Video: Hadrosaur running

Did four-legged dinosaurs gallop like a horse, run like an ostrich or hop like a kangaroo? All three have been suggested, but with only fossils to go on it’s a difficult puzzle to solve.

That’s why Bill Sellers, a computational zoologist at the University of Manchester, UK, has developed a new technique for simulating dinosaur movement and working out which gaits they most likely used.

Sellers and his team used a laser scanner to create a 3D computer model of the skeleton of an Edmontosaurus, a type of hadrosaur or “duck-billed” dinosaur, and added virtual muscles to make it move. Fossilisation does not preserve a dinosaur’s muscles, but educated guesses about how they worked can be made by studying animals alive today, such as ostriches.

Hopping not permitted

There’s more to motion than muscles, however, as Sellers discovered. His team began by using a supercomputer to try out different patterns of muscle activity at random and pick the pattern that moved the dinosaur furthest forward in 5 seconds. By slightly varying the most successful patterns and repeating the process thousands of times, the computer simulation produced a variety of possible gaits. And it turns out that a kangaroo-style hop on both legs gave a speed of 17 metres per second, while a four-legged gallop and two-legged run trailed at 16 m/s and 14 m/s respectively.


But there was a problem with this finding: fossils show no evidence that hadrosaurs could hop. This led Sellers to investigate why this gait was not possible. Further analysis revealed that the forces produced by hopping would shatter the dinosaur’s bones.

Now that Sellers could calculate the load on a dinosaur’s skeleton during motion, he could work out the maximum possible size of its muscles, beyond which the animal’s bones would have been damaged. This in turn helps to determine what gaits it would have been capable of. For the hadrosaurs, a four-legged gallop would also have put too much stress on their bones, so it is most likely they moved at slower speeds on four legs and reared up to run on two.

“The ability to simulate a variety of gaits in an extinct animal is exciting, but to get reliable bone stresses you need good muscle stresses and other data,” says John Hutchinson, a biomechanics expert at the Royal Veterinary College in London, who previously developed a model for Tyrannosaurus rex locomotion. “I’d like to see this proven with several living animals to see how wrong the answers can be,” he adds.

Journal reference: Palaeontologia Electronica, vol 12, issue 3, 11A