The family tree of the largest living land animal may have its roots deep in the water, a new study suggests.

Chemical signatures from fossil teeth reveal that at least one species of proboscidean, an ancient elephant relative, lived in an aquatic environment.

The teeth of the ancient animal, which belonged to a genus called Moeritherium, suggest that it ate freshwater plants and dwelled in swamps or river systems, said Alexander Liu of Oxford University's department of earth sciences.

"Essentially it's a hippo-like mode of life. That's the closest animal that we can think of today," said Liu, lead author of recent research on the teeth.

Living elephants and their extinct relatives share a common ancestor with manatees, dugongs and the