Study Claiming T. Rex Was Three Separate Species Receives Rebuttal
Earlier this year, researchers claimed that Tyrannosaurus rex (T. rex), one of the fiercest predators to ever roam the Earth, may have been three different dinosaur species, not just one. Researchers analyzed the skeletal remains of Tyrannosaurus as part of a study and found physical differences in the femur, other bones and tooth structure between the specimens. The differences suggest that the T. rex specimens should be reclassified into three separate groups or species.
However, the study claiming that T. rex was three species has recently been refuted.
The new study refuting the claim was recently published in the journal evolutionary biology. Led by paleontologists from the American Museum of Natural History (AMNH) and Carthage College, the study finds that the previous proposal lacks sufficient evidence to split the iconic species, according to a statement released by the AMNH.
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What the “Multiple Species” Study Said
The study claiming that T. rex was three different species was also published in Evolutionary biology. The researchers had named two potential new species of Tyrannosaurus based on their analysis. According to the study, the first species, Tyrannosaurus imperator (tyrant lizard emperor), is characterized by more robust femurs and usually two incisors compared to other species.
The second species, Tyrannosaurus regina (tyrant lizard queen), is characterized by thin femurs and an incisor tooth.
The study indicated that the recognized Tyrannosaurus rex (tyrant lizard king) had sturdier femurs but only one incisor tooth. The researchers concluded that the physical variation found in Tyrannosaurus specimens combined with their stratigraphy (scientific discipline concerned with the study of rock layers) is indicative of three potential groups that could be designated as two new species, the bulkier “T . imperator” and the slender “T. regina”, alongside the only recognized species to date, the standard T. rex.
However, the rebuttal of the “multiple species” study concludes that the proposal does not have enough evidence to hold.
What does the rebuttal study say?
In the AMNH statement, Steve Brusatte, co-author of the new study, said, “Tyrannosaurus rex remains the only true king of the dinosaurs.” Brusatte, a paleontologist at the University of Edinburgh, also said it’s true that T. rex fossils are somewhat variable in size and shape. But the researchers showed in the new study that the variation is minor and cannot be used to neatly separate the fossils into easily defined clusters, he added.
Brusatte said that based on all the fossil evidence researchers currently have, T. rex is the only giant predator from the late dinosaur era in North America.
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The researchers involved in the new study revisited the data presented in the previous paper and added data points from 112 species of living dinosaurs – birds – and four non-avian theropod dinosaurs. Theropods included all flesh-eating dinosaurs and were characterized by hollow bones and three toes and claws on each limb.
The researchers found that the multiple species argument was based on a limited comparative sample, non-comparable measurements, and inappropriate statistical techniques.
The “multiple species” study was based on an analysis of the leg bones and teeth of 38 T. rex specimens.
James Napoli, co-lead author of the rebuttal study, said the “multi-species” study claimed the variation in T. rex specimens was so high that they likely came from several closely related species of dinosaurs. giant meat eaters. He added that the claim was based on a very small comparative sample. Compared to data from hundreds of living birds, the authors of the new study found that T. rex is less variable than most living theropod dinosaurs, Napoli added.
The “multiple species” study said the sturdiness of the femur and variation in the size of the second tooth in the lower jaw indicated the presence of multiple species.
Researchers involved in the new study could not replicate the tooth for the results. Moreover, the authors obtained different results from their own measurements of the same specimens.
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Thomas Holtz, co-author of the new paper, said even the boundaries of living species are very difficult to define, and it becomes much more difficult when the species involved are ancient and only known to a relatively small number of people. specimens. He added that other sources of variation, including changes with growth, with region, and good old-fashioned individual differences, must be discarded before accepting the hypothesis that two sets of specimens are distinct species.
Thomas Carr, co-lead author of the paper, said the new study shows that rigorous statistical analyzes based on our knowledge of living animals are the best way to clarify the boundaries of extinct species. He said that in practical terms the three-species model is so ill-defined that many excellent specimens cannot be identified.
David Hone, co-author of the paper, said T. rex is an iconic and incredibly important specialty for paleontological research and communicating science to the public. He said there’s still a good chance there’s more than one species of Tyrannosaurus, but solid evidence is needed to make that kind of decision.