Paper No. 2
Presentation Time: 1:45 PM
ABELISAUROID THEROPOD DINOSAURS FROM THE LATE CRETACEOUS OF EGYPT: EVIDENCE FOR GONDWANAN COSMOPOLITANISM
Recent paleogeographic and paleobiogeographic scenarios postulate the isolation of continental Africa throughout the Late Cretaceous. The absence of abelisauroid theropods from Upper Cretaceous African strata has been employed as evidence of hypothesized African isolation, with acknowledgement that the paucity of African abelisauroids may be related to sampling rather than to their actual absence from the continent. Here we report on a shed theropod tooth from the Upper Cretaceous (Campanian-?Maastrichtian, ~70Ma) Duwi (Phosphate) Formation of the Eastern Desert of Egypt that was referred to Megalosaurus crenatissimus (=Majungatholus atopus) in 1921. Stepwise discriminant function analyses (DA) using squared Mahalanobis distances (D2) and including eight size and shape variables were run to test for morphological congruence between the Egyptian tooth and the dental morphologies of 16 well-established theropod taxa. The DA correctly classified 96.1% of the teeth in the sample and assigned the tooth to the Malagasy abelisaurid Majungatholus (29.95 D2, p <.0001). Given that current paleogeographic reconstructions posit that Madagascar had attained its current position relative to Africa before the beginning of the Late Cretaceous, it is unlikely that the Egyptian tooth actually pertains to Majungatholus. Nevertheless, its classification as an abelisaurid constitutes the first definitive evidence of this clade from the post-Cenomanian Cretaceous of the African continent. This result, combined with recent discoveries of abelisauroids from ~95Myr and older rocks in Niger and Morocco and ~95Myr-old remains from the Bahariya Oasis of Egypt that share dental characters with the abelisauroid Masiakasaurus, indicate that Abelisauroidea was actually a diverse group in continental Africa during the Late Cretaceous, existing in multiple places for at least ~25Myr. These results suggest that abelisauroids may have been more cosmopolitan than demonstrated by previous evidence and that faunal communication between South America and Africa might have remained possible for longer than has been generally hypothesized.