Osteology and phylogenetic relationships of <i>Tyrannotitan chubutensis</i> Novas, de Valais, Vickers-Rich and Rich, 2005 (Theropoda: Carcharodontosauridae) from the Lower Cretaceous of Patagonia, Argentina

The theropod clade Carcharodontosauridae is a broadly distributed group of large allosauroid theropods. The carcharodontosaurids recorded in the Albian–Cenomanian of Gondwana are the youngest and most derived members of this clade. <i>Tyrannotitan chubutensis</i>, from the Cerro Castaño Member of Cerro Barcino Formation (Albian; Chubut Group), Central Patagonia, Argentina, is of prime interest among Gondwanan carcharodontosaurids as it represents the oldest record of the group. Here we offer a detailed osteological comparative description of the holotype and paratype of <i>Tyrannotitan chubutensis</i> together with a new diagnosis of the species. The new information results in a better understanding of this taxon and Carcharodontosauridae. Furthermore, a comparative study of the anatomy of the pectoral girdle of <i>Giganotosaurus</i> is reinterpreted as very similar to that of <i>Tyrannotitan</i> and <i>Mapusaurus.</i> We also present a phylogenetic analysis of Carcharodontosauridae that recovers <i>Tyrannotitan</i> as a derived carcharodontosaurid, being the sister group of the clade formed by <i>Giganotosaurus</i> and <i>Mapusaurus</i>, all nested in the clade Giganotosaurini.