Therapsida is a clade composing of a major group of eupelycosaurian synapsids that includes mammals and their ancestors and close relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more underneath the body, as opposed to the sprawling posture of many reptiles and salamanders.
Gorgonopsia is an extinct clade of sabre-toothed therapsids from the Middle to the Upper Permian, possibly even up to the Early Triassic, roughly between 265 and 252 million years ago. They are characterised by a long and narrow skull, as well as elongated upper and sometimes lower canine teeth and incisors which were likely used as slashing and stabbing weapons. Postcanine teeth are generally reduced or absent. For hunting large prey, they possibly used a bite-and-retreat tactic, ambushing and taking a debilitating bite out of the target, and following it at a safe distance before its injuries exhausted it, whereupon the gorgonopsian would grapple the animal and deliver a killing bite. They would have had an exorbitant gape, possibly in excess of 90°, without having to unhinge the jaw.
Biarmosuchia is an extinct clade of non-mammalian synapsids from the Permian. Biarmosuchians are the most basal group of the therapsids. They were moderately-sized, lightly built carnivores, intermediate in form between basal sphenacodont "pelycosaurs" and more advanced therapsids. Biarmosuchians were rare components of Permian ecosystems, and the majority of species belong to the clade Burnetiamorpha, which are characterized by elaborate cranial ornamentation.
Inostrancevia is an extinct genus of large carnivorous therapsids which lived during the Late Permian in what is now European Russia and Southern Africa. The first-known fossils of this gorgonopsian were discovered in the Northern Dvina, where two almost complete skeletons were exhumed. Subsequently, several other fossil materials were discovered in various oblasts, and these finds will lead to a confusion about the exact number of valid species in the country, before only three of them were officially recognized: I. alexandri, I. latifrons and I. uralensis. More recent research carried out in South Africa has discovered fairly well-preserved remains of the genus, being attributed to the species I. africana. An isolated left premaxilla suggests that Inostrancevia also lived in Tanzania during the earliest Lopingian age. The whole genus is named in honor of Alexander Inostrantsev, professor of Vladimir P. Amalitsky, the paleontologist who described the taxon.
Therocephalia is an extinct clade of eutheriodont therapsids from the Permian and Triassic periods. The therocephalians ("beast-heads") are named after their large skulls, which, along with the structure of their teeth, suggest that they were carnivores. Like other non-mammalian synapsids, therocephalians were once described as "mammal-like reptiles". Therocephalia is the group most closely related to the cynodonts, which gave rise to the mammals, and this relationship takes evidence in a variety of skeletal features. Indeed, it had been proposed that cynodonts may have evolved from therocephalians and so that therocephalians as recognised are paraphyletic in relation to cynodonts.
Dinogorgon is a genus of gorgonopsid from the Late Permian of South Africa and Tanzania. The generic name Dinogorgon is derived from Greek, meaning "terrible gorgon", while its species name rubidgei is taken from the surname of renowned Karoo paleontologist, Professor Bruce Rubidge, who has contributed to much of the research conducted on therapsids of the Karoo Basin. The type species of the genus is D. rubidgei.
Euchambersia is an extinct genus of therocephalian therapsids that lived during the Late Permian in what is now South Africa and China. The genus contains two species. The type species E. mirabilis was named by paleontologist Robert Broom in 1931 from a skull missing the lower jaw. A second skull, belonging to a probably immature individual, was later described. In 2022, a second species, E. liuyudongi, was named by Jun Liu and Fernando Abdala from a well-preserved skull. It is a member of the family Akidnognathidae, which historically has also been referred by as the synonymous Euchambersiidae.
Sauroctonus is an extinct genus of gorgonopsian therapsids who lived during the end of the Middle Permian in what is now European Russia. The first fossils, discovered in Tatarstan, were initially believed to belong to a new species of the South African genus Arctognathus. The taxon was designated as such until 1940, when it was assigned to the genus Inostrancevia by Ivan Yefremov, before being definitively classified in a separate genus erected by Alexey Bystrow. The most complete, known fossils of S. progressus include cranial and postcranial elements, currently all recorded from Tatarstan. These elements show that the animal was a mid-sized gorgonopsian.
