| Steppesaurus | |
|---|---|
 | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Family: | † Sphenacodontidae |
| Genus: | † Steppesaurus Olson & Beerbower, 1953 |
| Species: | †S. gurleyi |
| Binomial name | |
| †Steppesaurus gurleyi Olson & Beerbower, 1953 | |
Steppesaurus is an extinct genus of basal Eupelycosauria belonging to the Sphenacodontidae, related to Dimetrodon and Sphenacodon , from the Late Permian San Angelo Formation of Texas.
A maxilla and dentary, holotype FMNH UR 148, were at the Pease River found by Everett Claire Olson in 1950, who named the genus in 1953, together with James R. Beerbower, after J. Steppe who had assisted in the excavation. [1]
The body length of Steppesaurus has been estimated as high as eighteen feet, making it the largest known sphenacodontid, [2] but this failed to take into account that its teeth, as restored, were more widely spaced. It likely had less teeth in its maxilla, which as a whole was not particularly large.
Olson in 1953 placed Steppesaurus in the Sphenacodontidae but in 1962 changed this to the Phthinosuchidae, making it a member of the Therapsida, as support for his hypothesis that these had been found in the Early Permian. [3] This has proven to be very controversial.
Dimetrodon is an extinct genus of non-mammalian synapsid that lived during the Cisuralian, around 295–272 million years ago (Ma). It is a member of the family Sphenacodontidae. The most prominent feature of Dimetrodon is the large neural spine sail on its back formed by elongated spines extending from the vertebrae. It walked on four legs and had a tall, curved skull with large teeth of different sizes set along the jaws. Most fossils have been found in the Southwestern United States, the majority coming from a geological deposit called the Red Beds of Texas and Oklahoma. More recently, fossils have been found in Germany. Over a dozen species have been named since the genus was first erected in 1878.
Diadectidae is an extinct family of early tetrapods that lived in what is now North America and Europe during the Late Carboniferous and Early Permian, and in Asia during the Late Permian. They were the first herbivorous tetrapods, and also the first fully terrestrial animals to attain large sizes. Footprints indicate that diadectids walked with an erect posture. They were the first to exploit plant material in terrestrial food chains, making their appearance an important stage in both vertebrate evolution and the development of terrestrial ecosystems.
Dimetrodon borealis, formerly known as Bathygnathus borealis, is an extinct species of pelycosaur-grade synapsid that lived about 270 million years ago (Ma) in the Early Permian. A partial maxilla or upper jaw bone from Prince Edward Island in Canada is the only known fossil of Bathygnathus. The maxilla was discovered around 1845 during the course of a well excavation in Spring Brook in the New London area and its significance was recognized by geologists John William Dawson and Joseph Leidy. It was originally described by Leidy in 1854 as the lower jaw of a dinosaur, making it the first purported dinosaur to have been found in Canada, and the second to have been found in all of North America. The bone was later identified as that of a pelycosaur. Although its current classification as a sphenacodontid synapsid was not recognized until after the discovery of its more famous relative Dimetrodonin the 1870s, Bathygnathus is notable for being the first discovered sphenacodont. A 2015 study by the researchers from U of T Mississauga, Carleton University and the Royal Ontario Museum reclassified the species into the genus Dimetrodon.
Sphenacodon is an extinct genus of synapsid that lived from about 300 to about 280 million years ago (Ma) during the Late Carboniferous and Early Permian periods. Like the closely related Dimetrodon, Sphenacodon was a carnivorous member of the Eupelycosauria family Sphenacodontidae. However, Sphenacodon had a low crest along its back, formed from blade-like bones on its vertebrae instead of the tall dorsal sail found in Dimetrodon. Fossils of Sphenacodon are known from New Mexico and the Utah–Arizona border region in North America.
Secodontosaurus is an extinct genus of "pelycosaur" synapsids that lived from between about 285 to 272 million years ago during the Early Permian. Like the well known Dimetrodon, Secodontosaurus is a carnivorous member of the Eupelycosauria family Sphenacodontidae and has a similar tall dorsal sail. However, its skull is long, low, and narrow, with slender jaws that have teeth that are very similar in size and shape—unlike the shorter, deep skull of Dimetrodon, which has large, prominent canine-like teeth in front and smaller slicing teeth further back in its jaws. Its unusual long, narrow jaws suggest that Secodontosaurus may have been specialized for catching fish or for hunting prey that lived or hid in burrows or crevices. Although no complete skeletons are currently known, Secodontosaurus likely ranged from about 2 to 2.7 metres (7–9 ft) in length, weighing up to 110 kilograms (250 lb).
Caseoides is an extinct genus of large caseid synapsids that lived in the Kungurian Age. It was about 3 metres (9.8 ft) long, and like many other caseids, it was herbivorous and aquatic. It weighed between 150 to 200 kilograms. Its fossils were found in San Angelo Formation, Texas. Caseoides was very similar to Casea, but was slightly larger in size. Caseoides was a heavily built creature, as are most of the Caseids. In the development of its proportionally thick, stout limbs it represents the culmination of the Casea lineage. Its relatives became smaller in size during the Roadian Age. Only poorly preserved postcranial material is known including limbs.
Diplocaulus is an extinct genus of lepospondyl amphibians which lived from the Late Carboniferous to Permian periods of North America and Africa. Diplocaulus is by far the largest and best-known of the lepospondyls, characterized by a distinctive boomerang-shaped skull. Remains attributed to Diplocaulus have been found from the Late Permian of Morocco and represent the youngest-known occurrence of a lepospondyl.
