WHALES: FROM LAND TO SEA
Early whales plied the shallows but still hauled themselves onto shore, probably to rest and to give birth. The fossil record tracks anatomical changes as whales adapted to conditions that favored a fully marine mammal. Modern whales appeared about 34 million years ago. Only selected whales are shown—these don't represent a "straight line" in evolution, but a sampling of some of the genera that existed.
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Mariel Furlong and Amanda Hobbs, NGM Staff; Art: John Burgoyne; Source: Philip D. Gingerich, University of Michigan