Two new species of ancient rodents discovered in Chile

Discovery of ancient fossils provides clues on the geological development of the Andes, as well as evidence of what may be the world’s oldest grasslands. 

It seems that you just can’t keep the chinchilla out of the news these days.
In a busy month for an animal that was once thought extinct, two new colonies of the Andean rodent were found in northern Chile, and now, paleontologists have uncovered the fossilized remains of two entirely new chinchilla species.
Unfortunately however, as the latest additions to the chinchilla ranks date back around 32.5 million years to the mid to late Eocene epoch, scientists remain skeptical toward their chances of making a comeback-from-the-dead as well.
But the research – led by the American Museum of Natural History’s (AMNH) Ornella Bertrand – does much more than just provide a prehistoric family tree for owners of the now popular exotic pet, it may also provide a geological history of the Andean mountain range, as well as provide evidence of what may well be the earliest grasslands to have developed in the world.
Ancient evidence
The new specimen were dubbed Andemys termasi, meaning “mouse of the Andes” and Eoviscaccia frassinettii, for the late Daniel Frassinetti, head of paleontology and longtime collaborator at the Chilean National Museum of Natural History.
They were discovered in the Tinguiririca river valley, high in the O’Higgins Region of central Chile, where AMNH curator Dr. John Flynn first discovered rodent fossils among the volcanic rock in the late 1980s. They are the second-oldest rodents yet known on the continent.
These two “newer” species are distinguished by a curious feature of their teeth, which may end up having a big impact on our understanding of the evolution of the world’s grasslands, from which human life would eventually spring.
It’s all in the teeth
Unlike earlier known fossils, the newly discovered chinchilla species have an extra-long crown, or layer of enamel, on their back teeth – an adaptation called hypsodonty that is associated with grazing animals like horses and cows in modern ecosystems.
“The new chinchilla fossil provides important new evidence that early rodents joined other South American mammals in evolving ways to cope with an abrasive diet long before horses, sheep and other mammal groups on other continents ‘invented’ similar adaptations for making their teeth wear out more slowly while eating tough grasses,” said Dr Flynn.
The find indicates that the ancient chinchilla probably lived in an savanna like environment, supporting evidence of the emergence of grasslands in this part of South America, some 15 million years before they would emerged elsewhere in the world.
Dating the Andes
Not only does the find support evidence that is forcing scientists to reassess the emergence of grassland ecosystems – it is also causing a major shake-up on the theory of the creation of the Andes mountains range.
That’s because, although the fossils were entombed in horizontal layers millions of years ago, today those layers tilt upwards sharply. This indicates that they were pushed up by the tectonic forces that formed the mountain range to rise up from the Earth.
The upshot of this discovery is that, where once the Andes were thought to have developed some 100 million years ago, they are now known to have emerged much later – perhaps between 15 and 18 million years ago.
The ANHM has published findings of its research into the ancient chinchillas in its peer-reviewed journal, American Museum Novitates. For more information head to the ANHM website.