Here we report the discovery of a small-bodied (similar to1.8 m) predatory
dinosaur from the Late Cretaceous (Maastrichtian) of Madagascar. Masiakasau
rus knopfleri, gen. et sp. nov., represented by several skull elements and
much of the postcranial skeleton, is unique in being the only known theropo
d with a highly procumbent and distinctly heterodont lower dentition. Such
a derived dental morphology is otherwise unknown among dinosaurs. Numerous
skeletal characteristics indicate that Masiakasaurus is a member of Abelisa
uroidea, an enigmatic clade of Gondwanan theropods. Previously, small-bodie
d abelisauroids were known only from Argentina(1-3). The occurrence of Masi
akasaurus on Madagascar suggests that small-bodied abelisauroids, like thei
r larger-bodied counterparts, were more cosmopolitan, radiating throughout
much of Gondwana and paralleling the diversification of small coelurosaur t
heropods in Laurasia.