Cetacea - Taxonomy

Taxonomy

The order Cetacea contains about 90 species, all marine except for 4 species of freshwater dolphins. The order contains two suborders, Mysticeti (baleen whales) and Odontoceti (toothed whales, which includes dolphins and porpoises). The species range in size from Commerson's dolphin, smaller than a human, to the Blue Whale, the largest animal ever known to have lived.

Cetaceans are mammals, that is, members of the class Mammalia. Their closest living relatives are the even-toed ungulates, such as the hippopotamus and deer.

Mammalian characteristics include warm-bloodedness, breathing air through their lungs, and suckling their young, and growing hair, although very little of it.

Another way of distinguishing a cetacean from a fish is the shape of the tail. Fish tails are vertical and move from side to side when the fish swims. Cetacea tails—called a fluke—are horizontal and move up and down, because cetacea spines bend in the same manner as a human spine.