Portal:Cetaceans/Intro
Cetacea (/sɪˈteɪʃə/; from Latin cetus 'whale', from Ancient Greek κῆτος (kêtos) 'huge fish, sea monster') is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel themselves through the water with powerful up-and-down movements of their tail, which ends in a paddle-like fluke, using their flipper-shaped forelimbs to steer.
While the majority of cetaceans live in marine environments, a small number reside solely in brackish or fresh water. Having a cosmopolitan distribution, they can be found in some rivers and all of Earth's oceans, and many species migrate throughout vast ranges with the changing of the seasons.
Cetaceans are famous for their high intelligence, complex social behaviour, and the enormous size of some of the group's members. For example, the blue whale reaches a maximum confirmed length of 29.9 meters (98 feet) and a weight of 173 tonnes (190 short tons), making it the largest animal ever known to have existed.
There are approximately 90 living species split into two parvorders: the Odontoceti or toothed whales, which contains 75 species including porpoises, dolphins, other predatory whales like the beluga and sperm whale, and the beaked whales and the filter feeding Mysticeti or baleen whales, which contains 15 species and includes the blue whale, the humpback whale and the bowhead whale, among others. Despite their highly modified bodies and carnivorous lifestyle, genetic and fossil evidence places cetaceans within the even-toed ungulates, most closely related to hippopotamus. (Full article...)