ODONTOCETES

	Skeletons of two dolphins, the Indo-Pacific Hump-Backed Dolphin (top, Sousa chinensis) and Risso's Dolphin (Grampus griseus). Redrawn from Howell (1930)

Odontocetes (toothed whales) include dolphins and porpoises and larger whales such as sperm whales. Most odontocetes live in the ocean. There are coastal and deep sea species, some are tropical and and others polar. Odontocetes are active hunters whose prey may include fish, squid (sperm whale), or sealions and other cetaceans (killer whale). Unlike mysticetes, odontocetes have teeth and echolocate; they emit high frequency sounds and determine shapesin their environment by listening to the reflections of these sounds. The extant families in the suborder Odontoceti, each have their own unique specializations. Among the most interesting odontocetes are the platanistoid river dolphins who inhabit the rivers of South Asia, South America, and China. They are derived from marine odontocetes. The largest odontocete is the sperm whale. The oldest odontocete is approximately 40 million years old and is derived from Eocene Cetaceans.

Characters of Modern Odontocetes

Simple conical or spatulate teeth
An organ called the melon on the forehead through which echolocation sounds are emitted
Ear bones adapted for reception of high frequency sound
Bones from the front of the skull moved to the back (telescoped)

	Killer whale Orcinus orca Length up to 31 feet (10 meters) Weight up to 9 tons (8200 kg)
	Sperm whale Physeter macrocephalus Length up to 60 feet (19 meters) Weight up to 50 tons (45,000 kg)

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