The document describes the key characteristics of different groups of vertebrates. It states that fish have scales, fins and tails and swim in water. Amphibians have smooth skin, most have four legs, and salamanders have tails. Reptiles have scales, many have four legs and tails, snakes do not have legs, and turtles have shells. Birds have feathers, two legs, two wings, and most can fly. Mammals usually have hair or fur, most have four legs, and many have tails.