What is Amphibian?
{{automatic taxobox | name = Amphibia | fossil_range = late [[Devonian]]–[[present]], fossil range 370 mya to present | image = Amphibians.png | image_upright = 1.15 | image_alt = Collage of amphibians | image_caption = Clockwise from top right: ''[[Seymouria]]'', Mexican burrowing [[caecilian]], eastern [[newt]] and leaf green [[tree frog]] | taxon = Amphibia | authority = [[John Edward Gray|Gray]] 1825 | subdivision_ranks = Subclasses | subdivision = * {{extinct}}[[Temnospondyli]] * [[Lissamphibia]] (modern amphibians) }} [[File:Eryops - National Museum of Natural History - IMG 1974.JPG|right|300px|thumb|''[[Eryops]]'', typical of the large-size early amphibians 310–295 million years ago]] '''Amphibians''' are members of the [[class (biology)|class]] '''Amphibia'''. The living ones are [[frog]]s (including [[toad]]s), [[salamander]]s (including [[newt]]s) and [[caecilian]]s. They are [[tetrapod|four-legged]] [[vertebrate]]s which are [[Ectotherm|cold blooded]]. Amphibians lay their eggs in water, usually in a [[foam]] [[nest]]. After [[wikt:hatch|hatching]] they are [[tadpole]]s, which live in the water and have [[gill]]s. The tadpoles change into adults in a process called [[metamorphosis]]. When they are adult, they have [[lung]]s to breathe instead of gills, and legs. Adult amphibians also use their skin to take in [[oxygen]], and some [[species]] of salamanders do not have lungs. The earliest amphibians [[evolution|evolved]] in the [[Devonian]] from [[sarcopterygii|lobe-finned]] [[fish]] which had jointed leg-like fins with digits. They could crawl along the sea bottom. Some had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian [[swamp]]s were low in [[oxygen]]. They could also use their strong fins to hoist themselves out of the water and onto dry land if necessary.<ref name=Jen>Clack, Jennifer A. 2002. ''Gaining ground: the origin and evolution of tetrapods''. Indiana University Press, Bloomington IN. {{ISBN|0-253-34054-3}}</ref><ref name=Bob/> For tens of mil