"Labyrinthodontia" is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras. Traditionally considered a subclass of the class Amphibia, modern classification systems recognize that labyrinthodonts are not a formal natural group (clade) exclusive of other tetrapods. Instead, they consistute an evolutionary grade, ancestral to living tetrapods such as lissamphibians and amniotes. "Labyrinthodont"-grade vertebrates evolved from lobe-finned fishes in the Devonian, though a formal boundary between fish and amphibian is difficult to define at this point in time.
Lepospondyli is a diverse taxon of early tetrapods. With the exception of one late-surviving lepospondyl from the Late Permian of Morocco, lepospondyls lived from the Early Carboniferous (Mississippian) to the Early Permian and were geographically restricted to what is now Europe and North America. Five major groups of lepospondyls are known: Adelospondyli; Aïstopoda; Lysorophia; Microsauria; and Nectridea. Lepospondyls have a diverse range of body forms and include species with newt-like, eel- or snake-like, and lizard-like forms. Various species were aquatic, semiaquatic, or terrestrial. None were large, and they are assumed to have lived in specialized ecological niches not taken by the more numerous temnospondyl amphibians that coexisted with them in the Paleozoic. Lepospondyli was named in 1888 by Karl Alfred von Zittel, who coined the name to include some tetrapods from the Paleozoic that shared some specific characteristics in the notochord and teeth. Lepospondyls have sometimes been considered to be either related or ancestral to modern amphibians or to Amniota. It has been suggested that the grouping is polyphyletic, with aïstopods being primitive stem-tetrapods, while recumbirostran microsaurs are primitive reptiles.
Lysorophia is an order of fossorial Carboniferous and Permian tetrapods within the Recumbirostra. Lysorophians resembled small snakes, as their bodies are extremely elongate. There is a single family, the Molgophidae. Currently there are around five genera included within Lysorophia, although many may not be valid.
Greererpeton burkemorani is an extinct genus of colosteid stem-tetrapods from the Early Carboniferous period of North America. Greererpeton was first described by famed vertebrate paleontologist Alfred S. Romer in 1969, based on a skull and partial skeleton from the Bluefield Formation. The skull was redescribed by Timothy R. Smithson in 1982, while postcranial remains were redescribed by Stephen J. Godfrey in 1989.
Nectridea is the name of an extinct order of lepospondyl tetrapods from the Carboniferous and Permian periods, including animals such as Diplocaulus. In appearance, they would have resembled modern newts or aquatic salamanders, although they are not close relatives of modern amphibians. They were characterized by long, flattened tails to aid in swimming, as well as numerous features of the vertebrae.
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 Texas and Oklahoma in the United States. The large number of specimens found make it the best-known caseid. Like all large herbivorous caseids, Cotylorhynchus had a short snout sloping forward and very large external nares. The head was very small compared to the size of the body. The latter was massive, barrel-shaped, and ended with a long tail. The limbs were short and robust. The hands and feet had short, broad fingers with powerful claws. The barrel-shaped body must have housed large intestines, suggesting that the animal had to feed on a large quantity of plants of low nutritional value. Caseids are generally considered to be terrestrial, though a semi-aquatic lifestyle has been proposed by some authors. The genus Cotylorhynchus is represented by three species, the largest of which could reach more than 6 m in length. However, a study published in 2022 suggests that the genus may be paraphyletic, with two of the three species possibly belonging to separate genera.
Cochleosaurus (“spoon lizard”, from the Latin cochlear "spoon" and Greek sauros “lizard”_ were medium-sized edopoid temnospondyls that lived in Euramerica during the Muscovian period. Two species, C. bohemicus and C. florensis, have been identified from the fossil record.
Micromelerpetontidae is an extinct family of dissorophoid temnospondyls that lived from the Late Carboniferous to the Early Permian in what is now Europe, with one Carboniferous species also known from North Africa. They were biologically similar to the related branchiosaurids, but proportionally akin to the unrelated microsaurs.
Nigerpeton is an extinct genus of crocodile-like temnospondyl amphibians from the late Permian (Changhsingian) period. These temnospondyls lived in modern-day Niger, which was once part of central Pangaea, about 250 million years ago. Nigerpeton is a member of the Cochleosauridae family, a group of edopoid temnospondyl amphibians known from the late Carboniferous (Pennsylvanian) and early Permian (Cisuralian).
Limnarchia is a clade of temnospondyls. It includes the mostly Carboniferous-Permian age Dvinosauria and the mostly Permian-Triassic age Stereospondylomorpha. The clade was named in a 2000 phylogenetic analysis of stereospondyls and their relatives. Limnarchia means "lake rulers" in Greek, in reference to their aquatic lifestyles and long existence over a span of approximately 200 million years from the Late Carboniferous to the Early Cretaceous. In phylogenetic terms, Limnarchia is a stem-based taxon including all temnospondyls more closely related to Parotosuchus than to Eryops. It is the sister group of the clade Euskelia, which is all temnospondyls more closely related to Eryops than to Parotosuchus. Limnarchians represent an evolutionary radiation of temnospondyls into aquatic environments, while euskelians represent a radiation into terrestrial environments. While many euskelians were adapted to life on land with strong limbs and bony scutes, most limnarchians were better adapted for the water with poorly developed limbs and lateral line sensory systems in their skulls.
