Ancient four-legged whale from Peru walked on land, swam in sea

Cheryl Sanders
April 6, 2019

A fossilized whale with four legs, webbed feet and hoofed toes is revealing new details about the evolution and geographical spread of whales across the globe.

The discovery of the remains of an ancient, four-legged whale along the coast of Peru suggests the earliest cetaceans arrived in the Americas at least 42 million years ago. Until now, the researchers believed that the first whales evolved in South Asia approximately 50 million years ago.

In the paper, the team, led by Olivier Lambert, of the Royal Belgian Institute of Natural Sciences, say Peregocetus measured 13 foot in length and had small hooves on the tips of what would have been its feet. The whale ancestor may have propelled itself through water by swimming in a similar manner, according to the researchers, though they note that the last tail vertebrae hasn't been found yet.

The skeleton shows that the whale would have been at home on the land and in water. Image credits Lambert et al.  Current Biology
The skeleton shows that the whale would have been at home on the land and in water. Image credits Lambert et al. Current Biology

According to Lambert, it is likely that whales would initially have had to return to land for certain activities such as mating and giving birth to young.

Lambert said they now plan to continue searching for more specimens in Peru's Pisco Basin: "Maybe we will find the skull of Peregocetus, and geologically older amphibious whales", he said.

Top image: What Peregocetus, the legged ancient whale might have looked like. Reaching the western coast of South America, Peregocetus is now the oldest species of whale to make it to the Americas. The newly discovered ancient four-legged whale which was unearthed from Peru, suggests that early whales managed to migrate from South Asia to South America, and then to North America.

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

As they spent longer in the water, their legs evolved into flippers - while their noses developed into the blow holes found in the top of whales' heads.

"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", added. How and when the animals came to America, was among the scientists in dispute. At the time, the distance between the continents was only about half as much as it is today, and currents running between them may have facilitated the crossing.

Once in South America, Peregocetus settled in the Pacific waters along the Peruvian coast, eventually moving into North America. Its fossil has now been found on the coastal plains of Peru, which are well known for their rich deposits of ancient marine fossils.

Over millennia, the pelvic bones uncoupled from the spine to enable more efficient swimming, while increased time in buoyant, gravity-easing water reduced the allocation of evolutionary resources to strong, weight-bearing legs.

"They went from small hoofed mammals to the blue whale we have today", Travis Park, a postdoctoral fellow at the Natural History Museum who studies cetacean evolution and was not involved in the recent study, tells the Guardian's Hannah Devlin.

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