Revision of the basal sphenacodonts (Haptodontinae): systematic and evolutionary implications

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Non-therapsid sphenacodonts dominate the early terrestrial tetrapod assemblages. This success began with the basal Sphenacodontia, referred to as haptodonts (previous subfamily Haptodontinae, type genus Haptodus). Their fossils are reported from the Late Pennsylvanian to the Early Permian from North America, England and continental Europe. Only few species have been described the modern way. Many descriptions date back between 1886 and 1925 (H. baylei, Palaeohatteria, Callibrachion, Datheosaurus, and Pantelosaurus) and therefore have to be revised based on new evidence. Furthermore, little is known about their evolution apart from the anatomical characters. This project aims to record the haptodont’s character diversity, leading to a taxonomical revision. Further, this is the basis for palaeobiological (including ontogenetical), ecological and phylogenetic conclusions. Using descriptive, cladistic and comparative zoological methods (anatomy, ontogeny, functional morphology), it will be the first complete study of haptodonts, important for understanding pre-mammal tetrapods. Of special interest is the revision of Palaeohatteria longicaudata Credner 1888, known from juvenile skeletons only, and its comparison to Pantelosaurus saxonicus von Huene 1925 from a nearby locality. As a result, the project will generate a complete characterization of the group, based on the study of all haptodont fossils, containing systematics, palaeobiology and their stratigrafic distribution.