New information on the craniofacial anatomy of Carnotaurus sastrei (Theropoda: Abelisauridae)

CERRONI, MAURICIO ANDRÉS; CANALE JUAN IGNACIO

Corrientes

Jornada; XXXII Jornadas Argentinas de Paleontología de Vertebrados; 2018

Carnotaurus sastrei Bonaparte, 1985 is a theropod dinosaur, perhaps the most iconic representative of the Abelisauridae. It is known by a fairly complete specimen, recovered from Upper Cretaceous beds of Patagonia. A reevaluation of the well-preserved skull of Carnotaurus including a detailed description of each bone, CT scans analyses and comparisons with several abelisaurid taxa expands the previous knowledge of this theropod; adding novel information concerning bones that remained undescribed such the palatal bones (i.e., palatines, pterygoids, and ectopterygoids). This study allowed the recognition of several features, including some new potential autapomorphies such as: antorbital fenestra dorsoventrally enlarged, medioventral recess on the pterygoid ramus of the quadrate, jugal deep and anteroposteriorly short, lateral fossa of vomeropalatine process of pterygoid. Among the features shared by abelisaurids, some of them includes: lateral fossa of the squamosal, lanceolate vomeropterygoid process of palatine, and angular process of the surangular. Furthermore, the CT scans revealed some pneumatic recesses in the lacrimal; similar to those present in Majungasaurus Depéret, 1896 and the tetanuran Allosaurus Marsh, 1877. Although, the most striking feature is a small pneumatic recess in the base of each frontal horn; it is difficult to trace the origin of the latter but likely was related to the lacrimal recesses. Frontal recesses are also present in Majungasaurus and Ceratosaurus Marsh, 1884. In sum, Carnotaurus provides one of the most complete skulls within abelisaurids, which provides several features of potential phylogenetic value and raises new questions about the presence and variability of pneumatic structures among ceratosaurs.