Dimetrodon is an extinct genus of non-mammalian synapsid belonging to the family Sphenacodontidae that lived during the Cisuralian age of the Early Permian period, around 295–272 million years ago. With most species measuring 1.7–4.6 m (5.6–15.1 ft) long and weighing 28–250 kg (62–551 lb), 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 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 these coming from a geological deposit called the Red Beds of Texas and Oklahoma. More recently, its fossils have also been found in Germany and 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.
Diadectomorpha is a clade of large tetrapods that lived in Euramerica during the Carboniferous and Early Permian periods and in Asia during Late Permian (Wuchiapingian), They have typically been classified as advanced reptiliomorphs positioned close to, but outside of the clade Amniota, though some recent research has recovered them as the sister group to the traditional Synapsida within Amniota, based on inner ear anatomy and cladistic analyses. They include both large carnivorous and even larger herbivorous forms, some semi-aquatic and others fully terrestrial. The diadectomorphs seem to have originated during late Mississippian times, although they only became common after the Carboniferous rainforest collapse and flourished during the Late Pennsylvanian and Early Permian periods.
Captorhinidae is an extinct family of tetrapods, typically considered primitive reptiles, known from the late Carboniferous to the Late Permian. They had a cosmopolitan distribution across Pangea.
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).
Platyhystrix is an extinct temnospondyl amphibian with a distinctive sail along its back, similar to the unrelated synapsids, Dimetrodon and Edaphosaurus. It lived during the boundary between the latest Carboniferous and earliest Permian periods throughout what is now known as the Four Corners, Texas, and Kansas about 300 million years ago.
Araeoscelidia or Araeoscelida is a clade of extinct amniotes superficially resembling lizards, extending from the Late Carboniferous to the Early Permian. The group contains the genera Araeoscelis, Petrolacosaurus, the possibly aquatic Spinoaequalis, and less well-known genera such as Kadaliosaurus and Zarcasaurus. This clade is usually considered to be the sister group to all later diapsids.
Limnoscelis was a genus of large diadectomorph tetrapods from the Late Carboniferous to early Permian 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.
Captorhinus is an extinct genus of captorhinid reptiles that lived during the Permian period. Its remains are known from North America and possibly South America.
Labidosaurikos is a genus of extinct captorhinid tetrapods 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.
Reiszorhinus is an extinct genus of captorhinid tetrapods known from the Early Permian of the United States. The type species is Reiszorhinus olsoni. Fossils have been found from the Waggoner Ranch Formation in north-central Texas. It is distinguishable by its recurved teeth and extremely large Meckelian foramen on the inner surface of the lower jaw. It has been considered a primitive member of its family because it has a single tooth along the margins of the jaws. While most single-tooth-rowed captorhinids are small, Reiszorhinus is relatively large. However, Reiszorhinus differs from other large captorhinids in that the cheek region is not wide and expanded.
Euconcordia is an extinct genus of Late Carboniferous captorhinid known from Greenwood County, Kansas of the United States.
Thuringothyris is an extinct genus of Early Permian eureptiles known from the Thuringian Forest in central Germany.
The Tambach Formation is an Early Permian-age geologic formation in central Germany. It consists of red to brown-colored sedimentary rocks such as conglomerate, sandstone, and mudstone, and is the oldest portion of the Upper Rotliegend within the Thuringian Forest Basin.
The Red Beds of Texas and Oklahoma are a group of Early Permian-age geologic strata in the southwestern United States cropping out in north-central Texas and south-central Oklahoma. They comprise several stratigraphic groups, including the Clear Fork Group, the Wichita Group, and the Pease River Group. The Red Beds were first explored by American paleontologist Edward Drinker Cope starting in 1877. Fossil remains of many Permian tetrapods have been found in the Red Beds, including those of Dimetrodon, Edaphosaurus, Seymouria, Platyhystrix, and Eryops. A recurring feature in many of these animals is the sail structure on their backs.
The Arroyo Formation, sometimes termed the Lower Clear Fork Formation, is a geologic formation in Texas. It preserves fossils dating back to the Kungurian stage of the Permian period. It is the lower-most portion of the Clear Fork Group, part of a series of fossiliferous Permian strata in the south-central United States known as the red beds.
The Nocona Formation is a geological formation in Texas, dating back to the Wolfcampian series. As part of the Texas red beds, it is one of several formations renowned for dense bonebeds of terrestrial vertebrate fossils.
The Organ Rock Formation or Organ Rock Shale is a formation within the late Pennsylvanian to early Permian Cutler Group and is deposited across southeastern Utah, northwestern New Mexico, and northeastern Arizona. This formation notably outcrops around Canyonlands National Park, Natural Bridges National Monument, and Monument Valley of northeast Arizona, southern Utah. The age of the Organ Rock is constrained to the latter half of the Cisuralian epoch by age dates from overlying and underlying formations. Important early terrestrial vertebrate fossils have been recovered from this formation in northern Arizona, southern Utah, and northern New Mexico. These include the iconic Permian terrestrial fauna: Seymouria, Diadectes, Ophiacodon, and Dimetrodon. The fossil assemblage present suggests arid environmental conditions. This is corroborated with paleoclimate data indicative of global drying throughout the early Permian.
Richards Spur is a Permian fossil locality located at the Dolese Brothers Limestone Quarry north of Lawton, Oklahoma. The locality preserves clay and mudstone fissure fills of a karst system eroded out of Ordovician limestone and dolomite, with the infilling dating to the Artinskian stage of the early Permian (Cisuralian), around 289 to 286 million years ago. Fossils of terrestrial animals are abundant and well-preserved, representing one of the most diverse Paleozoic tetrapod communities known. A common historical name for the site is Fort Sill, in reference to the nearby military base. Fossils were first reported at the quarry by workers in 1932, spurring a wave of collecting by local and international geologists. Early taxa of interest included the abundant reptile Captorhinus and microsaurs such as Cardiocephalus and Euryodus. Later notable discoveries include Doleserpeton, the most diverse assortment of parareptiles in the Early Permian, and the rare early diapsid Orovenator.
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