A British fossil hunter has found the remains of what is thought to be the world’s giant sea monster on the south coast of England.

The ferocious prehistoric creature, which was 52 feet long could belong to creature measuring up to 16 metres in length and lived 150 million years ago.

Pliosaurs were a form of plesiosaur, a group of giant aquatic reptiles that terrorised the ocean 150m years ago, around the same time that dinosaurs roamed the Earth.

It was so powerful it could have bitten a car in half and had a tyrannosaurus rex for breakfast, scientists said. The 8 feet long skull of the pliosaur was found on Dorset’s Jurassic Coast after storms brought down limestone cliffs.

Weighing up to 12 tonnes, the pliosaurs were a short-necked form of plesiosaur, a group of giant aquatic reptiles that dominated the oceans during the Jurassic and Cretaceous periods. They had immensely powerful jaws and a set of razor-sharp teeth.

Richard Forrest, a plesiosaur expert, said the discovery was fortunate because pliosaur skulls were generally found crushed flat “They had massive big muscles on their necks, and you would have imagined that they would bite into the animal and get a good grip, and then with these massive neck muscles they probably would have thrashed the animals around and torn chunks off. Measurements of its jaw and analysis of its teeth suggested that its bite was up to 11 times as strong as that of a Tyrannosaurus rex.

Palaeontologist Richard Forrest said the tyrannosaurus rex was a ”kitten” compared with the pliosaur.

”One of the things that is very clear from looking at this specimen is just how powerful this animal was,” he said. ”If we look at the lower jaw, this is the point at which the  muscles attach and then you’ve got the great beam coming forward; that bone is roughly the strength of steel.So it was an enormously powerful biting machine. These things were big enough and powerful enough to bite a small car in half … It would take T. rex in one gulp.”

Previously the largest marine carnivore ever found was another pliosaur, dubbed Predator X, which was dug up last year on Svalbard, a Norwegian Arctic island close to the North Pole.

Dr Martill said “We only have the head, so you cannot be absolutely precise. But it may be vying with the ones found in Svalbard and Mexico for the title of the worlds largest.”

Richard Edmonds, Dorset County Council’s earth science manager for the Jurassic Coast, said: “This part of the coastline is eroding really rapidly and that means the fossils that are trapped and buried are constantly tumbling out on to the beach.

The fossil, a lower jaw and upper skull, was found by Kevan Sheehan, a local collector and has been purchased by Dorset County Council for £20,000 using money from the Heritage Lottery Fund.

He started looking for fossils along a stretch of beach near Weymouth seven years ago following a landslide. He used his hands to pick through mud and rock to find the first pieces of fossilised bone. He then went back to the site almost every day for the next five years until he had assembled some 25 pieces.

It will be scientifically analysed before being put on public display at Dorset County Museum.