Eoabelisaurus

Eoabelisaurus (ˈiəʊəˌbɛlᵻˈsɔːrəs) is a genus of abelisaurid theropod dinosaur from the Lower Jurassic Cañadón Asfalto Formation of the Cañadón Asfalto Basin in Argentina, South America. The generic name combines a Greek ἠώς, (eos), "dawn", with the name Abelisaurus, in reference to the fact it represents an early relative of the latter. Only one species is currently recognized, E. mefi; the specific name honours the MEF, the Museo Paleontológico "Egidio Feruglio", where discoverer Diego Pol is active. It is characterized by reduced forelimb proportions that show primitive characteristics of the Abelisauridae family. In 2009, Argentinian paleontologist Diego Pol discovered the skeleton of a theropod near the village of Cerro Cóndor in Chubut Province. The remains were found in the Jugo Loco locality that is placed in a series of fine beds of mudstone, marlstone, and limestone in the Cañadón Asfalto Formation. In 2012, based on these remains, the type species Eoabelisaurus mefi was named and described by Pol and his German colleague Oliver Rauhut. Before discovery, the oldest known abelisaurids were represented only by fragmentary remains from the late Early Cretaceous of South America and Africa and older records of abelisauroids in general were questionable. With the discovery of Eoabelisaurus, the temporal range of the clade was extended for more than 40 million years into the Toarcian. The existence of a derived ceratosaur at that time indicated a rapid diversification of ceratosaurs during that time period, as all the major ceratosaurian lineages (ceratosaurids, noasaurids, and abelisaurids) had already been established. It was a bipedal carnivore that was estimated to have reached in length, although a comprehensive analysis of abelisaur size conducted in 2016 yielded a size estimate of . The holotype specimen, MPEF PV 3990, was uncovered in a layer of the Cañadón Asfalto Formation, a lacustrine deposit dating originally from the Aalenian-Bajocian, roughly 170 million years old, yet a recent advanced zircon datation constrained its age to the Middle-Late Toarcian (179-178 million years).