The surprising find of a freshwater, tropical turtle fossil in Arctic Canada suggests that the first turtles to migrate from Asia to North America may have taken the most direct route, swimming and island hopping straight through the Arctic Ocean. This was possible, researchers say, because the Arctic was warmer and ice-free 90 million years ago, when carbon dioxide levels were extraordinarily high.
"The fossil record is giving us more and more information about how ancient animals responded to a warming world," [says] geophysicist John Tarduno.... "They moved toward the poles" [Wired News].
The freshwater turtle was able to survive in the ocean, Tarduno says, because of a floating freshwater highway that led from Russia to Canada.
Numerous rivers from the adjacent continents would have poured fresh water into the ancient Arctic sea.... Fresh water, which is lighter than marine water, may have rested on top of the salty ocean ...
