The Lissamphibia is a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia, the Caudata, and the Gymnophiona.
Caecilians are a group of limbless, vermiform (worm-shaped) or serpentine (snake-shaped) amphibians with small or sometimes nonexistent eyes. They mostly live hidden in soil or in streambeds, and this cryptic lifestyle renders caecilians among the least familiar amphibians. Modern caecilians live in the tropics of South and Central America, Africa, and southern Asia. Caecilians feed on small subterranean creatures such as earthworms. The body is cylindrical and often darkly coloured, and the skull is bullet-shaped and strongly built. Caecilian heads have several unique adaptations, including fused cranial and jaw bones, a two-part system of jaw muscles, and a chemosensory tentacle in front of the eye. The skin is slimy and bears ringlike markings or grooves and may contain scales.
The Batrachia are a clade of amphibians that includes frogs and salamanders, but not caecilians nor the extinct allocaudates. The name Batrachia was first used by French zoologist Pierre André Latreille in 1800 to refer to frogs, but has more recently been defined in a phylogenetic sense as a node-based taxon that includes the last common ancestor of frogs and salamanders and all of its descendants. The idea that frogs and salamanders are more closely related to each other than either is to caecilians is strongly supported by morphological and molecular evidence; they are, for instance, the only vertebrates able to raise and lower their eyes. However, an alternative hypothesis exists in which salamanders and caecilians are each other's closest relatives as part of a clade called the Procera, with frogs positioned as the sister taxon of this group.
"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.
The Batrachomorpha are a clade containing recent and extinct amphibians that are more closely related to modern amphibians than they are to mammals and reptiles. According to many analyses they include the extinct Temnospondyli; some show that they include the Lepospondyli instead. The name traditionally indicated a more limited group.
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.
Reptiliomorpha is a clade containing the amniotes and those tetrapods that share a more recent common ancestor with amniotes than with living amphibians (lissamphibians). It was defined by Michel Laurin (2001) and Vallin and Laurin (2004) as the largest clade that includes Homo sapiens, but not Ascaphus truei. Laurin and Reisz (2020) defined Pan-Amniota as the largest total clade containing Homo sapiens, but not Pipa pipa, Caecilia tentaculata, and Siren lacertina.
Dissorophoidea is a clade of medium-sized, temnospondyl amphibians that appeared during the Moscovian in Euramerica, and continued through to the Late Permian and the Early Triassic of Gondwana. They are distinguished by various details of the skull, and many species seem to have been well adapted for life on land.
Temnospondyli or temnospondyls is a diverse ancient order of small to giant tetrapods — often considered primitive amphibians — that flourished worldwide during the Carboniferous, Permian and Triassic periods, with fossils being found on every continent. A few species continued into the Jurassic and Early Cretaceous periods, but all had gone extinct by the Late Cretaceous. During about 210 million years of evolutionary history, they adapted to a wide range of habitats, including freshwater, terrestrial, and even coastal marine environments. Their life history is well understood, with fossils known from the larval stage, metamorphosis, and maturity. Most temnospondyls were semiaquatic, although some were almost fully terrestrial, returning to the water only to breed. These temnospondyls were some of the first vertebrates fully adapted to life on land. Although temnospondyls are amphibians, many had characteristics such as scales and armour-like bony plates that distinguish them from the modern soft-bodied lissamphibians.
Eocaecilia is an extinct genus of gymnophionan amphibian from the early Jurassic Kayenta Formation of Arizona, United States. One species is described, Eocaecilia micropodia.
The Albanerpetontidae are an extinct family of small amphibians, native to the Northern Hemisphere during the Mesozoic and Cenozoic. The only members of the order Allocaudata, they are thought to be allied with living amphibians belonging to Lissamphibia. Despite a superficially salamander-like bodyform, their anatomy is strongly divergent from modern amphibians in numerous aspects. The fossil record of albanerpetontids spans over 160 million years from the Middle Jurassic to the beginning of the Pleistocene, about 2.13–2 million years ago.
Doleserpeton is an extinct, monospecific genus of dissorophoidean temnospondyl within the family Amphibamidae that lived during the Upper Permian, 285 million years ago. Doleserpeton is represented by a single species, Doleserpeton annectens, which was first described by John R. Bolt in 1969. Fossil evidence of Doleserpeton was recovered from the Dolese Brothers Limestone Quarry in Fort Sill, Oklahoma. The genus name Doleserpeton is derived from the initial discovery site in Dolese quarry of Oklahoma and the Greek root "herp-", meaning "low or close to the ground". This transitional fossil displays primitive traits of amphibians that allowed for successful adaptation from aquatic to terrestrial environments. In many phylogenies, lissamphibians appear as the sister group of Doleserpeton.
Rhynchonkos is an extinct genus of rhynchonkid microsaur. Originally known as Goniorhynchus, it was renamed in 1981 because the name had already been given to another genus; the family, likewise, was originally named Goniorhynchidae but renamed in 1988. The type and only known species is R. stovalli, found from the Early Permian Fairmont Shale in Cleveland County, Oklahoma. Rhynchonkos shares many similarities with Eocaecilia, an early caecilian from the Early Jurassic of Arizona. Similarities between Rhynchonkos and Eocaecilia have been taken as evidence that caecilians are descendants of microsaurs. However, such a relationship is no longer widely accepted.
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.
The Salientia are a total group of amphibians that includes the order Anura, the frogs and toads, and various extinct proto-frogs that are more closely related to the frogs than they are to the Urodela, the salamanders and newts. The oldest fossil "proto-frog" appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian, 265 million years ago.
The Amphibamidae are an ancient family of dissorophoid temnospondyls known from Late Carboniferous-Early Permian strata in the United States.
Pasawioops is an extinct genus of early Permian dissorophoid temnospondyl within the clade Amphibamiformes.
Chinlestegophis is a diminutive Late Triassic stereospondyl that has been interpreted as a putative stem caecilian, a living group of legless burrowing amphibians. If Chinlestegophis is indeed both an advanced stereospondyl and a relative of caecilians, this means that stereospondyls survived to the present day; historically the group was thought to have gone extinct by the early Cretaceous. Chinlestegophis jenkinsi, the type and only species, is known from two partial skulls discovered in the Chinle Formation in Colorado.
Amphibamiformes is an unranked clade with Dissorophoidea created by Schoch (2018). It encompasses all of the taxa traditionally considered to be "amphibamids", branchiosaurids, and hypothetically lissamphibians under the traditional temnospondyl hypothesis of lissamphibian origins. These taxa are typically small-bodied dissorophoids and form the sister group to Olsoniformes, which comprises dissorophids and trematopids.
Funcusvermis is an extinct genus of stem-caecilian from the Late Triassic of Arizona. It is based on a large sample of jaws and other skull and postcranial fragments, discovered in an approximately 220 million years old layer of rock in the Blue Mesa Member of the Chinle Formation at Petrified Forest National Park. There is a single species, called Funcusvermis gilmorei.
