A therapsid is a member of the clade Therapsida which is a major group of eupelycosaurian synapsids that includes mammals and their ancestors and 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.
Dinocephalians are a clade of large-bodied early therapsids that flourished in the Early and Middle Permian between 279.5 and 260 million years ago (Ma), but became extinct during the Capitanian mass extinction event. Dinocephalians included herbivorous, carnivorous, and omnivorous forms. Many species had thickened skulls with many knobs and bony projections. Dinocephalians were the first non-mammalian therapsids to be scientifically described and their fossils are known from Russia, China, Brazil, South Africa, Zimbabwe, and Tanzania.
Biarmosuchus is an extinct genus of biarmosuchian therapsids that lived around 267 mya during the Middle Permian period. Biarmosuchus was discovered in the Perm region of Russia. The first specimen was found in channel sandstone that was deposited by flood waters originating from the young Ural Mountains.
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.
Therocephalia is an extinct clade of eutheriodont therapsids from the Permian and Triassic. 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. This relationship takes evidence in a variety of skeletal features.
Estemmenosuchidae is an extinct family of large, very early herbivorous therapsids that flourished during the Guadalupian period. They are distinguished by horn-like structures, probably for display or agonistic behavior. Apart from the best known genus, Estemmenosuchus, the group is poorly known. To date, their fossils are known only from the Perm region of Russia.
Estemmenosuchus is an extinct genus of large, early omnivorous therapsid. It is believed and interpreted to have lived during the middle part of the Middle Permian around 267 million years ago. The two species, E. uralensis and E. mirabilis, are characterised by distinctive horn-like structures, which were probably used for intra-specific display. Both species of Estemmenosuchus are from the Perm region of Russia. Two other estemmenosuchids, Anoplosuchus and Zopherosuchus, are now considered females of the species E. uralensis. There were many complete and incomplete skeletons found together.
Viatkogorgon is a genus of gorgonopsian that lived during the Permian period in what is now Russia. The first fossil was found at the Kotelnich locality near the Vyatka River and was made the holotype of the new genus and species V. ivachnenkoi in 1999. The generic name refers to the river and the related genus Gorgonops—the gorgons of Greek mythology are often referenced in the names of the group. The specific name honors the paleontologist Mikhail F. Ivakhnenko. The holotype skeleton is one of the most complete gorgonopsian specimens known and includes rarely preserved elements such as gastralia and a sclerotic ring. A larger, but poorly preserved specimen has also been assigned to the species.
Lemurosaurus is a genus of extinct biarmosuchian therapsids from the Late Permian of South Africa. The generic epithet Lemursaurus is a mix of Latin, lemures “ghosts, spirits”, and Greek, sauros, “lizard”. Lemurosaurus is easily identifiable by its prominent eye crests, and large eyes. The name Lemurosaurus pricei was coined by paleontologist Robert Broom in 1949, based on a single small crushed skull, measured at approximately 86 millimeters in length, found on the Dorsfontein farm in Graaff-Reinet. To date, only two skulls of the Lemurosaurus have been discovered, so body size is unknown. The second larger, more intact, skull was found in 1974 by a team from the National Museum, Bloemfontein.
Ivantosaurus is an extinct genus of therapsid that lived in Russia during the Wordian stage of the Permian period, named in honor of paleontologist Ivan Antonovich Efremov.
Kamagorgon is an extinct genus of therapsids from the Middle Permian of Russia. The type and only species is Kamagorgon ulanovi. It is only known from an incomplete skull. The snout is short and the canine teeth are very large. Kamagorgon was named in 1998 and originally classified in the biarmosuchian family Eotitanosuchidae along with the poorly known therapsid Eotitanosuchus. More recently, Kamagorgon has considered as a primitive gorgonopsian rather than a biarmosuchian due to the length of the front jawbone and rear side of the skull. These features are commonly shared by the brithopodid and biarmosuchid lineages.
Paraburnetia is an extinct genus of biarmosuchian therapsids from the Late Permian of South Africa. It is known for its species P. sneeubergensis and belongs to the family Burnetiidae. Paraburnetia lived just before the Permian–Triassic mass extinction event.
Lobalopex is an extinct genus of biarmosuchian therapsids. It was alive during the Late Permian and has only been found in the Teekloof Formation in South Africa. The only known species of the genus is Lobalopex mordax. Lobalopex is part of the clade of Burnetiamorpha, which have fossil specimens located in multiple areas of Africa and Russia.
