Tyrannosaurus rex had the most powerful bite of any creature that has ever walked the Earth, say scientists.
Previous estimates of the prehistoric predator's bite suggested it was much more modest - comparable to modern predators such as alligators.
This measurement, based on a laser scan of a T. rex skull, showed that its bite was equivalent to three tonnes - about the weight of an elephant.
The findings are published in the journal Biology Letters.
"Then we could map the muscles onto that skull."
The scientists then reproduced the full force of a bite by activating the muscles to contract fully - snapping the digital jaws shut.
"Those [simulated] muscles closed the jaw as they would in life and... we measured the force when the teeth hit each other," Dr Bates explained to BBC Nature.
"The maximum forces we found - up at the [back] teeth - were between 30,000 and 60,000 Newtons," he said.
"That's equivalent to a medium-sized elephant sitting on you."
Previous studies had estimated that T. rex's bite had a force of 8,000-13,000 Newtons.
"Obviously, as its head got a lot bigger, there's an expected increase in bite force associated with that," Dr Bates explained.
But for T. rex, the power behind its bite increased disproportionately - much more than would be expected from a "straightforward linear increase", he said.
This suggests that the predator's diet changed as it matured, and that perhaps only adult T. rex could have punctured the tough hide of another dinosaur.
Dr Bill Sellers, who studies the physical capabilities of living and extinct animals at the University of Manchester, told BBC Nature: "I think everyone expected T. rex to have a strong bite force, but it's even stronger than we expected.
"And it gets stronger as it gets bigger, which is surprising."
He explained that studying dinosaurs shed light on the limits that living things were capable of.
"These animals are extremes - one of the biggest carnivores that ever lived," he said. "So it tells you a lot about the limitations of biology.
"We want to know how organisms work, but living organisms [today] are much smaller. And in terms of mechanics, size is really important."
Dr Karl Bates from the biomechanics laboratory at the University of Liverpool led the research.
He and his colleague, Peter Falkingham from the University of Manchester, used the life-sized copy of a T. rex skeleton exhibited at Manchester Museum as a model for their study. "We digitised the skull with a laser scanner, so we had a 3-D model of the skull on our computer," Dr Bates explained.