Faster Than You'd Think

Turtles got a lot more cosmopolitan in 1995. Until now, the oldest turtle fossils, about 210 million years old, came from Thailand, Greenland, and Germany--which at the time were all in the northern half of the supercontinent Pangaea. Researchers assumed that turtles originated there and then took 60 million years or so to reach places like South America and Africa. But this past year Guillermo Rougier, a paleontologist at the American Museum of Natural History, described turtle fossils from Argentina (including the one shown here) that were also 210 million years old--indicating that turtles had already spread over the planet by then. The Argentinean turtles were different from their northern contemporaries, though. Their shell extended over the neck--early turtles couldn’t yet retract it--whereas other turtles had evolved external spines to protect that sensitive spot. And the Argentineans lived in arid habitats, whereas most northern turtles lived in or near water. ...