Teenage tyrannosaurs haven’t had the crushing bite of adult bones

Adult tyrannosaurs were basically two-legged bone-crushing machines. New research suggests that juvenile tyrannosaurs might not match the same level of brutality, resulting in a distinctive bite that sets them apart from their adult counterparts.

Nothing like tyrannosaurs exists today, and thank goodness for that. As the quintessential Mesozoic predator, these megatheropods exhibited biting forces that stunned the imagination. The modern lion exerts a respectable force of 1300 Newtons when nibbling on prey, but T. rex– with its wide, deep jaw – exerted a whopping 60,000 Newtons of force with each horrible bite.

“Adult T. rex It is estimated to have possessed some of the highest impact bite forces recorded in any animal, with enough power to crush a car based on previous studies, ”wrote Andre Rowe, a geology doctoral student at the ‘University of Bristol, in an email. “While the animal’s massive size and huge muscles played a key role in its astounding bite, its shape also has significance, as we found that the slender mandible of younger forms was less able to withstand stress. from such a strong bite.

This is the main finding of a new study by Rowe, published Tuesday in the scientific journal Anatomical Record. The new paper provides additional evidence showing that juvenile tyrannosaurs were remarkably different from their adult versions, and that they occupied – and likely dominated – a distinct ecological niche.

The aim of the new study was to explore how the feeding techniques of large predatory dinosaurs changed during their different stages of growth. Previous research has shown that the juvenile T. rex had a thin jawbone, which eventually became the iconic deeply sunken jawbone in adults. Rowe and his colleagues “wanted to test the functional significance of this change,” he said.

To do this, the researchers executed 3D biomechanical models based on CT scans. T. rex skeletons, and inferences about the size, shape and placement of muscles. For a juvenile T. rex model, the researchers tested a young Mongolian tyrannosaurus named Raptorex kriegsteini.

“The main method we used in our study was an engineering technique called finite element analysis, which reveals stresses and strains in solid structures,” Rowe explained. “Areas of tested structures that present a high risk of failure will show a ‘warm’ color.rs like red and white, while the “ cold ” colorRs like green and blue indicate the points where the risk of breakage is the lowest. “

Tests on juvenile and adult tyrannosaurs at equal jaw lengths showed that juveniles experienced higher stresses, indicating the need for a deep and wide jaw shape in adults. Key to this finding was an analysis of the T. rex the pterygoid muscles, which are located at the lower end of the back of their mandibles.

“Since we were applying virtual muscles to these dinosaurs to get accurate bite results, we had the opportunity to test the significance of individual muscles during feeding,” Rowe said. “The pterygoid muscles decrease flexion stresses near the front of the jaw, where T. rex may have applied his high impact bites using his massive, tapered teeth. “

As an interesting side, modern crocodiles exercise their highest bite forces towards the back of their jaws, while in tyrannosaurs, it is forward.

Rowe’s new paper suggests that the slender jaws of adolescent tyrannosaurs would have been susceptible to severe damage had the shape of the mandible remained the same throughout maturity through adulthood. But this is not the case, because the larger adult T. rex the mandible is able to absorb the enormous forces required to crush the bone. In terms of details, a minor T. rex with a thin jaw – but the length of an adult jaw – would have had to endure 3.3 times the stress, which would not have worked. Hence the dramatic physical differences seen in juvenile and adult tyrannosaurs.

“Adult tyrannosaurs are known for their crunchy bite, that they used to swallow pieces of flesh and bones whole, but the juveniles were not equipped for such a bite and therefore may have used a sharp bite that would eventually become too large, ”explained Rowe.

So instead of hunting huge herbivores like Triceratops and Edmontosaurus, juvenile T. rexes probably hunted smaller dinosaurs, and possibly even the smaller mammal species that existed during the Late Cretaceous, a period that ended around 66 million years ago.

“While the adult T. rex remains an iconic apex killer, it’s quite remarkable that he started out as a slender-bodied animal that chased mammals while running, ”Rowe said.

Kat Schroeder, doctoral student at the University of Mexico who was not involved in the new study, said the new research supports an idea presented in its recent paper, that “juvenile tyrannosaurs were physically different enough from their parents to act as their own ‘morphospecia’, and could have outperformed other medium-sized theropods.“

Schroeder said the relatively small sample size used for the new study was “limiting”, but “the science is well done,And that “fits the hypothesis that tyrannosaurs drastically changed their hunting style as they grew older.” “

Looking ahead, Rowe would like to see more work on dinosaurs and other extinct animals, and how their eating styles change over time.

“Computed tomography and 3D modeling techniques have given us wonderful information about dinosaur biology, and the methods are applicable to living and extinct animals,” he said.