vertebrate: also called craniata, an animal derived from the phylum: chordates, sub-phylum vertebrata, having a backbone and bony skull that partly encloses a central nervous system. The hollow, dorsal nerve tube is now replaced by the spinal cord, which is now protected by a segmented vertebral, or spinal, column, composed of cartilage and/or bone. The head and brain house paired sense organs, that coordinate movement and sensation. Fish were the first vertebrates. Sub-phylum vertebrata includes 8 classes, including 4 classes of fish (including agnatha, chondrichthyes, and osteichthyes), and the additional classes: amphibia, reptilia, aves (birds), and mammalia (Anthro.Palomar.edu).