Bystrowiana is an extinct genus of bystrowianid chroniosuchian from upper Permian deposits of Vladimir Region, Russia and Jiyuan, China. Chroniosuchians are often thought to be reptiliomorphs, but some recent phylogenetic analyses suggest instead that they are stem-tetrapods. The genus is named in honour of the Russian paleontologist Alexey Bystrow. It was first described by Vyushkov in 1957 and the type species is Bystrowiana permira. Two species—B. permira and B. sinica—are known.
Biseridens is an extinct genus of anomodont therapsid, and one of the most basal anomodont genera known. Originally known from a partial skull misidentified as an eotitanosuchian in 1997, another well-preserved skull was found in the Qingtoushan Formation in the Qilian Mountains of Gansu, China, in 2009 that clarified its relationships to anomodonts, such as the dicynodonts.
Raranimus is an extinct genus of therapsids of the Middle Permian. It was described in 2009 from a partial skull found in 1998 from the Dashankou locality of the Qingtoushan Formation, outcropping in the Qilian Mountains of Gansu, China. The genus is the most basal known member of the clade Therapsida, to which the later Mammalia belong.
"Dixeya" nasuta is a species of the predatory gorgonopsian therapsids from the Late Permian of East Africa, known from fossils found in what is now Tanzania. The species has a complicated taxonomic history, it was originally named as a second species of the genus Dixeya which is now considered a junior synonym of Aelurognathus. "D." nasuta itself, however, was not moved to Aelurognathus, and although it was instead tentatively referred to Arctognathus at first it has since been recognised to not belong to this genus either. This situation leaves "Dixeya" nasuta without a formal genus name. It was proposed to belong to a new distinct genus, named "Njalila", that was informally proposed for the species in a PhD thesis, but this name has not yet been formally published and is currently a nomen nudum. "D." nasuta has been characterised from other gorgonopsians by a combination of its straight snout profile, upturned and "pinched" nose, and curved jaw margin.
Dromotectum is an extinct genus of bystrowianid chroniosuchians from the Late Permian of China and Early Triassic of Russia. Two species have been named: the type species D. spinosum and the species D. largum. D. spinosum, the first species to be named, comes from Lower Triassic deposits in the Samara Region of European Russia and is known from the holotype PIN 2424/23, which consists of armor scutes, and from PIN 2424/65, 4495/14 and 2252/397. It was found in the Staritskaya Formation of the Rybinskin Horizon and named by I.V. Novikov and M.A. Shishkin in 2000. The generic name means “corridor with hipped vault” + “roof” (tecton), and the specific name means “spinous”. A second species, D. largum, was named by Liu Jun, Xu Li, Jia Song-Hai, Pu Han-Yong, and Liu Xiao-Ling in 2014 from the Shangshihezi Formation near Jiyuan in Henan province, China on the basis of specimen IVPP V 4013.1, a large scute.
Shaanbeikannemeyeria is an extinct genus of dicynodont known from the Early Triassic of China. It contains a single species, S. xilougoensis, which was described in 1980 by Zheng-Wu Cheng from a skull catalogued as IGCAGS V315. The specimen was lost, and a neotype skull IVPP V 11674 was later designated. A second species, S. buergondia, was named by Jin-Lin Li in 1980 from a partial skeleton, but it has since been regarded as a synonym of S. xilougoensis.
Sinophoneus is an extinct genus of carnivorous dinocephalian therapsid belonging to the family Anteosauridae. It lived 272 to 270 million years ago at the beginning of the Middle Permian in what is now the Gansu Province in northern China. It is known by a skull of an adult individual, as well as by many skulls of juvenile specimens. The latter were first considered as belonging to a different animal, named Stenocybus, before being reinterpreted as immature Sinophoneus. Sinophoneus shows a combination of characters present in other anteosaurs. Its bulbous profile snout and external nostrils located in front of the canine are reminiscent of the basal anteosaur Archaeosyodon, while its massive transverse pterygoids processes with enlarged distal ends are more similar to the more derived anteosaurs Anteosaurus and Titanophoneus. First phylogenetic analyzes identified Sinophoneus as the most basal Anteosaurinae. A more recent analysis positioned it outside the Anteosaurinae and Syodontinae subclades, and recovers it as the most basal Anteosauridae.
