Ancient turtle migrated from Asia to America over a tropical Arctic

[Adsos Letter]

Source: e! Science News

In Arctic Canada, a team of geologists from the University of Rochester has discovered a surprise fossil: a tropical, freshwater, Asian turtle. The find strongly suggests that animals migrated from Asia to North America not around Alaska, as once thought, but directly across a freshwater sea floating atop the warm, salty Arctic Ocean.

Published today in the journal Geology, the finding also suggests that a rapid influx of carbon dioxide some 90 million years ago was the likely cause of a super-greenhouse effect that created extraordinary polar heat.

"We've known there's been an interchange of animals between Asia and North America in the late Cretaceous period, but this is the first example we have of a fossil in the High Arctic region showing how this migration may have taken place," says John Tarduno, professor of geophysics at the University of Rochester and leader of the Arctic expedition. "We're talking about extremely warm, ice-free conditions in the Arctic region, allowing migrations across the pole."

In 2006, Tarduno led an expedition to the Arctic to study paleomagnetism—the Earth's magnetic field in the distant past. Knowing from previous expeditions to the area that the rocks were rich with fossils, Tarduno kept an eye out for them and was rewarded when one of his undergraduate students uncovered the amazingly well preserved shell of a turtle. Together with collaborator Donald Brinkman of the Royal Tyrrell Museum of Canada, they later named the fossil Aurorachelys, or aurora turtle. The turtle strongly resembles a freshwater Mongolian species, which raised obvious questions about how it came to be in the marine waters of the North American Arctic.

http://esciencenews.com/articles/2009/02/01/ancient.turtle.migrated.asia.america.over.a.tropical.arctic

[BlooInBloo]

1. OMG - it's like Nemo!