A Tyrannosaurus rex would have had great difficulty
getting its jaws on fast, agile prey, a study confirms.
A US team has used detailed computer models to work out the
weight of a typical "king of the dinosaurs", and determine how it
ran and turned.
The results indicate that a 6-8 tonne T rex was unlikely
to have topped 40km/h (25mph) and would have taken a couple of
seconds to swivel 45 degrees.
The researchers report their findings in the Journal of
They build on previous work detailing the biomechanics of the
famous dinosaur, but add in new refinements.
"We've now got a pretty good estimate of its weight - over which
there's been some controversy," lead author Dr John Hutchinson
"We've shown there's no way it could weigh 3-4 tonnes as some
people have suggested. It had to have weighed 6-8 tonnes," the
scientist, who undertook the work at Stanford University,
The team's computer modelling system estimated the centre of
mass position and the inertia (resistance to turning), which have
ramifications for how T rex would have stood and moved and
what it would have looked like.
As well as predicting the dinosaur's likely body mass and top
speed (25-40km/h or 15-25mph), the computer calculations gave the
team an idea of the turning ability of a T rex. This has
never been done before.
The study indicates the animal would have changed direction
incredibly slowly due to its massive inertia, taking one or two
seconds to make a quarter-turn.
The species certainly could not have pirouetted rapidly on one
leg, as popular illustrations have sometimes pictured it, and other
large dinosaurs, doing.
More agile prey would have given the slip to a marauding T
rex quite easily, it seems.
The researchers believe their work will help palaeontologist
build up a more realistic picture of how the large dinosaurs lived.
"These were big clunky things - T rex and the animals it
probably preyed on. We have to slow down our view of that
ecosystem," said Dr Hutchinson, who is currently lecturing in
biomechanics at the Royal Veterinary College in the UK.
"It wasn't like the Serengeti today where everything is done at
Dr Paul Barrett, of London's Natural History Museum, commented:
"This is another finding that undermines the kind of idea of T
rex as a super-predator.
"The main reason for that is that it was a lot slower than we
used to think it was; but it has this huge mouth filled with 60-odd,
30cm-long teeth, so it was still a formidable animal."