Prehistoric synapsid genera

Dimetrodon ( or ; ) is an extinct genus of sphenacodontid synapsid that lived during the Cisuralian (Early Permian) epoch of the Permian period, around 295–272 million years ago. With most species measuring long and weighing , the most prominent feature of Dimetrodon is the large neural spine sail on its back formed by elongated spines extending from the vertebrae. It was an obligate quadruped (it could walk only 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 of

Edaphosaurus (, meaning "pavement lizard" for dense clusters of its teeth) 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. The 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 ' ("ground"; also "pavement") and (') ("lizard").

Sphenacodon (meaning "wedge point tooth") 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 (neural spines) 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.

Cotylorhynchus is an extinct genus of herbivorous caseid synapsids that lived during the late Lower Permian (Kungurian) and possibly the early Middle Permian (Roadian) in what is now the states of Texas and Oklahoma. The large number of specimens found make it the best-known caseid.

Secodontosaurus (meaning "cutting-tooth lizard") 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 ("two-measure tooth"), which has large, prominent canine-like teeth in front and smaller slicing teeth

Ctenospondylus ("comb vertebra") is an extinct genus of sphenacodontid synapsid.

Casea is a genus of herbivorous caseid synapsids that lived during the late Lower Permian (Kungurian) in what is now Texas, United States. The genus is only represented by its type species, Casea broilii, named by Samuel Wendell Williston in 1910. The species is represented by a skull associated with a skeleton (the holotype FMNH UC 656), a second skull (FMNH UC 698), a partial skull with a better preserved dentition than that of the preceding skulls (FMNH UC 1011), and several incomplete postcranial skeletons. Three other Casea species were later erected, but these are considered today to be

Varanops is an extinct genus of Early Permian varanopid 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. thumb|Reconstruction of Varanops brevirostris

Varanodon is an extinct genus of amniotes from the family Varanopidae. It has been found in the Chickasha Formation of Oklahoma, which dates to the Roadian stage of the Middle Permian. The largest varanopid known at the time of its description, with a skull length of , it was closely related to and lived alongside its much larger relative Watongia. The two may represent growth stages of a single animal.

270px|thumbnail|left|Restoration

left|thumb|159x159px|Life restoration Archaeovenator is an extinct genus of Late Carboniferous varanopid synapsids known from Greenwood County, Kansas of the United States. It was first named by Robert R. Reisz and David W. Dilkes in 2003 and the type species is Archaeovenator hamiltonensis. Archaeovenator hamiltonensis is known from the holotype KUVP 12483, a three-dimensionally preserved, nearly complete and articulated skeleton, including the skull, with limbs and girdles slightly separated from postcranial skeleton. It was collected in the Hamilton Quarry, from the Calhouns Shale Form

Eothyris is a genus of extinct synapsid in the family Eothyrididae from the early Permian. It was a carnivorous insectivorous animal, closely related to Oedaleops. Only the skull of Eothyris, first described in 1937, is known. It had a skull, and its total estimated length was . Eothyris is one of the most primitive synapsids known and is probably very similar to the common ancestor of all synapsids in many respects. The only known specimen of Eothyris was collected from the Artinskian-lower.

Aerosaurus (meaning "copper lizard") 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) (combining stem: aer-) “copper” and Greek sauros “lizard,” for El Cobre Canyon (from Spanish cobre “copper”) 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.

Elliotsmithia is a small varanopid synapsid found from the late Middle Permian of South Africa. It is the sole basal synapsid "pelycosaur" known from the supercontinent Gondwana and only two specimens have been yielded to date. Its species name longiceps is derived from Latin, meaning "long head". Both known Elliotsmithia fossils were recovered from Abrahamskraal Formation rocks—within the boundaries of the Tapinocephalus Assemblage Zone—of the lower Beaufort Group. It was named for the late Sir Grafton Elliot Smith in 1937.

Mycterosaurus (Greek as mykter/mykteros meaning nose/snout, sauros meaning "lizard") is an extinct genus of amniotes belonging to the family Varanopidae. It is classified in the varanopid subfamily Mycterosaurinae. Mycterosaurus is the most primitive member of its family, existing from 290.1 to 272.5 MYA, known to Texas and Oklahoma. It lacks some features that its advanced relatives have.