Endothiodon is an extinct genus of large dicynodont from the Late Permian. Like other dicynodonts, Endothiodon was an herbivore, but it lacked the two tusks that characterized most other dicynodonts. The anterior portion of the upper and lower jaw are curved upward, creating a distinct beak that is thought to have allowed them to be specialized grazers.
Labidosaurikos is a genus of extinct captorhinid anapsid reptile that lived around 279 to 272 million years ago during Kungurian age of the lower Permian. The American Paleontologist John Willis Stovall first described Labidosaurikos in 1950, naming it "Labidosaurus like" for the striking similarity of the holotype skull of his specimen to the cranial anatomy of another captorhinid Labidosaurus hamatus. Labidosaurus or generally called "lipped lizard" is another genus of the family Captorhinidae whose name is derived from the Greek "forceps lizard" based on τσιμπίδα and σαυρος ("lizard")
Kourerpeton is an extinct genus of dvinosaurian temnospondyl. Fossils of Kourerpeton were discovered in a window of a barber's shop in either Bisbee or Mesa, Arizona. Kourerpeton was named in 1976, with the type and only species being K. bradyi. It was originally assigned to the monotypic family Kourerpetidae, which has been alternatively spelled Kourerpetontidae.
Tersomius is an extinct genus of dissorophoid temnospondyl within the family Micropholidae. It is known from the early Permian of North America.
Slaugenhopia is an extinct genus of dvinosaurian temnospondyl within the family Tupilakosauridae. Fossils have been found from the Early Permian San Angelo Formation in Texas. The type and only species, S. texensis, was named in 1962. It may be closely related to the dvinosaur Kourerpeton. Slaugenhopia was once classified as a trimerorhachid but is now classified as a tupilakosaurid.
Aerosaurus is an extinct genus within Varanopidae, a family of non-mammalian synapsids. It lived between 252-299 million years ago during the Early Permian in North America. The name comes from Latin aes (aeris) “copper” and Greek sauros “lizard,” for El Cobre Canyon in northern New Mexico, where the type fossil was found and the site of former copper mines. Aerosaurus was a small to medium-bodied carnivorous synapsid characterized by its recurved teeth, triangular lateral temporal fenestra, and extended teeth row. Two species are recognized: A. greenleeorum (1937) and A. wellesi (1981).
Dimacrodon is an extinct genus of non-mammalian synapsid from the latest Early Permian San Angelo Formation of Texas. It is distinguished by toothless, possibly beaked jaw tips, large lower canines and a thin bony crest on top of its head. Previously thought to be an anomodont therapsid related to dicynodonts, it was later found to lack any diagnostic features of anomodonts or even therapsids and instead appears to be a 'pelycosaur'-grade synapsid of uncertain classification.
Delorhynchus is an extinct genus of lanthanosuchoid parareptile known from the late Early Permian Garber Formation of Comanche County, Oklahoma. It contains three species: the type species D. priscus is based on a series of maxillae. The second species to be described, D. cifellii, is known from a larger number of well-preserved skulls and skeletal material. The third species, D. multidentatus, is based on a fragmentary skull with several rows of teeth on its jaw.
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.
Acleistorhinus (ah-kles-toe-RYE-nuss) is an extinct genus of parareptile known from the Early Permian of Oklahoma It is notable for being the earliest known anapsid reptile yet discovered. The morphology of the lower temporal fenestra of the skull of Acleistorhinus bears a superficial resemblance to that seen in early synapsids, a result of convergent evolution. Only a single species, A. pteroticus, is known, and it is classified in the Family Acleistorhinidae, along with Colobomycter.
Cutleria is an extinct genus of basal sphenacodontids or derived stem-sphenacodontoid known from the Early Permian period of the Colorado, United States. It contains a single species, Cutleria wilmarthi.
Tappenosaurus is an extinct genus of synapsids from the Middle Permian of Texas. American paleontologists Everett C. Olson and James Beerbower described the genus in 1953 based on three specimens that were uncovered from the San Angelo Formation. It was named for Dr. Neil Tappen, who found the type specimen in 1951 as a member of the field party. The first specimen is a fragmentary skeleton including parts of the back of the skull, pieces of teeth and ribs, an axis vertebra, a dorsal vertebra, three neural spines, the ends of both humeri and a partial hip. The second specimen includes cervical vertebrae, a rib, and a scapulocoracoid. The third specimen is only represented by ribs. These bones are larger than comparable parts of the largest skeletons of Dimetrodon, a closely related and much better known sail-backed synapsid. Olson and Beerbower designated the type species Tappenosaurus magnus in reference to its large size, and also placed it in its own family, Tappenosauridae. Olson later estimated the total length of Tappenosaurus to be 18 feet (5.5 m), comparing it in size with the largest of the dinocephalians, a more advanced group of synapsids that lived later in the Permian.
Gorgodon is an extinct genus of basal synapsids. The genus is monotypic, known only from the type species Gorgodon minutus from the Early Permian of the southwestern United States. The only known remains of Gorgodon are two fossils consisting of fragments of the skull. Gorgodon was described and named by paleontologist Everett C. Olson in 1962 from the San Angelo Formation in Knox County, Texas. Based on what is known of Gorgodon—the squamosal, quadrate, and pterygoid bones of the back of the skull, the maxilla and premaxilla bones that make up the front of the skull, and several teeth—Gorgodon had a relatively large temporal fenestra and a pair large, conical caniniform teeth at the front of the jaw. Other distinguishing features of Gorgodon include the fused connection between the quadrate and squamosal bones and a long transverse process of the pterygoid.
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