THE SKULL BENEATH THE SKIN: CRANIAL OSTEOLOGY OF SKORPIOVENATOR BUSTINGORRYI (DINOSAURIA, THEROPODA, ABELISAURIDAE) FROM THE LATE CRETACEOUS OF PATAGONIA, ARGENTINA
TL;DR
The phylogenetic analysis conducted here recovers Skorpiovenator as a brachyrostran abelisaurid, nested within a subclade alongside other early Late Cretaceous Patagonian taxa, which forms the sister group to Furileusauria.
Abstract
In this study, we present a detailed comparative cranial anatomical description of the abelisaurid theropod Skorpiovenator bustingorryi. This specimen, recovered from the Cenomanian-Turonian Huincul Formation near the town of Villa El Chocón, Neuquén Province, northwestern Patagonia, Argentina, was thoroughly technically prepared and supplemented with CT scan-based reconstructions. Skorpiovenator represents one of the most complete abelisaurid skulls, and indeed one of the most complete of any South American theropod dinosaur documented to date. Its skull is moderately short and tall, featuring strongly ornamented facial bones, a characteristic common among abelisaurids. We re-evaluated previously proposed autapomorphies and suggest new ones to refine the diagnosis of the species. Furthermore, we discuss several cranial anatomical features, testing them within a phylogenetic framework to clarify its relationships among late branching ceratosaurians. The phylogenetic analysis conducted here recovers Skorpiovenator as a brachyrostran abelisaurid, nested within a subclade alongside other early Late Cretaceous Patagonian taxa. This subclade, in turn, forms the sister group to Furileusauria. Key cranial features discussed include the two pairs of prominences on the frontals, the low paired crests on the anterior portion of the nasals, the enlarged external mandibular fenestra, and its distinctive dentition. Notably, Skorpiovenator exhibits the highest maxillary and dentary tooth count recorded for an abelisaurid. A significant discovery is the identification of an additional small bone dorsal to the articular bone of the mandible, interpreted as the antarticular, which is likely sesamoid in origin. Although this bone has been reported only in the tetanuran theropod Allosaurus and is present in the craniomandibular articulation of extant birds, the element identified in Skorpiovenator represents the first record of such an ossification outside the Tetanurae lineage. The data presented in this work significantly enhance our anatomical understanding of abelisaurid crania and theropods in general, thereby contributing to a clearer understanding of phylogenetic relationships within ceratosaurian theropod dinosaurs.