The ancient kin of modern elephants may have spent much of
their time in lakes, rivers or swamps.
Creatures in the proboscidean genus Moeritherium have
been known for more than a century, but scientists have never agreed about how
the animals lived, says Alexander G.S.C. Liu, a paleontologist at the University of Oxford
in England.
Liu and his team analyzed fossils from 37-million-year-old
rocks southwest of Cairo.
Other fossils from the same sediments include terrestrial animals along with
sharks and marine fish. The shapes of Moeritherium skulls, placement of
their eyes and other features hint that the 300-kilogram animals lived aquatic
or semiaquatic lifestyles. However, he notes, the arrangement of bones in their
inner ears doesn’t suggest that the creatures could have heard well underwater.
They likely were not full-time swimmers.
Liu and his colleagues weighed in on the debate by analyzing
the ratio of oxygen-16 and oxygen-18 isotopes preserved in the teeth of Moeritherium
fossils. Most atoms incorporated in tooth enamel when a creature is alive don’t
readily swap out with those in the environment during fossilization. Therefore,
that isotope ratio, among others, can provide clues to various characteristics
of a creature’s environment, its metabolism or its dietary preferences.
