<P> Animals are divided by body plan into vertebrates and invertebrates . Vertebrates -- fishes , amphibians , reptiles , birds , and mammals -- have a vertebral column ( spine ) ; invertebrates do not . All vertebrates and most invertebrates are bilaterally symmetrical ( Bilateria ) . Invertebrates include arthropods , molluscs , roundworms , ringed worms , flatworms , and other phyla in Ecdysozoa and Spiralia . Echinoderm larvae are initially bilaterally symmetrical , but later as adults develop radial symmetry ; Cnidarians are radially symmetrical ; ctenophores are biradially symmetrical ; and sponges have no symmetry . </P>
distinctive characteristics of animals classified as vertebrates include
have a vertebral column