A skull belonging to one of the largest "sea monsters" ever unearthed is being unveiled to the public.
The beast, which is called a pliosaur, has been described as the most fearsome predator the Earth has seen.
The fossil was found in Dorset, but it has taken 18 months to remove the skull from its rocky casing, revealing the monster in remarkable detail.
Scientists suspect the creature, which is on show at the Dorset County Museum, may be a new species or even genus.
Richard Edmonds, Dorset County Council's earth science manager for the Jurassic Coast, said: "This is amazing. We saw this fossil initially as a pile of bones - and slowly, after a lot of hard work, it has come together.
"We are now told this skull is 95% complete, and probably one of the largest and certainly one of the most well-preserved and complete pliosaurs ever found anywhere in the world."
The 155-million-year-old fossil was discovered by local collector Kevan Sheehan between 2003 and 2008 as it gradually tumbled out of the cliffs near Weymouth.
He told BBC News: "It was sheer luck - I was sitting on the beach, and saw three pieces. I had no idea what they were, but I proceeded to drag them back. Then over several years, I'd go back every year and find a new piece. I'm a beach magpie."
At first it more closely resembled huge lumps of rock than a marine monster, but a lengthy preparation process that has been carried out by fossil expert Scott Moore-Faye has revealed the fine details of the fossil.
Looking somewhat like a crocodile on steroids, it is now easy to see the power of this "biting machine": pliosaurs, which lived during the Jurassic and Cretaceous Periods were the top predators of the oceans.
On show now are its eye sockets, perched upon the top of its head, revealing how it would have fixed its stare on any passing prey; the openings that held its it immensely powerful jaw muscles, allowing it to crunch down on anything that crossed its path; and the huge holes, running all the way down its snout, that contained its giant, razor-sharp teeth to help finish the meal off.
Palaeontologist Richard Forrest said: "This is an iconic specimen - one of the most exciting we have seen in years.
"It was probably the most fearsome predator that ever lived. Standing in front of the skull you can imagine this enormous beast staring straight back at you, fixing you with its binocular vision, and attacking. Just thinking about it raises the hairs on the back of your neck."
Its bulky body, which would have been powered through the water with four paddle-like limbs, has never been found - and may not even have fossilised.
But new estimates from scientists, based on the 2.4m-long skull, suggest that the predator would have measured between 15-18m from tip to tail.
Currently, the owner of the title of world's biggest sea monster is tricky to ascertain, as it is rare to find a complete fossil.
But pieces of potentially larger specimens have been found in the brick pits of Oxfordshire, and the skull of a species of pliosaur called Kronosaurus, from Australia, could be up to 3m (10ft) long. Recent finds in Svalbard, such as the aptly named "Monster" and "Predator X", as well as the "Monster of Aramberri", found in Mexico are also contenders.
However, scientists say that having a skull that is only missing the tip of its snout and a small piece of its jaw, gives them a rare chance to get a glimpse into the life of this ancient animal.
CT scans carried out by a team at the School of Engineering Sciences University of Southampton, which probe the fossil using X-rays, are now being studied to assess whether this creature is new to science.
Richard Edmonds said: "I've looked at some of the papers of described animals, and it looks different: it is much more massive, much more robust.
"But to determine whether it is anything new is a whole study in its own right. We'll have to go away, carefully compared to the existing species.
"But I wouldn't be surprised if in a year's time, we are standing here and looking at something that is new to science."
The fossil, which was purchased for £20,000 by the Dorset County Museum using Heritage Lottery Funds, with half of the money going to the collector and half to the landowner, is now going on public display. Sir David Attenborough is carrying out the opening ceremony.
David Tucker, Dorset County Museums Adviser said: "Our initial expectations have been more than met and the creature looks absolutely fabulous and we doubt whether there is a more complete pliosaur skull anywhere in the world.
"It is amazing to have the largest, most complete skull of the most powerful predator to live on Earth on display on the Jurassic Coast World Heritage Site, the home of the science of palaeontology"