The 22-foot-long 'Tyrannosaurus Rex of the Sea' has been unveiled by scientists, who discovered and researched the remains of two giant prehistoric crocodiles.
The two crocodiles - Plesiosuchus and the 17-foot-long Dakosaurus - were top of the marine food chain as they explored the shallow waters which covered south England 150 million years ago.
Dr Mark Young, of the University of Edinburgh, led an international team of scientists in exploring the remains, found buried in previously ocean-covered areas of Dorset and Cambridgeshire as well as in Germany.
Rather than the more laid-back style of modern-day crocodiles, the research team say the collossal beasts hunted aggressively and territorially in a mammal-like manner.
The team say that Dakosaurus and Plesiosuchus both had skulls more similar to Tyranodaurus rex and, in feeding manner, behaved much like North Atlantic killer whales.
Young told Discovery News: 'The skulls of these two sea croc species have some similarities to T. rex.
'The largest known skull of Plesiosuchus manselii was approximately four feet, three inches long, putting it in the size range of adult T Rex skulls.'
Young added: 'There are two "types" of North Atlantic killer whales: the first is large-bodied (more than 2m longer than the smaller type) and the teeth have no tooth wear, while the second is smaller-bodied and the teeth show extensive tooth wear.
'This is the same pattern we see in these fossil crocodiles.'
He added: 'The fact that two unrelated groups, separated by around 152 million years evolved a similar set of morphofunctional adaptations in western Europe came as quite a surprise.'
Dakosaurus and Plesiosuchus were part of a diverse group of marine crocodylians in the family Metriorhynchids. They varied hugely in body size, lifestyle and feeding strategy.
The team, which included researchers from the Natural History Museum, also found that Dakosaurus had skull and jaw characteristics like living suction-feeding dolphins, which would make Dakosaurus the first known suction-feeding crocodylian.
Young said: 'This way of eating involves being able to rapidly open the mouth wide, and generating negative pressure. This sucks a prey item into the mouth.'
He added: 'This research shows that crocodiles are not "living fossils".
'The long fossil record of crocodiles show they did many of the things living mammals do today.
'There were some terrestrial crocodiles with mammal-like teeth and also crocodiles that left the land and became fully marine.
'They evolved some remarkable adaptations for marine life, from flippers to a shark-like tail fin.'
Another question that has intrigued scientists is how such a large variety of top predators could live together side by side in the same ecosystem without competing with each other.
Dr Lorna Steel, from the Natural History Museum, said: 'The skull and tooth morphology show that they all ate different prey, and fed in different ways.
'We think that Plesiosuchus specialised in eating other marine reptiles, and Dakosaurus was a generalist, probably eating fish and whatever else it could get hold of, perhaps including the small metriorhynchid Geosaurus.'