The animal, which made large burrows through sediment at the bottom of desert wadis in Torbay some 260 million years ago, could be unknown to science.
Scientists from around the world will be informed of the mystery when the findings are officially published later this year.
It comes as nine other sites in the area have been officially recognised as of national and international importance geologically.
Geologist Kevin Page from Plymouth University, said they had been unable to find any known animal, alive or extinct, that would have been responsible for the kind of burrows found in the deposits.
"If it was something like a worm, it was a very big worm. It was older than dinosaurs," he said.
"It would have been active in the sediment of waterholes at the foot of limestone mountains.
"It must have been some strange creature – possibly burrowing around in the cool of the water during the day and possibly coming out to feed at night in the desert region.
"We have evidence of some giant millipedes in the Bay, but this is something different. It could be a completely new species."
He added: "Some of the burrows are two feet long while others are nest shaped.
"Further surveys and research will be carried out before the findings are published in a scientific journal later this year. Until that work is completed, the site location will be kept a secret to protect it."
When Torbay was south of the equator, millions of years ago, warm tropical seas teemed with creatures which are now extinct and massive corals grew.
The shells and skeletons of this tropical life formed layer upon layer to eventually create hard limestone.
Today these hard rocks form the two arms of the horseshoe that forms Tor Bay – Berry Head to the south and Hope's Nose to the north.
credited to telegraph.co.uk

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