THE VERTEBRATE FAUNA OF THE UPPER PERMIAN OF NIGER. V. THE PRIMITIVE TEMNOSPONDYL SAHARASTEGA MORADIENSIS

The skull of the temnospondyl amphibian Saharastega moradiensis, from the Upper Permian Moradi Formation (Izegouandane Group, Izegouandane Basin) of northwestern Niger, is described in detail. Saharastega mo- radiensis is the most primitive known temnospondyl from Gondwana and possesses a combination of plesiomorphic and apomorphic character states, which suggest affinities with the Edopoidea, a clade of basal temnospondyls from the Upper Carboniferous and Lower Permian of Euramerica. These include the exclusion of the lacrimal from the orbital margin, the exclusion of the vomers and palatines from the interpterygoid vacuities, and the presence of an intertemporal ossification. Autapomorphies of the new taxon include the presence of narrow and elongated, transversely oriented nostrils; an extensive tongue-and-groove contact between the premaxillae and maxillae; tabulars that possess exception- ally large, laterally and ventrally directed 'horns'; and an extraordinary 'occipital plate' that may be formed, at least in part, by a supraoccipital ossification. A phylogenetic analysis of select Paleozoic temnospondyls indicates that S. mora- diensis is the sister taxon to the edopoids, represented in this analysis by Chenoprosopus and Edops. This suggests that S. moradiensis represents a late-surviving member of a clade that is the sister group of the Edopoidea. Members of this clade may have been restricted to equatorial northwest Africa during the Late Carboniferous and Early Permian, an area that was not affected by the extensive glaciation that covered much of southern Pangea.