Caudata

Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela. Salamander diversity is highest in eastern North America and most species are found in the Holarctic realm, with some species present in the Neotropical realm.

Salamanders split off from the other amphibians during the mid- to late Permian, and initially were similar to modern members of the Cryptobranchoidea. Their resemblance to lizards is the result of symplesiomorphy, their common retention of the primitive tetrapod body plan, but they are no more closely related to lizards than they are to mammals. Their nearest relatives are the frogs and toads, within Batrachia. The earliest known salamander fossils have been found in geological deposits in China and Kazakhstan, dated to the middle Jurassic period around 164 million years ago.

Salamanders are found only in the Holarctic and Neotropical regions, not reaching south of the Mediterranean Basin, the Himalayas, or in South America the Amazon Basin. They do not extend north of the Arctic tree line, with the northernmost Asian species, Salamandrella keyserlingii occurring in the Siberian larch forests of Sakha and the most northerly species in North America, Ambystoma laterale, reaching no farther north than Labrador and Taricha granulosa not beyond the Alaska Panhandle. They had an exclusively Laurasian distribution until Bolitoglossa invaded South America from Central America, probably by the start of the Early Miocene, about 23 million years ago. They also lived on the Caribbean Islands during the early Miocene epoch, confirmed by the discovery of Palaeoplethodon hispaniolae, found trapped in amber in the Dominican Republic. However, possible salamander fossils have been found in Australia at the Murgon fossil site, representing the only known salamanders known from the continent.

There are about 760 living species of salamander. One-third of the known salamander species are found in North America. The highest concentration of these is found in the Appalachian Mountains region, where the Plethodontidae are thought to have originated in mountain streams. Here, vegetation zones and proximity to water are of greater importance than altitude. Only species that adopted a more terrestrial mode of life have been able to disperse to other localities. The northern slimy salamander (Plethodon glutinosus) has a wide range and occupies a habitat similar to that of the southern gray-cheeked salamander (Plethodon metcalfi). The latter is restricted to the slightly cooler and wetter conditions in north-facing cove forests in the southern Appalachians, and to higher elevations above 900 m (3,000 ft), while the former is more adaptable, and would be perfectly able to inhabit these locations, but some unknown factor seems to prevent the two species from co-existing.

One species, the Anderson's salamander, is one of the few species of living amphibians to occur in brackish or salt water.