Last year, we learned that Tyrannosaurus rex was up to 30% bigger than we once thought. Now, new evidence suggests we may have vastly underestimated its jaw strength, as well.
Recent computer models predict that the back teeth on an adult T. rex were capable of generating a bite force between 30,000 and 60,000 Newtons. That's about how much force you'd experience if you found yourself trapped beneath a sitting elephant. It also makes T. rex 's bite the most powerful of any creature to ever walk the Earth.
The research, which is published in today's issue of Biology Letters, was led by biomechanics researcher Karl Bates. Bates and his colleague Peter Falkingham used three-dimensional laser scans to create a digitized model of a T. rex skull (pictured below), add in a variety of muscular configurations, and run a number of simulations to predict T. rex's bite force. According to the researchers, these latest estimates outstrip previous predictions by a staggering 20,000—40,000 Newtons.
Using computer models to study the biomechanics of dinosaurs is a relatively new analytical strategy. (Bates was also on the team of researchers that revealed T. rex may have weighed 30% more than previous estimates — a conclusion also drawn from laser-generated, digital computer models). According to Bates, these simulations have distinct advantages over traditional methods of estimation, which for many years have been made by comparing the prehistoric creature's skeleton to those of similar, modern-day specimens.
The most important aspect of these computational approaches, explained Bates in an interview with io9, is that they are direct — something that is especially important when a suitable modern-day analogue does not exist for the extinct species being analyzed. For years, researchers have used modern day species like alligators to study T. rex biomechanics, but this comparison is far from ideal. According to Bates:
If you want to know how fast a dinosaur could run or how forcefully it could bite, [these new approaches] allow you to generate a model of that dinosaur that incorporates all the major anatomical and physiological components that actually determine that aspect of mechanical performance. There is no need for analogy or statistical inference; it is a direct approach.
Granted, there are limitations to this digital method of analysis. The most obvious example stems from the fact that soft tissues are not preserved in 65-million-year-old specimens; this fact, explained Bates, meant that he and Falkingham had to make explicit assumptions about the muscularity of T. rex's jaw, estimating, for example, "how large the muscles were, or how long their component fibres were."
One way to address the uncertainty inherent in these assumptions is to run simulations on a wide range of muscle configurations, repeat the method on living animals (like humans and alligators), and compare the results. This, explains Bates, left him and Falkingham "with a suitable range of predictions that reflect the extent to which we [could] honestly and objectively constrain the biological reality." Hence the 30,000—60,000 N range mentioned earlier.
But to really drive their point home, the researchers used their digitized models to scale up the skulls of a human, alligator, juvenile T. rex and Allosaurus to the size of an adult T. rex. In every single instance, the bite forces increased along with skull size, but none were able to match the force of the adult T. Rex.
This is interesting for a couple of reasons. The first is that these findings suggest T. rex had the most powerful bite of any animal on Earth. Ever. That's an impressive discovery in its own right, because it reinforces the commonly challenged belief that T. rex was one of the most dangerous predators of all time (as opposed to, say, an opportunistic scavenger).
But the researchers' results are also significant for what they tell us about these dinosaurs' lifelong eating habits. For example, the fact that the younger T. rex jaws could not match the strength of the adult — even when they were scaled to the same size — suggest that the tyrant lizard's bite strength increased at a rate that outstripped the rest of its growth. In modern carnivores, explain the researchers, age-dependent variations in bite performance such as this are often associated with shifts in diet. The fact that juvenile T. rex relied on its bite strength less than its larger counterparts, hypothesize the researchers, "may have allowed adult T. rex to function as a 'large prey specialist,' alleviating direct competiton from smaller, more agile carnivores, including juvenile T. rex."
The researchers findings are published in the latest issue of Biology Letters.