Adult tyrannosaurs were, in fact, bone-crushing machines on two feet. New research suggests juvenile tyrannosaurs couldn’t match the same level of ferocity, resulting in a signature bite that set them apart from their adult counterparts.
Today, nothing like tyrannosaurs exists, and thank goodness for that. As the quintessential apex predator of the Mesozoic, these megatheropods displayed bite forces that capture the imagination. The modern lion exerts a respectable 1,300 Newtons of force when chewing prey, but T. rex– with its wide and deeply set jaw – applied a whopping 60,000 Newtons of force with every gruesome bite.
“Grown up T. rex It is estimated that some of the greatest impact bite forces recorded in any animal possessed enough force to crush a car based on previous studies, ”wrote Andre Rowe, a geology PhD student at the University of Bristol, in an e -mail. “While the animal’s sheer size and massive muscles were key to delivering its dizzying bite, there is also significance in its shape, as we found that the slender lower jaws of the younger forms were less able to withstand the stresses of it. such a powerful bite. “
That’s the main finding of a new study led by Rowe, published Tuesday in the scientific journal Anatomical Record. The new paper provides further evidence showing that juvenile tyrannosaurs were markedly different from their adult versions, occupying – and likely dominating – a separate ecological niche.
The aim of the new study was to investigate how the feeding techniques of large predatory dinosaurs changed during their different growth stages. Previous research showed that it was juvenile T. rex had a slender jaw, which eventually grew into the iconic deeply set jaw seen in adults. Rowe and his colleagues “wanted to test the functional significance of this change,” he said.
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To do this, the researchers performed 3D biomechanical models based on complete CT scans T. rex skeletons, and inferences about muscle size, shape and placement. For a young person T. rex model, the researchers tested a young tyrannosaurus from Mongolia named Raptorex kriegsteini
“The main method we used in our research was a technical technique called finite element analysis, which reveals stress and strain in solid structures,” explains Rowe. “Areas of tested structures that are at high risk of breakage will show a ‘hot’ colorrs such as red and white, while “cold” colorrs such as green and blue indicate points where the risk of breakage is minimal. “
Tests of the juvenile and adult tyrannosaurs at equal jaw lengths showed that the juveniles experienced higher tensions, indicating the need for a deep, wide jaw shape in adults. The key to this finding was an analysis of the T. rex pterygoid muscles, which are located at the bottom of their lower jaws.
“Because we applied virtual muscles to these dinosaurs to get accurate bite results, we had the opportunity to test the meaning of individual muscles during feeding,” said Rowe. “The pterygoid muscles have been found to reduce flexural stresses in the front of the jaw, true T. rex may have exerted its greatest impact bites with the help of its massive, conical teeth. “
As an interesting aside: modern crocodiles practice 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 if the shape of the mandible had remained the same throughout adulthood into adulthood. But that’s not the case, as the broader adult T. rex mandible is able to withstand the tremendous forces required to crush bone. In terms of particulars, a juvenile T. rex with a slender jaw – but the length of an adult jaw – would have had to endure 3.3 times the stress, which wouldn’t have worked. Hence the dramatic physical differences seen in young and adult tyrannosaurs.
Adult tyrannosaurs are known for their bone-cracking bite, which they used to swallow pieces of meat and bone whole, but the juveniles were not equipped for such a bite and therefore may have used a cutting bite that he would eventually outgrow, ”explained Rowe.
So instead of hunting huge herbivores like Triceratops and Edmontosaurus, youthful T. rexes probably hunted smaller dinosaurs, and possibly even the small mammal species that existed during the Late Cretaceous, a period ending some 66 million years ago.
While the adult T. rex remains an iconic top killer, it is quite remarkable to think that it started as a lean body hunting for mammals, ”said Rowe.
Kat Schroeder, a PhD student at the University of Mexico who was not involved in the new study, said the new research supports an idea presented in her recently paper, that “juvenile tyrannosaurs were physically different enough from their parents to act as their own” morphospecies, “and possibly compete with other medium-sized theropods.
Schroeder said the relatively small sample size used for the new study was “ limiting, ” but the “ science is done right, ”“And it” fits the hypothesis that tyrannosaurs drastically changed their hunting style as they grew. “
Looking ahead, Rowe would like to see more work done on dinosaurs and other extinct animals, and how their feeding styles change over time.
“CT scanning and 3D modeling techniques have given us wonderful insights into dinosaur biology, and the methods are applicable to both living and extinct animals,” he said.