A Middle Jurassic abelisaurid from Patagonia and the early diversification of theropod dinosaurs

摘要: Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls and extremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedingly rare Northern Hemisphere. The oldest definitive abelisaurids so far come from late Early Cretaceous South America Africa, early evolutionary history is still poorly known. Here, we report new abelisaurid Middle Jurassic Patagonia, Eoabelisaurus mefi gen. et sp. nov., which predates known secure member this lineage by more than 40 Myr. almost complete skeleton reveals earliest stages distinctive features abelisaurids, such as modification forelimb, started with reduction distal elements. find underlines explosive radiation theropod dinosaurs indicates an unexpected diversity ceratosaurs at that time. apparent endemism abelisauroids to southern Pangean times might be due presence central Gondwanan desert. This that, apart continent-scale geography, aspects regional geography climate important reconstruct biogeographical Mesozoic vertebrates.