Ancient Extinct Tortoise Fossil May Reveal the Rise of the Andes Mountains

Ancient reptile fossils may be telling scientists a bit more about the history of the Andes mountains. The fossils have shown that the tall plateaus found in the Andes may have once been less than a kilometer above sea level about 13 million years ago.

"We're trying to understand how tectonic plate activity and changing climate affected species diversity in the past," said Darin Croft, one of the researchers, in a news release. "One way all this diversity we see in the South American tropics today was generated was through elevation. Mountains create many different climates and ecosystems in a small area, which promotes speciation."

In this latest study, the researchers found tortoise remains in the arid Andes Mountains on a plateau. They found other, more fragmentary tortoise and turtle remains, as well.

The tortoise itself was a member of the same genus as the Galapagos tortoise, Chelonoidis. The extinct freshwater turtles belong to the genus Acanthochelys, whose surviving members occur throughout much of tropical South America.

It's like that the ancient tortoise wouldn't have been able to survive in altitudes that are found today in the Andes due to the cooler temperatures. This may mean that the Andes were far lower than they are today.

Researchers already knew that the Andes were formed by subduction, which is a process in which one tectonic plate is shoved under another. How quickly the mountains rose to their current elevation, though, remains a mystery.

If the Andes Mountains were less than 1 kilometer high during the late Miocene, as the fossils suggest, then they would have had a much smaller effect on global circulation than if they were two or three times as high, close to their modern elevation near Quebrada Honda. This is important to note when determining what ancient climate conditions were like and how climate is influenced by these mountains today.

The findings are published in the Journal of South American Earth Sciences.

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