Ancient four-legged whale with webbed feet and toe hooves discovered in Peru

Peregocetus
© Artistic reconstruction of two individuals of Peregocetus, one standing along the rocky shore of modern Peru and the other preying upon sparid fish. (A. Gennari)

A skeleton of the bizarre land-walking whale provides answers about how whales first spread around the world.

So here's a doozy: Cetaceans (the group that includes whales and dolphins) originated in south Asia more than 50 million years ago from small, four-legged, hoofed mammals the size of a dog. Named Pakicetus and hailing from what is now Pakistan, the animals had components of the inner ear now found only in cetaceans. Ladies and gentleman, allow us to present the “first whale.”

But this isn't a story about Pakicetus. A lot about the strange evolution of whales is already well known, but what is less understood is how they got from Pakistan and India to the rest of the world. Now, the discovery of an ancient whale skeleton in Peru is providing some answers.

The bones were found in 42.6-million-year-old marine sediments along the coast of Peru. The wacky four-legged whale had small hooves on the tip of its fingers and toes, and its hip and limbs morphology all point to the belief that the whale walked on land. But that's not all it could do: Anatomical features of the tail and feet, including long, likely webbed appendages, similar to an otter, indicate that it was a good swimmer too, say the researchers.

"This is the first indisputable record of a quadrupedal whale skeleton for the whole Pacific Ocean, probably the oldest for the Americas, and the most complete outside India and Pakistan," says Olivier Lambert of the Royal Belgian Institute of Natural Sciences.

The discovery came about when study co-author Mario Urbina of Museo de Historia Natural-UNMSM, Peru, found a site he presumed would be fruitful for fossils in the coastal desert of southern Peru. In 2011, an international team arranged a field expedition, during which they uncovered the remains of this ancient whale they've since named Peregocetus pacificus, meaning, "the traveling whale that reached the Pacific."

"When digging around the outcropping bones, we quickly realized that this was the skeleton of a quadrupedal whale, with both forelimbs and hind limbs," Lambert says.

whale boines© Bones of Peregocetus, including the mandible with teeth, scapula, vertebrae, sternum elements, pelvis, and fore- and hind limbs. (G. Bianucci)

The sediment layers dated the whale to the middle Eocene, 42.6 million years ago. The geological age of the whale and its location on the western coast of South America are strong evidence for the hypothesis that early cetaceans reached the New World across the South Atlantic, from the western coast of Africa to South America, the researchers report.

"The whales would have been assisted in their travel by westward surface currents and by the fact that, at the time, the distance between the two continents was half what it is today," they say. After having reached South America, the amphibious whales likely migrated northward, finally reaching North America.

This video explaining the research has some excellent visuals to help explain the discovery and its significance.

So there you have it. From a dog-like mammal with whale ears to a four-legged creature with webbed feet and toe hooves to the majestic marine mammals we know and love today, the whale's journey has been a long and fascinating one. For now, the team is studying the remains of other whales and dolphins from the area, and plans to look further for even older cetaceans in Peru.

"We will keep searching in localities with layers as ancient, and even more ancient, than the ones of Playa Media Luna, so older amphibious cetaceans may be discovered in the future," Lambert says.

Given how different whales were 50 million years ago, one can only imagine what they might become in another 50 millions years. I'm secretly hoping they come back on land to rule the world.

You can see the full research in Current Biology.

Ancient four-legged whale with webbed feet and toe hooves discovered in Peru
A skeleton of the bizarre land-walking whale provides answers about how whales first spread around the world.

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