A Mexican biologist announced the rare discovery of a small tree frog completely preserved in amber and estimated to have lived about 25 million years ago.
The amber (fossilized tree resin) piece, encasing the 0.4-inch (1 cm) frog was dug in 2005 by a miner from Mexico's Chapas state and sold to a private collector.
The collector offered the piece for investigation to scientists.
By now, only four preserved frogs have been discovered encased in amber, from the Dominican Republic and belonged to Eleutherodactylus genus (Leptodactylidae family).
Like the frogs from Dominica, which belong to a still living genus,
the Chapas frog belongs to a current genus Craugastor (from the same Leptodactylidae family), still inhabiting Central America.
"Like those, the frog found in Chiapas appears to be of the genus Craugastor, whose descendants still inhabit the region," said biologist Gerardo Carbot of the Chiapas Natural History and Ecology Institute.
"If authenticated, the preserved frog would be the first of its kind found in Mexico," said David Grimaldi, a biologist and curator at the American Museum of Natural History, not involved in the research.
The age of 25 million years is estimated based on the geological strata where the amber was discovered.
"The frog's age has yet to be authenticated. But it was recovered from earthen deposits dating back 25 million years to the Oligocene epoch," said Carbot.
Carbot said he would like to drill a small hole into the amber, to extract DNA from the fossilized frog, for species identification, but he knows the odds are against him.
"I don't think [the stone's owner] will allow it, because it's a very rare, unique piece," said Carbot.
Grimaldi believes this would be "highly, highly unlikely,'' as many researchers have noted that genetic material tends to break down over time.
Others agree with Carbot.
"If it's well-preserved ... and none of the frog has been exposed to the outside, where air could enter in and oxidize the DNA, it could be possible to get DNA,'' said George O. Poinar, an entomologist at Oregon State University and the founder of the Amber Institute. Photo credit: George Poinar.