New theropod remains from the Late Jurassic Cañadón Calcáreo formation of Chubut, Argentina

Abstract

Late Jurassic South American theropod faunas are still extremely poorly known, with large-sized ceratosaurids and megalosaurids having been identified on the basis of isolated teeth, whereas the only named taxa, Chilesaurus and Pandoravenator, are probable tetanurans of uncertain affinities. Here we describe two new specimens of medium-sized to large theropods from the Oxfordian-Kimmeridgian Cañadón Calcáreo Formation of Chubut, Argentina; an isolated and rather well-preserved anterior cervical vertebra and a very fragmented, but associated assortment of bones, including cranial and vertebral remains. Both specimens show ceratosaurian and, most probably, abelisaurid affinities. A faunal analysis underlines the relative abundance of ceratosaurs and the absence of coelurosaurs as main differences of Late Jurassic Gondwanan theropod faunas from their Laurasian counterparts. The presence of abelisaurids in both the Tendaguru Formation and the Cañadón Calcáreo Formation indicates a wide distribution of this clade already in the Late Jurassic in the Southern Hemisphere.