The Lissamphibia are a group of tetrapods that includes all modern amphibians. Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata (salamanders, newts, and their extinct relatives), and the Gymnophiona (the limbless caecilians and their extinct relatives). A fourth group, the Allocaudata, was moderately successful, spanning 160 million years from the Middle Jurassic to the Early Pliocene, but became extinct 2.5 million years ago.