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The dinosaur formerly known as Majungatholus ("Majunga dome") until its current name took precedence for paleontological reasons, Majungasaurus was a one-ton theropod native to the Indian Ocean island of Madagascar. Technically classified as an abelisaur--and thus closely related to the South American Abelisaurus--Majungasaurus was distinguished from others of its kind by its unusually blunt snout and the single, tiny horn on top of its skull. Like another famous abelisaur, Carnotaurus, Majungasaurus possessed unusually short arms, which presumably wasn't a major hindrance in the pursuit of prey.
Although it certainly wasn't the habitual cannibal portrayed on breathless TV documentaries (most famously Jurassic Fight Club), there’s good evidence that at least some Majungasaurus adults occasionally preyed on their own kind: paleontologists have discovered Majungasaurus bones bearing Majungasaurus tooth marks. What's unknown is whether the adults of this genus actively hunted down their living relatives, or simply feasted on the carcasses of already-dead family members (and if the latter is the case, this behavior wouldn't have been unique to Majungasaurus, dinosaur-wise, or for that matter to any living creature except modern human beings).
Like many other large theropods of the late Cretaceous period, Majungatholus has proven difficult to classify. When it was first discovered, researchers mistook it for a pachycephalosaur, or bone-headed dinosaur, thanks to that odd protrusion on its skull ("tholus," meaning "dome," in its original name Majungatholus, is a root usually found in pachycephalosaur names). Today, the closest relatives of Majungasaurus are a subject of dispute; some paleontologists point to obscure genera like Ilokelesia and Ekrixinatosaurus, while others throw up their (presumably not so tiny) arms in frustration.