The superclass Tetrapoda contains the four-limbed vertebrates known as tetrapods ; it includes living and extinct amphibians, reptiles and mammals, as well as earlier extinct groups. Tetrapods evolved from a group of animals known as the Tetrapodomorpha, who in turn evolved from ancient Sarcopterygii lobe-finned fishes around 390 million years ago in the middle Devonian period; their forms were transitional between lobe-finned fishes and the four-limbed tetrapods.