Tyrannosaurus Rex is much bigger than scientists thought

A new study has shown that the most famous dinosaur could be 70% larger than scientists used to think. On a Tyrannosaurus scale, this means it could have weighed up to 15 tons.

Researchers estimate that between 70.6 and 66.043 million years ago, about 2.5 billion tyrannosaurs lived on Earth . All of them lived on the territory of modern North America , which at that time was the island of Laramidia. To date, about 50 more or less complete skeletons of these dinosaurs have been found (of which 32 belonged to adults), as well as many individual fragments. 



Artistic illustration of Tyrannosaurus Rex. It is the only valid species in the group of theropod dinosaurs of the tyrannosaurid family. Image: Fausto Garcia-Menendez/ Unsplash

It is believed that the length of a Tyrannosaurus rex averaged about 10.6 m, height to the hip – 3.4 m, and weight – about 7-9 tons. But these data are constantly refined and questioned by paleontologists.

For example, in 2009, a method for measuring the mass of dinosaurs was tested on elephants, and this led to the conclusion that the mass of fossils was significantly overestimated. But then a new way of measuring was created, based on the set of sections and multiplying their average area by the length of the body. He showed that the mass of large tyrannosaurs could reach 9.5 tons and even more.

At the end of 2022, at the annual conference of the Society of Vertebrate Paleontology in Toronto, scientists from the Canadian Museum of Nature in Ottawa presented new data on the size of tyrannosaurs.

They ran a series of calculations using the fossils that are available today and taking into account the total population and average lifespan of these dinosaurs.

At the same time, two models were built, one of them assumed strong dimorphism, that is, a difference in size between male and female individuals. But according to this version, the largest tyrannosaurus could weigh up to 24 tons, which was a clear exaggeration. Therefore, a model that does not take into account sexual dimorphism was recognized as correct.



Skeleton replica of the largest Tyrannosaurus rex, Scotty, housed at the National Museum of Nature and Science in Tokyo . Image: Kumiko

It is believed that male and female tyrannosaurs were indeed about the same size. But it is impossible to say this with absolute certainty, because it is almost impossible to understand from the fossils what gender the individual was.

In the entire history of the study, it was possible to determine the sex of only one dinosaur – MOR 1125, nicknamed Bi-rex. Soft tissues were found in several bones , and some of them turned out to be medullary, that is, specialized tissues necessary for the female during ovulation to form the egg shell. The same tissues are found in modern birds .

Therefore, as a working model, we left the model without taking into account dimorphism and, based on the available data, built a growth curve for a Tyrannosaurus rex throughout life in order to estimate the maximum possible size for it. It amounted to about 15 tons, which is much more than the current estimates of 7-9 tons.

Of course, this model will remain purely theoretical unless T-rex remains of the appropriate size are found.

At the moment, the largest specimen of RSM P2523.8, nicknamed Scotty, was found in the Canadian province of Saskatchewan in 1991. At the time of his death, he was approximately 23-27 years old, he weighed about 8870 kg and reached 13 meters in length. Scotty was only fully described in 2019, and up to that point, the largest specimen was considered to be FMNH PR2081, also known as Sue. It was 12.3 meters long and weighed approximately 8.4-9.5 tons.



A reconstructed skeleton of Sue’s Tyrannosaurus rex at the Field Museum of Natural History in Chicago . Image: The Field Museum of Natural History

But it is important that in addition to the new theory about the mass of tyrannosaurs, the study also demonstrates the fact that it is very difficult for paleontologists to draw conclusions about dinosaurs based on the available material. The sample size is still so small that it severely limits scientists’ understanding of the tyrannosaurus population, which could include much more diverse individuals, including those larger than Scotty or the hypothetical 15-ton specimen.

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