vertebrates Definition

any of a subphylum (Vertebrata) of chordates that comprises animals (such as mammals, birds, reptiles, amphibians, and fishes) typically having a bony or cartilaginous spinal column which replaces the notochord, a distinct head containing a brain which arises as an enlarged part of the nerve cord, and an internal usually bony skeleton and that includes some primitive forms (such as lampreys) in which the spinal column is absent and the notochord persists throughout life