Sperm whales or Physeter macrocephalus are part of the Odontoceti (toothed whales). The Sperm whale is the largest toothed mammal in the world! Like most. Sperm whale description. The sperm whale (Physeter macrocephalus) is the largest of the toothed whales, with males growing up to 20 metres in length. The huge heads of sperm whales contain a large cavity, the spermaceti organ, filled with a waxy liquid called spermaceti oil.