The cranial morphology, phylogenetic position and biogeography of the upper Permian dicynodont Compsodon helmoedi van Hoepen (Therapsida, Anomodontia)

Compsodon helmoedi is an obscure dicynodont originally described based on a single specimen from the upper Permian of the Karoo Basin. The discovery of three new specimens of Compsodon from the Luangwa Basin of Zambia and two additional specimens from South African museum collections facilitates a reassessment of its cranial morphology and phylogenetic position. Compsodon is diagnosed by an autapomorphic secondary palate morphology: medial depression at anterior end of premaxillary secondary palate; medial anterior palatal ridges absent; lateral anterior palatal ridges prominent and extend to posterior end of secondary palate; Y-shaped anterior end of posterior median palatal ridge; embayment of palatal rim anterior to caniniform process divided into two depressions by a posteromedially-trending ridge. Other important characters include the presence of maxillary ‘postcanines’ and a postcaniniform keel; long interpterygoid vacuity; palatine pad smooth and pierced by a foramen; pineal for...