DK Nature: Vertebrates

Fish are the largest vertebrate group, with more species than all the other groups put together.

6,000 species include crocodiles, lizards, snakes, and turtles.

9,000 species include eagles, gulls, parrots, ducks, and perching birds.

4,500 species include rodents, bats, whales, and primates.

4,000 species include frogs, toads, newts, and salamanders.

26,000 species include bony fish, sharks, rays, hagfish, and lampreys.

The skeleton is a strong frame that supports the body and anchors the muscles. Bones such as ribs protect the heart and other delicate parts, and the skull shields the brain. Most vertebrates have bony skeletons, but shark skeletons are rubbery cartilage.

Most vertebrates apart from fish have four limbs. In birds and bats, the front limbs evolved (developed) into wings for flying. A fish’s limbs are its fins, which vary in number between species. Snakes evolved from four-legged ancestors millions of years ago.

Like all vertebrates, snakes have a skull, backbone, and ribs. The backbone is made of many individual bones called vertebrae.