The pliosaur species lived about 150 million years ago, the BBC reports. The Spitsbergen specimen was 50 feet long, about the size of a whale shark and half the size of the largest blue whales.

"We have carried out a search of the literature, so we now know that we have the biggest. It's not just arm-waving anymore," Jorn Hurum of the University of Oslo told the the BBC. "The flipper is 3 meters (almost 10 feet) long with very few parts missing. On Monday, we assembled all the bones in our basement and we amazed ourselves -- we had never seen it together before."

The previous holder of the title of biggest marine reptile was the Kronosaurus, a fossil pliosaur found in Australia. The Spitsbergen specimen, about 20 percent larger, has been nicknamed The Monster.

The Monster is one of about 40 marine reptile fossils found at a site on Spitsbergen.