Megawhaitsia is an extinct genus of large therocephalian therapsids who lived during the Late Permian (Wuchiapingian) in what is now Eastern Europe. The only known species is M. patrichae, described in 2008 from several fossils discovered in various oblasts of European Russia. The fossils are representative of a large animal whose skull size is estimated to be 40–50 cm (16–20 in) long.
Bullacephalus is an extinct genus of biarmosuchian therapsids belonging to the family Burnetiidae. The type species B. jacksoni was named in 2003. It is known from a relatively complete skull and lower jaw, discovered in the Late Permian Tapinocephalus Assemblage Zone of the Beaufort Group of South Africa. This genus of therapsida lived during the Late Permian period, approximately 250 million years ago. The name Bullacephalus comes from the Latin words "bullatus," meaning "bossed" or "knobbed," and "cephalus," meaning "head." This name refers to the distinctive bony knob on the top of the therapsid's skull, which contributes to the history of this genus. This stem based taxon includes Ictidorhinus or Hippasaurs. Bullacephalus can even be characterized as having a, “skull moderately to greatly pachyostotic; swollen boss present above the postorbital bar formed by the postfrontal and postorbital; deep linear sculpturing of the snout; exclusion of the jugal from the lateral temporal fenestra”. These Therapsids have spongy bone skull roof, palatal process of premaxilla are long, diverticulum of naris adding them to the Burnetiamorph. Furthermore, the discovery of Bullacephalus has helped to refine the taxonomic classification of therapsids. Prior to its discovery, there was uncertainty regarding the relationship between different groups of therapsids, particularly the Burnetiamorpha and the Biarmosuchia. However, the distinctive features of Bullacephalus suggest that it is a member of the Burnetiamorpha, and provides a bridge between this group and the Biarmosuchia. The discovery of Bullacephalus has also highlighted the importance of continued exploration and excavation in areas that have yielded few therapsid fossils. The Beaufort Group of South Africa, where Bullacephalus was discovered, has been an important site for therapsid fossils, but much of the area remains unexplored. Further discoveries in this region and other areas around the world may provide new insights into the evolution and diversification of therapsids, as well as other groups of extinct animals. These discoveries will also help to refine our understanding of the history of life on Earth and the processes that have shaped the diversity of organisms that exist today.
Lycaenodon is an extinct genus of biarmosuchian therapsids from the Late Permian of South Africa. It is known from a single species, Lycaenodon longiceps, which was named by South African paleontologist Robert Broom in 1925. Both are small-bodied biarmosuchians. Two specimens are known, and both preserve only the front portions of the skull. These specimens come from the Cistecephalus Assemblage Zone of the Karoo Basin. Broom attributed the back portion of a third skull to Lycaenodon, but subsequent examiners considered it to belong to a gorgonopsian or dinocephalian and not a biarmosuchian. Most of the distinguishing features of Lycaenodon come from its palate. As a member of Biarmosuchia, the most basal group of therapsids, Lycaenodon shares many features with earlier and less mammal-like synapsids like Dimetrodon.
Niaftasuchus is an extinct genus of therapsids. Its type and only named species is Niaftasuchus zekkeli.
Herpetoskylax is an extinct genus of biarmosuchians which existed in South Africa. The type species is Herpetoskylax hopsoni. It lived in the Late Permian Period.
Phthinosuchia is an extinct group of therapsids including two poorly known species, Phthinosuchus discors and Phthinosaurus borrisiaki, from the Middle Permian of Russia. Phthinthosuchus is known a partial crushed skull and Phthinosaurus is known from an isolated lower jaw. The two species have traditionally been grouped together based on their shared primitive characteristics, but more recent studies have proposed that they are more distantly related. Phthinosuchus is either a carnivorous gorgonopsian relative or an anteosaurian dinocephalian while Phthinosaurus is either a herbivorous rhopalodont dinocephalian or a therocephalian.
Phorcys is an extinct genus of gorgonopsian that lived during the Middle Permian period (Guadalupian) of what is now South Africa. It is known from two specimens, both portions from the back of the skull, that were described and named in 2022 as a new genus and species P. dubei by Christian Kammerer and Bruce Rubidge. The generic name is from Phorcys of Greek mythology, the father of the Gorgons from which the gorgonopsians are named after, and refers to its status as one of the oldest representatives of the group in the fossil record. Phorcys was recovered from the lowest strata of the Tapinocephalus Assemblage Zone (AZ) of the Beaufort Group, making it one of the oldest known gorgonopsians in the fossil record—second only to fragmentary remains of an indeterminate gorgonopsian from the older underlying Eodicynodon Assemblage Zone.
