Colossal pliosaur fossil secrets revealed by CT scanner

The innermost secrets of a colossal "sea monster" skull are being revealed by one of the UK's most powerful CT scanners.

The X-rays are helping to build up a 3D picture of this ferocious predator, called a pliosaur, which terrorized the oceans 150m years ago.

The 2.4m-long (7.9ft) fossil skull was recently unearthed along the UK's Jurassic coast, and is thought to belong to one of the biggest pliosaurs ever found.

The scans could establish if the giant is a species that is new to science.

Pliosaurs are aquatic reptiles belonging to the plesiosaur family. Paddle-like limbs would have powered their huge bulky bodies through the water, and they had enormous crocodile-like heads, packed full of razor-sharp teeth.

Pliosaurs were the top predators of the oceans

The skull, which was unearthed by a local fossil collector and then purchased by Dorset Country Council using Heritage Lottery Funds, would have belonged to one of the most fearsome beasts the seas have ever seen.

Scientists estimate the creature would have measured 10-16m (33-52ft) in length and weighed between seven and 12 tonnes.

The fossil, which comprises a lower jaw and upper skull, is currently being removed from its rocky casing by preparator Scott Moore-Fay.

He said this work would take more than 1,000 hours to complete.

He told BBC News: "It's incredibly exciting. Nobody has ever seen this fossil, so I get to see it as it is coming out of the rock - it is almost like magic."

However, while preparatory work can reveal the surface of the fossil in remarkable detail, a more hi-tech solution is needed to probe deeper inside.

After spotting the BBC's exclusive report on the discovery of the pliosaur last year, Professor Ian Sinclair from the University of Southampton got in contact with the fossil's owners to tell them about a new, powerful CT scanner that was being constructed in the university's engineering sciences department.

The CT scanner is powerful enough to penetrate the dense fossil

He said: "When we have the situation of rare samples that are precious, like the pliosaur, we have to extract the most information from them and we certainly don't want to destroy them, so this really is the perfect tool."

The CT scanner, which has been funded by the Engineering Physical Science Research Council (EPSRC) and the University of Southampton, is one of the most powerful machines of its kind in the UK, and one of the largest.

This is essential for scanning such large, dense lumps of fossil, but in the future the team also plans to use the scanner to look at a diverse range of objects - from musical instruments, to car engines, parts of aircraft and even crops.

It works in much the same way as a hospital CT scanner, although at much higher energy and resolution, by taking thousands of X-rays to build up an image of whatever object is inside.

University of Southampton engineer Dr Mark Mavrogordato explained: "At the end, you have a 3D volume representing your original specimen. And you can slice it, dice it, however you want, as if you could dissect it with a knife, but you are doing it digitally and non-destructively."

New species?

The team has begun scanning the prepared fossil one piece at a time to reveal as complete a pliosaur picture possible, including information about the internal bone structure and the positioning of hidden teeth.

The scans reveal the internal structure of the skull

Palaeontologist Richard Forrest said: "This creature had an enormously powerful bite, it could have bitten a car in half.

"We hope that these CT scans will show the internal structure of the jaws, and how they are built to withstand such incredible forces.

"By understanding this, we can learn more about its behaviour - how it hunted and attacked other creatures."

The scans will also help to confirm whether this species is new to science.

Mr Forrest said: "From the outside, it looks similar to other pliosaurs found in the UK, although much much bigger.

"By looking at the inner architecture of the skull, in particular the brain-case, we should be able to establish if this is a species that we have not seen before."

After the scientific analysis is complete and the fossil is fully prepared and mounted, it will go on display to the public in summer 2011 at the Dorset County Museum in Dorchester.

David Tucker, museums adviser for Dorset, said: "The pliosaur will be displayed with its mouth agape, allowing people to get the best possible understanding of what the beast would have looked like in life.

"We'll also have a massive, life-sized model of the head that will demonstrate how terrifying its teeth were"