Description and Classification

The initial description of Majungatholus centered on the distinctive partial skull roof notable for its thickened, dome-like prominence. This specific feature bore a strong resemblance to the cranial domes characteristic of pachycephalosaurs, a group of ornithischian dinosaurs recognized for their bony head adornments. Consequently, Majungatholus was first classified within the Pachycephalosauridae family. Its identification as such was particularly noteworthy, as it would have represented the only known pachycephalosaur from the Southern Hemisphere landmasses of Gondwana.

Subsequent paleontological work in Madagascar unearthed more complete skull and skeletal material from the same geological deposits. These fossils were assigned to the theropod dinosaur Majungasaurus crenatissimus. Careful study demonstrated that the “dome” of the original Majungatholus specimen was, in fact, the highly textured and thickened fused frontal bones that formed a single, central horn or boss on the head of Majungasaurus. This anatomical understanding confirmed that the type specimen of Majungatholus was from an adult Majungasaurus. Thus, Majungatholus is now recognized as the same animal as Majungasaurus, which is classified as an abelisaurid theropod. Abelisaurids, including relatives like Carnotaurus from South America and Abelisaurus, were dominant predators across Gondwana during the Cretaceous. The animal referred to as Majungatholus was a medium-sized carnivore, typically 6 to 7 meters (20 to 23 feet) in length and weighing approximately 1.1 metric tons (1.2 short tons). It possessed a stocky body, a characteristically short and deep skull, and extremely reduced forelimbs with tiny fingers, a hallmark of many abelisaurids.

Distinguishing Features

The dinosaur originally named Majungatholus (now recognized as Majungasaurus) possessed several unique characteristics:

• A single, thickened, and often rough-textured dome or horn-like structure on the top of its skull, formed by the frontal bones. This was the feature initially mistaken for a pachycephalosaur dome.
• An unusually short and deep snout, with the upper surface of the nasal bones being highly sculptured and rugged.
• Very short forelimbs with even smaller, probably non-functional, fingers. This is a common trait among abelisaurid theropods.
• Numerous teeth that were relatively short and stout, designed for gripping and tearing, which were replaced frequently throughout its life.
• A robust and heavily built skeleton for its size, suggesting a powerful musculature.

Paleoenvironment and Diet

Majungatholus lived in what is now northwestern Madagascar during the Late Cretaceous period, specifically the Maastrichtian age, about 70 to 66 million years ago. It inhabited the Maevarano Formation, an environment that at the time was a seasonal, semi-arid floodplain crisscrossed by rivers that flowed periodically. This ecosystem supported a diverse range of animal life, including the large sauropod dinosaur Rapetosaurus, the smaller noasaurid theropod Masiakasaurus, various crocodilians like the large Mahajangasuchus and the pug-nosed Simosuchus, as well as turtles, snakes, and early birds.

As likely the apex predator of its environment, Majungatholus would have hunted a variety of animals available in its habitat. Evidence from tooth marks found on bones strongly suggests that it preyed upon large sauropods like Rapetosaurus and possibly other smaller dinosaurs. Remarkably, Majungatholus is one of the few dinosaurs for which there is direct fossil evidence of cannibalism. Distinctive tooth marks matching the teeth of Majungatholus have been discovered on the bones of other Majungatholus individuals. This indicates that it sometimes ate members of its own species, perhaps as a result of fights over territory or resources, or by scavenging on carcasses.

Significance and Ongoing Research

The scientific story of Majungatholus is significant because it clearly illustrates how our understanding of dinosaurs can evolve with new fossil discoveries and more detailed analytical methods. The reclassification of the original fossil from a supposed Southern Hemisphere pachycephalosaur to an abelisaurid theropod underscores the critical importance of finding complete specimens in paleontological research. Fossils of the animal once named Majungatholus (now definitively known as Majungasaurus) are relatively abundant, making it one of the best-understood theropods from the ancient supercontinent of Gondwana. These remains have provided invaluable insights into the anatomy, growth patterns, behavior, and evolutionary history of abelisaurids.

Ongoing research continues to focus on various aspects of Majungatholus. Current studies include detailed examinations of its skull structure and how it functioned, including the purpose of its unique cranial horn and internal air sinuses. Scientists are also investigating its feeding mechanics, how it moved, and its growth rates from juvenile to adult. The Maevarano Formation in Madagascar remains an important site for paleontological excavations, holding the promise of more discoveries that could further illuminate the world of Majungatholus and the other creatures that lived alongside it millions of years ago.