The sperm whale superfamily, called Physteroidea, includes only 3 living species; the sperm whale, the dwarf sperm whale and the pygmy sperm whale. Sperm whales are in a different genus than their smaller counterparts, but all three species share some similar features that are unique to this superfamily. All members of this group have relatively small and thin, under-slung lower jaws and simple teeth. Teeth may not erupt or may even be absent from the upper jaw. They have asymmetrical nasal bones, with a single blowhole on the top left of their heads. They also have a spermaceti organ; an organ unique to this group that is filled with a waxy, semi-liquid white substance called spermaceti which may serve as ballast for diving and aid in buoyancy control. 

Sperm Whale Species

The sperm whale is the largest odontocete species. It is also the most sexually dimorphic cetacean, with females growing to only 11 m long and 13,607 kg while males grow up to 16 m long and weighing up to 40,823 kg. Their lifespan is unknown, but females stop growing after 30 years and males after 50. They are a cosmopolitan species, inhabiting the deep water of all oceans between 60°N and 60°S. Their diet includes large squid (usually between 0.1 and 10 kg), sharks, skates and fish. They make long, deep foraging dives averaging 35 minutes and 400m deep. Sperm whales are capable of diving for over an hour and to depths greater than 2,000 m.

Sperm whales have the largest brain of any animal living today. The average weight of adult male sperm whales brain is 7.8 kg, and their heads comprise 25–35% of their total body length. Different populations exhibit different cultures, and many form tight social bonds. In the tropics, an average family unit typically includes 12 females and their young. At the ages of 4–21, males may leave their families and form "bachelor schools". The largest males are often found around polar pack ice, alone.

Their predators include humans, orcas and sharks. They are sometimes harassed by pilot whales, but it is not known if this harassment is lethal. Sperm whales are hunted in Lembata. Threats to the sperm whale include ship strikes, entanglement in fishing gear, anthropogenic noise (particularly in areas of oil and gas exploration), and pollution.