A Living Fossil

Scientists have discovered that an Asian rodent belongs to a family of animals that had been thought to be extinct.

Imagine going to the museum to see fossils of animals that scientists thought had become extinct millions of years ago. Then, imagine walking outside and seeing one of this family of animals scurrying around in your backyard. That would be a pretty exciting discovery, wouldn’t it?

A team of international biologists recently experienced that very feeling when they confirmed that a member of a supposedly long-extinct family of rodentlike animals is actually alive and well.

Two travelers set off on a quest to find a living Laotian rock rat. Last year, they took this photo.

Uthai Treesucon and David Redfield /FSU Research in Review Magazine

In 1996, a wildlife-survey team purchased several rodentlike creatures at a food market in Laos, which is a country in Asia. They’d never seen or heard of this particular animal before and decided to call it the Laotian rock rat. Laotian locals, on the other hand, had known about the furry mammal for generations. They call it kha-nyou and enjoy eating it roasted.

The creatures are squirrel-size animals with dark fur, round ears, and puffy tails. True to its name, the rock rat lives in rocky outcroppings.

At first, the scientists were excited because they thought that the animals brought back by the survey team were members of a new, previously unknown family of mammals. If so, it would have been the first new family of mammals to have been discovered in more than 30 years.

But other scientists didn’t agree. They observed that the rock rat bore a striking resemblance to fossils of a mammal family group known as the Diatomyidae. That family supposedly became extinct close to 11 million years ago. Could it be that the entire Diatomyidae family wasn’t extinct, after all?

To resolve the debate, researchers in five countries performed a detailed analysis of rock rat DNA. All the groups concluded, based on the DNA evidence, that the rock rat is not a member of a new family of mammals after all. It’s actually a living representative of the Diatomyidae family—in other words, a living fossil.—J.L. Pegg

Going Deeper:

Milius, Susan. 2007. Living fossil: DNA puts rodent in family that’s not extinct after all. Science News 171(April 28):260. Available at http://www.sciencenews.org/articles/20070428/fob3.asp .

Sohn, Emily. 2006. New monkey business. Science News for Kids (May 17). Available at http://www.sciencenewsforkids.org/articles/20060517/Note3.asp .

______. 2005. New mammals. Science News for Kids (May 25). Available at http://www.sciencenewsforkids.org/articles/20050525/Note2.asp .

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