Ever since the first Tyrannosaurus skeleton was put on display in 1905, the tyrant lizard has captivated the world. Now, researchers say that the Tyrannosaurus may have actually developed into three distinct species beyond just the infamous Tyrannosaurus Rex.
A team of three researchers led by paleontologist Gregory Paul said on Monday that variations of about three dozen fossils indicated that two additional species deserved recognition. Paul and the fellow researchers dubbed these two new species Tyrannosaurus Imperator and Tyrannosaurus Regina.
“After over a century of all specimens being placed into one species without the issue being carefully examined, the first and only analysis finds that the variation in Tyrannosaurus is beyond the norms for dinosaurs, and is distributed over time in a manner that indicates that Darwinian speciation from one (species) to two new species had occurred before the final dinosaur extinction cut off further evolution,” Paul said in an abstract published to Evolutionary Biology, first reported by Reuters.
Paul cited differences in size and shape of several features: Femurs, thighbones, and the number of small teeth in the lower tip of the jaw.
Some researchers, however, disagree with Paul and his partners’ findings.
“Ultimately, to me, this variation is very minor and not indicative of meaningful biological separation of distinct species that can be defined based on clear, explicit, consistent differences,” University of Edinburgh paleontologist Steve Brusatte said. “It’s hard to define a species, even for animals today, and these fossils have no genetic evidence that can test whether there were truly separate populations.”
If accepted as true, Paul’s new findings would indicate that Sue, a Tyrannosaurus skeleton exhibited at Chicago’s Field Museum, is actually a T-Imperator rather than a T-Rex. Sue stands more than 40 feet long and 13 feet wide, making it the largest Tyrannosaurus specimen ever discovered, as well as the most complete assembly of Tyrannosaurus fossils.
Another paleontologist by the name of Thomas Carr, who published a 2020 study finding no species variation in the Tyrannosaurus, similarly disagreed with Paul’s findings.
“Perhaps most damning is the fact that the authors were unable to refer several excellent skulls to any of the three species,” Carr said. “If their species are valid, then more than just two features should identify them: nearly every detail — especially in the head — should be different.”
Joseph Knoop is a writer/producer for IGN.