Just how Fast a Runner was Tyrannosaurus rex

It seems that the debate over the top running speed of theropod dinosaurs is continuing unabated.  These stars of stage (Walking with Dinosaurs) and screen (all those dinosaur movies), the big, meat-eating dinosaurs such as T. rex continue to puzzle scientists as to the top running speeds and their walking pace.  The difficulty lies in the fact that there is nothing around on the planet, any extant animals for example that resemble them.  This coupled with the relatively poor fossil record for many large theropods and the fact that no one has ever seen the likes of T. rex is going to cause this debate to rumble on and on.

Theropod Locomotion

However, perhaps one of the most detailed studies into dinosaur locomotion has been carried out by scientists at Manchester University and one of the papers detailing some of the scientist’s work is being presented at the annual conference of the Society of Vertebrate Palaeontologists at Bristol University.

Karl Bates, a PhD student, nominated for the Society’s Romer Prize (recognising the contribution of newcomers in the field of Vertebrate Palaeontology), has been using sophisticated computer modelling to calculate the running and walking speeds of one such theropod.  The theropod in question is Acrocanthosaurus (A. atokensis), a  large member of the Tetanurae, whose fossils have been found in the USA.  This 8-12 metre long giant lived many millions of years before T. rex (125-100 million years ago approximately).  It was the apex predator and would have been an active hunter, but just how fast it could run was not known until Mr Bates, combined anatomical measurements and assumptions with a sophisticated computer programme that permitted the cursorial speeds of this dinosaur to be estimated.

Safari Ltd have introduced a variety of theropod figures and replicas into their range.  To view the extensive Safari Ltd. Wild Safari Prehistoric World range: Safari Ltd. Wild Safari Prehistoric World Models and Figures.

A Scale Drawing of Acrocanthosaurus

Picture credit: Everything Dinosaur

Safari Ltd have also introduced a Wild Safari Dinos Acrocanthosaurus dinosaur model and a variety of other theropods including several models of Tyrannosaurus rex and feathered dinosaurs.

Commenting on the issue of theropod locomotion, Karl stated:

“The speeds you see in Jurassic Park are just ridiculous.  Even a really simple biomechanical model shows that a T. rex chasing down a jeep that is going at 50 mph [80kph] is beyond the realms of all possibility”.

Studying Acrocanthosaurus

Using measurements taken from an Acrocanthosaurus skeleton at the Natural History Museum in North Carolina, plus we suspect some data from the superb fossil cast of the hip bones and sacral vertebrae of an Acrocanthosaurus we were given the opportunity to see at Manchester University, Karl was able to produce a computer model estimating the travelling speed of this dinosaur.

This young scientist’s model indicates that an adult Acrocanthosaurus would have had an average running speed of 15.2 mph (24.2 kph) and would have walked at around 5.6 mph (9 kph).

Similar studies have been carried out by University of Manchester researchers and a number of theropods plus living animals today have been put on the University’s virtual race track.  For example, Tyrannosaurus rex when modelled in this way produced a slightly faster top running speed, about as fast as a professional footballer.  The longer femur making it better adapted for running than the Acrocanthosaurus.

To read an article about T. rex outrunning footballers: T. rex Chasing Down David Beckham.

The article link above also includes a table that compares T. rex locomotion with other animals extinct and alive today.  The computer models produced by the University of Manchester team have proved very accurate in their assessment of the top speeds of animals around today.  The computer models predicting the maximum velocities of extant creatures such as emus and human beings.

Biomechanical Models

A similar biomechanical model allowed Dr Hans Eriksen and colleagues at the University of Oslo to predict a time of below 9.6 seconds in the 100m sprint for Usain Bolt. Bolt’s world record time is 9.58 seconds.  This athlete is certainly exceptional, for example he takes just 41 steps to compete 100 metres whilst the rest of the field in an Olympic final would take nearer 48 steps.  However, the computer models are proving to be very accurate and such data helps to reassure palaeontologists that the information produced from studies on extinct animals must be near the mark.

One unresolved problem with the computer simulation is that the model dinosaur relies almost entirely on the muscles in its upper legs, without flexing muscles around its ankles, which is not physiologically plausible.

By including more prior knowledge about what types of movement are realistic, Mr Bates hopes to refine the model to give a more realistic portrayal of how large predators would have moved.  There is one other specific problem associated with Acrocanthosaurus.  We must acknowledge that in common with most other large theropod dinosaurs there is little fossil material to study.  However, Acrocanthosaurus means “high spined lizard”, it got its name from the neural spines that run down the backbone from the neck to the tail.

The purpose of these spines is unclear.  We can’t remember whether there are ossified tendons associated with these spines, but perhaps these spines in some way supported a flexible sail-like structure that stored energy in the hip region like a giant shock absorber.   A sort of spring device to help reduce the energy and effort required to move this giant dinosaur.  Kangaroos have tendons in the legs that help them save energy when bounding along, we are not suggesting that this dinosaur hopped like a Wallaby but maybe the swinging motion of the body coupled with the neural spines helped it to reduce the amount of energy used as it ran.

Trackways attributed to Acrocanthosaurus can provide supporting evidence of locomotive speed (the Alexander formula), once an estimate of hip height has been made.  These footprints always look so dainty to our eyes.  The feet of Acrocanthosaurus also seem relatively small considering the size of the animal.

Like we said earlier, the mysteries surround theropod locomotion are going to rumble on.