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Was there more than one species of Tyrannosaurus? Charleston professor thinks there may have been.

Were there three species of Tyrannosaur instead of the one that is now accepted?  A College of Charleston paleontologist and his colleagues think maybe so.
Jim Tsorlinis
Were there three species of Tyrannosaur instead of the one that is now accepted? A College of Charleston paleontologist and his colleagues think maybe so.

A College of Charleston paleontologist and his colleagues have hypothesized that there were three, not one, species of Tyrannosaur ruling the age of dinosaurs.

Tyrannosaurus rex always has been one of the most famous dinosaurs, but recently a College of Charleston paleontologist thinks he may have made a new discovery about the “king of the tyrant lizards:” there may have been not one, but three species of tyrannosaur.

Dr. Scott Persons and two colleagues studied the bones and teeth of 30 tyrannosaur skeletons. Persons said traits that the different skeletons exhibited pointed his team to its hypothesis.

Among those traits were how thick the different bones were, said Persons. In addition, “Some tyrannosaurus specimens have got two sets of lower front teeth. They’ve got a very distinct chisel-like shape to them, whereas other specimens only have one such set. The third element was looking at where in the rock layers you find the different skeletons, with older, lower level rock units versus higher level, younger units.”

Tyrannosaurus is a genus, the category above species, the professor explained. By running many tests on the data they collected, Persons’s group has tentatively added the species names regina – or queen, and imperator, to the list along with rex.

Tyrannosaurus rex lives alongside, in the upper layers with Tyrannosaurus regina, sort of the co-rulers at the very end of the age of dinosaurs,” Persons speculated. “And both of them, we think, are probably descended from a third variety that we have called Tyrannosaurus imperator, or the ‘tyrant lizard emperor.’”

Persons’s colleague Jay Van Raalte, a math graduate of the College of Charleston, ran statistical tests on the bone thickness measurements, among other tests. She said the team reached its finding after considering many factors.

“We established that there was a lot of variation, an unusual amount of variation among the specimens, then we presented four major potential explanations,” she said. “Individual variation - there are tall people and short people, maybe it’s just that. Maybe it’s sexual dimorphism, male v. female. Maybe it’s age. As dinosaurs get bigger or older, these things change. And then our final potential explanation, speciation.

“We did find major correlations that kind of refute the idea of just totally random individual variation. So altogether, it seems like speciation is the most consistent with the data.”

Van Raalte said the group’s research has spurred thought among scientists. I think, and I think many paleontologists believe, that there is some speciation within Tyrannosaur. They may or may not agree that we’ve actually found the designations, but I do believe that this group of specimens represents multiple species. And maybe we didn’t find it, but maybe we got the conversation going, and the next person who looks into it does find it. And if that happens, we’ve positively contributed to science.”

The statistician said a hypothesis can be valuable regardless of whether it’s eventually accepted as fact, because even if it’s proven untrue, it’s a reminder that science is a constantly changing discipline that requires solid evidence, but that even something as substantial and known as T-rex can be challenged, and even the search for truth “can more nuance to our understanding.”

Persons said the research has led him to believe that the reasoning process behind their findings can be used to consider dinosaur discoveries in the future. “I don’t think what we’ve done is really unique to Tyrannosauruses. I very much, though, suspect that for the vast majority of dinosaur genera that we know of, as we find more and more specimens, we’re going to discover that there’re going to be multiple species associated with just about every genus.”

As a scientist who relies on evidence, Persons said even he is not completely convinced of his own hypothesis. But echoing Van Raalte, he said that even if their idea is refuted in the future, that knowledge itself will still move science forward.