| Mastersonia Temporal range: [1] | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | Therapsida |
| Suborder: | † Dinocephalia |
| Genus: | † Mastersonia Olson, 1962 |
| Species: | †M. driverensis |
| Binomial name | |
| †Mastersonia driverensis Olson, 1962 | |
Mastersonia is an extinct genus of non-mammalian therapsids from the Lower Permian of San Angelo Formation, Texas. [1] It is only known from a few, very large vertebrae. [2]
Synapsids are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes reptiles and birds. The group includes mammals and every animal more closely related to mammals than to sauropsids. Unlike other amniotes, synapsids have a single temporal fenestra, an opening low in the skull roof behind each eye orbit, leaving a bony arch beneath each; this accounts for their name. The distinctive temporal fenestra developed about 318 million years ago during the Late Carboniferous period, when synapsids and sauropsids diverged, but was subsequently merged with the orbit in early mammals.
Therapsida is a major group of eupelycosaurian synapsids that includes mammals, 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.
The cynodonts are a clade of eutheriodont therapsids that first appeared in the Late Permian, and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety of lifestyles, including carnivory and herbivory. Mammals are cynodonts, as are their extinct ancestors and close relatives, having evolved from advanced probainognathian cynodonts during the Late Triassic. All other cynodont lines went extinct, with the last known non-mammalian cynodont group, the Tritylodontidae, having its youngest records in the Early Cretaceous.
Eucynodontia is a clade of cynodont therapsids including mammals and most non-mammalian cynodonts. The oldest eucynodonts are known from the Early Triassic and possibly Late Permian. Eucynodontia includes two major subgroups, Cynognathia and Probainognathia.
Biarmosuchians are an extinct clade of non-mammalian synapsids from the Permian. They are the most basal group of the therapsids. All of them 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 suborder 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.
Microurania is an extinct genus of therapsids from the Middle Permian first named and described by Mikhaïl Ivakhnenko. It is known from a single partial skull found in the region of Orenburg, Russia. According to Kammerer, 2011, it likely represents the remains of a juvenile dinocephalian.
Brachyprosopus is an extinct genus of dicynodont therapsid from the middle Permian Tapinocephalus Assemblage Zone in the Abrahamskraal Formation belonging to the Beaufort Group of the Karoo Basin, South Africa.
Driveria is an extinct genus of non-mammalian synapsids the Lower Permian of San Angelo Formation, Texas. It is mostly known from several postcranial bones, including the scapula, pelvis, and a few vertebrae and ribs, although a fragment of the skull that might pertain to the upper temporal fenestra is also associated with this species.
Eosyodon is a dubious genus of extinct non-mammalian synapsids from the Permian of Texas. Its type and only species is Eosyodon hudsoni. Though it was originally interpreted as an early therapsid, it is probably a member of Sphenacodontidae, the family of synapsids that includes Dimetrodon.
Ictidognathus is an extinct genus of therocephalian therapsids that lived in South Africa during the Late Permian. Fossils are found in the Tropidostoma and Cistecephalus Assemblage Zones of the Beaufort Group in the Western Cape.
Glanosuchus is a genus of scylacosaurid therocephalian from the Late Permian of South Africa. The type species G. macrops was named by Robert Broom in 1904. Glanosuchus had a middle ear structure that was intermediate between that of early therapsids and mammals. Ridges in the nasal cavity of Glanosuchus suggest it had an at least partially endothermic metabolism similar to modern mammals.
Knoxosaurus is an extinct genus of non-mammalian synapsids containing the species Knoxosaurus niteckii that existed approximately 279.5 to 268 million years ago. It was named by American paleontologist Everett C. Olson in 1962 on the basis of fragmentary fossils from Middle Permian-age deposits in the San Angelo Formation of Texas in the United States. Olson placed Knoxosaurus in a new infraorder called Eotheriodontia, which he considered a transitional group between the more reptile-like "pelycosaurs" and the more mammal-like therapsids. Knoxosaurus and Olson's other eotheriodonts were later considered to be undiagnostic remains of basal synapsids, no more closely related to therapsids than are other pelycosaur-grade synapsids.
Molybdopygus is an extinct genus of estemmenosuchid dinocephalians from the Middle Permian of Russia. It is known from a single pelvis.
Oudenodon is an extinct genus of dicynodont. It was common throughout southern Africa during the Late Permian. Several species of Oudenodon are known. Both O. bainii, the type species, and O. grandis are known from South Africa. Specimens of O. luangwensis have been found from Zambia. One species, O. sakamenensis, is the only Permian therapsid yet known from Madagascar. It is the type genus of the family Oudenodontidae, which includes members such as Tropidostoma.
Pristerodon is an extinct genus of dicynodont therapsid from the Late Permian of South Africa, Zambia and India.
Watongia is an extinct genus of non-mammalian synapsids from Middle Permian of Oklahoma. Only one species has been described, Watongia meieri, from the Chickasha Formation. It was assigned to family Gorgonopsidae by Olson and to Eotitanosuchia by Carroll. Reisz and collaborators assigned the genus in Varanopidae.
Venyukovia is an extinct genus of therapsids from the Middle Permian of Russia. Venyukovia is known from many partial skull remains and was a common animal from the Isheevo fauna in Russia. Venyukovia had a 12 centimetres (4.7 in) long skull.
Ulemica is an extinct genus of venjukoviid therapsids. It was a basal member of the suborder Anomodontia that existed during the Middle Permian in Russia. The type species, U. invisa, was assigned to the genus Venjukovia prior to being placed within its own genus in 1996. This small anomonodont is only known from a partial skull found in the Amanakskaya Formation.
Eutheriodontia is a clade of therapsids which appear during the Middle Permian and which includes therocephalians and cynodonts, this latter group including mammals and related forms.
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