 Many examples of species showing transitional features have been discovered . Ichthyostega was one of the first primitive amphibians , with nostrils and more efficient lungs . It had four sturdy limbs , a neck , a tail with fins and a skull very similar to that of the lobe @-@ finned fish , <unk> . Amphibians evolved adaptations that allowed them to stay out of the water for longer periods . Their lungs improved and their skeletons became heavier and stronger , better able to support the weight of their bodies on land . They developed " hands " and " feet " with five or more digits ; the skin became more capable of retaining body fluids and resisting desiccation . The fish 's <unk> bone in the hyoid region behind the gills diminished in size and became the stapes of the amphibian ear , an adaptation necessary for hearing on dry land . An affinity between the amphibians and the teleost fish is the multi @-@ folded structure of the teeth and the paired supra @-@ occipital bones at the back of the head , neither of these features being found elsewhere in the animal kingdom . 
