Whales are divided into two suborders; the toothed whales, or Odontoceti, and baleen whales, or Mysticeti. The sperm whale (Physeter macrocephalus or Physeter catodon) is the largest of all toothed whales. The sperm whale has 20 to 26 teeth on each side of its lower jaw. The teeth are cone-shaped and weigh up to 1 kilogram (2.2 lb) The purpose of the teeth is unknown. Teeth do not appear to be necessary for capturing or eating squid, and well-fed sperm whales have been found in the wild without teeth. One hypothesis is that the teeth are used in aggression between males. Bull sperm whales often show scars which seem to be caused by the teeth of other bulls. Rudimentary teeth are also present in the upper jaw, but these rarely emerge into the mouth.