What are the six criteria used to build a complete evolutionary branch of vertebrates?
Dichotomy in each of the six following criteria builds the vertebrate evolutionary branch: absence of mandibles divides cyclostomes from others; absence of limbs divides fishes from the remaining; absence of osseous skeleton divides chondrichthian (cartilaginous) fishes from osteichthyes; absence of impermeable skin divides amphibians from the terrestrial vertebrates; absence of warm blood (homeothermic body) divides reptiles from birds and mammals; absence of mammary glands and hair divides birds from mammals.