Posted: 10 April 2001

Common name for any animal of the vertebrate class lying between fishes and reptiles on the evolutionary scale. Emerging from the oceans almost 408 million years ago, amphibians were the first vertebrates (animals with a backbone) to live on land. The class, with about 4,400 existing species, includes three living orders: the tailed amphibians, consisting of the salamanders (including newts) and sirens; the tailless amphibians, which include frogs and toads; and the caecilians, which are worm-like amphibians that are limbless and blind.With their slender bodies and long tails, some amphibians, such as the salamanders, may be mistaken for lizards and other reptiles. Unlike reptiles, however, amphibians have no scales, and most must stay close to water to survive.