Cetacea of any animal on earth, averaging and in mature males. The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. In some whales, however, it is less than half that of humans: 0.9% versus 2.1%. The sperm whale ("Physeter macrocephalus") is the largest of all toothed predatory animals and possesses the largest brain. The cetacean skeleton is largely made up of cortical bone, which stabilizes the animal in the water. For this reason, the usual terrestrial compact bones, which are finely woven cancellous bone, are replaced with lighter and more elastic
Blue whale penis immature categorized whale was and the smallest penis of a mature whale was . By comparison the average blue whale penis is nearly 3 times the size of that of a sei whale. Specimen measurements indicate that a blue whale measuring in length had a vestigial mammary slit of width and length, with a penis measurement of . In another specimen in which the length of the whale was and weighed 50.9 metric tons, the brain weighed only . The Icelandic Phallological Museum has a portion of a blue whale's penis measuring long and weighing , which "Iceland Review" has