Kammerer was unsure if Leontosaurus, Clelandina, Dinogorgon, and Rubidgea all represent the same taxon or not (for which Dinogorgon has priority), but he decided to classify all of them in the tribe Rubidgeini pending further examination. In 2018, Kammerer and Russian palaeontologist Vladimir Masyutin identified a new genus Nochnitsa as the basalmost known gorgonopsians, and found that all Russian taxa (except Viatkogorgon, which is in the outclade) form a completely separate clade from the African taxa. Also in 2018, palaeobiologist Eva-Maria Bendel, Kammerer, and colleagues resurrected Cynariops. In 2022, Kammerer and fellow palaeontologist Bruce S. Rubidge described Phorcys from South Africa. Evolution Synapsida has traditionally been split into the basal "Pelycosauria" and the derived Therapsida. The former comprises cold-blooded creatures with a sprawling gait and presumably lower metabolism which evolved in the Upper Carboniferous. Through the middle to late 20th-century, American palaeontologist Everett C. Olson investigated synapsid diversity in the Middle Permian San Angelo, Flowerpot, and Chickasha Formations in North America, and noted that pelycosaur diversity reduced from six to three in these formations, and that they coexisted with several fragmentary specimens which he interpreted as therapsids. He then suggested the adaptive shift from pelycosaur-grade to therapsid-grade took place during the Middle Permian (Olson's Extinction); however, the classification of those "therapsids" and the age of the formations have since been challenged. Thus, the exact timing of the therapsid takeover is unclear, but the seven major therapsid groups (Biarmosuchia, Dinocephalia, Anomodontia, Gorgonopsia, Therocephalia, and Cynodontia) had evolved by 265 million years ago during the Wordian. The oldest gorgonopsian specimen is a partial snout (genus undeterminable) from the Eodicynodon Assemblage Zone of the Karoo Basin, roughly dating to the Wordian. Phorcys from the lowermost end of Karoo's Tapinocephalus Assemblage Zone, roughly dating a little later to the Wordian/Capitian boundary, is the oldest identifiable gorgonopsian taxon. The Permian progressively became dryer and dryer. In the Upper Carboniferous and Lower Permian, pelycosaurs seem to have clung to the everwet coal swamp habitats near the equator (fossils known within 10° of either side of the palaeoequator); beyond this to about 30° was an expansive desert which extended all the way to the coast, separating the swamps from the temperate regions. By the Middle Permian, the equatorial forests had switched to a seasonal wet/dry system, but the swamps were connected to the temperate zones via coastal passages along East Pangaea, allowing cross-continental migration from what is