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Cetaceans are members of the class Mammalia, commonly called mammals. The closest living relative of cetaceans is the hippopotamus. As mammals, cetaceans have characteristics that are common to all mammals: They are warm-blooded, breathe in air through their lungs, bear their young alive and suckle them on their own milk, and have hair, although very little of it. Another way of discerning a cetacean from a fish is by the shape of the tail. The tail of a fish is vertical and moves from side to side when the fish swims. The tail of a cetacean – called a fluke – is horizontal and moves up and down, as cetaceans' spines bend in the same manner as a human spine. The order Cetacea includes whales, dolphins and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal," was more general. It comes from Ancient Greek κῆτος (kētos), “whale" or "any huge fish or sea monster." Cetology is the branch of marine science associated with the study of cetaceans. Cetaceans are the mammals most fully adapted to aquatic life. Their body is fusiform (spindle-shaped). The forelimbs are modified into flippers. The tiny hindlimbs are vestigial; they do not attach to the backbone and are hidden within the body. The tail has horizontal flukes. Cetaceans are nearly hairless, and are insulated by a thick layer of blubber. As a group, Cetaceans are noted for their high intelligence. The order Cetacea contains ninety species, all marine except for five species of freshwater dolphins. The order is divided into two suborders, Mysticeti (baleen whales) and Odontoceti (toothed whales, which includes dolphins and porpoises). The classification here closely follows Dale W. Rice, Marine Mammals of the World: Systematics and Distribution (1998), which has become the standard taxonomy reference in the field. There is very close agreement between this classification and that of Mammal Species of the World: 3rd Edition (Wilson and Reeder eds., 2005). Any differences are noted using the abbreviations "Rice" and "MSW3" respectively. Further differences due to recent discoveries are also noted. ORDER CETACEASuborder Mysticeti: Baleen whales Family Balaenidae: Right whales and Bowhead Whale Genus Balaena - Bowhead Whale, Balaena mysticetus
Genus Eubalaena - North Atlantic Right Whale, Eubalaena glacialis
- North Pacific Right Whale, Eubalaena japonica
- Southern Right Whale, Eubalaena australis
Family Balaenopteridae: Rorquals † Genus Eobalaenoptera - † Harrison's Whale, Eobalaenoptera harrisoni
Family Eschrichtiidae Genus Eschrichtius - Gray Whale, Eschrichtius robustus
Family Neobalaenidae: Pygmy Right Whale Genus Caperea - Pygmy Right Whale, Caperea marginata
Suborder Odontoceti: toothed whales Family Delphinidae: Dolphin Family Monodontidae Genus Delphinapterus - Beluga, Delphinapterus leucas
Genus Monodon - Narwhal, Monodon monoceros
Family Phocoenidae: Porpoises Genus Neophocaena - Finless Porpoise, Neophocaena phocaenoides
Genus Phocoena - Spectacled Porpoise, Phocoena dioptrica
- Harbour Porpoise, Phocoena phocaena
- Vaquita, Phocoena sinus
- Burmeister's Porpoise, Phocoena spinipinnis
Genus Phocoenoides - Dall's Porpoise, Phocoenoides dalli
Family Physeteridae: Sperm Whale family Genus Physeter - Sperm Whale, Physeter macrocephalus
Family Kogiidae - MSW3 treats Kogia as a member of Physeteridae Genus Kogia - Pygmy Sperm Whale, Kogia breviceps
- Dwarf Sperm Whale, Kogia sima
Superfamily Platanistoidea: River dolphins Family Ziphidae, Beaked whales
†Extinct |
