Vertebrate

Vertebrates are the animals of the group Vertebrata, a subphylum of the phylum Chordata. Their name refers to the vertebral column, or backbone, a chain of separate segments of bone or cartilage called vertebrae that surrounds and protects the spinal cord. They also have a cranium, a skull that encloses the brain. Like all chordates, vertebrate embryos have a notochord, a dorsal hollow nerve cord, pharyngeal slits and a tail behind the anus, and as they develop the notochord is largely replaced by the backbone.

Living vertebrates include jawless fishes such as lampreys and hagfishes, cartilaginous fishes like sharks and rays, bony fishes, amphibians, reptiles, birds and mammals; birds are now understood to belong within the reptile lineage. Most vertebrates have jaws, paired fins or limbs, and an internal skeleton that grows with the body, unlike the shed exoskeleton of an insect.

Although they include the largest and most familiar animals, vertebrates make up only a small fraction of animal species; the rest are invertebrates. Humans are vertebrates, so much of human anatomy is easiest to understand by comparison with other vertebrates.