However, many questions remain. Scientists can only guess at the exact shape of the animals, the size of the fins, or how quickly they could swim.
And no fossil has yet been found with stomach contents that would offer direct evidence of what they were dining on.
Dr Nick Longrich, a paleontologist at the University of Bath, said his hunch was that they were mainly preying on ammonites.
However, like the modern octopus, they would have been opportunistic and voracious predators, and wouldn’t have passed up other prey if they had the chance.
“It’s going to take a while before we figure this thing out,” he said. “It’s a bit of a mystery.”
For now, the fossils offer a tantalising glimpse of a giant of the deep that may have roamed ancient seas, armed with a crushing jaw, powerful arms, and a brain that may have helped it compete with other top predators.
The research is published in the journal, Science, external.
