Tyrannosaurus rex was a lumbering giant incapable of even breaking into a gentle jog, say two specialists in biomechanics. Their work suggests that the popular, Jurassic Park-inspired image of T. rex as an adept sprinter, capable of catching a speeding car, is artistic licence literally going a step too far.
John Hutchinson and Mariano Garcia of the University of California at Berkeley calculated that a six-tonne T. rex could not have carried enough leg muscle to break into a run. Instead it could only walk at a respectable five metres per second, just half the top speed clocked for an elephant or a top human sprinter.
Palaeontologists have been arguing about the top speed of giant predatory dinosaurs for years. In a bid to resolve the dispute, Hutchinson, now at Stanford University, developed a model for calculating the muscle mass an animal would need to run on two-legs, based on its size, weight and posture.
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Fatal fall
The requirements increase with body mass. A running chicken in their model would need at least 4.7 per cent of its body mass in muscle in each leg; an actual chicken has 8.8 per cent. In contrast, a full-size T. rex would have needed muscle weighing 43 per cent of its body mass in each leg to get up a bit of speed 鈥� a practical impossibility.
Hutchinson is confident the model 鈥渋s going to hold for large dinosaurs in general鈥�. That means T. rex would still have been able to catch its ambling herbivorous prey.
The model seems reasonable, says Jim Farlow of Indiana University-Purdue University, Fort Wayne. The tracks of a large dinosaur recently discovered in Britain indicate the animals were moving about eight metres per second, Farlow estimates, but that includes a large margin of error.
He has also suggested that running too fast would have been a bad idea for giants such as T. rex because a fall could have been lethal.
Journal reference: Nature (vol 415, p 1018)