Mesenosaurus is an extinct genus of synapsid belonging to the family Varanopidae. This genus includes two species: the type species Mesenosaurus romeri from the middle Permian (upper Kazanian) Mezen River Basin of northern Russia, and Mesenosaurus efremovi from the early Permian (Artinskian) Richards Spur locality (Oklahoma, United States). M. romeri’s stratigraphic range is the middle to late Guadalupian while M. efremovi’s stratigraphic range is the Cisuralian.

Ennatosaurus is an extinct genus of caseid synapsid that lived during the Middle Permian (late Roadian - early Wordian) in northern European Russia. The genus is only represented by its type species, Ennatosaurus tecton, which was named in 1956 by Ivan Antonovich Efremov. The species is known from at least six skulls associated with their lower jaws (two of them preserved with the hyoid apparatus), as well as from the postcranial bones of several juvenile individuals. Ennatosaurus has the typical caseid skull with a short snout tilted forward and very large external nares. However, it differs

Neosaurus ('New Lizard') is an extinct genus of pelycosaur-grade synapsids from the Late Carboniferous-Early Permian of the Jura region of France. It is known only from a partial maxilla or upper jaw bone and an associated impression of the bone. The teardrop shape of the teeth in the jaw indicate that Neosaurus belongs to the family Sphenacodontidae, which includes the better-known Dimetrodon from the Southwestern United States. The maxilla was first attributed to an early diapsid reptile in 1857, and later a crocodylomorph in 1869, before finally being identified as a sphenacodont synapsid i

Protoclepsydrops is an extinct genus of early synapsids, found in Joggins, Nova Scotia. The name means 'first Clepsydrops', and refers to it being the predecessor of the other early synapsid Clepsydrops.

thumb|left|Outline of Steppesaurus maxilla with skull of Sphenacodon for comparison, showing that the latter had more teeth in a given stretch of upper jaw 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.

Oedaleops is an extinct genus of caseasaur synapsids from the Early Permian of the Southwestern United States. Fossils have been found in the Cutler Formation in New Mexico, which dates back to the Wolfcampian stage of the Early Permian. All remains belong to the single known species Oedaleops campi. Oedaleops was closely related to Eothyris, and both are part of the family Eothyrididae. Like Eothyris, it was probably an insectivore.

Glaucosaurus is an extinct genus of edaphosaurid synapsid from the Early Permian of Texas. The type species, G. megalops, was named in 1915.

Heleosaurus scholtzi is an extinct species of basal synapsids, known as pelycosaurs, in the family of Varanopidae during the middle Permian. At first H. scholtzi was mistakenly classified as a diapsid. Members of this family were carnivorous and had dermal armor, and somewhat resembled monitor lizards. This family was the most geologically long lived, widespread, and diverse group of early amniotes. To date only two fossils have been found in the rocks of South Africa. One of these fossils is an aggregation of five individuals.

Ascendonanus (meaning "climbing dwarf") is an extinct genus of possible varanopid amniote from the Early Permian of Germany. It is one of the earliest specialized arboreal (tree-living) tetrapods currently known and outwardly resembled a small lizard. The animal was about 40 cm long, with strongly curved claws, short limbs, a slender, elongated trunk, and a long tail. It would have preyed on insects and other small arthropods.

Caseoides is an extinct genus of large caseid synapsids that lived in the Kungurian Age (late Early Permian epoch). It was about long, and like many other caseids, it was herbivorous and aquatic. It weighed between . 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 (except Caseopsis). In the development of its proportionally thick, stout limbs it represents the culmination of the Casea lineage. Its relatives became smaller during the Roadian Age. Only p

Angelosaurus is an extinct genus of herbivorous caseid synapsids that lived during the late Lower Permian (Kungurian) and early Middle Permian (Roadian) in what is now Texas and Oklahoma. Like other herbivorous caseids, it had a small head, large barrel-shaped body, long tail, and massive limbs. Angelosaurus differs from other caseids by the extreme massiveness of its bones, particularly those of the limbs, which show a strong development of ridges, processes, and rugosities for the attachment of muscles and tendons. Relative to its body size, the limbs of Angelosaurus were shorter and wider t

species of reptile (fossil)

