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

CERRONI, M.A.; CANALE, JUAN I.

Congreso; Jornadas Argentinas de Paleontología de Vertebrados XXXII; 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 re-evaluation of the wellpreservedskull of Carnotaurus including a detailed description of each bone, CT scans analyses and comparisons with severalabelisaurid taxa expands the previous knowledge of this theropod; adding novel information concerning bones thatremained undescribed such the palatal bones (i.e., palatines, pterygoids, and ectopterygoids). This study allowed the recognitionof 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 fossaof vomeropalatine process of pterygoid. Among the features shared by abelisaurids, some of them includes: lateral fossaof the squamosal, lanceolate vomeropterygoid process of palatine, and angular process of the surangular. Furthermore, theCT scans revealed some pneumatic recesses in the lacrimal; similar to those present in Majungasaurus Depéret, 1896 andthe tetanuran Allosaurus Marsh, 1877. Although, the most striking feature is a small pneumatic recess in the base of eachfrontal horn; it is difficult to trace the origin of the latter but likely was related to the lacrimal recesses. Frontal recessesare also present in Majungasaurus and Ceratosaurus Marsh, 1884. In sum, Carnotaurus provides one of the most completeskulls within abelisaurids, which provides several features of potential phylogenetic value and raises new questions aboutthe presence and variability of pneumatic structures among ceratosaurs.