This strategy of crushing and ingesting bones would have been particularly useful for the T. rex, according to the researchers, because the giant dinosaur was not only an efficient killing machine, but also an opportunistic scavenger. If a T. rex came across a carcass, it could still enjoy an easy meal.
Dr. Erickson became curious with figuring out the bite force of the T. rex as a graduate student in the mid-1990s when a colleague showed him a fossilized triceratops pelvis riddled with about 80 bite marks.
“I remember saying to him, ‘Gosh, it looks like Clifford the Big Red Dog chewed it up,’” Dr. Erickson said.
His first question was whether the gashes were the work of some prehistoric giant crocodile or a tyrannosaur. In 1996, he and his colleagues reported that the puncture wounds had come from a T. rex. In subsequent research, Dr. Erickson and his colleagues also found evidence of digested bones in the fossilized excrement of a T. rex, showing that the beast had consumed bones.
How exactly the T. rex could break bones was unclear. So the researchers calculated the prehistoric predator’s bite force using a computer model they had created while studying the biting power of live crocodiles and alligators.
To figure out the bite force of a long-extinct T. rex, the team created a digital T. rex jaw based off muscle features found on close modern-day relatives to dinosaurs, like birds and crocodilians. They also examined several T. rex skulls to figure out how it had chewed. Using that information, they came up with an idea of how the jaw muscles in the T. rex were arranged, then calculated the bite force.
They found that an adult T. rex could snap its mouth shut with a force of nearly 8,000 pounds. Today’s champion chomper, the Australian saltwater crocodile, can exert about 3,700 pounds of force. Humans munch with a meager 200 pounds of force.
The researchers also found that the tips of each T. rex tooth generated a pressure of about 431,000 pounds per square inch, which is higher than any animal ever estimated. The shape, size and spacing of the T. rex’s long, conical teeth made it well equipped to channel the force from its jaws into bone-crushing results.
Previous studies tried to quantify how strong the T. rex’s bite was. One study in 2012 said the beast had bitten down with about 12,800 pounds of force, while older studies put that estimate at more than 50,000 pounds. But those studies either did not use a model that had been tested on live animals or made estimates that simply extrapolated what a crocodile bite would do if delivered by a large dinosaur’s body.
“This is the first really solid empirical estimate of what the bite force in Tyrannosaurus rex was based on engineering principles,” said Mark Norell, a paleontologist with the American Museum of Natural History, who was not involved in the study. He added that the power of the T. rex jaws “would cause bones to basically explode.”
Stephen Brusatte, a paleontologist from the University of Edinburgh who reviewed the paper, said the ability to bite through bones made tyrannosaurs unique.
“It was one of those superpowers that made T. rex stand apart from all other dinosaurs,” Dr. Brusatte said in an email message. “If you were a triceratops being chased by a T. rex, it just wasn’t fair.”
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