Cetacea Cetacea Cetacea () is a widely distributed and diverse clade of aquatic mammals that today consists of whales, dolphins, and porpoises. Cetaceans are carnivorous and finned. Most species live in the sea, some in rivers. The name is derived from the Latin "cetus" "whale", itself from the Greek κῆτος "kētos" "huge fish". There are around 89 extant species, which are divided into two groups or parvorders, the Odontoceti or toothed whales, a group of more than 70 species that includes the dolphins, porpoises, belugas, narwhals, sperm and beaked whales, and the Mysticeti or baleen whales, of which there are now
Toothed whale dolphins. Toothed whales consist of some of the most widespread mammals, but some, as with the vaquita, are restricted to certain areas. Odontocetes feed largely on fish and squid, but a few, like the killer whale, feed on mammals, such as pinnipeds. Males typically mate with multiple females every year, but females only mate every two to three years, making them polygynous. Calves are typically born in the spring and summer, and females bear the responsibility for raising them, but more sociable species rely on the family group to care for calves. Many species, mainly dolphins, are highly sociable, with