Family Physeteridae - Sperm Whale (1 species in 1 genus)
The sperm whale is the largest toothed cetacean and has the highest degree of sexual dimorphism. There is a low dorsal hump, followed by a series of crenulations. It has a large head with a squarish profile, narrow underslung lower jaw, and functional teeth only in the lower jaw (these fit into sockets in the upper jaw). The blowhole is located at the left front of the head. The head is highly modified, and is divided into sections called the “junk” and the spermaceti organ, or “case.” The spermaceti organ is a large oil-filled reservoir, the function of which is controversial. Sperm whales have a dish shape to the facial area of the skull, extreme cranial asymmetry, and a long rostrum. Sperm whales are known to be capable of very deep, long dives.
Genera
Genus Physeter containing 1 species:
Physeter macrocephalus (Sperm whale)