The most famous dinosaur of all time likely corresponds to at least three different species, which had subtle distinctions from one another in terms of anatomy, when they lived and perhaps in behavior, a new study says.
The hypothesis, proposed by a trio of US researchers, could dismember the classification of the famous Tyrannosaurus rexestablishing two other species: T. imperator and T. regina.
Not coincidentally, all scientific names are variations of “rex”, or “rei”, in Latin — “regina” means “queen” and “imperator” is, of course, “emperador” in the ancestral language of Portuguese.
The analysis that underlies the “triple personality” From tyrannosaurs just appeared in the scientific journal Evolutionary Biology. The study was coordinated by independent researcher Gregory Paul and is also signed by Scott Persons and Jay Van Raalte, from the College of Charleston, South Carolina.
About 12 meters long, o Tyrannosaurus rex lived between 68 million and 66 million years ago in a wide region of what would become present-day North America. Both the vast geographic distribution and the duration of the animal’s existence open the possibility that speciation events have occurred, that is, the formation of new species of tyrannosaurs from a common ancestor.
Paul and his colleagues analyzed this possibility by taking into account the already known variation in the fossils of T. rex, one of the best-studied dinosaur species with relatively abundant skeletons. It is known, for example, that there were more graceful forms (that is, with relatively lighter bones) and other more robust forms of the animal. In addition, there are variations in teething.
Some animals have only one tooth called incisiform (by analogy with the incisors of mammals) on each side of the jaw, while others have two incisiforms.
The scientists’ goal was to assess how these differences compare to the variability of other dinosaurs, both in relative terms (being larger or smaller than the differences that separate other species) and over time.
This type of analysis would also help to estimate whether T. rex variability could only correspond to natural differences between individuals (such as between tall and short humans, say) or whether it could be linked to sexual dimorphism, that is, distinctions between males. and females.
Gregory Paul and his colleagues worked with 37 specimens classified as T. rex, from which it was possible to analyze the strength of the femur (thigh bone) of 24 animals. Of those, only 12 had both teeth and femurs available.
One of the main findings is that the variability in bone strength is as high as 30%, which exceeds what you see in related dinosaurs that are classified together.
Older forms are more robust and tend to have two small incisiforms, while newer forms include both robust and graceful animals with only one incisiform.
This led the researchers to propose that the oldest robust form, with two incisiforms, would be named T. imperator, while the more recent ones would be T. rex proper (also robust) and T. regina (more graceful). , both with a single incisor.
Was there any difference in habits between the trio? For Paul, one possibility would be the difference in prey, with the more robust animals specializing in attacking the powerful Triceratops herbivores, which resemble dinosaur-shaped rhinos.
“It appears that at the end of the Cretaceous the robust T. rex and the more gracile T. regina were living together. The second could have evolved to hunt Edmontosaurs [herbívoros com bico semelhante ao de patos] —we have skeletons of them with tail injuries that suggest this possibility,” the researcher told sheet.
For paleontologist Rafael Delcourt, a specialist in the evolution of big dinosaurs carnivores and postdoctoral researcher at USP in Ribeirão Preto, the new research brings interesting discussions, but the data presented are still far from sufficient to establish the “tripartition” of T. rex.
“You need to look at these specimens more carefully and go beyond femur strength and teething differences,” he says.
“In any case, the analyzes are important for drawing attention to the ecological niche occupied by tyrannosaurs, which may have varied both during their evolutionary history and during the development of individuals throughout life, with younger and smaller animals capturing different prey than adults, for example.”
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