It swam in a primordial ocean 400 million years ago and could deliver a more powerful bite than any living fish, including the biggest sharks of today.
Scientists have discovered that the vice-like grip of its jaws enabled Dunkleosteus terrelli to exert a force of 11,000 pounds on its prey, enough to bite the toughest into two.
The extinct creature, which grew 33ft long and weighed up to four tons, was armed with a formidable array of bladed teeth which exerted a pressure of 80,000 pounds per square inch at the tip of its fangs.
A study of the fossilised skull of the fish also revealed that it could open its jaws in one-fiftieth of a second, creating such a strong suction that it would have quickly pulled prey to its mouth.
The fish was the top marine predator of its day but until now biologists were not aware of just how good it was at biting its way up the food chain.
"Dunkleosteus was able to devour anything in its environment," said Philip Anderson, of the University of Chicago, who led the study published in the Royal Society journal Biology Letters.
The scientists recreated the muscles around the jaw of the heavily armour-plated fish to estimate the sort of forces that were involved in shutting and indeed opening its mouth.
A mechanical model of the mouth of the fish revealed that it possessed a highly mobile skull controlled by a unique mechanism based on four rotational joints working in harmony. This gave it the strongest bite of any fish that ever lived and one that rivalled the strongest bites in the animal world, including those of large alligators and the biggest carnivorous dinosaur, Tyrannosaurus rex.
Mark Westneat, the curator of fishes at Chicago's Field Museum, said: "The most interesting part of this work for me was discovering that this heavily armoured fish was both fast during jaw opening and quite powerful during jaw closing.
"This is possible due to the unique engineering design of its skull and different muscles used for opening and closing.
"And it made this fish into one of the first true apex predators seen in the vertebrate fossil record."
The bladed jaw of the D . terrelli enabled the fish to rip apart prey that was bigger than its mouth, a technical feat that sharks did not acquire until 100 million years later.
D. terrelli lived during the period known as the Devonian, before the advent of the dinosaurs, and it probably fed on other armour-plated fish, including sharks, as well as tough invertebrates protected by shells and other types of body armour.
Dr Anderson said: "Overall, this study shows how useful mechanical engineering theory can be in studying the behaviour of fossil animals.
"We cannot actually watch these animals feed or interact, but we can understand the range of possible behaviours by examining how the preserved parts are shaped and connected to each other."