What are the Major Groups of Amphibian?
Amphibians, class Amphibia, are an ancient lineage that evolved directly from lobe-finned fish in the late Devonian period, about 365 million years ago. At one point it contained three subclasses: labyrinthodonts, lepospondyls, and lissamphibians. Today, only lissamphibians still exist, counting all surviving amphibians among its members: newts and salamanders (an order called Caudata or Urodela), frogs and toads (order Anura), and the rarely-seen limbless caecilians (order Gymnophiona or Apoda). Among the surviving groups of amphibian, the most successful are the frogs and toads (5,453 species), followed by salamanders and newts (560 species), and caecilians (171 species). It is thought that all these amphibians share a common ancestor, though some workers argue that salamanders and newts descended from a different ancient ancestor than the rest. The number of amphibian species is roughly comparable to the number of mammal species — both have about 6,000 — but obviously mammals are mu
