Scientists from the University of Oslo announced their discovery of a fossilized, 150 million-year-old "sea monster" on Spitspergen, in the Arctic island chain of Svalbard.

The 50 ft. sea reptile, nicknamed "The Monster", is the biggest on record, and is one of 40 such fossils discovered on the island. A prior field expedition in the area revealed remains of another large pliosaur that is thought to be among the same species as "The Monster".

©Tor Sponga, BT
A fossilised "sea monster" unearthed on an Arctic island is the largest marine reptile known to science, Norwegian scientists have announced.

Dr. Jorn Hurum, the expedition's director, said the new Svalbard fossil is 20% larger than the previous biggest marine reptile, a massive pliosaur from Australia named Kronosaurus.

"We have carried out a search of the literature, so we now know that we have the biggest [pliosaur]. It's not just arm-waving anymore," Dr Hurum told BBC News.

Pliosaurs were a short-necked, teardrop-shaped form of plesiosaur, extinct reptiles that lived in oceans during the age of the dinosaurs. The pliosaurs had two sets of powerful flippers they used to push themselves through water.

"These animals were awesomely powerful predators," said paleontologist Richard Forrest in a BBC News report.

"If you compare the skull of a large pliosaur to a crocodile, it is very clear it is much better built for biting... by comparison with a crocodile, you have something like three or four times the cross-sectional space for muscles. So you have much bigger, more powerful muscles and huge, robust jaws. A large pliosaur was big enough to pick up a small car in its jaws and bite it in half," he explained.

"The flipper is 3 meters 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," he said.

©J. Hurum
The Monster's flipper alone measures 3m in length

The fossilized "Sea Monster" was excavated in August 2007. Researchers had to remove hundreds of tons of rock by hand, enduring perilous conditions such as high winds, fog, rain, freezing temperatures and under constant threat of attack by polar bears.

The team was able to recover the animal's snout, some teeth, the shoulder girdle, much of the neck and back, and a nearly complete flipper. Regrettably, a small river running through where the head lay had washed away much of the skull.

A preliminary analysis of the bones suggested the animal was of a previously unknown species.

The Reptile has been taken to the Natural History Museum in Oslo.

The researchers plan to return to Svalbard later this year to excavate the new pliosaur. A few pieces of skull, some broken teeth and vertebrae from this second large specimen are already exposed and the researchers believe much more may be waiting to be excavated.

It's a large one, and has the same bone structure as the previous one we found," said Oslo Natural History Museum's Espen Knutsen, who is studying the fossils.

Dr. Hurum and his colleagues have now identified a total of 40 marine reptiles from Svalbard, including many long-necked plesiosaurs and ichthyosaurs in addition to the two pliosaurs. Long-necked plesiosaurs are said to resemble Scotland's legendary Loch Ness monster, while Ichthyosaurs resemble modern dolphins but with upright tail fins.

Richard Forrest told BBC News, "Here in Svalbard you have 40 specimens just lying around, which is like nothing we know.

"Even in classic fossil exposures such as you have in Dorset [in England], there are cliffs eroding over many years and every so often something pops up. But we haven't had 40 such finds from Dorset in 200 years."

The fossils were found in black shale rock, a fine-grained sedimentary rock. The researchers believe the animals sank to the bottom of a cold, shallow sea after they died, and then became covered by mud.

Dr. Hurum said the oxygen-free, alkaline chemistry of the mud could explain the fossils' remarkable preservation.

The discovery of another large pliosaur dubbed the "Monster of Aramberri" was announced in 2002, named after the site in north-eastern Mexico where it was discovered. The reptile could be just as large as the Svalbard specimen, according to the discovery team. However paleontologists told BBC News a much more detailed analysis of these fossils was required before a true picture of its size could be obtained.