Dolphins Are Whales, Just Not the Giant Kind You Picture

Dolphins are whales too: they belong to the toothed-whale group, which means whale is the broader category and dolphin is a more specific one.

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Dolphins may look very different from the huge whales people usually picture, but scientifically they are part of the whale family tree. Whales, dolphins, and porpoises are cetaceans, a group of aquatic mammals that breathe air, give birth to live young, and nurse them with milk. Modern cetaceans are divided into two major living groups: baleen whales and toothed whales. Dolphins belong to the toothed-whale group. The group includes familiar dolphins as well as porpoises, sperm whales, beaked whales, and several other toothed cetaceans. The oceanic dolphin family also includes orcas, which are the largest members of the dolphin family. So the everyday distinction between a dolphin and a whale is not the same thing as their biological classification. Dolphin is a more specific name nested within the broader whale and cetacean grouping. This is a useful example of how common names can make animal relationships seem more separate than they really are. The modern whale lineage evolved from land-dwelling mammals more than 50 million years ago, eventually producing the diverse cetaceans living in oceans and some rivers today. The result is a group that ranges from tiny toothed cetaceans to the enormous baleen whales, with dolphins occupying one branch of that larger evolutionary story.

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