A fossil from an ancient whale found in Antarctica may be the oldest fully aquatic whale yet found.
Swedish and Argentine scientists said the jawbone dates back 49 million years, according to Clarin.
A scientist not involved in the find said it could suggest that whales evolved much more quickly from their amphibious precursors than previously thought, reports the Associated Press.
Earlier proto-whales lived on both the land and in the sea.
"The relevance of this discovery is that it's the oldest known completely aquatic whale found yet," said Marcelo Reguero, who leads research for the Argentine Antarctic Institute.