Researchers Discover 41 Million Old Rodent Fossils
October 12, 2011

Researchers Discover 41 Million Old Rodent Fossils

Researchers have discovered the oldest rodent fossils yet along the Ucayali River near Contamana, Peru.

The fossils are comprised of the tiny teeth of a mouse-and rat-sized animal that lived at least 41 million years ago.

These fossils are about 10 million years older than all previous rodent discoveries made.

"This really pushes back the date of the first South American rodents," said Darin Croft, an anatomy professor at Case Western Reserve University School of Medicine, Cleveland, said in a press release.

The researchers said the shape and teeth and other factors point to the ancient animals being most closely related to African rodents.

The team said dental features indicate the rodents probably ate soft seeds and plant parts like small rodents today do.

Pollen extracted from the fossilized mud that contained the teeth suggest the rodents lived in a rain forest. 

The scientists said new species are smaller than nearly all caviomorph rodents today.  This group of rodents includes the largest living rodent, which can get up to 150 pounds.

"This study shows that where we're looking for fossils has a major effect on what we think we know about mammal evolution," Croft said in a press release. "There are still a lot of great fossils to be discovered.""

He said that he doubts much older caviomorph fossils will be found.

"Odds are pretty low that we would push back the date for these rodents by more than a million years or two," he said in a press release.

The study was published online on Tuesday in the Proceedings of the Royal Society B.


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