About 25 million years ago a tiny tree frog was engulfed in tree sap and died in what is now southern Mexico.

In 2005, a miner in Chiapas uncovered the chunk of amber encasing the 0.4-inch frog and sold it to a private collector. The collector loaned it to scientists for study.

Biologist Gerardo Carbot of the Chiapas Natural History and Ecology Institute, who announced the discovery, said it was the first such frog found in amber in Mexico.

Carbot said he would like to extract a sample from the frog's remains to see if they contain well-preserved DNA, in order to identify the frog's species.

However, he expressed doubt that the stone's owner would allow researchers to drill a small hole into the chunk of amber.

"I don't think he will allow it, because it's a very rare, unique piece," said Carbot.

Only a few preserved frogs have been found in chunks of amber -- a stone formed by ancient tree sap -- mostly in the Dominican Republic. Like those, the frog found in Chiapas was of the genus Craugastor, whose relatives still inhabit the region.

(Agencies)