1. Utah Museum of Natural History and Department of Geology and Geophysics, University of Utah, 1390 East Presidents Circle, Salt Lake City, Utah 84112-0050, USA
2. Department of Anatomical Sciences, Health Sciences Center, State University of New York, Stony Brook, New York 11794-8081, USA

Correspondence to: Scott D. Sampson¹ Correspondence and requests for materials should be addressed to S.D.S. (e-mail: Email: ssampson@umnh.utah.edu).

Abstract

Here we report the discovery of a small-bodied (1.8 m) predatory dinosaur from the Late Cretaceous (Maastrichtian) of Madagascar. Masiakasaurus knopfleri, gen. et sp. nov., represented by several skull elements and much of the postcranial skeleton, is unique in being the only known theropod 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 Abelisauroidea, an enigmatic clade of Gondwanan theropods. Previously, small-bodied abelisauroids were known only from Argentina^{1, 2, 3}. The occurrence of Masiakasaurus on Madagascar suggests that small-bodied abelisauroids, like their larger-bodied counterparts, were more cosmopolitan, radiating throughout much of Gondwana and paralleling the diversification of small coelurosaur theropods in Laurasia.