April 15, 2008

Ancient Elephant Lived Amphibious Lifestyle

Researchers from Oxford University and Stony Brook University have discovered an ancient water-dwelling mammal that had close ties to modern day elephants.

The animal is similar to a tapir, a hoofed mammal that resembles a cross between a horse and a rhino.

"It has often been assumed that elephants have evolved from fully terrestrial ancestors and have always had this kind of a lifestyle," said DR. Erik Seiffert, co-author of the study published in Proceedings of the National Academy of Sciences.

"Now we can really start to think about how their lifestyle and behavior might have been shaped by a very different kind of existence in the distant past.

"It could help us to understand more about the origins of the anatomy and ecology of living elephants."

Researchers were able to link the mammals by analyzing chemical signatures in fossil teeth of two species related to the elephant and the sea cow from northern Egypt during the Eocene Epoch.

Alexander Liu of the University of Oxford and Erik Seiffert of Stony Brook University, New York, analyzed the patterns of different oxygen and carbon atoms, or isotopes, to study the diet of the two species.

They found that the so-called Barytherium and Moeritherium, were largely aquatic, feeding on freshwater vegetation in rivers or swamps.

"The isotopic pattern preserved in their teeth is very similar to that of living aquatic mammals," Dr Seiffert said.

"It supports the hypothesis that, at some point early in the evolution of elephants, these animals were very dedicated to either a fully aquatic or amphibious lifestyle - they probably spent most of their life in water."

Co-author Alexander Liu said the aren't certain how the ancient mammal adapted to live a life away from the water, but one theory suggests that it was forced to do so by a cooling event at the end of the Eocene that could have dried up swamps and rivers.

"It seems that [Moeritherium] was almost certainly an animal that ate freshwater plants and led a semi-aquatic lifestyle, similar to that of hippos," said Liu.

"There's little real evidence yet to suggest that's true. We've got an awful lot of pieces in the puzzle; if we could find one more example of an aquatic or semi-aquatic elephant that would be extremely convincing."


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Proceedings of the National Academy of Sciences