Cetacea is a scientific order of large aquatic mammals that have forelimbs modified into flippers, a horizontally flattened tail, one or two nostrils at the top of the head for breathing, and no hind limbs. Cetaceans include all whales, dolphins, and porpoises.
The word "cetacean" is derived from the Greek word for whale, kētos.
Living cetaceans are further divided into two suborders: the Odontoceti (toothed whales) and the Mysticeti (baleen whales).
Suborder - Odontoceti
Odontoceti is a scientific suborder of whales characterized by having teeth and a single blowhole. The word "Odontoceti" comes from the Greek word for tooth, odontos.
Odontoceti are characterized by having teeth.
Scientists group most dolphins in the scientific family Delphinidae, part of the suborder Odontoceti. Delphinids (at least 36 species of ocean dolphins) include such well known dolphins as bottlenose dolphins and common dolphins, as well as pilot whales and killer whales.
bottlenose dolphin, Tursiops truncatus
short-finned pilot whales, Globicephala macrorhynchus
killer whale, Orcinus orca
Scientists believe that early whales arose 50 million years ago from (now extinct) primitive mammals that ventured back into the sea. Two small rod-shaped pelvic bones, buried deep in the body muscle of toothed whales, may be remnants of the hind limbs of these primitive mammals.