T.rex and Allosaurus were mouthy monsters of the dinosaur world
You might not have said it to his face, but T.rex was a real big mouth, scientists have discovered.
New research shows that Hollywood depictions of Tyrannosaurus rex with terrifying gaping jaws full of teeth are probably right.
The giant predator was able to open its mouth really wide, achieving an angle of 80 degrees between the upper and lower jaws.
Another lighter-built meat-eating dinosaur, Allosaurus, was even more mouthy, having a gape that extended as far as 92 degrees.
In contrast, a related two-legged "therapod" dinosaur, Erlikosuarus, that fed on plants, had a much more restricted 49 degree jaw-opening angle.
Tests showed that of the two carnivores, T. rex was able to produce a more sustained bite force for a wide range of jaw angles, which would have helped its six-inch (15cm) teeth slice and crunch through flesh and bone.
Lead scientist Dr Stephan Lautenschlager, from the School of Earth Studies at the University of Bristol, said: "Theropod dinosaurs, such a Tyrannosaurus rex or Allosaurus, are often depicted with widely-opened jaws, presumably to emphasise their carnivorous nature. Yet, up to now, no studies have actually focused on the relation between jaw musculature, feeding style and the maximal possible jaw gape.
"All muscles, including those used for closing and opening the jaw, can only stretch a certain amount before they tear. This considerably limits how wide an animal can open its jaws and therefore how and on what it can feed.
"We know from living animals that carnivores are usually capable of larger jaw gapes than herbivores, and it is interesting to see that this also appears to be the case in theropod dinosaurs."
The research, published in the journal Royal Society Open Science, was conducted using computer-generated virtual models of dinosaur jaws and by making comparisons with crocodiles and birds.