ambulocetus hunting black-backed butterflyfish in the ocean

ambulocetus natans whale cetacean early walking aquatic semiaquatic animal mammal pakistan india eocene epoch era period age otterlike ancestor ancient tethys sea warm coastal waters shallow seas brackish rivers amphibious lifestyle flipperlike hind feet webbed crocodilelike snout creature themes vertebrate organism primitive primeval prehistoric genus species wildlife wild blackbacked butterflyfish fish chaetodon melannotus nature ocean saltwater indopacific area underwater undersea marine reef life tropical rendering hunting black-backed modern day walk land hunt prey