus type specimen: tooth, vertebrae and ungual.

: Majungasaurus crenatissimus type specime

Majungasaurus crenatissimus skeleton
Majungasaurus crenatissimus skeleton
Summary of phylogenetic, temporal, and biogeographic relationships of nonavian theropod genera from the Cretaceous of Gondwana. Taxa include most named genera recovered from Cretaceous deposits on Gondwanan landmasses (modified from Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998).
Summary of phylogenetic, temporal, and biogeographic relationships of nonavian theropod genera from the Cretaceous of Gondwana
Stratigraphically calibrated phylogeny of Abelisauridae (modified from Krause, Sampson, Carrano and O'Connor, 2007).
Stratigraphically calibrated phylogeny of Abelisauridae

Deperet, 1896. Note on the sauropod and theropod dinosaurs from the Upper Cretaceous of Madagascar. Bulletin de la Societe Geologique de France, 3rd series, vol. 24 176-194.

Thevenin, 1907. Dinosauriens (Paleontologie de Madagascar IV). Annales de Paleontologie. 2, 121-136.

Lavocat, 1955. Etude des gisements de Dinosauriens de la region de Majunga (Madagascar). Travaux du Bureau Geologique. 69, 1-19.

Lavocat, 1955. Sur une portion de mandibule de Theropode provenant du Cretace superieur de Madagascar. Bull. Mus. Hist. Nat. Paris 27 256-259, 1 fig.

Lavocat, R., 1957. Sur les couches a dinosauriens de Madagascar. CCTA and Service Geologique de Madagascar, Comptes Rendus. Comites regionaux Centre, Est et Sud Conference de Tananarive, Avril 1957, Geology, Second Volume: 363-364.

Sues and Taquet, 1979. A pachycephalosaurid dinosaur from Madagascar and a Laurasia-Gondwanaland connection in the Cretaceous. Nature. 279:633-635.

Sues, H.D. 1980. A pachycephalosaurid dinosaur from the Upper Cretaceous of Madagascar and its paleobiogeographical implications. Journal of Paleontology 54:954–962.

Sampson, Krause, Dodson and Forster, 1996. The premaxilla of Majungasaurus (Dinosauria: Theropoda) with implications for Gondwanan Paleobiography. Journal of Vertebrate Paleontology. 16 (4): 601-605.

Sampson, Witmer, Forster, Krause, O'Connor, Dodson and Ravoavy, 1998. Predatory dinosaur remains from Madagascar: Implications for the Cretaceous biogeography of Gondwana. Science, 280: 1048-1051.

Rogers, R. R., D. W. Krause, and K. Curry Rogers. 2003. Cannibalism in the Madagascan dinosaur Majungatholus atopus. Nature 422: 515–518.

O'Connor, P. M. 2006. Pulmonary pneumaticity: an evaluation of softtissue influences on the postcranial skeleton and the reconstruction of pulmonary anatomy in archosaurs. Journal of Morphology 267: 1199–1226.

Krause, Sampson, Carrano and O'Connor, 2007. Overview of the history of discovery, taxonomy, phylogeny, and biogeography of Majungasaurus crenatissumus (Theropoda: Abelisauridae) form the Late Cretaceous of Madagascar. in Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8. 1-20.

Rogers, Krause, Curry Rogers, Rasoamiaramanana and Rahanarisoa, 2007. Paleoenivronment and paleoecology of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. in Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8. 21-31.

Sampson and Witmer, 2007. Craniofacial anatomy of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. in Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8. 32-102.

Smith, 2007. Dental morphology and variation in Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. in Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8. 103-126.

O'Connor, 2007. The postcranial axial skeleton of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. in Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8. 127-162.

Carrano, 2007. The appendicular skeleton of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. in Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8. 164-179.

Farke and O'Connor, 2007. Pathology in Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. in Sampson and Krause (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. SVP Memoir 8. 180-184.

© Tetrapoda Database Roman Ulansky roman.ulansky@gmail.com or adios85@mail.ru



Hosted by uCoz