The mighty Tyrannosaurus rex has just been taken down yet another peg by some meddling paleontologists. While we already knew that a running T. rex would to catch the fleeing jeep in Jurassic Park, its preferred walking speed has also now been downgraded from a brisk 6.7 miles per hour to a , easily achievable for an . In prehistoric times, you could have strolled down the street and chatted with your friendly neighborhood T. rex without even breaking a sweat.
This is based on the motion of the T. rex’s flexible tail . The tail acts as a counter balance for the T. rex’s giant body but also as a suspension system, storing and releasing energy as it sways up and down with each step. Researchers used a model of the tail’s motion to figure out how fast it would have moved up and down in its natural lowest-energy state, which corresponds with the preferred walking speed. Once you know how often a T. rex takes a step and estimate the length of each step using the animal’s overall size, you can how fast it is moving. And the answer is not very fast.
To its credit, this new flexible tail model could actually have the opposite impact on estimates of the dinosaur’s maximum running speed. That top speed is currently thought to be limited by bone strength, since supporting 6 tons of body weight creates a lot of stress. Using the tail as a shock damper would allow the T. rex to run a fair bit without shattering its bones under its own weight. More research is needed to figure out exactly how fast that is, but you’re probably still pretty safe in a jeep.