 The first major groups of amphibians developed in the Devonian period , around 370 million years ago , from lobe @-@ finned fish which were similar to the modern coelacanth and lungfish . These ancient lobe @-@ finned fish had evolved multi @-@ jointed leg @-@ like fins with digits that enabled them to crawl along the sea bottom . Some fish had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen . They could also use their strong fins to hoist themselves out of the water and onto dry land if circumstances so required . Eventually , their bony fins would evolve into limbs and they would become the ancestors to all tetrapods , including modern amphibians , reptiles , birds , and mammals . Despite being able to crawl on land , many of these prehistoric <unk> fish still spent most of their time in the water . They had started to develop lungs , but still breathed predominantly with gills . 
