Amphibians evolved from lobe-finned fishes 365 million years ago and once had three subclasses, but only lissamphibians survive today. Frogs and toads are the most successful group with 5,453 species. The common ancestor of lissamphibia lived about 290 million years ago, and the discovery of the Gerobatrachus fossil showed that modern amphibians are descended from temnospondyls. The Chinese giant salamander is an example of a relatively large amphibian species, but many amphibians are critically endangered.
Amphibians, class Amphibia, are an ancient lineage that evolved directly from lobe-finned fishes in the Late Devonian, about 365 million years ago. At one point it contained three subclasses: labyrinthodonts, lepospondyls, and lissamphibians. Only lyssanphibians still exist today, 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).
Of the surviving amphibian groups, the most successful are frogs and toads (5,453 species), followed by salamanders and newts (560 species) and caecilians (171 species). All of these amphibians are thought to share a common ancestor, although some workers argue that salamanders and newts are descended from a different ancient ancestor. The number of amphibian species is roughly comparable to the number of mammal species – both have around 6,000 – but obviously mammals are far more numerous and successful.
The common ancestor of lissamphibia probably lived about 290 million years ago. A fossil from that time, Gerobatrachus, is referred to as a frogamander due to its clear combination of frog-like and salamander-like traits. Called the “frog-eared stubby-tailed salamander,” the rediscovery of this fossil in 2004 showed that the common ancestor of frogs and salamanders lived more recently than otherwise thought. The common ancestor of caecilians and other amphibians may be 10-20 million years older. The discovery of Gerobatrachus has shown that modern amphibians are descended from an ancient group called temnospondyls. The amphibian lineage controversy had been considered one of the most significant in vertebrate evolution before the discovery of the frog fossil.
Although ancient amphibians were relatively large, filling many of the niches occupied by reptiles and mammals today, today’s reptiles are relatively small. One species reminiscent of this long-lost amphibian past is the Chinese giant salamander (Andrias davidianus), a river dweller reaching sizes of 64 kg (140 lb) and 1.83 m (6 ft). Like many other amphibians, the Chinese giant salamander is critically endangered and today inhabits only the most remote mountain streams. Other amphibian species that are currently critically endangered are the Malagasy rainbow frog, Darwin’s frog of Chile, ghost frogs, Seychelles frog, Sagalla caecilian, Mexican lungless salamanders, and the midwife’s betic toad.
Protect your devices with Threat Protection by NordVPN
