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 separates cyclostomes from others; absence of limbs separates fishes from the remaining; absence of osseous skeleton separates chondrichthian (cartilaginous) fishes from osteichthyes; absence of impermeable skin separates amphibians from the terrestrial vertebrates; absence of warm blood (homeothermic body) separates reptiles from birds and mammals; absence of mammary glands and hair separates birds from mammals.
