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An ancient four-legged whale with hooves has been discovered, providing new information on how the ancestors of the largest mammals on Earth have made the transition from land to sea.
The giant fossil 42.6 m long, discovered in marine sediments along the coast of Peru, seems to have been adapted to a semi-aquatic lifestyle. His sabotaged feet and the shape of his legs suggest that he would have been able to support the weight of his voluminous body four meters long and walk on land. Other anatomical features, including a powerful tail and webbed feet similar to those of an otter, suggest that it was also a powerful swimmer.
"Whales are this iconic example of evolution," said Travis Park, a former whale expert at the Natural History Museum in London, who did not participate in the latest study. "They've gone from little hoofed mammals to the blue whale we have today. It's so interesting to see how they conquered the oceans. "
Older and smaller four-limbed whale ancestors had been discovered, but the last specimen fills a crucial gap in the knowledge of how creatures evolved and spread in the world's oceans.
"Other examples from this era were more fragmentary, less complete specimens," said Olivier Lambert, a scientist at the Royal Belgian Institute of Natural Sciences and first author of the study. "We had no clear indication on their swimming and walking abilities."
The last specimen proves that the first whales can swim for days, even weeks, while maintaining their ability to move on land.
"Even though he could swim in the water [with] No problem, he still had small clogs on his fingers and toes, "Park said. "It would be much more capable than seals to move on land."
Its pointed teeth and long snout suggest that the first whales may have eaten fish or shellfish.
The location of the latest discovery is also critical. In India and Pakistan, much older ancestors of whales, dating back about 53 million years, have already been discovered. Until now, scientists have questioned when and how whales first dispersed in America and elsewhere.
The Peruvian fossil suggests that the first whales would have crossed the South Atlantic, helped by the west-facing surface currents and by the fact that, at the time, the distance between the two continents was half of what she is today.
The last vertebrae of the tail are missing and it is not clear if the tail of the creature would have featured the large paddle, called moat, which allows some modern whales to propel themselves at a speed greater than 48 km / h . But it must have been a swimmer who had survived for days or even weeks at sea.
The fossil was unearthed in 2011 by an international team composed of members from Peru, France, Italy, the Netherlands and Belgium. He has since been appointed Peregocetus pacificus, meaning "the whale traveler who has reached the Pacific".
According to Lambert, it is likely that whales would first have to return to the ground for certain activities such as mating and calving. The first fully aquatic whales date from about 41 to 35 million years ago. They occupied an ecological niche left vacant when the last marine reptiles, as well as the dinosaurs, were extinct 66 million years ago.
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