"Stone" identified as 240-million-year-old fossil

The fossil, which is 14.5cm long and 13cm wide - the largest of its kind ever found - belongs to the Gastropoda branch, Mollusca tree, of the Naticopsis species, according to Nguyen Huu Hung, a specialist from the museum.

"The snail dates back 242-247 million years and has been preserved perfectly," Hung said.

"The discovery is very meaningful to scientists. We believe it is the largest snail fossil from the Triassic Age found to date."

Palaeobiologists across the world have found the fossils of 85 snails belonging to the Naticopsis species, Hung said.

Truong Van Dai, a worker at a stone quarry in Quynh Loc commune in the central province of Nghe An, found the fossil by chance seven years ago.

He noticed the odd-shaped stone looked like a snail. Intrigued by the stone's shape, he decided to keep it. He would sometimes show it to his friends, but none of them could say what it was. He recently contacted the museum in the hope that scientists would be able to identify it.