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Dino-Era "Sea Monster" Found on Arctic Island

James Owen
for National Geographic News
October 6, 2006
 
A dinosaur-era Davy Jones's locker of large, predatory sea reptiles—including a giant that scientists have nicknamed "the Monster"—has been discovered by fossil hunters on an Arctic island.

The ancient graveyard once lay deep underwater during the Jurassic period, about 200 million to 145 million years ago (take a virtual swim with Jurassic sea monsters).

The site now sits on the island of Spitsbergen, part of the Norwegian-owned Svalbard archipelago, which lies about 600 miles (966 kilometers) from the North Pole (map of Norway).

In total, 28 well-preserved skeletons of marine reptiles that lived some 150 million years ago have been identified at the site, reports a team from the University of Oslo Natural History Museum in Norway.

The fossil haul includes the Monster, an estimated 33-foot-long (10-meter-long) pliosaur that has not yet been fully excavated. (See images of the newly found sea monster.)

Pliosaurs were the top marine predators during a time when the oceans were teeming with large, meat-eating reptiles.

"It was the T. rex of the ocean," said Jørn Hurum, co-leader of the research team. "It would have eaten everything."

So far the team has found the Monster's skull, which measures 6.9 feet (2.1 meters) in length, along with dinner plate-size neck vertebrae and portions of the lower jaw containing teeth as thick as cucumbers.

The fossil specimen may represent the largest complete pliosaur ever found, Hurum says.

"It looks very promising, because we've got 6 meters [20 feet] of vertebrae and the skull and part of a flipper, so it's probably complete," Hurum said.

Black Mud

In addition to the Monster, the researchers uncovered 6 ichthyosaurs and 21 plesiosaurs during a two-week expedition to Spitsbergen in August.

Plesiosaurs were marine reptiles with long necks and large flippers (related news: "Long-Necked Sea Reptiles Had Unexpected Diet, Fossils Show" [October 2005]).

Pliosaurs are believed to be closely related to plesiosaurs. But pliosaurs had short necks and massive jaws that would have been capable of lifting a car and biting it in half.

Such strength likely helped the pliosaurs hunt prey such as plesiosaurs and ichthyosaurs, another group of marine reptiles.

Ichthyosaurs resembled dolphins but used an upright tail fin, as opposed to dolphins' sideways tail fins, to propel themselves through the water.

Most ichthyosaurs averaged 13 to 20 feet (4 to 6 meters) in length, but some reached 75 feet (23 meters).

The new find follows up on fieldwork on Spitsbergen in 2004, when University of Oslo researchers excavated parts of the skulls of an ichthyosaur and two plesiosaurs.

The fossils from both digs were found in a layer of black shale—a type of sedimentary rock—that is between 65 to 100 feet (20 to 30 meters) thick.

"There's something special about the chemistry of the shale which has preserved all the bones in this layer," Hurum said.

According to Hurum, when the reptiles died they probably sank to the ocean floor, where conditions were right for preserving their bodies.

"It's deep water and black mud that they fell into. There were no animals living close to the bottom that could eat these big things that were decaying," he said.

"One specimen [we found] was probably scavenged before it fell to the bottom, but the others look quite complete, and that's amazing," Hurum said.

This summer marine reptile expert Pat Druckenmiller, of Montana State University in Bozeman, accompanied the team to Svalbard.

Druckenmiller, who identified the large pliosaur, said that "it is certainly likely that some of these animals represent new types of plesiosaurs and ichthyosaurs that are unknown to science."

The paleontologist says that many of the fossil reptiles are well articulated.

"This means that if you find the tail sticking out of the hill and you follow it in, you have a good chance of finding the rest of the skeleton—including the all-important skull—also attached," he said.

"This type of preservation, in black shale, is one of the settings considered likely to preserve traces of the animals' soft tissues, such as skin impressions," he added.

Dreams of Eggs

Druckenmiller says that the find shows that the Svalbard island chain is "significant at a global level," in terms of the quality of fossil preservation and the number and different types of marine reptiles found.

The site also provides "a relatively complete chapter from the late Jurassic, about 150 million years ago," he added.

"This age is considered one of the heydays of marine reptile life, but what we know of life from this specific window of time only comes from scattered sites around the globe."

The Oslo team is hopeful that the fossil graveyard will yield important new clues to the history and biology of these ocean predators.

"The dream is that one of the plesiosaurs or the pliosaur was pregnant" when it died, the University of Oslo's Hurum said. "A pregnant one, or one with eggs inside, is not known anywhere in the world."

Researchers still aren't sure if these creatures gave birth to live young underwater or if they hauled themselves on land to lay eggs like modern sea turtles.

Also, having the remains of both young and adult plesiosaurs could shed light on how the reptiles grew and matured, Hurum adds.

The researchers will return to the Arctic island next summer, when they plan to finish excavating the pliosaur and several other specimens.

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