Page "Amphibian" Paragraph 24

All modern amphibians are included in the subclass Lissamphibia, superorder Salientia, which is usually considered a clade, a group of species that have evolved from a common ancestor.

The three modern orders are Anura ( the frogs and toads ), Caudata, alternatively known as Urodela ( the salamanders ), and Gymnophiona ( the caecilians ).

It has been suggested that salamanders arose separately from a Temnospondyl-like ancestor, and even that caecilians are the sister group of the advanced reptiliomorph amphibians, and thus of amniotes.

Although the fossils of several older proto-frogs with primitive characteristics are known, the oldest " true frog " is Prosalirus bitis, from the Early Jurassic Kayenta Formation of Arizona.

It is anatomically very similar to modern frogs.

The oldest known caecilian is Eocaecilia micropodia, also from Arizona, while the earliest salamander is Beiyanerpeton jianpingensis from the Late Jurassic of northeastern China.