Phylogenetic relationships of the Triassic theropod Zupaysaurus rougieri from NW Argentina

Abstract

The anatomy and phylogenetic relationships of the Upper Triassic theropod Zupaysaurus rougieri are reviewed. This taxon is represented by a nearly complete skull and fragmentary postcranial remains recovered from the Los Colorados Formation (Norian), NW Argentina. Originally, Zupaysaurus rougieri was considered a basal member of the Tetanurae, but its anatomy closely resembles that of the Coelophysoidea, supporting its nesting within this theropodan subclade. Thus reinterpreted, Zupaysaurus represents the first record of coelophysoids in South America. Phylogenetic analyses perfomed in this study depict Zupaysaurus as a non-coelophysid coelophysoid. Autopomorphic traits of Zupaysaurus include: maxillary-jugal ventral margin forming an obtuse angle in lateral view, tibia with a very deep and caudally open caudal fossa for the reception of an astragalar caudal process. Within the phylogenetic context outlined here, the derived features shared with Tetanurae (e.g. maxillary fenestra, caudally forked ascending ramus of the maxilla) are better interpreted as homoplasies rather than tetanuran derived features.

Keywords:

• Phylogeny
• Basal Theropoda
• Coelophysoidea
• Late Triassic
• Argentina

Acknowledgements

We want to thank Sergio Martin (PULR) for allowing access to the holotype specimen of Z. rougieri under his care. The authors also want to thank Max Langer and the reviewers Matthew Carrano and Oliver Rauhut for their comments which improved the qualitity of the manuscript.

Notes

^† [email protected].

Additional information

Notes on contributors

Fernando E. Novas

† † [email protected].