THE FEARSOME Tyrannosaurus Rex could have been outrun by a fleet-footed human and, when not pursuing prey, ambled over the Jurassic landscape at the pace of a leisurely window shopper.
Structural engineering techniques show that dinosaurs' musculoskeletal structure would have made it impossible for them to move at the speeds hitherto imagined by generations of archaeologists, natural historians and Hollywood film makers, claimed Leeds University emeritus professor of zoology McNeill Alexander.
Speaking at a lecture entitled 'the dynamics of dinosaurs and other extinct animals', Alexander used standard engineering principles, including beam, mechanical advantage and displacement theories, to demonstrate that dinosaurs' skeletons could not have coped with the huge muscular forces required for rapid movement.
Though distantly related to present day reptiles, most big dinosaurs moved more like modern mammals or birds, Alexander said, with footsteps close to their centre line.
Dinosaurs would have been subject to the same biomechanical laws as animals, including chickens, humans, buffalo, rhinoceros and elephant, he claimed.
Small, athletic animals can get away with having very delicate bones because they have low mass. They require a relatively light muscular system for mobility and impacts are low.
But as animals are scaled up, their limb length and mass grows disproportionately. Doubling of the animal's height cubes its mass up to a much greater bulk.
To achieve the same kind of agility as an animal half its size, a Tyrannosaurus Rex would have needed proportionately much more powerful muscles. In turn, its bones - particularly leg and pelvic bones - would have had to be far thicker.