A prehistoric "Jaws" that roamed the seas 400 million years ago had the most powerful bite of any known fish.
The fish would have been a formidable predator
The extinct creature, Dunkleosteus terrelli, could bring its jaws together with a remarkable force of 5,000 Newtons (1,100lbs-force).
This performance surpasses all living fish, including today's great white shark, and puts it up with some of the most powerful bites in all animals.
Details appear in the UK Royal Society journal Biology Letters.
US researchers Mark Westneat and Philip Anderson tell the journal that higher bite forces have only been reported for some large alligators and dinosaurs.
T. rex, for example, could clamp down on its meal with a crushing force of 13,000 Newtons (3,000lbs-force); but a modern spotted hyena, by comparison, exerts a force of only 2,000 Newtons (500lbs-force) when it cracks bones in its mouth.
The team developed its biomechanical model of Dunkleosteus by studying the fossil remains of the fish, which probably grew up to 10m (30ft) in length.
The scientists say the way its teeth were organised in the jaw meant it could focus its bite into a small area - the fang tip - with the incredible pressure of nearly 150 million Pascals (22,000lbs per sq inch).
Even more surprising is the fact that Dunkleosteus could also open its mouth very quickly - in just one fiftieth of a second - which created a strong suction force, pulling fast prey into its mouth.
"This heavily armoured fish was both fast during jaw opening and quite powerful during jaw closing," said Westneat, who is curator of fish at The Field Museum in Chicago.
"This is possible due to the unique engineering design of its skull and different muscles used for opening and closing."
Usually, a fish has either a powerful bite or a fast bite, but not both.
The formidable fish was a placoderm, a diverse group of armoured fish that dominated aquatic ecosystems during the Devonian Period, from 415 million to 360 million years ago.
"Dunkleosteus was surrounded by possible prey that all required really high bite force," said Anderson, who works out of the University of Chicago.
"There were free-swimming, fast animals that all had a hard armour; most of the other fish were other placoderms which had the same hard bony covering. And then there were large molluscs with hard shells and really large crustaceans," he told BBC News.