A thick-skulled theropod (Dinosauria, Saurischia) from the Upper Cretaceous of Morocco with implications for carcharodontosaurid cranial evolution

In this study, we erect Sauroniops pachytholus gen. et sp. nov., a large-bodied theropod dinosaur from the Cenomanian (Upper Cretaceous) of Morocco, on the basis of an almost complete frontal showing a unique combination of features including a naso–frontal suture extended along 40% of the frontal length, a thick dome in the anterolateral corner of the dorsal surface, a trapezoidal prefrontal facet that is restricted to the anterodorsal margin of the lateral surface of the frontal with no participation in the orbital roof and separated from the lacrimal facet by a narrow vertical lamina, a hypertrophied ‘D-shaped’ lacrimal facet that is four times the anterior depth of the postorbital facet, and a raised posteromedial margin of the dorsal surface describing a saddle with the anterolateral dome and confluent with a series of anteromedial rugosities. Phylogenetic analysis found robust support for placing Sauroniops among the basal carcharodontosaurids and related to Eocarcharia, showed that some of the unusual features of the new theropod were convergently acquired by abelisaurids, and revealed a mosaic pattern in the evolution of the carcharodontosaurid skull table. The frontals of Sauroniops and Carcharodontosaurus, both from the ‘Kem Kem compound assemblage’ of Morocco, show comparable size but differ in the extent of the naso–frontal articulation, the shape and disposition of the prefrontal and lacrimal articulations, the development of dorsal ornamentation and the morphology of the supratemporal fossa. Among carcharodontosaurids, the skull table developed unique configurations among each lineage and appears diagnostic at the species-level. The dome-like frontal in Sauroniops may indicate head-butting behaviour in this taxon or evolved for visual display.