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

POL, D.; RAUHUT, O.W.

PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON. SERIES B: BIOLOGICAL SCIENCES.

ROYAL SOC

Lugar: Londres; Año: 2012 vol. 279 p. 3170 - 3175

0962-8452

Abelisaurids are a clade of large, bizarre predatory dinosaurs, most notable for their high, short skulls andextremely reduced forelimbs. They were common in Gondwana during the Cretaceous, but exceedinglyrare in the Northern Hemisphere. The oldest definitive abelisaurids so far come from the late EarlyCretaceous of South America and Africa, and the early evolutionary history of the clade is still poorlyknown. Here, we report a new abelisaurid from the Middle Jurassic of Patagonia, Eoabelisaurus mefigen. et sp. nov., which predates the so far oldest known secure member of this lineage by more than40 Myr. The almost complete skeleton reveals the earliest evolutionary stages of the distinctive featuresof abelisaurids, such as the modification of the forelimb, which started with a reduction of the distalelements. The find underlines the explosive radiation of theropod dinosaurs in the Middle Jurassic andindicates an unexpected diversity of ceratosaurs at that time. The apparent endemism of abelisauroidsto southern Gondwana during Pangean times might be due to the presence of a large, central Gondwanandesert. This indicates that, apart from continent-scale geography, aspects such as regional geography andclimate are important to reconstruct the biogeographical history of Mesozoic vertebrates.