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Ancient four-legged whales knew how to hoof it — on land By Hannah Devlin, The Guardian, adapted by Newsela staff on 04.15.19 Word Count 560 Level 1210L The latest fossil proves that early whales could swim for days or possibly weeks at a time while retaining their ability to rove around on land. Photograph: A. Gennari/CellPress Scientists have discovered the remains of an ancient four-legged whale with hooves. The find provides new insights into how the ancestors of the Earth's largest mammals made the transition from land to sea. The giant 42.6-million-year-old fossil was discovered in marine sediments along the coast of Peru. It appears to have adapted to a semi-aquatic lifestyle. Its hoofed feet and the shape of its legs suggest it would have been capable of bearing the weight of its bulky 13-foot-long body and walking on land. Other anatomical features, including a powerful tail and webbed feet similar to an otter, suggest it was also a strong swimmer. "Whales are this iconic example of evolution," said Travis Park, an ancient whale expert at the Natural History Museum in London, England, who was not involved in the latest study. "They went from small hoofed mammals to the blue whale we have today. It's so interesting to see how they conquered the oceans." This article is available at 5 reading levels at https://newsela.com. Older and smaller whale ancestors with four limbs had been discovered previously. However, the latest specimen fills in a crucial gap in knowledge about how the creatures evolved and spread throughout the world's oceans. "Other examples from this time were more fragmentary, less complete specimens," said Belgian scientist Olivier Lambert, who led the team that made the latest discovery. "We didn't have a clear indication about their swimming and walking abilities." On Land, And At Sea The latest specimen proves that early whales had it both ways. They could swim for days or possibly weeks at a time while retaining their ability to rove around on land. "Even though it could swim in the water with no problem, it still had little hooves on its fingers and toes," said Park. "It'd be a lot more capable than seals at getting around on land." Its sharp teeth and long snout suggest the early whales may have eaten fish or crustaceans. The location of the latest discovery is also critical. Previously, far older whale ancestors dating to about 53 million years ago have been discovered in India and Pakistan. Until now scientists have disputed when and how whales first dispersed to the Americas and beyond. The Peruvian fossil suggests the first whales crossed the South Atlantic. They would have been helped by westward surface currents and the fact that, at the time, the distance between the two continents was half what it is today. Did They Have Flukes? The fossil is nearly complete. However, the last few tail vertebrae are missing, so it's not clear if the creature's tail featured the large paddle, known as a fluke, that allows some modern whales to power themselves along at speeds of more than 30 miles per hour. In any case, it must have been an accomplished swimmer to have survived for days or even weeks at sea. The newly discovered species of whale has been named Peregocetus pacificus, meaning "the traveling whale that reached the Pacific." 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. The first fully aquatic whales emerged around 41 to 35 million years ago, and became the new kings of the sea — a position once held by the marine reptiles, who became extinct 66 million years ago, along with the dinosaurs. This article is available at 5 reading levels at https://newsela.com.