SCIENCE
01/29/2016 02:05 pm ET

Nanotyrannus May Have Been Scarier Than T. Rex, And Here's Why

It's been described as the "cheetah" of the dinosaur world, but many paleontologists disagree on whether it even existed.
An illustration of a Nanotyrannus stalking a herd of Corythosaurus dinosaurs.
Stocktrek Images via Getty Images
An illustration of a Nanotyrannus stalking a herd of Corythosaurus dinosaurs.

If Tyrannosaurus rex was the lion of the Cretaceous dinosaur world, then the Nanotyrannus would have been the cheetah.

That's according to Scott Persons, a graduate student in paleontology at the University of Alberta in Canada. He led a new study, published in the journal Scientific Reports on Wednesday, revealing that Nanotyrannus would have been the carnivorous dinosaur best adapted for speed more than 65 million years ago -- that is, if the dinosaur even existed.

"It is hotly debated if Nanotyrannus was really a separate species or if its skeletons are just those of juvenile Tyrannosaurus," Persons told The Huffington Post. 

"I think Nanotyrannus probably was a separate species," he said. "Nanotyrannus lived alongside T. rex, but was more lightly built and had proportionately much longer legs -- indicating that it was a much faster runner."

Persons and his supervisor at the university, paleontologist Dr. Philip Currie, analyzed the lower-leg lengths and body masses of 53 different carnivorous theropod dinosaurs. Theropods are the group of bipedal dinosaurs that includes T. rex, Allosaurus and Velociraptor.

Persons then used the analysis to develop a math equation to estimate each dinosaur's speed: The longer the lower leg is compared to the upper leg, the faster the animal likely could have traveled, CBC News reported.

A comparative infographic of speed adaptation scores for (from left to right) Guaibasaurus, Velociraptor, Allosaurus, Tyranno
University of Alberta
A comparative infographic of speed adaptation scores for (from left to right) Guaibasaurus, Velociraptor, Allosaurus, Tyrannosaurus and the controversial Nanotyrannus.

Based on the equation, the researchers found that the 5-meter-long Nanotyrannus would have been the fastest of all carnivorous theropods.

"As far as I'm concerned, it was the scariest dinosaur," Persons said in a statement. "Sure, it might take it four to five bites to eat you, while T. rex could do it in just one or two. But eaten is eaten -- and no dinosaur was better adapted to chase you down."

Other scientists, however, think that more research is needed to verify these new findings.

The idea behind the study is "really interesting," Dr. Kevin Middleton, an anatomist at the University of Missouri, told USA Today. "They might be totally and completely right. But my view is we don’t know yet."

T. rex and Nanotyrannus probably feasted on the same kinds of herbivorous dinosaurs, Persons said. But while T. rex was able to attack heavily armored creatures such as Triceratops, Nanotyrannus was better equipped to chase down smaller, swifter animals.

How would the two have measured up in a theropod-on-theropod battle? Persons said Tyrannosaurus still would have won that fight.

"I doubt they fought often," he said. "Tyrannosaurus so massively outclasses Nanotyranus that Nanotyrannus would put its speed to good use and run from any aggressive T. rex ... and it was fast enough to escape."

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