Osteology of Austroraptor cabazai (Paraves: Theropoda): a southern gigantic unenlagiid from the Late Cretaceous of Patagonia

Austroraptor cabazai is the largest known paravian from Gondwana. The two known specimens consist of cranial and postcranial elements recovered from the Allen Formation (Campanian – Maastrichtian) beds of Río Negro Province, Argentina. The aim of this contribution is to provide a detailed description and analysis of Austroraptor and offering a new interpretation of the available material, cranial morphology, and the diagnosis of the taxon. CT scans revealed internal structures of cranial and vertebral bones, including notable pneumatic structures. Additionally, dental and cranial characteristics shared by Austroraptor and other unenlagiids support the hypothesis of piscivorous habits within this group. Finally, the estimated large size of Austroraptor, in comparison to smaller unenlagiids such as Buitreraptor, suggests a correlation between short arms and relative gigantism among closely related paravians. The present contribution on Austroraptor provides new insight into the anatomical disparity and paleoecology of Southern Hemisphere paravians.