Microposaurus casei, a poorly known temnospondyl from Subzone B of the Cynognathus Assemblage Zone (Middle Triassic) of the Karoo of South Africa, is redescribed in detail following additional preparation of the holotype skull. New and previously misinterpreted aspects of the skull roof, palate, and occiput are described, revealing an unusual skull morphology and a suite of autapomorphies. Contrary to some previous interpretations, M. casei is unequivocally shown to be a member of the stereospondyl group Trematosauroidea, as it shares a number of synapomorphies of that group. Within the Trematosauroidea, M. casei most closely resembles the slightly older, Laurasian platystegids Inflectosaurus and Platystega.