Fossilized four-legged whale once swam like an otter | Science News

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Peruvian fossils yield a four-legged otterlike whale with hooves

The find is the oldest whale skeleton in the New World

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3:22pm, April 5, 2019
Peregocetus pacificus

BY LAND AND BY SEA  The newly described Peregocetus pacificus (illustrated) had feet optimized for swimming and walking — though its long toes might not have made the animal a great runner.

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An ancient four-legged whale walked across land on hooved toes and swam in the sea like an otter.

The newly discovered species turned up in 2011 in a cache of fossilized bones in Playa Media Luna, a dry coastal area of Peru. Jawbones and teeth pegged it as an ancient cetacean, a member of the whale family. And more bones followed.

“We were definitely surprised to find this type of whale in these layers, but the best surprise was its degree of completeness,” says Olivier Lambert, a paleontologist at the Royal Belgian Institute of Natural Sciences in Brussels.

Jaw, tooth and spine features, described April 4 in Current Biology, don’t quite match anything else in the fossil record, setting the skeleton apart as a new species, dubbed Peregocetus pacificus (meaning “the traveling whale that reached the Pacific Ocean”). At 42.6 million years old, it’s the oldest whale skeleton found in the New World, though some fossilized whale teeth from North America may be even older.

mandible bone

Big, possibly webbed feet and long toes would have allowed P. pacificus to dog-paddle or swim freestyle. And like modern otters and beavers, this whale’s vertebrae suggest that its tail also functioned as a paddle. With tiny hooves and strong legs and hips, the animal could walk on land. But “it was definitely a better swimmer than walker,” Lambert says.

Whales got their start on land and gradually adapted to a water-dwelling lifestyle. The first amphibious whales emerged more than 50 million years ago near what’s now India and Pakistan. The new species shares some similar features with Maiacetus and Rodhocetus, two early whales from that area. P. pacificus’ age supports the idea that whales migrated across the South Atlantic and around South America to the Pacific Ocean in their first 10 million years of existence.

Citations

O. Lambert et al. An amphibious whale from the Middle Eocene of Peru reveals early south Pacific dispersal of quadrupedal cetaceans. Current Biology. Published online April 4, 2019. doi:10.1016/j.cub.2019.02.050.

Further Reading

L. Hamers. Ancient whale tells tale of when baleen whales had teeth. Science News. Vol. 191, June 10, 2017, p. 12.

H. Thompson. New fossil suggests echolocation evolved early in whales. Science News Online, August 5, 2016.

S. Perkins. Earliest whales gave birth on land. Science News. Vol. 179, February 28, 2009, p. 5.

B. Harder. New fossils resolve whale's origin. Science News. Vol. 160, September 22, 2001, p. 180.

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