Researchers from Case Western Univ., Universidad Autónoma Tomás Frías, and Yachay Tech Univ. have discovered and identified the remains of an ancient five-foot tortoise, found in an area of the Andes Mountains in Bolivia. The find marks the first records of fossilized turtles from the Miocene epoch in Bolivia, and indicates the Altiplano region was less than one km above sea level around 13 million years ago.
Case Western Univ. anatomy professor Darin Croft found the remains after getting turned around on a path near the town Quebrada Honda enroute to his usual research site. The fragmentary tortoise remains were located in an embankment.
The researchers also found fossilized shell pieces from an aquatic, freshwater turtle nearby. They published their findings in the Journal of South American Earth Sciences.
“The occurrence of a giant tortoise and a freshwater turtle suggests that the paleoelevation of the region when the fossils were deposited was lower than has been estimated by stable isotope proxies, with a maximum elevation probably less than 1,000 m,” the researchers wrote.
The previous isotype-based study estimated that the Altiplano plateau was between 2 and 3.2 km high during the Miocene epoch.
At elevations over 1,000 m “cool temperatures would have been beyond the tolerable physiological limits for these turtles and other giant ectotherm reptiles,” the researchers wrote.
Co-author Edwin Cadena, a turtle expert at Yachay Tech Univ., placed the newfound tortoise in the genus Chelonoidis, the same genus as the Galapagos tortoise. The extinct freshwater turtle he placed in the Acanthochelys genus, surviving members of which can be found throughout tropical South America.
These modern day counterparts, according to the researchers, thrive at altitudes below 500 m.
Today, the Altiplano’s elevation averages 3,750 m. According to National Geographic, the plateau is one of the largest in the world, second only to Tibet. It formed when oceanic crust wedged itself under continental crust in a process called subduction.
Today, the geological behemoths hold sway over global air circulation patterns and the global climate. During the Miocene epoch, the Andes Mountains would have had little influence over such factors, based on current elevation estimations.
“We’re trying to understand how tectonic plate activity and changing climate affected species diversity in the past,” said Croft. “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.”