The fastest creature on two legs was a tiny dinosaur about the size of a small cat, new research has suggested.

The sleek, lizard-like Compsognathus,which lived about 150 million years ago and weighed just 3kg (6.5lb), could run 100 metres in a little over six seconds, a speed that would leave modern Olympic athletes more than a third of the track behind.

An average specimen could reach a top speed of almost 40mph (64km/h), according to a new computer simulation.

This would make it faster than the ostrich, the quickest on land of all modern bipeds.

The simulation found that a 65kg ostrich should have a top speed of 34.5mph (55.4km/h) - much faster than humans but a slowcoach next to Compsognathus.

It would also have far outpaced all the other dinosaurs tested so far with the biomechanics model developed at the University of Manchester. Even Velociraptor, famed for its terrifying leg speeds in the film Jurassic Park, clocked in a full 15mph slower than its miniature rival.

Bill Sellers, a biomechanics expert who led the study with Philip Manning, a palaeontologist, said it was plausible that Compsognathus was the fastest animal on two legs ever to have lived.

“It is certainly by far the quickest in terms of our results,” he said. “It would have done the 100 metres in about six seconds, leaving the Olympic champion well behind.”

In the study, which is published in the journal Proceedings of the Royal Society, Dr Sellers and Dr Manning used a supercomputer to reconstruct the speeds of five dinosaurs: Compsognathus, Velociraptor, Tyrannosaurus rex, Dilophosaurus and Allosaurus.

All were two-legged predators belonging to the theropod group of dinosaurs, but they ranged in size from 3kg for an average-sized Compsognathus to six tonnes for T. rex.

The computer used details of each dinosaur’s anatomy to work out its most efficient gait, taking up to a week to learn the optimum biomechanics for each animal. It started with a clumsy stumble, and gradually learnt the right posture and stride to run as fast as possible.

The model was calibrated using data from a 71kg man with the muscle and bone structure of a professional athlete, and a predicted top speed of 17.7mph (28.4km/h). Although this is slower than the 23mph or so top speeds reached by Olympic sprinters, it is representative of a very fit man such as a footballer. Data from a 65kg ostrich and a 27kg emu were then fed into the system, producing top speeds of 34.5mph and 29.8mph respectively.

The dinosaurs had an even wider spread of top speeds. T. rex was the slowest, at 17.9mph, but even this was slightly faster than a human.

Dr Manning said: “The figures we have produced are the best estimate to date as to how fast these prehistoric animals could run.

“Since the movie Jurassic Park, scientists have questioned the speed of these dinosaurs and some have wondered whether Tyrannosaurus could have run at all.

“Our research, which used the minimum leg-muscle mass T. rex required for movement, suggests that while not incredibly fast, this carnivore was certainly capable of running and would have little difficulty in chasing down the footballer David Beckham for instance.”

Ostriches have been timed at about 5mph faster than the model’s predicted speed in the past, but the scientists said it was likely that some Compsognathus specimens could also run faster than the simulation suggests.

“Our data have probably underestimated the speed of ostriches a bit, but the same is probably true for Compsognathus,” Dr Sellers said. “All the estimates are at the lower bounds. The model just finds a good way of running, not necessarily the best one.”

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