The enormous prehistoric crocodiles, Plesiosuchus and the 17-foot-long Dakosaurus, were such ravenous carnivores that their methods have been compared to today's killer whales and a famous, iconic, meat-loving dinosaur.
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.
Dakosaurus and Plesiosuchus both had skulls more similar to Tyranodaurus rex and, in feeding manner, behaved much like North Atlantic killer whales.
"The skulls of these two sea croc species have some similarities to T rex," Young told 'Discovery News'.
"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 said.
"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," he said.
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.
Researchers also found that Dakosaurus had skull and jaw characteristics like living suction-feeding dolphins, which would make Dakosaurus the first known suction-feeding crocodylian.
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.
The study is published in the journal 'PLoS ONE'.
