Amphibians are ectothermic, anamniotic, four-limbed vertebrate animals that constitute the class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all tetrapods excluding the amniotes. All extant (living) amphibians belong to the monophyletic subclass Lissamphibia, with three living orders: Anura, Urodela (salamanders), and Gymnophiona (caecilians). Evolved to be mostly semiaquatic, amphibians have adapted to inhabit a wide variety of habitats, with most species living in freshwater, wetland or terrestrial ecosystems. Their life cycle typically starts out as aquatic larvae with gills known as tadpoles, but some species have developed behavioural adaptations to bypass this.
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.
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 Visean stage of the Early Carboniferous 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.
Boulengerula taitana is a species of caecilian. It is endemic to the Taita Hills region of southeast Kenya. Boulengerula taitana are unique caecilians in appearance, fertilization type, and parental care. From their similar shape and presentation to worms, and their internalized fertilization, they set themselves apart from many other amphibians. D. taitana interactions between mothers and newly hatched young are unique in that the mother uses her own skin as a food resource for offspring. This species also has physiological adaptations in place to increase oxygen uptake and affinity to fit their underground lifestyle. The Boulengerula taitana differentiates itself from its close relatives in ways rarely documented and researched before.
Boulengerula niedeni, the Sagalla caecilian, is a worm-like amphibian first described in 2005. The species was described from a specimen discovered on Sagala Hill, an isolated mountain block of the Taita Hills in Kenya, and is not known from other areas.
Atretochoana eiselti is a species of caecilian originally known only from two preserved specimens discovered by Sir Graham Hales in the Brazilian rainforest, while on an expedition with Sir Brian Doll in the late 1800s, but rediscovered in 2011 by engineers working on a hydroelectric dam project in Brazil. Until 1998, it was known only from the type specimen in the Naturhistorisches Museum, Vienna. Originally placed in the genus Typhlonectes in 1968, it was reclassified into its own monotypic genus, Atretochoana, in 1996. It was also found to be more closely related to the genus Potamotyphlus than Typholonectes. The species is the largest of the few known lungless tetrapods, and the only known lungless caecilian.
Chthonerpeton indistinctum is a species of caecilian in the family Typhlonectidae. It is found in northeastern Argentina, Paraguay, Uruguay, and southeastern Brazil. The common name Argentine caecilian has been coined for it.
Dermophis mexicanus, also known commonly as the Mexican burrowing caecilian or the Mexican caecilian, and locally as the tapalcua or tepelcua, is a species of limbless amphibian in the family Dermophiidae. The species is native to Mexico and Central America, where it burrows under leaf litter and plant debris.
Oscaecilia zweifeli is a species of caecilian in the family Caeciliidae. It is a poorly known species only known from few specimens: the holotype from the imprecise type locality, "a small creek tributary to Río Mazaruni" in Guyana, one from similarly imprecise Cayenne in French Guiana, and another one from the Nouragues research station in French Guiana. The specific name zweifeli honors Richard G. Zweifel, an American herpetologist. Common names Zweifel's caecilian and tributary caecilian have been coined for it.
Siphonops annulatus, the ringed caecilian, is a species of caecilian in the family Siphonopidae endemic to South America. It may have the broadest known distribution of any terrestrial caecilian species.
Typhlonectes natans, also incorrectly called the rubber eel, is a species of caecilian in the family Typhlonectidae found in Colombia, Venezuela, and possibly Trinidad and Tobago. Its natural habitats are dry savanna, subtropical or tropical dry shrubland, subtropical or tropical moist shrubland, subtropical or tropical seasonally wet or flooded lowland grassland, and rivers. T. natans is commonly kept as an aquarium pet, and is sometimes sold as a "fish" in aquarium stores.
The Koh Tao Island caecilian is a species of amphibian in the family Ichthyophiidae found in Cambodia, Laos, Myanmar, Thailand, and Vietnam. Also known as the Ichthyophis bannanicus, the Banna caecilian, it is also found in southern China.
Rhinatrema nigrum, the black caecilian, is a species of caecilian in the family Rhinatrematidae found in Guyana, Venezuela, and possibly Brazil. Its natural habitats are subtropical or tropical moist lowland forests, subtropical or tropical moist montane forests, rivers, and intermittent rivers.
Rhinatrema is a genus of caecilians in the family Rhinatrematidae. Their common name is two-lined caecilians. The genus is known from the Guyanas and adjacent Brazil. Most Rhinatrema are known to inhabit and live in areas of tropical forests where there is an abundance of dense, dead vegetation matter.
The western clawed frog is a species of frog in the family Pipidae, also known as tropical clawed frog. It is the only species in the genus Xenopus to have a diploid genome. Its genome has been sequenced, making it a significant model organism for genetics that complements the related species Xenopus laevis, a widely used vertebrate model for developmental biology. X. tropicalis also has a number of advantages over X. laevis in research, such as a much shorter generation time, smaller size, and a larger number of eggs per spawn.
Gerobatrachus is an extinct genus of amphibamid temnospondyl that lived in the Early Permian, approximately 290 million years ago (Ma), in the area that is now Baylor County, Texas. When it was first described in 2008, Gerobatrachus was announced to be the closest relative of Batrachia, the group that includes modern frogs and salamanders. It possesses a mixture of characteristics from both groups, including a large frog-like head and a salamander-like tail. These features have led to it being dubbed a frogamander by the press. Some more recent studies place Gerobatrachus as the closest relative of Lissamphibia, the group that contains all modern amphibians including frogs, salamanders, and caecilians, or place modern amphibians far from Gerobatrachus within a group called Lepospondyli.
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.
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.
Cranial kinesis is the term for significant movement of skull bones relative to each other in addition to movement at the joint between the upper and lower jaws. It is usually taken to mean relative movement between the upper jaw and the braincase.
