The skull of Carnotaurus sastrei Bonaparte 1985 revisited: insights from craniofacial bones, palate and lower jaw

is perhaps the most iconic representative of the Abelisauridae family. It is known by a fairly complete specimen, recovered from Upper Cretaceous beds of southern Argentina. Here we present a re-study of the skull of Carnotaurus including detailed osteological descriptions, CT scans analyses and comparisons with abelisaurid taxa. Novel information concerning bones that remained undescribed (i.e., palate) is also offered. The present study allowed the recognition of several features, including some new potential autapomorphies diagnostic of Carnotaurus, such as nasolacrimal conduct with an accessory canal, ventral excavation on the quadrate and lateral fossa of the pterygoid. We identify some additional features of Carnotaurus shared with other abelisauroids, including: dorsal row of nasal foramina, lateral fossa on the squamosal, lanceolate vomeropterygoid process of palatine, apneumatic ectopterygoid and narrow and pointed angular process of surangular. CT scans revealed pneumatic recesses in the lacrimal which are similar to those present in other theropods. Furthermore, a striking feature is the presence of a small pneumatic recess on each frontal horn. Carnotaurus provides one of the most complete skulls within Abelisauridae, which allows recognising several traits of potential phylogenetic value and raises new questions regarding variability of cranial pneumaticity among ceratosaurs.