Argentine scientists say they have found the jawbone of an ancient whale in Antarctica that is perhaps the oldest fully aquatic whale yet discovered.
Paleontologist Marcelo Reguero says the jawbone that the team found in February dates back 49 million years.
In evolutionary terms, that's not far off from even older proto-whales dating from 53 million years ago. Those creatures were amphibians, able to walk on land as well as swim in the sea, and plenty of their fossils have turned up in warmer latitudes.
University of Chicago paleontologist Paul Sereno says that if the find withstands the scrutiny of other scientists, it will mean that the earliest whales evolved more quickly than previously thought.
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