A marine monster described as the most fearsome animal ever to swim in the oceans boasted a bite up to 11 times as strong as that of Tyrannosaurus rex.

The fossil remains of the huge pliosaur were dug up last summer from the permafrost on Svalbard, a Norwegian island close to the North Pole.

Analysis revealed that it was a turbo-charged swimmer. Its front flippers allowed the creature, dubbed Predator X, to cruise along comfortably but when prey came into range the power of its hind flippers kicked in to provide extra acceleration.

Measurements of its jaw and the killing power of its dagger-like teeth have shown that it could bite down with a force of 33,000 pounds per square inch compared with T. rex's 3,000lb per square inch. Alligators have the strongest bite today with about 2,500 pounds per square inch.

Researchers have been astonished by the size of the reptile, which exceeded even that of another pliosaur, called The Monster, which was found at the same site a year earlier.

Predator X is thought to have been at least 50 feet long, perhaps more, and measurements of its bulk suggest that it would have weighed in at 45 tons.

Its discovery was announced yesterday in Oslo by Joern Hurum, of the University of Oslo, who led the expedition to dig up the remains. At least 20,000 fragments have been recovered including most of the jaws, which were 10 feet long. Dr Hurum said: "It was the most ferocious hunter ever. It's like a turbo-charged predator. This is a very, very large carnivore."

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