Let's say you travel back in time to the Cretaceous Period and find yourself face to face with a hungry tyrannosaur. Can you outrun the beast?
If you believe the headline atop an article describing new research on a set of dinosaur footprints in present-day Wyoming, maybe so. It reads "You could probably have outrun a T. rex."
But one of the scientists who conducted the research says not so fast, and for good reason.
The spacing of the rare footprints -- each measuring about 18 inches in length -- suggests a gait of 4.5 to 8 kilometers per hour (2.8 to 5 miles per hour), according to a paper describing the research. That is slower than the average human, who can run about 11 miles per hour over short distances.
But "the tyrannosaur that made the footprints was just walking, and it was walking over muddy, mucky ground," said the scientist, Scott Persons, a graduate student in paleontology at the University of Alberta. "And it was clearly a walk and not a run because of how the feet were positioned" -- offset, indicating a sort of "bowlegged" gait.
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The series of three footprints in sandstone dating back 66 million years are believed to have been made by a young T. rex (or possibly a smaller tyrannosaur known as Nanotyrannus lancensis). The stride length and hip height were plugged into a standard equation to arrive at the estimate of the dinosaur's gait speed.
The finding "discounts previous speculation that tyrannosaur walking speeds were notably slower than those of other large theropods," Persons and his co-authors wrote in the paper, which was published in the June 2016 issue of the journal Cretaceous Research. But it says little about tyrannosaurs' maximum speed.
So just how fast could a T. rex go? Persons said there's no scientific consensus even after decades of debate. Some say it could manage no more than about 10 miles per hour, others that it could run 45 miles per hour.
No matter what, it's probably not something you'd want to find out firsthand.
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