Natures wonders: whale series true amphibian (Introduction)

by David Turell , Wednesday, August 02, 2023, 17:24 (269 days ago) @ David Turell

New from Peru:

https://www.sciencenews.org/article/peru-fossils-four-legged-otter-whale-hooves

"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.

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"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.

"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."

Comment: this shows the developing whale series had intermediate forms. We can assume many branches had intermediate forms not yet discovered to show more gradual transitions from legs to flippers. These were minor adaptations compared to the many physiological and phenotypical changes required for full aquatic life.