Researchers have found how the dreaded Tyrannosaurus rex could bite with a force so hard that it shattered the bones of its prey without breaking the predator's own skull - a puzzle that had baffled scientists for years.
The study, published in the journal The Anatomical Record, argued that the T. rex's skull was stiff like the cranium of hyenas and crocodiles, and not flexible like that of snakes and birds which was the previously held opinion among scientists.
The researchers, including those from the University of Missouri (MU) in the US, said that the T. rex had a skull that was six feet long, five feet wide, and four feet high.
A study published in 2017 from the Florida State University in the US had found that the prehistoric reptile could bite down on its prey with nearly 8,000 pounds of force -- more than twice the bite force of the largest living crocodiles.
"Previous researchers looked at this from a bone-only perspective without taking into account all of the connections -- ligaments and cartilage -- that really mediate the interactions between the bones," said Kaleb Sellers, a graduate student in the MU School of Medicine.
The team observed how the roof of the T. rex's mouth reacted to chewing related stresses and strains using a combination of imaging, anatomy and engineering analysis.
They analysed models of how a gecko and a parrot -- two present day relatives of the T. rex -- chewed and applied that to how the T. rex's skull worked.
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"Dinosaurs are like modern-day birds, crocodiles, and lizards in that they inherited particular joints in their skulls from fish -- ball and socket joints, much like people's hip joints -- that seem to lend themselves, but not always, to movement like in snakes," said co-author Casey Holliday of the MU School of Medicine.
Holliday said that a heavy bite force came with a trade-off between movement and stability.
"Birds and lizards have more movement but less stability. When we applied their individual movements to the T. rex skull, we saw it did not like being wiggled in ways that the lizard and bird skulls do, which suggests more stiffness," he said.
The researchers believe that their findings can help advance human and animal medicine by providing better models of how joints and ligaments interact.
"In humans, this can also be applied to how people's jaws work, such as studying how the jaw joint is loaded by stresses and strains during chewing," said Ian Cost, the lead researcher on the study and a former doctoral student in the MU School of Medicine.
Cost said that understanding how joints were structured and moved in animals could help veterinarians treat exotic animals such as parrots, which suffer from arthritis in their faces.