Majungasaurus (; ) 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, making it one of the last known non-avian dinosaurs that went extinct during the Cretaceous–Paleogene extinction event. The genus contains a single species, Majungasaurus crenatissimus. This dinosaur is also called Majungatholus, a name which is 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 hind limbs 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.
The genus is one of the first abelisaurs to be discovered, first being found in 1896 (although it was thought to be a species of Megalosaurus) and being named in 1955. 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.
Discovery and naming
French paleontologist Charles Depéret described the first theropod remains from northwestern Madagascar in 1896. These included two teeth, a claw, and some vertebrae discovered along the Betsiboka River by a French army officer and deposited in the collection of what is now the Université Claude Bernard Lyon 1. Depéret referred these fossils to the genus Megalosaurus, which at the time was a wastebasket taxon containing any number of unrelated large theropods, as the new species M. crenatissimus. This name is derived from the Latin word crenatus ("notched") and the suffix -issimus ("most"), in reference to the numerous serrations on both front and rear edges of the teeth. Depéret later reassigned the species to the North American genus Dryptosaurus, another poorly known taxon.
Numerous fragmentary remains from Mahajanga Province in northwestern Madagascar were recovered by French collectors over the next 100 years, many of which were deposited in the Muséum National d'Histoire Naturelle in Paris. In 1955, René Lavocat described a theropod dentary (MNHN.MAJ 1) with teeth from the Maevarano Formation in the same region where the original material was found. The teeth matched those first described by Depéret, but the strongly curved jaw bone was very different from both Megalosaurus and Dryptosaurus. Based on this dentary, Lavocat created the new genus Majungasaurus, using an older spelling of Mahajanga as well as the Greek word (meaning "lizard"). Hans-Dieter Sues and Philippe Taquet described a dome-shaped skull fragment (MNHN.MAJ 4) as a new genus of pachycephalosaur (Majungatholus atopus) in 1979. This was the first report of a pachycephalosaur in the Southern Hemisphere.
In 1993, scientists from the State University of New York at Stony Brook and the University of Antananarivo began the Mahajanga Basin Project, a series of expeditions to examine the fossils and geology of the Late Cretaceous sediments near the village of Berivotra, in Mahajanga Province. Among these scientists was paleontologist David W. Krause of Stony Brook. The first expedition turned up hundreds of theropod teeth identical to those of Majungasaurus, some of which were attached to an isolated premaxilla that was described in 1996. The following seven expeditions would turn up tens of thousands of fossils, many of which belonged to species new to science. The Mahajanga Basin Project claims credit for quintupling the known diversity of fossil taxa in the region.