A mid-Permian (Guadalupian epoch) extinction event at approximately 260 Ma has been mooted for two decades. This is based primarily on invertebrate biostratigraphy of Guadalupian -Lopingian marine carbonate platforms in southern China, which are temporally constrained by correlation to the associated Emeishan Large Igneous Province (LIP). Despite attempts to identify a similar biodiversity crisis in the terrestrial realm, the low resolution of mid-Permian tetrapod biostratigraphy and a lack of robust geochronological constraints have until now hampered both the correlation and quantification of terrestrial extinctions. Here we present an extensive compilation of tetrapod-stratigraphic data analysed by the constrained optimization (CONOP) algorithm that reveals a significant extinction event among tetrapods within the lower Beaufort Group of the Karoo Basin, South Africa, in the latest Capitanian. Our fossil dataset reveals a 74 -80% loss of generic richness between the upper Tapinocephalus Assemblage Zone (AZ) and the mid-Pristerognathus AZ that is temporally constrained by a U-Pb zircon date (CA-TIMS method) of 260.259 + 0.081 Ma from a tuff near the top of the Tapinocephalus AZ. This strengthens the biochronology of the Permian Beaufort Group and supports the existence of a mid-Permian mass extinction event on land near the end of the Guadalupian. Our results permit a temporal association between the extinction of dinocephalian therapsids and the LIP volcanism at Emeishan, as well as the marine end-Guadalupian extinctions.

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Discoveries of burnetiamorph therapsids in the last decade and a half have increased their known diversity but they remain a minor constituent of middle-late

The terrestrial vertebrate fauna underwent a substantial change in composition between the lower and middle Permian. The lower Permian fauna was characterized by diverse and abundant amphibians and pelycosauriangrade synapsids. During the middle Permian, a therapsid-dominated fauna, containing a diverse array of parareptiles and a considerably reduced richness of amphibians, replaced this. However, it is debated whether the transition is a genuine event, accompanied by a mass extinction, or whether it is merely an artefact of the shift in sampling from the palaeoequatorial latitudes to the palaeotemperate latitudes. Here we use an up-to-date biostratigraphy and incorporate recent discoveries to thoroughly review the Permian tetrapod fossil record. We suggest that the faunal transition represents a genuine event; the lower Permian temperate faunas are more similar to lower Permian equatorial faunas than middle Permian temperate faunas. The transition was not consistent across latitudes; the turnover occurred more rapidly in Russia, but was delayed in North America. The argument that the mass extinction is an artefact of a latitudinal biodiversity gradient and a shift in sampling localities is rejected: sampling correction demonstrates an inverse latitudinal biodiversity gradient was prevalent during the Permian, with peak diversity in the temperate latitudes.

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The middle Permian Eodicynodon Assemblage Zone is the lowermost biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup) and occurs in the southwestern part of the main Karoo Basin. It is host to a diverse assemblage of basal therapsid genera of which Eodicynodon is the most abundant. The biozone reaches a maximum thickness of 1 100 m in the Prince Albert Road area and thins to the east and west. The biozone corresponds to the Combrinkskraal and Grootfontein members of the Abrahamskraal Formation, directly overlies the Waterford Formation of the Ecca Group, and records the earliest middle Permian terrestrial environments of Gondwana. Rocks of the biozone were deposited along the southern shoreline of the Karoo Basin in a subaerial delta plain environment as part of large-scale fan systems draining to the north and northeast within a second-order highstand systems tract.

New specimens of the oldest gorgonopsian taxon Eriphostoma microdon from the Pristerognathus Assemblage Zone (AZ) of South Africa significantly improve our understanding of the anatomy of this taxon. The new specimens consist of nearly complete skulls and lower jaws and allow for a more complete diagnosis of Eriphostoma than was possible based on the poorly preserved holotype. In addition to the characteristic palatal dentition and delta‐shaped palatine bosses previously recognized for Eriphostoma, this taxon can be diagnosed by the presence of three close‐packed upper postcanines occupying an indented margin of the maxilla, a large, tetragonal‐to‐rounded preparietal bone, and large, paired interorbital depressions expanding outwards in front of the pineal boss. The revised diagnosis permits Eoarctops vanderbyli, Galesuchus gracilis, and Scylacognathus parvus to be synonymized with Eriphostoma microdon, as previously suspected. Among gorgonopsians, Eriphostoma is most similar to Aelurosaurus and Gorgonops, although these similarities are likely plesiomorphic for Gorgonopsia. Eriphostoma ranges from the Tapinocephalus AZ (where it is the only valid gorgonopsian known from the Karoo Basin) through the Pristerognathus AZ (where it co‐occurs with Gorgonops).