Ancient Mammals Fill Elephant Family Tree

The oxygen isotopes suggest Moeritherium lived in shallow tropical rivers or swamps and that Barytherium was probably a semi-aquatic creature.

The new findings, combined with prior molecular data, suggest that the two extinct animals were indeed relatives of elephants, manatees, dugongs and hyraxes -- which are perhaps the most unlikely members of the group, given their diminutive, furry bodies.

"You have to remember that although modern hyraxes are small and cute, in the Eocene they were the dominant terrestrial herbivore in the Fayum (Egyptian) region, with a lot of diversity in size and shape," said Liu.

"It is possible to excavate hyrax skulls that are themselves the size of modern hyraxes, and some hyracoids could easily have rivaled Moeritherium in size," he added.

Liu speculates that a drought ended the ancient animals' tropical existence. Elephants and hyraxes might have later been pushed into more terrestrial habitats, while dugongs and manatees might have already become adapted to salt water.

University of Michigan paleontologist Bill Sanders told Discovery News that he found the isotope analysis to be "first-class work, with very clever and convincing interpretations to confirm that these proboscideans were likely to have been semi aquatic."

Sanders, however, questioned the relevance of such ancient elephant relatives, since modern elephants only first appeared 7 million years ago.

"Nearly all of the proboscideans that lived in the intervening time between moeritheres and elephants were terrestrial," he said, adding that the Egyptian site of the teeth finds might also have affected the findings, since other early elephant relatives could have lived in less water-dominant environments.

Despite these reservations, Sanders believes the new research "sets a good framework" for additional studies on the elephant family tree. He hopes Liu and his team will study remains from other elephant relatives, such as Phosphatherium and Numidotherium, in the future.

Related Links:

Jennifer Viegas' blog: Born Animal

Animal Planet

Elephant Fact Sheet

The Magnificent Manatee

African Wildlife Foundation Hyrax Page