The axial osteology of the theropod dinosaur Piatnitzkysaurus floresi from the Early Jurassic of Patagonia, Argentina

Abstract

Piatnitzkysaurus floresi is a theropod dinosaur from the Lower Jurassic deposits of the Cañadón Asfalto Formation of the Chubut Province, Patagonia, Argentina. This species is known from two specimens and is one of the few Early Jurassic tetanurans recorded worldwide. The braincase and the frontal were redescribed in detail, but the rest of the skull elements (two maxillae and a dentary) and the vertebrae have only been briefly described and illustrated in the original description of the species almost 40 years ago. In the present work, we reinterpret certain attributes of the braincase and redescribe in detail the preserved tooth-bearing bones and vertebral column of Piatnitzkysaurus floresi. Computed tomography scans of one of the maxillae and the dentary improve our knowledge about dental development in early tetanurans. We also emend the diagnosis of Piatnitzkysaurus floresi based on the redescription carried out here and in a previous study. The new information about Piatnitzkysaurus floresi improves our knowledge about the evolution of early averostrans and will provide useful data for phylogenetic analyses on the origins and early diversification of Tetanurae, the most ecomorphologically diverse clade of theropods.