Dimetrodon meaning "two measures of teeth,” is an extinct genus of non-mammalian synapsid that lived during the Cisuralian, around 295–272 million years ago (Mya). 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. 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").
Dissorophidae is an extinct family of medium-sized, temnospondyl amphibians that flourished during the late Carboniferous and early Permian periods. The clade is known almost exclusively from North America.
Brachytrachelopan is a short-necked sauropod dinosaur from the Late Jurassic of Argentina. The holotype and only known specimen was collected from an erosional exposure of fluvial sandstone within the Cañadón Calcáreo Formation on a hill approximately 25 kilometres (16 mi) north-northeast of Cerro Cóndor, Chubut Province, in west-central Argentina, South America. Though very incomplete, the skeletal elements recovered were found in articulation and include eight cervical, twelve dorsal, and three sacral vertebrae, as well as proximal portions of the posterior cervical ribs and all the dorsal ribs, the distal end of the left femur, the proximal end of the left tibia, and the right ilium. Much of the specimen was probably lost to erosion many years before its discovery. The type species is Brachytrachelopan mesai. The specific name honours Daniel Mesa, a local shepherd who discovered the specimen while searching for lost sheep. The genus name translates as "short-necked Pan", Pan being the god of the shepherds.
Seymouria is an extinct genus of seymouriamorph from the Early Permian of North America and Europe. Although they were amphibians, Seymouria were well-adapted to life on land, with many reptilian features—so many, in fact, that Seymouria was first thought to be a primitive reptile. It is primarily known from two species, Seymouria baylorensis and Seymouria sanjuanensis. The type species, S. baylorensis, is more robust and specialized, though its fossils have only been found in Texas. On the other hand, Seymouria sanjuanensis is more abundant and widespread. This smaller species is known from multiple well-preserved fossils, including a block of six skeletons found in the Cutler Formation of New Mexico, and a pair of fully grown skeletons from the Tambach Formation of Germany, which were fossilized lying next to each other.
Hypselorhachis is a genus of extinct reptile, possibly a ctenosauriscid archosaur related to Ctenosauriscus. It lived during the Triassic Period. It is currently known only from a single vertebra found from the Middle Triassic Manda Beds in Tanzania. The vertebra is preserved in reasonably good condition, as although the tall neural spine is chipped in several places it is not broken despite being quite slender, only around 20 mm thick transversely.
Westlothiana is a genus of reptile-like tetrapod that lived about 338 million years ago during the latest part of the Visean age of the Carboniferous. Members of the genus bore a superficial resemblance to modern-day lizards. The genus is known from a single species, Westlothiana lizziae. The type specimen was discovered in the East Kirkton Limestone at the East Kirkton Quarry, West Lothian, Scotland in 1984. This specimen was nicknamed "Lizzie the lizard" by fossil hunter Stan Wood, and this name was quickly adopted by other paleontologists and the press. When the specimen was formally named in 1990, it was given the specific name "lizziae" in homage to this nickname. However, despite its similar body shape, Westlothiana is not considered a true lizard. Westlothiana's anatomy contained a mixture of both "labyrinthodont" and reptilian features, and was originally regarded as the oldest known reptile or amniote. However, updated studies have shown that this identification is not entirely accurate. Instead of being one of the first amniotes, Westlothiana was rather a close relative of Amniota. As a result, most paleontologists since the original description place the genus within the group Reptiliomorpha, among other amniote relatives such as diadectomorphs and seymouriamorphs. Later analyses usually place the genus as the earliest diverging member of Lepospondyli, a collection of unusual tetrapods which may be close to amniotes or lissamphibians, or potentially both at the same time.
Ctenospondylus is an extinct genus of sphenacodontid synapsid
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).
Ctenosauriscus is an extinct genus of sail-backed poposauroid archosaur from Early Triassic deposits of Lower Saxony in northern Germany. It gives its name to the family Ctenosauriscidae, which includes other sail-backed poposauroids such as Arizonasaurus. Fossils have been found in latest Olenekian deposits around 247.5-247.2 million years old, making it one of the first known archosaurs.
Limnoscelis was a genus of large diadectomorph tetrapods from the Late Carboniferous of western North America. It includes two species: the type species Limnoscelis paludis from New Mexico, and Limnoscelis dynatis from Colorado, both of which are thought to have lived concurrently. No specimens of Limnoscelis are known from outside of North America. Limnoscelis was carnivorous, and likely semiaquatic, though it may have spent a significant portion of its life on land. Limnoscelis had a combination of derived amphibian and primitive reptilian features, and its placement relative to Amniota has significant implications regarding the origins of the first amniotes.
Sclerothorax is an extinct genus of temnospondyl amphibian from the Early Triassic of Germany. It is distinguished from other temnospondyls by its short and very wide skull and the elongated neural spines that form a ridge along its back. Sclerothorax is a basal member of Capitosauria, a large clade of temnospondyls that lived throughout the Triassic.
Arizonerpeton is an extinct genus of nectridean lepospondyl. It contains a single species, Arizonerpeton wellsi. It lived in what is now the Swisshelm Mountains of modern-day Arizona, United States. This locality belongs to the Black Prince Limestone Formation, which is dated to the middle Pennsylvanian sub-period of the Carboniferous period.
Ostodolepis is an extinct genus of microsaur within the family Ostodolepidae. It is known from the Arroyo Formation in Texas.
Platyrhinops is an extinct genus amphibamid temnospondyl from the Late Carboniferous of Ohio and the Czech Republic. It is known from many partial skeletons from the Linton site in Saline Township, Ohio and at least 6 partial specimens from the Nýřany site from the Nýřany Member of the Kladno Formation in the Czech Republic.
Plagiobatrachus is an extinct genus of plagiosaurid temnospondyl. It is known from the Rewan Formation, an Early Triassic formation in Australia.
Trihecaton is an extinct genus of microsaur from the Late Pennsylvanian of Colorado. Known from a single species, Trihecaton howardinus, this genus is distinctive compared to other microsaurs due to possessing a number of plesiomorphic ("primitive") features relative to the rest of the group. These include large intercentra, folded enamel, and a large coronoid process of the jaw. Its classification is controversial due to combining a long body with strong limbs, features which typically are not present at the same time in other microsaurs. Due to its distinctiveness, Trihecaton has been given its own monospecific family, Trihecatontidae.
Anthracodromeus is an extinct genus of Late Carboniferous "protorothyridid" eureptile known from Ohio. It is known from the holotype AMNH 6940, a nearly complete skeleton. It was collected in the Linton site in Jefferson County, from the upper Freeport Coal Member. A. longipes was first assigned by Edward Drinker Cope in 1875 to a species of Sauropleura. The genus was first named by Robert L. Carroll and Donald Baird in 1972 and the type species is Anthracodromeus longipes.It is amongst the oldest known tetrapods to display adaptations for climbing.
