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Which animals belong to the order Cetacea?

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Illustration showing various cetaceans, including baleen whales like the blue whale, fin whale, humpback whale, gray whale, sei whale, northern right whale, and bowhead whale, as well as toothed whales such as the sperm whale, narwhal, beluga, Baird's beaked whale, killer whale, dolphins, and porpoises. Each species is labeled with its scientific name and typical or maximum length, with a size scale in the corner for reference. — cetacean Whales (order Cetacea).

The order Cetacea comprises an entirely aquatic group of mammals that includes whales, dolphins, and porpoises. While they were historically and incorrectly grouped with fishes due to their body shape, they are true mammals that breathe air, give birth to live young, produce milk, and possess hair.12

Taxonomically, modern cetaceans are divided into two primary suborders based on their feeding structures:3

Baleen whales (suborder Mysticeti): This group includes species such as the blue whale, humpback whale, gray whale, and various rorquals.1
Toothed whales (suborder Odontoceti): This diverse group includes dolphins, porpoises, sperm whales, killer whales, belugas, narwhals, and beaked whales.41

The order also includes extinct lineages, such as the genus Basilosaurus and Pakicetus, which provide insight into the evolutionary history of these marine mammals.1