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.
Edaphosaurus is a genus of extinct edaphosaurid synapsids that lived in what is now North America and Europe around 303.4 to 272.5 million years ago, during the late Carboniferous to early Permian periods. American paleontologist Edward Drinker Cope first described Edaphosaurus in 1882, naming it for the "dental pavement" on both the upper and lower jaws, from the Greek edaphos έδαφος and σαῦρος ("lizard").
Ctenospondylus is an extinct genus of sphenacodontid basal Eupelycosauria.
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).
Varanops is an extinct genus of Early Permian varanopid synapsids known from Texas and Oklahoma of the United States. It was first named by Samuel Wendell Williston in 1911 as a second species of Varanosaurus, Varanosaurus brevirostris. In 1914, Samuel W. Williston reassigned it to its own genus and the type species is Varanops brevirostris.
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.
Casea is an extinct genus of medium to large-bodied, herbivorous, pelycosaur synapsids from the late Carboniferous until the middle Permian. The name Casea references its appearance from the Caseasauria which developed new morphology of their external naris and snout. Casea were known to be about 1.2 meters long. It weighed between 150 kg to 200 kg. It was slightly smaller than the otherwise very similar Caseoides. Casea was one of the first amniote herbivores, sharing its world with animals such as Dimetrodon and Eryops. It was possibly also aquatic.
Angelosaurus was a basal synapsid in the family Caseidae. The type species, Angelosaurus dolani, is known from a partial skull from the Middle San Angelo Formation, Knox County, Texas, USA dating from the Kungurian. The specimen represented an individual that was from three to three and a half metres long and weighed about 300 kilograms. Like its contemporary Cotylorhynchus, another caseid, it was large, heavily built, and herbivorous. It also shared its environment with the caseids Caseoides and Caseopsis. It may have been preyed upon by the large sphenacodont pelycosaur Dimetrodon.
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.
Trimerorhachis is an extinct genus of dvinosaurian temnospondyl within the family Trimerorhachidae. It is known from the Early Permian of the southwestern United States, with most fossil specimens having been found in the Texas Red Beds. The type species of Trimerorhachis, T. insignis, was named by American paleontologist Edward Drinker Cope in 1878. Cope named a second species from Texas, T. mesops, in 1896. The species T. rogersi and T. greggi are also from Texas, and the species T. sandovalensis is from New Mexico.
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.
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.
Ruthenosaurus is an extinct genus of large caseid synapsids from Early (Artinskian-Kungurian) or Middle (Roadian-Wordian) Permian deposits of southern France. It is known from the holotype MNHN.F.MCL-1 an articulated partial postcranial skeleton. It was collected by D. Sigogneau-Russell and D. Russell in 1970 in the upper part of the M2 Member, Grès Rouge Group, in the Rodez Basin, near the village of Valady, in Occitanie Region. It was first named by Robert R. Reisz, Hillary C. Maddin, Jörg Fröbisch and Jocelyn Falconnet in 2011, and the type species is Ruthenosaurus russellorum.
Euromycter is an extinct genus of medium-sized caseid synapsids from Early (Artinskian-Kungurian) or Middle (Roadian-Wordian) Permian deposits of Southern France. The holotype and only known specimen of Euromycter (MNHN.F.MCL-2) includes the complete skull with lower jaws and hyoid apparatus, six cervical vertebrae with proatlas, anterior part of interclavicle, partial right clavicle, right posterior coracoid, distal head of right humerus, left and right radius, left and right ulna, and complete left manus. It was collected by D. Sigogneau-Russell and D. Russell in 1970 at the top of the M1 Member, Grès Rouge Group, near the village of Valady, Rodez Basin. It was first assigned to the species "Casea" rutena by Sigogneau-Russell and Russell in 1974. More recently, it was reassigned to its own genus, Euromycter, by Robert R. Reisz, Hillary C. Maddin, Jörg Fröbisch and Jocelyn Falconnet in 2011. The preserved part of the skeleton suggests a size between 1,70 m (5,5 ft) and 1,80 m (5,9 ft) in length for this individual.
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.
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.
Alierasaurus is an extinct genus of caseid synapsid that lived during the early Middle Permian (Roadian) in what is now Sardinia. It is represented by a single species, the type species Alierasaurus ronchii. Known from a very large partial skeleton found within the Cala del Vino Formation, Alierasaurus is one of the largest known caseids. It closely resembles Cotylorhynchus, another giant caseid from the Middle Permian San Angelo Formation in Texas. The dimensions of the preserved foot elements and caudal vertebrae suggest an estimated total length of about 6 or 7 m for Alierasaurus. In fact, the only anatomical features that differ between Alierasaurus and Cotylorhynchus are found in the bones of the feet; Alierasaurus has a longer and thinner fourth metatarsal and it has ungual bones at the tips of the toes that are pointed and claw-like rather than flattened as in other caseids. Alierasaurus and Cotylorhynchus both have very wide, barrel-shaped rib cages indicating that they were herbivores that fed primarily on high-fiber plant material.
Gordodon is an extinct genus of non-mammalian synapsid that lived during the Early Permian of what is now Otero County, New Mexico. It was a member of the herbivorous sail-backed family Edaphosauridae and contains only a single species, the type species G. kraineri. Gordodon is unusual among early synapsids for its teeth, which were arranged similarly to those of modern mammals and unlike the simple, uniform lizard-like teeth of other early herbivorous synapsids. Gordodon had large incisor-like teeth at the front, followed by a prominent gap between them and a short row of peg-like teeth at the back. Gordodon was also relatively long-necked for an early synapsid, with elongated and gracile vertebrae in its neck and back. Like other edaphosaurids, Gordodon had a tall sail on its back made from the bony neural spines of its vertebrae. The spines also had bony knobs on them, a common trait of edaphosaurids, but the knobs of Gordodon are also unique for being more slender, thorn-like and randomly arranged along the spines. It is estimated to have been rather small at 1 m in length excluding the tail and 34 kg (75 lb) in weight.
