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Wednesday, 27 February, 2002, 21:39 GMT
Plodding with dinosaurs
Fewer than 30 T. rex specimens have been recovered
Animals caught in the gaze of the fearsome Tyrannosaurus rex had an excellent chance of staying alive if they could run fast enough.

A new study suggests that the "king" of the dinosaurs was probably something of a slowcoach, incapable of breaking into a sprint and catching the most agile of prey.

That's why you don't see elephants climbing trees or flying

Dr John Hutchinson
Drs John Hutchinson and Mariano Garcia used a computer model to calculate how much muscle an animal needs to move at different speeds and postures.

When applied to a T. rex that weighed 6,000 kilograms, their work shows a top speed of between 18 kilometres per hour and 40 km/h (11 miles per hour to 25 mph) might have been achievable, with the lower figure more likely.

This is a great deal slower than the 72 km/h (45 mph) gallop that some scientists have postulated for the dinosaur, and makes the famous movie sequence in Jurassic Park in which a T. rex chases a car seem rather comical.

Hot debate

"My colleague and I built a simple model that showed that a running Tyrannosaur at 45 mph would need far too much muscle mass than is reasonably possible in order to maintain that speed," John Hutchinson told the BBC.

"Most of its body mass - more than 80% - would need to be concentrated in its legs, leaving little room in other parts of the body for anything else. As animals get larger, the ability of their muscles to generate enough force to support their own weight becomes less and less. Therefore, they have to use less extreme activities.

"That's why you don't see elephants climbing trees or flying, for example."

TR, John Hutchinson
What holds for chickens and alligators should also hold for dinosaurs
Hutchinson and Garcia checked their model against living animals - alligators and birds, as well as humans.

Some researchers are likely to attempt to use the study to back up their argument that Tyrannosaurus was more of a scavenger than a predator - a theory that has become more popular in recent years as paleontologists have recovered and studied more bones.

But Hutchinson and Garcia say their work has little impact on what they regard as a "nonsensical debate". They said in a statement: "This dichotomy is false; living carnivores generally scavenge and hunt opportunistically.

Unknown factors

And if the prey T. rex was hunting was also large then these animals "were likely just as inept at running as Tyrannosaurus was. In fact, these potential prey might have been even slower than Tyrannosaurus".

The Californians' work, which is published in the journal Nature, has had a mixed reception.

Chris Brochu, a palaeontologist at the University of Iowa, praised the paper as "the firmest statement yet made on how fast a large, bipedal dinosaur could have moved - its running ability or lack thereof".

Martin Lockley, a professor of geology at the University of Colorado at Denver, however, said the computer model could not reproduce the complexities of the real animal.

"Animals are not machines," he said. "These animals were dynamic and flexible, and tissue is very hard to reduce to numbers."

And Julia Day, a palaeontologist at Cambridge University, UK, said there was no real consensus on how T. rex; it could have weighed a lot less than some scientists think.

"They're not taking everything into account," she said. "There are just so many unknowns."

John Hutchinson is currently at Stanford University, California, US, and Mariano Garcia is at Borg-Warner Automotive, New York, US.

Dr John Hutchinson
"Most of its body mass would need to be concentrated in the legs"
See also:

30 Jan 02 | Sci/Tech
Dino feet leave their mark
18 May 99 | Sci/Tech
Caught in their tracks
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