Secrets behind T rex's bone crushing bites unveiled

The giant Tyrannosaurus rex pulverised bones by biting down with forces equalling the weight of three small cars while simultaneously generating world record tooth pressures, according to a new study.

Researchers, including those from Florida State University in the US, said that T rex could pulverise 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 allow for chewing up bones.

They 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.

At the same time, their long, conical teeth generated an astounding 431,000 pounds per square inch of bone-failing tooth pressures. This 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," said Paul Gignac, assistant professor at Oklahoma State University in the US.

The researchers built on their extensive experience testing and modelling 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 realised that high bite forces were only part of the story.

To understand how the giant dinosaur consumed bone, researchers also needed to understand how those forces were transmitted through the teeth, a measurement they call tooth pressure. "Having high bite force does not necessarily mean an animal can puncture hide or pulverise bone, tooth pressure is the biomechanically more relevant parameter," said Gregory Erickson from Florida State University.

"It is like assuming a 600 horsepower engine guarantees speed. In a Ferrari, sure, but not for a dump truck," said Erickson.

In current day, well-known bone crunchers like spotted hyenas and gray wolves have occluding teeth that 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 specialised, occluding dentition, researchers said.

The study was published in the journal Scientific Reports.