Amphibians evolved from fish about 400 million years ago, when the amount of dry land on Earth increased greatly. Certain fish adapted to these changing conditions by developing limbs to crawl with, and lungs to breathe. They came to be called ‘amphibians’, and were the first animals with backbones to live on land. The largest variety of amphibians lived around 360 million to 230 million years ago, when the climate was constantly alternating between wet and dry.
The first amphibians were Temnospondyls. They were long-headed amphibians with a sprawling gait and distinctive look. The early Temnospondyls were the size of large fish. They had stubby feet, and probably couldn’t move very fast. Temnospondyls grew in size and diversity until some even grew as large as crocodiles. This animal, Prionosuchus is the largest amphibian known. Lissamphibians, the group that includes all modern amphibians and their common ancestors, emerged about 300 million years ago.
