Whales, dolphins and porpoises
Whales, dolphins and porpoises belong to the order Cetacea. These are aquatic mammals that have streamlined bodies evolved for swimming. Their hind limbs have become vestigial as part of this streamlining. All whales, dolphins and porpoises are cetaceans, including the biggest animal ever to have lived - the blue whale.
Featured in the following Radio programmes
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Catch Up
Nature: Series 3, The Sea of Cortez
Tessa McGregor explores the Sea of Cortez, a whale and dolphin hotspot off Mexico.
Family
Dolphins, killer whales and allies (Delphinidae)Dolphins, killer whales and pilot whales make up the Delphinidae, which is the largest family of cetaceans. They travel in groups, known as pods, and are renowned for their intelligence.
Eschrichtiidae
Grey whale (species)Monodontidae
Beluga whale (species)
Rorquals (Balaenidae)Rorquals are one of the types of baleen whale, and include the blue whale - the largest animal ever to have lived - in their number. The smallest rorqual is the minke whale.
Earth News
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Hearing clue to whale evolution
The evolution of whales from four-legged land dwellers into streamlined swimmers has been traced in fossilised ears, the journal Nature reports.
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Whale 'missing link' discovered
The whale is descended from a deer-like animal that lived 48 million years ago, according to fossil evidence.
More news stories
About
The order Cetacea (pronounced /sɨˈteɪʃ(i)ə/, L. cetus, whale, from Greek) 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), meaning "whale" or "any huge fish or sea monster". In Greek mythology the monster Perseus defeated was called Ceto, which is depicted by the constellation of Cetus. Cetology is the branch of marine science associated with the study of cetaceans.
Cetaceans are the mammals best 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, they are noted for their high intelligence.
The order Cetacea contains about ninety species, all marine except for four species of freshwater dolphins. The order is divided into 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 known to have lived.
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Scientific Classification
Order: Cetacea
Other Mammalia
- Anteaters and sloths (Pilosa)
- Bats (Chiroptera)
- Carnivora
- Dasyuromorphia (family: Dasyurid marsupials)
- Dugongs and manatees (Sirenia)
- Even-toed ungulates (Artiodactyla)
- Hares, rabbits and pikas (Lagomorpha)
- Kangaroos, possums and allies (Diprotodontia)
- Monotremata (species: Platypus)
- Perissodactyla (family: Rhinoceroses)
- Primates
- Rodents (Rodentia)
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