Inostrancevia africana, the first diagnosable gorgonopsian (Therapsida, Synapsida) from the Metangula graben (Mozambique): new anatomical observations and biostratigraphic implications

Abstract The diversity of the fauna of the late Permian K6 Formation of the Metangula graben of northern Mozambique is coming to light thanks to recent discoveries made by the PaleoMoz Project. Here we describe the first diagnosable gorgonopsian remains from the K6a2 Member of the Metangula graben, specimen PPM2018-7Z. This specimen is a large-bodied gorgonopsian, and shows several features similar to the latest late Permian species Inostrancevia africana. PPM2018-7Z shares various autapomorphies with Inostrancevia africana including the extremely narrowed jugal ventral to the orbit, the pineal foramen being positioned far posteriorly, the anteroposteriorly expanded ventral portion of postorbital bar, the orbit being larger than the temporal fenestra and by having prefrontal rugosities and foramina. The tooth morphology of Inostrancevia africana is here accessed based on the left canine of PPM2018-7Z, which is characterised by low labial ridges, a short mesial carina and thick basal denticles of the mesial carina. PPM2018-7Z is phylogenetically recovered close to Inostrancevia africana within the “Russian clade gorgonopsians”. PPM2018-7Z and Inostrancevia africana do not possess an interorbital ridge that is present in some rubidgeines such as Clelandina and Dinogorgon. Furthermore, PPM2018-7Z and inostranceviines retain a postfrontal with a posterior process that extends posteriorly invading the parietal border, unlike in rubidgeines in which the posterior process of the postfrontal is absent. The presence of Inostrancevia africana in the K6a2 Member of the Metangula graben helps correlating this member to the Daptocephalus Assemblage Zone in the Karoo Basin of South Africa.