Sphenodontia is a reptile group represented nowadays only by the Tuatara of New Zealand, but with a rich fossil record during the mid- to late Mesozoic. We describe a new sphenodontian lepidosaur from the Upper Triassic of Germany, found together with one skeleton of the iconnic dinosaur Plateosaurus. The material is composed of an almost complete skull, represented by the dermal skull roof and by the complete maxilla and temporal region, as well as parts of the palate, braincase, and lower jaw, making it the oldest known articulated sphenodontian skull from Europe and one of the oldest in the world. A phylogenetic assessment recovers it as a basal sphenodontian closely related to Planocephalosaurus robinsonae and to Eusphenodontia, making it the earliest-diverging sphenodontian known with an articulated skull. Its cranial anatomy is generally similar to the well-known British Diphydontosaurus avonis, showing that this successful phenotype was already established in the clade around 10 million years earlier than assumed. Using this newly recovered data in an analysis of evolutionary change rates recovers high rates of evolution in basal sphenodontians, with decreasing rates throughout the evolution of the group. This is mostly in agreement with previous studies, but, contrary to them, reversals in this trend were also identified, indicating additional peaks of evolutionary change. These results improve our understanding of the early sphenodontian diversity in Europe, providing critical information on evolutionary trends throughout the history of the clade and sparking renewed interest in its evolution.
Di, 23.04. 15 Uhr Museum am Löwentor und Online (via Zoom), Dr. Gabriela Sobral, Naturkundemuseum Stuttgart