Urumchia is an extinct genus of therocephalian therapsids from the Early Triassic of China. The type species Urumchia lii was described by Chinese paleontologist C. C. Young in 1952 from the Jiucaiyuan Formation in Xinjiang. The holotype skull has been lost, but Young was able to describe the species on the basis of a detailed cast of the skull. Urumchia is similar to the South African therocephalian Regisaurus in having an expanded pair of vomer bones on the underside of the skull that form a secondary palate. In Urumchia the front end of the vomers narrow to a point, while in Regisaurus they do not. Urumchia has six incisors on either side of the upper jaw, a primitive condition among baurioid therocephalians that usually have fewer incisors.
Ordosiodon is an extinct genus of therocephalian therapsids from the Early Triassic of China. It includes two species, O. lincheyuensis and O. youngi.
The Ermaying Formation is a geological formation of Anisian age in north-central China. It is found across much of the Ordos Basin, at outcrops within the provinces of Shaanxi, Shanxi, and Inner Mongolia. It is composed of up to 600 m thick sequence of mudstone and sandstone, overlying the Heshanggou Formation and underlying the Tongchuan Formation. In the southern part of the Ordos Basin, the Zhifang Formation is equivalent to the Ermaying Formation.
Jiyuanitectum is an extinct genus of chroniosuchian tetrapod from the Late Permian Shangshihezi Formation of China. It is known from a single bony scute from Jiyuan in Henan province, ascribed to the type species Jiyuanitectum flatum in 2014. Plate-like scutes, which formed armor-like coverings on the backs of chroniosuchians, are the most commonly found chroniosuchian remains. They are also the most informative when it comes to distinguishing between species due to small variations in scute anatomy between different taxa. For example, a shallow groove along the midline of the scute is unique to Jiyuanitectum. The flatness of the scute is another unusual characteristic, giving it the species name flatum. Jiyuanitectum shares several features in common with the chroniosuchians Synesuchus and Bystrowiella, including the upper surface of the scute being covered in ridges that are mostly oriented perpendicular to the midline, and the absence of a bony projection on the front of the scute called the anteromedial articular processes, which is seen in other chroniosuchians. These features suggest that Jiyuanitectum belongs to the family Bystrowianidae. The narrowness of the scute suggests that it may be one of the most basal members of the group.
Alveusdectes is an extinct genus of diadectid tetrapod from the Late Permian of China. Like other diadectids, it was a large-bodied terrestrial herbivore capable of eating tough fibrous plant material. It was described in 2015 on the basis of a single partial skull and lower jaw found in the Shangshihezi Formation near the city of Jiyuan in Henan. This skull was found in a layer of the Shangshihezi Formation that dates to about 256 million years ago and contains the remains of many other terrestrial tetrapods including pareiasaurs, chroniosuchians, and therapsids. Alveusdectes is the youngest known diadectid by 16 million years and is also the only diadectid known from Asia. It likely represents a late-surviving lineage of diadectids that radiated eastward from western Laurasia into north China. Diadectids are otherwise absent from eastern Laurasia, which may reflect their low diversity at the time. Diadectids first appeared in the Late Carboniferous and were the first animals to have ever occupied the niche of large-bodied herbivores, allowing them to undergo an evolutionary radiation in the Early Permian. By the Late Permian many other groups of tetrapods had entered that niche, and increased competition among herbivores likely resulted in the eventual extinction of diadectids. Alveusdectes may have been able to persist because the fauna of north China seems to have been isolated from other Laurasian faunas during the Late Permian, meaning that fewer herbivores were competing for the same ecological space.
