Animals with backbones are . All animals with backbones are , animals that at some time in their lives have a large running down their backs. Vertebrates have an , which is an internal skeleton that supports the body. Most vertebrates have two sets of paired , such as fins, arms, or legs.
Vertebrates are grouped into seven classes. include hagfish and lampreys. include sharks, rays, and skates. are the largest class of fish. include frogs, toads, and salamanders. include snakes, turtles, lizards, crocodiles, and alligators. have feathers, wings, lightweight bones, and beaks without teeth. feed their young with milk made by the mother.