Dolphin

Informal classification of marine mammals, closely related to whales and porpoises

A dolphin is any one of the 40 extant species of aquatic mammal from the cetacean families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the brackish dolphins), and the probably extinct Lipotidae (baiji or Chinese river dolphin). All these families belong to the parvorder Odontoceti, i.e., toothed whales, which also include the closely related families Monodontidae (beluga and narwhal) and Phocoenidae (porpoises), as well as the more distant families Physeteroidea (sperm whales) and Ziphiidae (beaked whales). Dolphins range in sizes from the human-sized 1.7-metre-long (5 ft 7 in) and 50-kilogram (110-pound) Maui's dolphin; to the 9.5 m (31 ft) and 10-tonne (11-short-ton) apex predator, the orca.

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