Four-legged prehistoric whale fossil with webbed feet found in Peru

Paleontologists discovered the fossilized bones of a four-legged prehistoric whale with webbed feet, off Peru's western coast in 2011. Even stranger, its fingers and toes had little hooves on them. It possessed razor-sharp teeth that it used to catch fish.

In 2011, paleontologists found a well-preserved fossil of a four-legged amphibious ancestor of whales named Peregocetus pacificus — a discovery that sheds new light on the mammals’ transition from land to the ocean.

Four-legged prehistoric whale fossil with webbed feet found in Peru 1
Peregocetus is a genus of early whale that lived in what is now Peru during the Middle Eocene epoch. Its fossil was uncovered in 2011 in the Yumaque Formation of the Pisco Basin at Playa Media Luna by a team consisting of members from Belgium, Peru, France, Italy, and the Netherlands. © Alberto Gennari / Fair Use

The ancestors of whales and dolphins walked on Earth about 50 million years ago in the regions that now comprise Indian subcontinent.

Paleontologists 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.

This particular new specimen, described in a study published in the April 2019 journal Current Biology, was 42.6 million years old and provided 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.

Four-legged prehistoric whale fossil with webbed feet found in Peru 2
The prepared left mandible of Peregocetus. © Insider

Based on its anatomy, the scientists came to the conclusion that this cetacean of about 13 feet (four meters) long could both walk and swim.

Four-legged prehistoric whale fossil with webbed feet found in Peru 3
Life restoration of Peregocetus resting at a cliff. Peregocetus was essentially a four-legged whale: however, it had webbed feet with small hooves on the tips of its toes, making it more capable of moving on land than modern seals. It featured sharp teeth and a long snout which suggests it fed on fish and/or crustaceans. From its caudal vertebrae, it has been suggested that it might have possessed a flattened tail similar to a beaver. © Wikimedia Commons

According to the lead author Olivier Lambert of the Royal Belgian Institute of Natural Sciences, “part of the tail’s vertebrae showed similarities with that of present-day semi-aquatic mammals like otters.”

“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,” stated Lambert.

Pieces of four-legged whales were previously found in Egypt, Nigeria, Togo, Senegal and Western Sahara, but they were so fragmented that it was impossible to decisively conclude whether they could swim.

“This is the most complete specimen ever found for a four-legged whale outside of India and Pakistan,” said Lambert.

If the whale in Peru could swim like an otter, the researchers hypothesized that it likely crossed the Atlantic from the western coast of Africa to South America. As a result of continental drift, the distance was half that of today, around 800 miles, and the east-west current of the time would have facilitated their travel.

This finding would make less likely another hypothesis according to which whales reached North America via Greenland.

The Pisco Basin, off Peru’s southern coast, likely holds numerous fossils, given its excellent conditions for preservation. Paleontologists assume that “they have work for at least the next 50 years.”

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