First trematosaurid temnospondyl from the Lystrosaurus Assemblage Zone of South Africa and its biostratigraphic implications

A large temnospondyl mandible from the Lystrosaurus Assemblage Zone (Early Triassic) of South Africa is referred to the higher-level taxon Trematosaur idae. The mandible is remarkably similar to that described for Trematosauru s from the Middle Buntsandstein of Germany, a genus closely related to the South African Trematosuchus, for which the mandible is unknown. However, th e mandible cannot be referred unequivocally to either of these taxa. Tremat osuchus is considered to be restricted to the lowermost subzone of the over lying Cynognathus Assemblage Zone, which, based principally on the temnospo ndyl and therapsid fauna, is considered to be of Upper Olenekian age. The m andible described here extends back the range of the Trematosauridae to the underlying Lystrosaurus Assemblage Zone and argues against the long-held n otion of a sharp palaeontological break between the faunas of the Lystrosau rus and Cynognathus Assemblage zones. It also supports the hypothesis that the Lystrosaurus Assemblage Zone extended up to the Upper Olenekian.