Wasn’t the Tyrannosaurus rex the only one of its kind? † Science

The Tyrannosaurus rex, loosely translated triannic lizard king, was first described in 1905 and was the only species in the genus Tyranossaurus for all that time. But a group of three researchers, led by American paleontologist Gregory Paul, now propose that there are two other species in this genus: the ‘Tyrannosaurus imperator’, loosely translated tyrannical lizard emperor, and the ‘Tyrannosaurus regina’ or tyrannical lizard queen. The team of paleontologists examined and analyzed the bones and teeth of 37 Tyrannosaurus fossils, noting several variations.

“After more than a century of placing all specimens in one species, without examining the matter closely, the first and only analysis shows that the variation in Tyrannosaurus is greater than the standard for dinosaurs, and that it is divided into the time in a way that indicates Darwinian speciation has taken place from one species to two new species, before the final extinction of the dinosaurs concluded further evolution,” said Paul.

The researchers now state that the differences between the femurs and teeth do not indicate a different species of dinosaur, but rather a different species within the genus Tyrannosaurus. That’s why the team proposes the ‘Tyrannosaurus imperator’ and the ‘Tyrannosaurus regina’.

According to the researchers, the imperator, or emperor, is said to be the oldest and the species lived the longest ago. The animal would have had relatively sturdy thighs and four small incisors in the lower jaw. The rex and the regina would have had only two incisors. They would have been the younger species of the Imperator. The regina would have had slimmer thighs and a lighter build, according to researchers. In other words, the T-rex would have had an ancestor and a sister species.

However, Paul and his team admit that it is also possible that the variations observed could also be due to individual differences of the specific fossils. Although those would be very extreme, the researchers say. Paul compares the differences observed with the differences between the tiger and the lion. “Lions and tigers belong to the same genus, Panthera, but they are recognized as separate species because the differences are large enough,” said Paul.

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According to other paleontologists, the new study by Paul and his team might not be quite right. They argue that the researchers drew conclusions too quickly. “I understand the temptation to divide the T-rex into different species, because there is indeed some variation in the bones that we know. But in the end, as far as I’m concerned, that variation is very small. Until I see stronger evidence, this will just remain T-rex to me,” Stephen Brusatte, a paleontologist at the University of Edinburgh, told the British weekly New Scientist this week.

And Thomas Carr, a paleontologist at Carthage College, also thinks the research isn’t quite right. He did a study in 2020 into the possible variants in the genus Tyrannosaurus, but found no clues. “I think they just see what they want to see,” he says in the same magazine. “If their species were valid, they would have to be identified by more than just two features: almost every detail would have to be different.”

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