Just how strong was the T. rex bite?
TDale Gnidovec
his is a great time to be a paleontologist, especially one studying dinosaurs. Not only are new species being discovered on an almost weekly basis, but sophisticated imaging methods are allowing us to extract more information from those fossils, whether they were collected recently or a hundred years ago.
Also, computer modeling of the biomechanics of dinosaurs allows us to deduce more about how those wonderful beasts worked as living animals.
Tyrannosaurus rex, the large bipedal carnivorous dinosaur that lived in western North America 66 million years ago at the end of the Cretaceous Period, has probably been studied biomechanically more than any other prehistoric animal.
Recent studies of its probable body mass, made by scanning skeletons with lasers, are converging on an estimate of 14,300 to 15,500 pounds (about 7 tons) for a full-size adult. Estimates of its maximum running speed, once all over the map, are now converging on 18 mph, based on things such as the strength of its leg bones and how much muscle could be packed on its frame.
That trend of converging estimates does not apply to another interesting thing we would like to know about T. rex: How strong was its bite? Recent estimates have varied by a tremendous amount, from 4,000 to 12,000 pounds of force. To put that in perspective, the numbers for an adult human male are 250 pounds; a wolf, 350; a great white shark 700; a lion 950; a hyena, 1,000; an American alligator, 3,000; and a saltwater crocodile, 3,700.
A new bit of research in the Journal of Anatomy looked at the reasons why the estimates for T. rex varied so much.
A main conclusion of the study was that the results came from different reconstructions of the jaw muscles. Reconstructing muscles that decayed millions of years ago isn’t easy — you can’t just measure the distance between the spot on a bone where a muscle starts (called the origin) and the spot on the other bone where it attaches (called the insertion).
At its simplest, a muscle’s strength is controlled by its thickness divided by the average length of the individual muscle fibers. Complicating factors include the angle at which the force is working, the distance from the joint, and how much of the length between origin and insertion is muscle and how much is tendon, but the main one is length of the fibers.
To get a better handle on that, the researchers compiled data from dissections of 1,100 muscles of terrestrial ( land-dwelling) vertebrates (animals with bony skeletons). They found that the ratio of fiber length to muscle length varied tremendously.
Unfortunately for the question at hand — how hard could Tyrannosaurus rex bite? — most of the measurements in the literature were from limbs. Only 2 percent were for jaw muscles, so many more measurements of muscle fiber length are needed.
To learn more about prehistoric animals, we need to learn more about those that are living today.