Tyrannosaurus rex is thought to have had one of the most powerful bites of any animal that ever lived. So strong, in fact, that not only could it crush the bones of its prey, but it should have shattered its own skull too.
Clearly, this was not the case. However, scientists have long struggled to explain what prevented this from happening. Now, a study conducted by researchers from the University of Missouri (MU) may have provided the answer—a stiff skull.
“T. rex bites were strong enough to pierce or crush the meat and bones of just about any animal it happened upon,” Casey Holliday, an author of the study, told Newsweek. “It bit with about three times the force of really large crocodiles or great white sharks and about 60 times our bite force.”
“We know T. rex could break the bones of other large dinosaurs—like Triceratops—thanks to fossilized remains of bones that have bite marks and fractures. It’s amazing how strong these animals were,” he said. “We also know they swallowed bones from fossilized feces.”
Previously, other groups of scientists have suggested that the dinosaur’s skull contained flexible joints in the skull—much like those of snakes and birds. This feature is called “cranial kinesis”—essentially, the cranial joints are mobile relative to the braincase.
“They thought this because of the shape and seemingly loose-fitting nature of some joints between bones in its skull up in the roof of the mouth, or the palate,” Holliday said. “T. rex shares these joints with birds and lizards because of their evolutionary relationships, and some birds and lizards can wiggle them considerably, like parrots, geckos and snakes.”
However, the MU team found this idea problematic from a biomechanics perspective given that tetrapods—a superclass of animals that includes amphibians, reptiles, mammals and birds (which are essentially non-avian dinosaurs)—with powerful bites usually have rigid skulls rather than those with movable joints.
“Based on our research on how reptile skulls are built and how they work, we didn’t think an animal that has evolved to bite this strong as T. rex would want to have a flexible, wiggly skull as these joints would make the skull unstable,” Holliday said. “So we decided to test this idea.”
For a study published in the journal The Anatomical Record, the scientists created one of the first 3D models to show how the ligaments and joints in a T. rex skull functioned.
“We first explored the anatomy of the bony joints, jaw muscles and other features of T. rex and many other dinosaurs, birds and reptiles,” Holliday said. “We then built 3D engineering models of tokay geckos, grey parrots—two species that can move the bones in their palates—and T. rex made of bones, ligaments and muscles that we then ‘wiggled’ in an anatomically accurate computer simulation.”
The study found that the dinosaur did not have cranial kinesis, but instead had a rather rigid skull more like that of crocodiles, hyenas and humans.
“We found that these bones in T. rex would fail when wiggled in ways similar to the lizard and bird. This suggests that it had a stiffer, more rigid skull than previously suggested,” Holliday said. “This is cool because it again demonstrates what a pinnacle of evolution and performance Tyrannosaurus seems to have become by the Late Cretaceous, converging on a body plan similar to that of crocodilians in terms of having hard-biting skulls, but walking around on two legs.”
“This suggests that land-living predators, at least, or animals that bite hard, converge upon growing stiff skulls, as opposed to squishy ones,” he said. “I was surprised at how well we think we can reconstruct the anatomy of a 67-million-year-old animal given only its bones. That’s still pretty cool to realize how similar we all are in anatomy.”
The researchers say that their latest findings could even have implications beyond the study of dinosaurs.
“Our findings will lead other biologists to better explore the trade-offs between feeding behaviors and skull shape in animals that evolved to bite hard, or bite quickly, or those that handle their food dexterously,” Holliday said.
“The models we built and their results will be useful to not only paleontologists studying the origins of cranial kinesis in birds, snakes or other dinosaurs, but also veterinarians and biomedical engineers looking to treat arthritis because parrots get arthritis in their palate and facial joints,” he said.
Earlier this month, another study led by Holliday was published, revealing more fascinating details about the skull of Tyrannosaurus Rex.
For decades, scientists thought that two holes in the roof of the dinosaur’s skull—known as the dorsotemporal fenestra—were involved in the movements of the fearsome predator’s jaws, because they were believed to be filled with muscles.
However, Holliday and his team suggested that, in fact, these holes acted like an air conditioner for its head.
