Most everyone has probably seen at least one installment of the Jurassic Park series. For those of you in the small population, the main plot of each movie is running away from a ferocious predator, usually a Tyrannosaurus Rex or some similar carnivorous dinosaur. The protagonist typically has the job of running, driving, or otherwise hiding to avoid being eaten alive.
Much like in the movies, the world of dinosaurs, at least in the research of dinosaurs, has thought that a T-Rex had the capability to run and catch fast prey.
Certain research articles suggest that dinosaurs like a T-Rex could run upwards to 50-60 kilometers per hour, or about 37 miles per hour(Paul, 1998). That’s pretty damn fast.
However, a recent study published in Peer J suggests that a T-Rex was actually incapable of running. In this particular study, running was defined as a gait that would be running without having both feet off of the ground at the same time, for example a horse gallop.
So with Velociraptors being the actual size of our modern turkey, and a T-Rex being unable to run, Jurassic Park may not be such a bad idea after all….Just kidding.
But how in the world can a T-Rex be incapable of running?
The study that previously mentioned a high speed for the T-Rex suggested so due to their long and strong legs and specialized hip structure. This new study indicates that the legs of a T-Rex was actually the reason why they couldn’t run. In fact, their top speed reached about 12 mph.
How can two studies contradict each other when they are looking at the exact same information?
The answer of course, is in the details.
If you get a chance to read the Peer J article (which I always recommend), the introduction focuses on previous studies and the various mechanisms used to determine speed. While we don’t have enough time to go over all of them, I figured one may be beneficial to our readers.
Gregory S. Paul published an article in 1998 suggesting that a T-Rex, with its specialized pelvis and leg structures being similar to modern tetrapods (four legged creatures), would be able to run at a reasonable pace. In case you are unfamiliar with the running patterns of different species (which I was until researching for this article), it’s important to note that a Rhinoceros, having a similar pelvic and leg structure is able to run at a reasonable pace. They are also quite large. Meanwhile, an elephant, which is more comparable in weight to a large T-Rex has a very different bone structure and is designed specifically for walking (see figure above). Elephants also have an ankle that prevents mobility (which differs from ours, a Rhino’s, and a T-Rex) and have a “flat” pelvis more similar to humans. In addition, examining the shape and orientation of the hip bones of Tyrannosaurus suggests that it is better suited to maintain the weight of its owner and can give it the ability of running.
Paul continues to discuss the correlations of femur bone length and speed where there appears to be a positive correlation between speed and the length of your thigh bone. He also goes on to discuss how bone shapes and certain structures can suggest how fast an animal is able to run.
He then focuses on other studies that suggest a T-Rex is unable to run. One in particular highlights the frailty of the leg bone, and how running could not be possible with the average weight of these gigantic creatures. Paul points out that the femur of a T-Rex may be able to support more weight than expected with these models, largely due to the thicker walls of the femur. He also mentioned discrepancies with the weight they predicted and the fossils analyzed have damage that would confound the data.
As I am sure you have noticed by now, there appears to be a slight conflict in regard to the speed of our beloved dinosaur.
So what does this new study have to say?
The Paul study we just previously mentioned, and other studies that conflict with it all have one thing in common. The research is focused only on bone morphology. All of these scientists spent time studying fossil structures and comparing them to bones of modern animals to “tweak out” clues of what life being a T-Rex was like.
But there is one aspect missing; the tissue.
Bone alone cannot work to move our limbs. Soft tissues like muscles are needed to let our bodies twist and turn. And these soft tissues can have an impact of how we can move.
Recent advances in technology have given scientists the opportunity to estimate how muscles connected to bone, and how they affected movement in extinct species. This technique is what the Peer J article primarily utilizes.
The figure above shows an estimation of various muscle structures and limb interactions might have been like for the T-Rex. By scanning the bones and calculating joint positions and range of motion, muscle structure could then be predicted.
After this, computer models can be simulated. The output from the computer simulations were able to give a maximum velocity. The answer? Eh, about 8 meters per second. The data also calculated the estimated stride of the dinosaur (at its peak about 8 meters), and the Froude number (used to compare speeds with other animals) that suggested a T-Rex can only reach a walking stride.
Additional data that focuses on the change in kinetic and gravitational potential energy also confirms that a T-Rex could not gain the energy differences to achieve a running speed.
While I think this study makes valid points, and uses technology that can estimate at a much higher efficiency than previous analyses, there is still much to weed out. Unfortunately, soft tissue does not preserve well and we most likely will not find a perfectly preserved T-Rex. However as technology increases in power, and as we work to understand how other tissues might have impacted the movement of the large dinosaurs, much more is left to be discovered. I do think this study is moving in the right direction, and gives us more information than we had previously. If you are interested in either of the articles I discussed today, the links are below. Attached here is also a link to videos the scientists produced with their program of the simulated T-Rex walking!
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Remember to always be curious, and stay mindful!
1.May, Ashely. Sorry, ‘Jurassic Park’ fans: The T. rex couldn’t run, new research says. USA Today, July 19, 2017. https://www.usatoday.com/story/news/nation-now/2017/07/19/t-rex-couldnt-run-new-research-says/491122001/
2. Paul, Gregory. Limb Design, Function, and Running performance in Ostrich-Mimics and Tyrannosaurs. Gaia 15. December, 1998. http://gspauldino.com/GaiaLimbdesign.pdf
3. Sellers, William. Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis. Peer J. July 18,2017. https://peerj.com/articles/3420/.
4. Title picture source- https://www.pinterest.com/pin/474003929501926665/