Acherontiscus is an extinct genus of stegocephalians that lived in the Early Carboniferous of Scotland. The type and only species is Acherontiscus caledoniae, named by paleontologist Robert Carroll in 1969. Members of this genus have an unusual combination of features which makes their placement within amphibian-grade tetrapods uncertain. They possess multi-bone vertebrae similar to those of embolomeres, but also a skull similar to lepospondyls. The only known specimen of Acherontiscus possessed an elongated body similar to that of a snake or eel. No limbs were preserved, and evidence for their presence in close relatives of Acherontiscus is dubious at best. Phylogenetic analyses created by Marcello Ruta and other paleontologists in the 2000s indicate that Acherontiscus is part of Adelospondyli, closely related to other snake-like animals such as Adelogyrinus and Dolichopareias. Adelospondyls are traditionally placed within the group Lepospondyli due to their fused vertebrae. Some analyses published since 2007 have argued that adelospondyls such as Acherontiscus may not actually be lepospondyls, instead being close relatives or members of the family Colosteidae. This would indicate that they evolved prior to the split between the tetrapod lineage that leads to reptiles (Reptiliomorpha) and the one that leads to modern amphibians (Batrachomorpha). Members of this genus were probably aquatic animals that were able to swim using snake-like movements.
Odonterpeton is an extinct genus of "microsaur" from the Late Carboniferous of Ohio, containing the lone species Odonterpeton triangulare. It is known from a single partial skeleton preserving the skull, forelimbs, and the front part of the torso. The specimen was found in the abandoned Diamond Coal Mine of Linton, Ohio, a fossiliferous coal deposit dated to the late Moscovian stage, about 310 million years ago.
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.
Utaherpeton is an extinct genus of lepospondyl amphibian from the Carboniferous of Utah. It is one of the oldest and possibly one of the most basal ("primitive") known lepospondyls. The genus is monotypic, including only the type species Utaherpeton franklini. Utaherpeton was named in 1991 from the Manning Canyon Shale Formation, which dates to the Mississippian-Pennsylvanian boundary. It was originally classified within Microsauria, a group of superficially lizard- and salamander-like lepospondyls that is now no longer considered to be a valid clade or evolutionary grouping, but rather an evolutionary grade consisting of the most basal lepospondyls. Utaherpeton has been proposed as both the most basal lepospondyl and the oldest "microsaur", although more derived lepospondyls are known from earlier in the Carboniferous. However, its position within Lepospondyli remains uncertain due to the incomplete preservation of the only known specimen. The inclusion of Utaherpeton in various phylogenetic analyses has resulted in multiple phylogenies that are very different from one another, making it a significant taxon in terms of understanding the interrelationships of lepospondyls.
Ostodolepidae, also spelled Ostodolepididae, is an extinct family of Early Permian tetrapods. Initially they were considered microsaurs, but later were assigned to the group Recumbirostra. Ostodolepids were relatively large, reaching lengths of up to 2 feet (61 cm), terrestrial, and presumably fossorial. Ostodolepid remains have been found from Early Permian beds in Texas, Oklahoma, and Germany.
Recumbirostra is a clade of tetrapods which lived during the Carboniferous and Permian periods. They are thought to have had a fossorial (burrowing) lifestyle and the group includes both short-bodied and long-bodied snake-like forms. At least one species, the long-bodied molgophid Nagini mazonense, lost its forelimbs entirely. Recumbirostra includes the families Pantylidae, Gymnarthridae, Ostodolepidae, Rhynchonkidae and Brachystelechidae, with additional families such as Microbrachidae and Molgophidae being included by some authors. Brachystelechidae and Molgophidae have also been grouped together in the suggested clade Chthonosauria.
Huskerpeton is an extinct genus of recumbirostran from the Early Permian period. They belong to the order Microsauria, which was established in 1863 by Dawson, and was quickly expanded to include many different small taxa. They lived in what is now Nebraska and Kansas. The holotype of Huskerpeton was uncovered at the Eskridge formation in Nebraska, which is part of how it got its name.
Proxilodon is an extinct genus of recumbirostran microsaur from the Early Permian Speiser Formation of Kansas, United States. It contains a single species, Proxilodon bonneri,.
Ascendonanus is an extinct genus of 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.
Stenokranio is a genus of eryopid temnospondyl from the Permo-Carboniferous Remigiusberg Formation of Germany. It is represented by the type species, Stenokranio boldi, which was named for two specimens collected from the Remigiusberg quarry near Kusel, Saar–Nahe Basin, southwest Germany.
