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
Whale lungs can hold about 5,000 litres of air. Spout shapes differ among species, which facilitates identification. The heart of a whale weighs about 180–200 kg. It is 640 times bigger than a human heart. The heart of the blue whale is the largest of any animal, and the walls of the arteries in the heart have been described as being "as thick as an iPhone 6 Plus is long". All whales have a thick layer of blubber. In species that live near the poles, the blubber can be as thick as 11 inches. This blubber can help with buoyancy (which