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

Abstract

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. Tyrannotitan chubutensis, 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 Tyrannotitan chubutensis 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 Giganotosaurus is reinterpreted as very similar to that of Tyrannotitan and Mapusaurus. We also present a phylogenetic analysis of Carcharodontosauridae that recovers Tyrannotitan as a derived carcharodontosaurid, being the sister group of the clade formed by Giganotosaurus and Mapusaurus, all nested in the clade Giganotosaurini.

Keywords::

• Theropoda
• Carcharodontosauridae
• Tyrannotitan
• Patagonia
• Argentina

Acknowledgements

The authors would like to thank Eduardo Ruigómez (MEF), Rodolfo Coria (MCF), Jorge Calvo (MUC), Alejandro Kramarz (MACN), Mike Getty (UMNH), Vince Schneider (NCSM), Paul Sereno (University of Chicago, USA), Rodney Scheetz (BYU) for allowing access to specimens under their care. Federico Agnolín made comments on early drafts of the manuscript. We also thank Andrea Cau (Museo Geologico ‘Giovanni Capellini’, Bologna, Italy) and an anonymous reviewer for their improving and useful comments on the manuscript, especially Dr Cau for his suggestions about axial pneumaticity. Miguel O. Manceñido helped with taxonomic and nomenclatural aspects.

Notes

^1. Email: [email protected]

^2. Email: [email protected]

Additional information

Funding

Travel finance to carry out this work was provided by the Jurassic Foundation (to JIC). The program TNT is made freely available, thanks to a subsidy by the Willi Hennig Society.