Phylogenetic overview. Diapsida, represented by the archosaur Hyperodapedon sanjuanensis in our study, are the sister-group to Synapsida. Synapids include the pelycosaur-grade Dimetrodon limbatus and Therapsida. From Therapsida, the dinocephalian Keratocephalus moloch, the anomodonts Stahleckeria potens and Tetragonias njalilus, the gorgonopsian Sauroctonus parringtoni, and the cynodont Belesodon magnificus were included in this study.