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Its name may translate as ‘king of the tyrant lizards’ but Tyrannosaurus Rex could not have outrun a speedy human, scientists have concluded, making a mockery of Jurassic Park.
Although it was previously thought the dinosaur could sprint at around 45mph, German scientists have discovered that the lumbering beast was so massive it would have struggled to accelerate beyond a medium trot.
In fact, researchers calculated that T Rex could only have clocked a running speed of 16.5mph, just one mph faster than the average human, and a 11 mph slower than Usain Bolt, the fastest man on Earth.
And the dinosaur certainly would not have been capable of keeping up with a moving Jeep, as shown in Spielberg's Jurassic Park.
However even Bolt could not have out-run a velociraptor, who would have been one of the fastest dinosaurs with the ability to run at 34 mph.
Researchers at the German Centre for Integrative Biodiversity Research, Leipzig, looked at almost 500 species, ranging from molluscs to whales, to find out how size was related to speed.
Zoologist Dr Myriam Hirt, of the German Centre for Integrative Biodiversity Research, Leipzig, said: "Palaeontologists have long debated the potential running speeds of large birds and dinosaurs, that roamed past ecosystems.
"This is consistent with theories claiming Tyrannosaurus was very likely to have been a slow runner."
Under Dr Hirt’s hypothesis, animals have only a finite amount of time to accelerate from a standing start before they can accelerate no longer.
They find this is because the acceleration phase requires muscles to function anaerobically, without oxygen, during which only limited stores of energy are available.
Larger animals take longer than smaller ones to accelerate to their maximum speed.
So if acceleration time in the anaerobic phase exceeds the amount of energy that can be made available to muscles, the maximum achievable speed reaches an upper limit.
Dr Hirt said: "Put simply, small to intermediately sized animals accelerate quickly and have enough time to reach their theoretical maximum speed, whereas large animals are limited in acceleration time and run out of readily mobilisable energy before being able to reach their theoretically possible maximum.
“In nature, the fastest running or swimming animals such as cheetahs or marlins are of intermediate size.”
The team found maximum speed falls rapidly as animals grow beyond average size.
For huge animals such as T Rex, which weighed up to nine tons, the time required to accelerate to faster speeds outstrips the time available for acceleration.
The research was published in the journal Nature Ecology & Evolution.