Ctenorhachis (Greek for "comb spine") is an extinct genus of the family Sphenacodontidae. Ctenorhachis lived in the Early Permian epoch. Ctenorhachis was related to Dimetrodon, but did not belong to the same subfamily as Dimetrodon and Sphenacodon, being a more basal member of Sphenacodontidae. Two specimens are known that have been found from the Wichita Group outcropping in Baylor and Archer counties, north-central Texas. Only the vertebrae and pelvis are known. Articulated vertebrae from the holotype specimen possess blade like neural spines that are greatly enlarged, although not nearly to

Apsisaurus is an extinct genus of Early Permian varanopid synapsids known from Texas of the United States. It was first named by Michel Laurin in 1991 and the type species is Apsisaurus witteri. Apsisaurus witteri is known from the holotype MCZ 1474, a three-dimensionally preserved partial skeleton including an incomplete skull and mandibles. The skull roof of Archeria is also articulated to the postcranial skeleton. It was collected in the Archer City Bonebed 1 site, from the Archer City Formation of the Wichita Group, dating to the Early Permian epoch. Apsisaurus was formerly assigned a

Ianthasaurus is an extinct genus of small edaphosaurids from the Late Carboniferous.

Caseopsis is an extinct genus of large pelycosaurs that was about long. Caseopsis lived in the late Early Permian epoch (Kungurian Age), before the pelycosaurs were replaced by the more advanced therapsids (in the next age). It was a lightly built, agile creature. It may have been possible for this species to outpace and escape large predators such as Dimetrodon.

Datheosaurus ("Dathe's lizard") is an extinct genus of caseasaur. It was at least in length. It lived during the Latest Carboniferous to Early Permian in Poland. It was named for Ernst Dathe (1845–1917), the German geologist who first announced the fossil find.

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. Based on comparisons of its vertebrae with other varanopids, it was the largest varanopid with a body length of approximately . It was a contemporary of its closest relative, the much smaller Varanodon; the two may possibly represent growth stages of a single animal.

Oromycter is an extinct genus of caseid synapsids from the Early Permian of Oklahoma. The sole and type species, Oromycter dolesorum, was named in 2005 by Robert R. Reisz.

Tappenosaurus ("Tappen's lizard") 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 Neil Tappen, who found the type specimen in 1951 as a member of the field party.

Pyozia is an extinct genus of basal Middle Permian varanopid synapsids known from Russia. It was first named by Jason S. Anderson and Robert R. Reisz in 2004 and the type species is Pyozia mesenensis. Pyozia mesenensis is known from the holotype PIN 3717/33, a three-dimensionally preserved partial skeleton including a nearly complete skull. It was collected from the Krasnoschelsk Formation, dating to the Capitanian stage of the Guadalupian epoch, about 264.28-263 million years ago.

Trichasaurus is an extinct genus of caseid synapsids.

Nitosaurus is an extinct genus of non-mammalian synapsids.

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 San Angelo Formation in Texas. The dimensions of the preserved foot elements and caudal vertebrae suggest an estimated total length of about for Alierasaurus. In fact, the only anatomical feat

Arisierpeton is an extinct genus of synapsids from the Early Permian Garber Formation (Sumner Group) of Richards Spur, Oklahoma. It contains a single species, Arisierpeton simplex.

Lalieudorhynchus is an extinct genus of caseid synapsids that lived during the Guadalupian (= Middle Permian) in what is now Southern France. The genus is only known by its type species, Lalieudorhynchus gandi, which was named in 2022 by Ralf Werneburg, Frederik Spindler, Jocelyn Falconnet, Jean-Sébastien Steyer, Monique Vianey-Liaud, and Joerg W. Schneider. Lalieudorhynchus is represented by a partial postcranial skeleton discovered in the Lodève basin in the central part of the Hérault department in the Occitanie region. It belongs to an individual measuring approximately in length. The degr

Gordodon (meaning "fat tooth", referring to its large incisor-like front teeth) 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

