London (PTI): Modern-day elephants descended from an early ancestor which lived in water nearly 37 million years ago, a fossil study has revealed.

A team of international scientists analysed chemical signatures preserved in fossil teeth of the animal said to be similar to a tapir, a hoofed mammal which looks like a cross between a horse and a rhino.

The teeth analysis indicated that the animal grazed on plants in rivers or swamps and had a similar lifestyle to that of a hippo, according to the scientists.

"We know from molecular data that modern elephants share a common ancestry with the sirenians -- aquatic sea cows and dugongs. Now, we have substantial evidence to suggest that elephants do have ancient relatives which lived primarily in water," the study's lead author Alexander Liu said.

In fact, in their study, Liu of Oxford University and colleagues from Stony Brook University in New York looked at fossil teeth of two species belonging to an extinct family of mammals related to the elephant and the sea cow which lived in northern Egypt during the Eocene Epoch, 37 million years ago.

The researchers analysed the patterns of different oxygen and carbon atoms, or isotopes, laid down in the tooth enamel and concluded that Barytherium and Moeritherium were largely aquatic, feeding on freshwater vegetation in swamps.