Evolutionary History

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About 65 million years ago (mya) when dinosaurs became mostly extinct, marine mammals began to evolve from their land-dwelling ancestors. Their evolution into sea-dwelling mammals is thought to be a result of the availability of new marine food sources and a way to escape from their terrestrial predators.

Marine mammals evolved from land mammals over millions of years, and their evolution is characterized by a number of key features:
  • Multiple Origins
Each group of marine mammals evolved from a different group of land mammals, including carnivores, artiodactyls, and proboscideans. 
  • Convergent Evolution
Despite their different origins, marine mammals have evolved similar features, such as streamlined bodies, paddle-like limbs, and tails. 
  • Complex Adaptations
Marine mammals have evolved complex adaptations to their new marine environment, including changes to their reproductive physiology, structure, and behavior. 
  • Transition from land to water
The transition from land to water was aided by the availability of new food sources and the need to escape predators. 
  • Intermediate Fossils
A series of intermediate fossils document the transition from land to water, including the remains of Ambulocetus natans, which had strong legs and a tail but lacked flukes.

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