WASHINGTON: Paleontologists have found a well-preserved fossil of a four-legged amphibious ancestor of whales, a discovery that sheds new light on the mammals' transition from land to the ocean.
The ancestors of whales and dolphins walked on Earth about 50 million years ago in the regions that now comprise India and Pakistan.
Paleontologists have previously found partial fossils of the species in North America that were 41.2 million years old suggesting that by this time, the cetaceans had lost the ability to carry their own weight and walk the Earth.
The new specimen, described in a study published Thursday in the journal Current Biology, is 42.6 million years old and provides fresh information on the evolution of cetaceans.
The fossil was found about 0.6 miles (one kilometer) inland from Peru's Pacific coast, at Playa Media Luna.
Its mandibles grazed the desert soil and during excavations, the researchers found the lower jaw, teeth, vertebrae, ribs, parts of front and back legs, and even the whale ancestor's long fingers that were likely webbed.
Based on its anatomy, the scientists say this cetacean of about 13 feet (four meters) long could both walk and swim.
"Part of the tail's vertebrae showed similarities with that of present-day semi-aquatic mammals like otters," lead author Olivier Lambert of the Royal Belgian Institute of Natural Sciences told AFP.
"This would therefore have been an animal that would have started to make growing use of its tail to swim, which differentiates it from older cetaceans in India and Pakistan."