A 450-million-year-old fossil of a rare, ancient sea creature, which appears to be shaped like an ice cream cone, has just been discovered. The fossil, which was found by an international team of researchers, was discovered in the Appalachian Mountains, near Hummelstown in Pennsylvania, and has stumped palaeontologists.

The newly discovered fossil of the mysterious, prehistoric sea creature dates back to the Ordovician period. Oddly enough, the fossil was well-preserved, despite the fact that the rocks in which it was discovered, was found to have been "cooked" during mountain building – which should have hindered the preservation of the specimen. The ancient soft-bodied sea creature's fossil may help palaeontologists get a better idea of what life was like around 450 million years ago.

"The ancient world of the Ordovician, some 450 million years ago, was one of a huge expansion of life in the seas of our planet," Jan Zalasiewicz, a professor at the University of Leicester's School of Geography, Geology and the Environment, said in a statement. "Fossils are abound in Ordovician strata, but almost all of them are of creatures with hard shells or support structures, and so our understanding of booming Ordovician life is almost completely based on skeleton-bearing animals.

"There are few of those rare, precious localities where softer-bodied animals might be found, to give a wider insight into the life of those times. Was this creature an important but usually unpreserved part of ocean life, or just a bit player among the Ordovician animal communities? It is a new puzzle for palaeontologists."

"That this fossil still has the soft bits preserved, even though the rocks that hold it have been squeezed and twisted, is remarkable. This enigmatic organism has major implications for how we look for well-preserved fossils," said Mike Meyer of the Carnegie Institute of Science.

"It's a small fossil with a big story," Bob Ganis, consulting geologist from the University of Leicester, said.

The findings of the new discovery have been published in the journal Palaios.