March 26, 2008—The remarkably well-preserved fossil of a dinosaur-era sea creature found in a Canadian mine is turning out to be a gold mine for paleontologists.

The Cretaceous-period reptile, dubbed Nichollsia borealis, is not only a new species—it represents a whole new genus, scientists announced on March 20.

It's also one of the oldest and most complete plesiosaur fossils ever unearthed in North America.

Plesiosaurs were carnivorous reptiles that roamed the seas between about 205 million to 65 million years ago.

Mine workers found the intact creature about 200 feet (60 meters) deep in a surface mine in Alberta in 1994. The Syncrude company extracts oil from the mine's sandy soil.

A "tomb" of sandstone preserved the 8.5-foot-long (2.6-meter-long) creature almost perfectly—unlike other plesiosaur fossils that are often found in porous shale.

The fossil ended up at the Royal Tyrrell Museum in Drumheller, Alberta, where University of Calgary paleontologists Patrick Druckenmiller and Anthony Russell recently ran 3-D CT scans of its braincase.

The scans and other analyses of the reptile have provided more detail than for any other plesiosaur ever found, they said.

The newfound reptile also gave them a window into an ancient seaway that once cut through North America and teemed with marine life.

(See pictures of a sea monster that lived in the Arctic.)

"This individual was a pioneer in the marine waters that would eventually become the Cretaceous Western Interior Seaway," Druckenmiller said in a statement.

"It represents the oldest known forerunner of this amazing period in North American prehistory."

Their research appeared in the German journal Palaeontographica Abteilung A.

N. borealis is now on display at the Discoveries Gallery at the Royal Tyrrell Museum.

—Christine Dell'Amore