Living sperm whales are found in all the world's oceans from the tropics to chilly polar waters. They consist of the familiar giant sperm whale, Physeter macrocephalus, and the less familiar dwarf sperm whale, Kogia sima, and pygmy sperm whale, Kogia breviceps. The giant sperm whales are the largest living toothed whales, reaching body lengths of 11 meters (36 feet) for females and 15-20 meters (50-65 feet) for males. They are famous for deep dives and battles with giant and colossal squid, although much smaller squid make up the majority of its diet. Both dwarf and pygmy sperm whales are considerably smaller, reaching lengths of 2.7 and 3.5 meters (9 and 11.5 feet) respectively. Both species have shorter dives, and feed at middle-level depths.
These three whale species share many anatomical and behavioral features including having teeth restricted to the mandible but usually not in the upper jaw and a spermaceti organ. The spermaceti organ is large and sack-like, located in the forehead above the upper jaws and is filled with waxy material. The organ is thought to help amplify the whale's vocalization; the clicks of giant sperm whales are the loudest of all animal sounds. The spermaceti organ extends above and in front of the upper jaws, making the face to appear very tall. Additionally, the diet of all three species is focused largely on squid, although they also take fish and crustaceans.
Sperm whales are the only living members of the clade (group) Physeteroidea, which is itself part of the toothed whale evolutionary radiation, Odontoceti. Toothed whales consist of the physeteroids, the beaked whale clade Ziphioidea, and a broad and diverse dolphin clade, Delphinoidea. The beaked whales are generally rare and poorly known oceanic species that have a large number of excellent deep divers. Their jaws are made up of particularly dense bone and resemble beaks. The delphinoids not only contain the river and oceanic dolphins, but porpoises, narwhals, belugas, pilot whales, and orcas or killer whales. Like the beaked whales, they tend to have jaws extending in front of their foreheads, making them look superficially beak-like as well.