Old four-legged whale with characteristics similar to those of an otter found on the coast of Peru

Cetaceans, a group consisting of whales and dolphins, are native to Southeast Asia, more than 50 million years ago, from a small ancestor on all fours and hooves. Today, researchers have announced the discovery of an ancient four-legged whale, found in marine sediments 42.6 million years old along the coast of Peru, which allows to better understand the evolution and dispersion of whales around the world. The results are reported in the newspaper Current biology April 4th.

The anatomy of the ancient whale

The presence of small hooves at the fingertips and toes of the whale and the morphology of his hips and limbs suggests that this whale could walk on land, according to the researchers. On the other hand, they say that the anatomical features of the tail and feet, including long webbed appendages that may look like an otter, indicate that he was also a good swimmer.

According to Olivier Lambert of the Royal Belgian Institute of Natural Sciences.

"This is the first indisputable record of a quadruped whale skeleton for the whole Pacific Ocean , probably the oldest of the Americas and the most complete outside India and Pakistan. "

This figure shows the bones of Peregocetus, the ancient whale, including the toothed mandible, scapula, vertebrae, sternum elements, pelvis, anterior limbs and hind limbs. (G. Bianucci / Cell press / fair use )

The area where the ancient whale was discovered

A few years ago, Mario Urbina, co-author of the Museo de Historia Natural-UNMSM in Peru, discovered a promising area for digging fossils in the coastal desert of southern Peru, called Playa Media Luna. In 2011, an international team, including members from Peru, France, Italy, the Netherlands and Belgium, organized a field expedition during which they searched the remains of the country. an ancient whale that they have since named Peregocetus pacificus. It means "the traveling whale that has reached the Pacific".

"Digging around the flush bones, we quickly realized that it was the skeleton of a quadruped whale, with its forelegs and hind limbs," Lambert said.

Retained parts of the skeleton of Peregocetus pacificus, the ancient whale. (G. Bianucci / Cell press / fair use )

With the aid of microfossils, the sediment layers in which the skeleton was placed date precisely from the middle Eocene, 42.6 million years ago. The anatomical details of the skeleton allowed them to infer that the animal was able to maneuver its large body (up to 4 meters long, tail included), both on land and in l & # 39; water. For example, the characteristics of the caudal vertebrae (in the tail) are reminiscent of those of beavers and otters, suggesting a significant contribution of the tail during swimming.

Where did the old whale come from?

The geological age of the new four-branched whale and its presence along the west coast of South America strongly support the hypothesis that primitive cetaceans would have reached the New World through the Atlantic South, from the west coast of Africa to South America, researchers reported. The whales would have been helped in their journey by the west surface currents and by the fact that at the time, the distance between the two continents was half of what it is today. The researchers suggest that it was only after reaching South America that amphibious whales migrated north to finally reach North America.

Distribution of protocol whales during the middle Eocene, period of the ancient whale. (G. Bianucci / Cell press / fair use )

The international team continues to study the remains of other whales and dolphins of Peru. "We will continue to search in areas as old and even older as Playa Media Luna, so that older amphibian cetaceans can be discovered in the future," Lambert said.

Top image: What would Peregocetus, the old legged whale, look like? Source: © Alberto Gennari 2018 / Cell press (Fair use)

The article titled "Old four-legged whale with otter-like features found along the coast of Peru" was originally published in Science Daily.

Source: Cell Press. " Old four-legged whale with otter-like features found along the coast of Peru "ScienceDaily. ScienceDaily. April 4, 2019.