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Whales & Dolphins

Cetacea

Cetaceans (order Cetacea) are an entirely aquatic group of mammals that includes whales, dolphins, and porpoises. Living cetaceans are commonly divided into baleen whales (Mysticeti) and toothed whales (Odontoceti); dolphins and porpoises are toothed whales. Most cetaceans live in the ocean, but a few (notably some dolphins) live in freshwater rivers. Fossil and genetic evidence shows cetaceans evolved from land-dwelling mammals related to today’s hippos more than 50 million years ago (Eocene). Today, cetaceans, along with sirenians (manatees and dugongs), are among the mammals most fully adapted to life in water: they are obligately aquatic (unable to live on land) but must still surface to breathe air.

Cetaceans (order Cetacea) are an entirely aquatic group of mammals that includes whales, dolphins, and porpoises. Living cetaceans are commonly divided into baleen whales (Mysticeti) and toothed whales (Odontoceti); dolphins and porpoises are toothed whales. Most cetaceans live in the ocean, but a few (notably some dolphins) live in freshwater rivers. Fossil and genetic evidence shows cetaceans evolved from land-dwelling mammals related to today’s hippos more than 50 million years ago (Eocene). Today, cetaceans, along with sirenians (manatees and dugongs), are among the mammals most fully adapted to life in water: they are obligately aquatic (unable to live on land) but must still surface to breathe air.