Definition: The order of marine mammals that includes toothed whales and toothless, filter-feeding (baleen) whales. Cetaceans are a unique and highly-specialized group of mammals with hairless bodies, flipper like forelimbs, and reduced back limbs that are located within the body wall (since these back limbs are no longer used they are considered to be vestigal).
The toothed whales (Suborder Odontoceti) are a diverse group, making up more than 90% of all cetaceans. Toothed whales include porpoises, dolphins, river dolphins, sperm whales, beaked whales, and white whales.
Filter feeding whales (also known as baleen whales, Suborder Mysticeti) include the northern right whale, gray whale, bowhead, fin whale, blue whale, humpback whale, minke whale, and others.
The term cetacean is used in a general sense to refer to a dolphin, a whale, or a porpoise.
