Gorgonops and Endothiodon (Synapsida: Therapsida) from the Madumabisa Mudstone Formation: Evidence of a Previously Unreported Tetrapod Biozone in the Mid-Zambezi Basin of Southern Zambia.

Fossils referable to the gorgonopsian Gorgonops sp. and to the dicynodont Endothiodon sp. are described from the Permian Madumabisa Mudstone Formation of the Mid-Zambezi Basin of southern Zambia. Specimens of the former taxon conform to recent diagnoses of the genus (e.g., five postcanine teeth, transverse flange of the pterygoid backswept, postorbital bar rugose and moderately expanded), but differ slightly from South African material in some respects (e.g., reduced dentition on the transverse flange of the pterygoid). Fossils of the latter are less complete, but show diagnostic features such as a dentary with numerous teeth, a ventral boss, and a shallow posterior dentary sulcus, oval palatine pads, and a narrow intertemporal region of the skull, although a species-level identification is not currently possible. Although the relevant fossils were never described, a vertebrate fossil assemblage including Endothiodon was previously reported from the Madumabisa Mudstone Formation in northern Zimbabwe (i.e., K5d), suggesting that this biozone was relatively broadly distributed across the Mid-Zambezi Basin. The Mid-Zambezi Basin of southern Zambia was previously demonstrated to host Guadalupian Tapinocephalus Assemblage Zone-equivalent strata, with rhinesuchids, burnetiamorphs, tapinocephalids, and dicynodonts recognized. The recognition of Lopingian Endothiodon Assemblage Zone-age rocks expands the stratigraphic range of vertebrate-bearing horizons in southern Zambia. [ABSTRACT FROM AUTHOR]