There is a famous scene from “Jurassic Park” in which a Tyrannosaurus rex chases the protagonists of the film, who flee in a Jeep. The bites of the enormous dinosaur come dangerously close on a couple of occasions to a vehicle that is traveling at a considerable speed before the panicked cries of its passengers. According to science, this scene is part of fiction, since Tyrannosaurus rex was a slow animal that would have nothing to do with the speed of a motorized vehicle.
The daily life of a T. rex
The king of the lizards. One of the greatest predators in the history of our planet. Certainly the most famous of all. A star of cinema and popular culture. But his forte was not speed.
One of the scientific debates with the greatest media coverage has been going on for years: the maximum speed of Tyrannosaurus rex. Previously it was estimated that he could run at a speed of between 17 and 53 kilometers per hour. If reality were adjusted to the highest figures, this predator could reach any human, since the fastest only reaches 43 kilometers per hour.
However, few studies have looked at the common gait speed of Tyrannosaurus rex . That is, how fast did this walking dinosaur used to travel? One study relied on technology to draw its own conclusions.
a matter of perspective
For decades, many paleontologists have devoted themselves to establishing the speed at which T. rex could run by analyzing only part of its skeleton. That is, one compared the long limbs of the dinosaur with those of an ostrich and thought that it could be a fast animal. Another looked only at the hip and thought that it would prevent him from running much. One of the most widespread ideas about the race of Tyrannosaurus rex had this animal as a fast dinosaur, but over short distances. This inability to maintain his career may have been the theory followed by the “Jurassic Park” writers for the Jeep chase to end quickly with the dinosaur simply stopping his pursuit.
In any case, the previously used research methods have been superseded thanks to technology applied to science . Biomechanical models make it possible to interpret the movement of T. rex taking into account many factors such as its weight, the size of its bones, the movement of its limbs, etc. According to John Hutchinson, an expert in evolutionary biomechanics at the Royal Veterinary College in London:
“You need to put all the parts together to get a complete picture. Looking only at the morphology you get nothing”.
They walked at the same speed as humans
With this new perspective, it has been possible to determine how fast tyrannosaurs used to move. According to a 2021 study published in the journal “The Royal Society”, the common speed of Tyrannosaurus rex was about 5 kilometers per hour, the average speed at which humans walk . Considering that an adult T. rex was about 12 meters long, 4 meters tall, and weighed between 6 and 9 tons, that doesn’t seem like a very spectacular figure.
This new method of investigation represents a great advance, although it runs the risk of falling into the same mistake as previous paleontologists, focusing excessively on a single part of the body, in this case the tail. According to Pasha van Bijlert, lead author of the study:
“Dinosaur tails were vital to the way they moved. Not only did they serve as a counterweight, the tail also produced much of the force needed to move the body forward through two large muscles: the caudofemorals, which pull legs back during each step.
Until now, the role of the tail in the gait of Tyrannosaurus rex had not been taken into account. However, this limb is half the length of the dinosaur and could weigh a ton . Therefore, it must have had an important weight in the movements of this carnivorous predator (pun intended).
How is the speed of a dinosaur measured?
Animal species save as much energy as we can by moving at a regular cadence. While humans move our legs at an appropriate pace according to our body and accompany them with our arms in a rhythmic swing, it is difficult to determine the movement of an animal that has been extinct for millions of years. Even more so in the case of Tyrannosaurus rex , which has very short front legs, very long back legs and an even more impressive tail.
To study the movement of T. rex , a three-dimensional digital model of the skeleton of a 66-million-year-old specimen was created. They added the muscles and ligaments of the tail to the model. Fossil footprints were used to conclude that the stride of T. rex was 1.94 meters. On the other hand, by measuring the swing of the tail and the rhythmic movement of the body, they found that T. rex had a stride of 1.28 meters per second. Putting these data together, they were able to determine that Tyrannosaurus rex walked at 4.6 kilometers per hour .
Based on these results, van Bijlert calculates that the most famous predator among the dinosaurs could run at about 30 kilometers per hour:
“There are those who aim for even greater speed, but that way the legs could have been broken. Although I hope to study this in the future.”
References:
Ferrer, I. 2021. The ‘Tyrannosaurus rex’ walked at a speed of 4.6 kilometers per hour, like humans. elpais.com.
Van Bijlert, P. A. et al. 2021. Natural Frequency Method: estimating the preferred walking speed of Tyrannosaurus rex based on tail natural frequency. The Royal Society 8, 4. DOI: 10.1098/rsos.201441.
