Vertebrate

A vertebrate is a member of the animal kingdom that has a spinal column. The classes of vertebrates are:


 * Fish - a vague grouping that includes several distinct classes; the Chondrichthyes (including sharks) and the actinopterygii (ray-finned fishes).
 * Amphibians - the first vertebrates to develop true legs and live on the land; most still have to return to the water to breed.
 * Reptiles - distinguished from amphibians by their ability to withstand dry conditions and to breed on land by means of shelled eggs. The reptile class is possibly a redundant group according to cladistics.
 * Birds - the only class with feathers; their fossil record indicates they evolved from the dinosaurs.
 * Mammals - they have fur and suckle their young.