Ambulocetus (meaning “walking whale”) was an early cetacean with short limbs and large feet used for swimming. Along with other members ofAmbulocetidae, it is a transitional fossil that shows how whales evolved from land-living mammals. While its name stems from the historical hypothesis that it was capable of walking on land, more recent research suggests that it was fully aquatic like modern cetaceans.

Ambulocetus was probably fully aquatic like modern cetaceans, with a similar thoracic morphology, and it probably swam by undulating its back vertically. Chemical analysis of its teeth shows that it could move between salt and fresh water. It also lacked external ears. Its skull had a long snout and eyes facing sideways (they faced upward in pakicetids), located high on the skull like in modern hippos.

Several features shared with other basal cetaceans indicate the close affinities of Ambulocetus with these animals; it had an adaptation in the nose that enabled it to swallow underwater, and its periotic bone’s structure was like those of whales, enabling it to hear well underwater. In addition, its teeth are similar to those of other early cetaceans.

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Scientific classification

  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Artiodactyla
  • Infraorder: Cetacea
  • Family: †Ambulocetidae
  • Genus: †Ambulocetus
    Thewissen et al., 1994
  • Species: †A. natans

Binomial name

  • Ambulocetus natans