Page "Amphibian" Paragraph 26

The superclass Tetrapoda is divided into four classes of vertebrate animals with four limbs.

Reptiles, birds and mammals are amniotes, the eggs of which are either laid or carried by the female and are surrounded by several membranes, some of which are impervious.

Lacking these membranes, amphibians require water bodies for reproduction, although some species have developed various strategies for protecting or bypassing the vulnerable aquatic larval stage.

They are not found in the sea with the exception of one or two frogs that live in brackish water in mangrove swamps.

On land, amphibians are restricted to moist habitats because of the need for their skin to be kept damp.