W hales belong to the scientific order Cetacea. Other well-known members of this mammalian order include dolphins, porpoises, killer whales, sperm whales, baleen whales and narwhals. These two suborders of modern whales are distinct from one another in the structure and function of the mouths. Some odontocetes, such as the Sperm Whale , have teeth only in the lower jaw. The most well-known of the toothed whales, the Orca , or killer whale, has large teeth in both upper and lower jaws.
Cetaceans tend to live in social groups and have relatively large brains.
Altogether, there are now about 75 species of cetaceans, divided into eleven families.