New morganucodontans from an Early Jurassic fissure filling in Wales (United Kingdom)

Abstract

Two new genera and species of morganucodontans, Bridetherium dorisae and Paceyodon davidi, are recognized as members of the Morganucodon-sphenodont fauna preserved in a fissure filling (Pant 4) exposed in Pant Quarry, Vale of Glamorgan, southern Wales. Both taxa are based on isolated molariforms. Mode of occlusion of upper and lower molariforms in B. dorisae differs from the embrasure shearing pattern of Megazostrodon and the offset pattern characteristic of Morganucodon. Lack of a clear correlation between different patterns of occlusion and morphologies of their molariforms supports the working hypothesis that a close correlation between function and morphology of the molars characteristic of therian mammals, for example, was not present in morganucodontans. P. davidi is based on an isolated morganucodontan molariform that is significantly larger than any yet discovered. Several isolated morganucodontan-like molariforms cannot be referred to these taxa. The new Welsh morganucodontans added to records from other sites indicate the group achieved considerable taxonomic diversity and a near global distribution by the Early Jurassic. © The Palaeontological Association.