Phreatophasma is an extinct genus of synapsids from the Middle Permian of European Russia. It includes only one species, Phreatophasma aenigmatum, which is itself known from a single femur found in a mine near the town of Belebei in Bashkortostan. Phreatophasma comes from a fossil assemblage that is latest Ufimian to earliest Kazanian in age under the Russian stratigraphic scheme, correlating with the Roadian Age (earliest Middle Permian, about 270 million years ago) under the international stratigraphic timescale. Because the species is based on a single specimen with few diagnostic anatomica

Callibrachion is an extinct genus of caseid synapsids that lived in east-central France during the Lower Permian (Asselian). The holotype and only known specimen (MNHN.F.AUT490) is represented by an almost complete postcranial skeleton associated with skull fragments discovered at the end of the 19th century in the Permian Autun basin in Saône-et-Loire department, in the Bourgogne-Franche-Comté region. It belongs to an immature individual measuring less than 1.50 m in length. Callibrachion was long considered a junior synonym of the genus Haptodus and classified among the sphenacodontid pelyco

Euromycter is an extinct genus of caseid synapsids that lived in what is now Southern France during the Early Permian (late Artinskian) about 285 million years ago. 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

Lupeosaurus is an extinct genus of pelycosaurian synapsids, assigned to the family Edaphosauridae. Lupeosaurus was about long and weighed around .

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.

Ruthenosaurus is an extinct genus of caseid synapsids that lived in what is now Southern France during the Early Permian (late Artinskian) about 285 million years ago. 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 (département of Aveyron), 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 Ruthe

Thrausmosaurus is a genus of synapsid pelycosaurs from the extinct family Varanopidae. Like all that resemble members of Varanopidae, Thrausmosaurus most likely resembled the modern monitor lizard and may have had the same lifestyle. The type and only species was described by R. C. Fox in 1962, from three fossilized jaw fragments bearing teeth. The specimens were recovered from the fissure-fill deposits uncovered in a Limestone Quarry, north of Fort Sill, Comanche County, Oklahoma, USA. These deposits are dated to the Kungurian (Leonardian) of the Lower Permian.

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

Eocasea is an extinct genus of caseid synapsids from the Late Pennsylvanian of Kansas. It is known from a single type species, Eocasea martini.

Microvaranops is a Middle Permian synapsid of the family Varanopidae from the Abrahamskraal Formation of South Africa. It includes one species, Microvaranops parentis, which was probably arboreal. A slab containing five specimens of Microvaranops indicates that it gathered or lived in groups.

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—Gorgodo

Tambacarnifex (meaning "Tambach butcher") is an extinct genus of varanodontine synapsids known from the Early Permian Tambach Formation of Free State of Thuringia, central Germany. It was first named by David S. Berman, Amy C. Henrici, Stuart S. Sumida, Thomas Martens and Valerie Pelletier in 2013 and the type species is Tambacarnifex unguifalcatus.

Martensius is an extinct genus of caseid synapsid from the Early Permian of Germany. The type species is '''Martensius bromackerensis.'''

Vaughnictis is an extinct genus of synapsid from the Early Permian of Colorado in the family Eothyrididae. It was originally assigned to the genus Mycterosaurus before it was assigned to the new genus Vaughnictis. It is known from a partial skull, hindlimb, and a few ribs. It is closely related to Eothyris.

Xyrospondylus is an extinct genus of non-mammalian synapsids belonging to the Edaphosauridae. The type species, X. ecordi, was named in 1982; it was originally named as a species of Edaphosaurus in 1957.

Macromerion (Macro- is Greek/Latin for "large") is an extinct genus of non-mammalian synapsids, specifically Pelycosaurs, in the family Sphenacodontidae from Late Carboniferous deposits in the Czech Republic. It was named as a species of Labyrinthodon in 1875 and as its own genus in 1879.

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.

Dendromaia is an extinct genus of varanopid from the Carboniferous of Nova Scotia. It contains a single species, Dendromaia unamakiensis. Dendromaia is the oldest known varanopid and the only one found in Nova Scotia. Known from a large partial skeleton preserved with its tail wrapped around a much smaller partial skeleton, Dendromaia may also represent the oldest known occurrence of parental care in the fossil record. While the larger skeleton possessed certain mycterosaurine-like features, the smaller skeleton resembled basal varanopids such as Archaeovenator and Pyozia, creating uncertainty