Majungasaurus: A Biopsy (Day Eighteen)

Today's featured article on Wikipedia took me back to when in second grade my grandfather drove me 53 miles to our nearest theater to see Jurassic Park.  

Majungasaurus (/məˌdʒʌŋɡəˈsɔrəs/; "Mahajanga lizard") "is a genus of abelisaurid theropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period. The genus contains a single species, Majungasaurus crenatissimus. This dinosaur was briefly called Majungatholus, a name which is now considered a junior synonym of Majungasaurus."

Like other abelisaurids, Majungasaurus was a bipedal predator with a short snout. Although the forelimbs are not completely known, they were very short, while the hindlimbs were longer and very stocky. It can be distinguished from other abelisaurids by its wider skull, the very rough texture and thickened bone on the top of its snout, and the single rounded horn on the roof of its skull, which was originally mistaken for the dome of a pachycephalosaur. It also had more teeth in both upper and lower jaws than most abelisaurids.

Known from several well-preserved skulls and abundant skeletal material, Majungasaurus has recently become one of the best-studied theropod dinosaurs from the Southern Hemisphere. It appears to be most closely related to abelisaurids from India rather than South America or continental Africa, a fact that has important biogeographical implications. Majungasaurus was the apex predator in its ecosystem, mainly preying on sauropods like Rapetosaurus, and is also one of the few dinosaurs for which there is direct evidence of cannibalism.

Majungasaurus is perhaps most distinctive for its skull ornamentation, including the swollen and fused nasals and the frontal horn. Other ceratosaurs, including Carnotaurus, Rajasaurus, and Ceratosaurus itself bore crests on the head. These structures are likely to have played a role in intraspecific competition, although their exact function within that context is unknown. The hollow cavity inside the frontal horn of Majungasaurus would have weakened the structure and probably precluded its use in direct physical combat, although the horn may have served a display purpose. While there is variation in the ornamentation of Majungasaurus individuals, there is no evidence for sexual dimorphism.

Computed tomography, also known as CT scanning, of a complete Majungasaurus skull (FMNH PR 2100) allowed a rough reconstruction of its brain and inner ear structure. Overall, the brain was very small relative to body size, but otherwise similar to many other non-coelurosaurian theropods, with a very conservative form closer to modern crocodilians than to birds. One difference between Majungasaurus and other theropods was its smaller flocculus, a region of the cerebellum that helps to coordinate movements of the eye with movements of the head. This suggests that Majungasaurus and other abelisaurids like Indosaurus, which also had a small flocculus, did not rely on quick head movements to sight and capture prey.