Oklahoma State University Center for Health Sciences
Oklahoma State University Center for Health Sciences

Anatomy and Vertebrate Paleontology

RESEARCH DISCOVERS SECRETS BEHIND T-REX’S BONE CRUSHING BITES

T-Rex Jaw Muscles
Jaw muscles in Tyrannosaurus rex that helped it generate 8,000-pound bite forces and an astounding 431,000 pounds per square inch of bone-failing tooth pressures.

The giant Tyrannosaurus rex pulverized bones by biting down with forces equaling the weight of three small cars while simultaneously generating world record tooth pressures, according to new research by an Oklahoma State University-Florida State University research team.

In a study published today in Scientific Reports, Paul Gignac, assistant professor of Anatomy and Vertebrate Paleontology at Oklahoma State University Center for Health Sciences and Florida State University Professor of Biological Science Gregory Erickson explain how T. rex could pulverize bones — a capacity known as extreme osteophagy that is typically seen in living carnivorous mammals such as wolves and hyenas, but not reptiles whose teeth do not occlude allowing for chewing up bones.

Gignac and Erickson found that this prehistoric reptile could chow down with nearly 8,000 pounds of force, which is more than two times greater than the bite force of the largest living crocodiles — today’s bite-force champions. At the same time, their long, conical teeth generated an astounding 431,000 pounds per square inch of bone-failing tooth pressures.

Section of bone removed by repetitive biting
Triceratops pelvis bearing nearly 80 T. rex bite marks. Bracket shows region where the carnivore repetitively removed sections of bone without the benefit of occluding teeth.
These allowed T. rex to drive open cracks in bone during repetitive, mammal-like biting and produce high-pressure fracture arcades, leading to a catastrophic explosion of some bones.

“It was this bone-crunching acumen that helped T.rex to more fully exploit the carcasses of large horned-dinosaurs and duck-billed hadrosaurids whose bones, rich in mineral salts and marrow, were unavailable to smaller, less equipped carnivorous dinosaurs,” Gignac said.

The researchers built on their extensive experience testing and modeling how the musculature of living crocodilians, which are close relatives of dinosaurs, contribute to bite forces. They then compared the results with birds, which are modern-day dinosaurs and generated a model for T. rex.

From their work on crocodilians, they realized that high bite forces were only part of the story. To understand how the giant dinosaur consumed bone, Gignac and Erickson also needed to understand how those forces were transmitted through the teeth, a measurement they call tooth pressure.

“Having high bite force doesn’t necessarily mean an animal can puncture hide or pulverize bone, tooth pressure is the biomechanically more relevant parameter,” Erickson said. “It is like assuming a 600 horsepower engine guarantees speed. In a Ferrari, sure, but not for a dump truck.”

In current day, well-known bone crunchers like spotted hyenas and gray wolves specialized, occluding teeth are used to finely fragment long bones for access to the marrow inside — a hallmark feature of mammalian osteophagy. Tyrannosaurus rex appears to be unique among reptiles for achieving this mammal-like ability but without specialized, occluding dentition.

The new study is one of several by the authors and their colleagues that now show how sophisticated feeding abilities, most like those of modern mammals and their immediate ancestors, actually first appeared in reptiles during the Age of the Dinosaurs.

This work was supported by grants from the National Science Foundation and the National Geographic Society.

 

Contact:

Dan Threlkeld
Oklahoma State University Center for Health Sciences
918-200-2617
dan.threlkeld@okstate.edu
@OSUCHS

Kathleen Haughney
Florida State University
850-644-1489
khaughney@fsu.edu
@FSUResearch

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