Juvenile Tyrannosaurs Had Powerful Bite, New Study Shows
For the study, University of Wisconsin Oshkosh’s Professor Joseph Peterson and colleagues made a replica of the scimitar-shaped tooth of a young Tyrannosaurus rex using a dental-grade cobalt chromium alloy.
They then mounted the metal tooth in a mechanical testing frame and pushed it slowly, at a millimeter per second, into a fresh-frozen and thawed humerus of a cow.
Forces required to replicate punctures were recorded and puncture dimensions were measured.
“What we did, an actualistic study, is to say, Let’s actually stab the thing with a tooth and see what it does,” Professor Peterson said.
“What we are finding is that our estimates are slightly different than other models, but they are within a close enough range — we are on the same page.”
The paleontologists determined that juvenile Tyrannosaurus rexes could have exerted up to 5,641 newtons of force, somewhere between the jaw forces exerted by a hyena and a crocodile.
Compare that to the bite force of an adult Tyrannosaurus rex — about 35,000 newtons — or to the puny biting power of humans: 300 newtons.
Previous bite force estimates for juvenile Tyrannosaurus rexes — based on reconstruction of the jaw muscles or from mathematically scaling down the bite force of adult Tyrannosaurus rexes — were considerably less, about 4,000 newtons.
“If you are up to almost 6,000 newtons of bite force, that places them in a slightly different weight class,” Dr. Tseng said.
“By really refining our estimates of juvenile bite force, we can more succinctly place them in a part of the food web and think about how they may have played the role of a different kind of predator from their larger, adult parents.”
The study revealed that juvenile Tyrannosaurus rexes, while not yet able to crush bones like their 30- or 40-year-old parents, were developing their biting techniques and strengthening their jaw muscles to be able do so once their adult teeth came in.
“This actually gives us a little bit of a metric to help us gauge how quickly the bite force is changing from juvenile to adulthood, and something to compare with how the body is changing during that same period of time,” Professor Peterson said.
“Are they already crushing bone? No, but they are puncturing it. It allows us to get a better idea of how they are feeding, what they are eating.”
“It is just adding more to that full picture of how animals like tyrannosaurs lived and grew and the roles that they played in that ecosystem.”
J.E. Peterson et al. 2021. Bite force estimates in juvenile Tyrannosaurus rex based on simulated puncture marks. PeerJ 9: e11450; doi: 10.7717/peerj.11450