DENTAL MORPHOLOGY AND VARIATION IN MAJUNGASAURUS CRENATISSIMUS (THEROPODA: ABELISAURIDAE) FROM THE LATE CRETACEOUS OF MADAGASCAR

ABSTRACT

Despite the known diversity of abelisaurid theropod dinosaurs, their dental anatomy remains poorly understood. Discoveries of elements preserving in situ dentition of the Late Cretaceous (Maastrichtian) Malagasy taxon Majungasaurus crenatissimus, coupled with recent progress in morphometric analysis of theropod teeth, provide an opportunity to document dental morphology and quantitatively evaluate positional variation in an abelisaurid dentition. Majungasaurus possesses an unusually static dental formula of 4/17/17 and a relatively even pattern of tooth replacement. The teeth are brachydont, moderately heterodont, and exhibit fairly well-developed interdenticular sulci/caudae. The premaxillary teeth are significantly wider, more elongate, and less curved than those in the maxilla and dentary, whereas the dentary crowns are shorter and more ‘squat’ than those in the upper dentition. Knowledge gained from teeth preserved within jaws demonstrates that isolated crowns recovered from the same deposits in the Maevarano Formation of the Mahajanga Basin, and assigned to Majungasaurus by earlier workers, can be confidently referred to that species. Qualitative and quantitative differences are demonstrated between the teeth of Majungasaurus and those of the only other known non-avian theropod in the Maevarano assemblage, the noasaurid Masiakasaurus knopfleri. Documentation of the intra-individual and intraspecific variation in Majungasaurus tooth anatomy provides a standard against which other abelisaurids can be compared and provides a suite of dental features that potentially can be used to assist in evaluation of the phylogenetic position of Majungasaurus among abelisaurids and Abelisauridae among theropods.