Chubby cheeks? How a local paleontology student discovered a new muscle in dino jaws

Research by University of Alberta student Henry Sharpe shows dinosaurs may have had chubby cheek muscles. CTV News Edmonton's Jeremy Thompson has the details.

Our understanding of how dinosaurs looked and lived is evolving thanks to a recent discovery by a University of Alberta grad student.

Paleontology master’s student Henry Sharpe has found a new jaw muscle that could help complete the picture of how dinosaurs dined.

Sharpe said he was working on his undergrad when something jumped out at him while studying a duck-billed dinosaur from Drumheller named Gary.

“I was looking at the cheekbone,” Sharpe said. “And I was just thinking, ‘This doesn’t look right. There’s this big kind of triangle coming down from it. There shouldn’t be anything there.’

“It almost looks like a muscle attachment.”

Sharpe explained that, normally, in an animal without a cheek muscle, there is a straight line from the jawbone to the back of the skull.

Gary’s skull, with a flange on the jaw, got him thinking. But, because whole dino heads are rare, he had to scale down to start investigating.

“Thankfully, most of what we find are isolated bones,” Sharpe said. “So I just took isolated cheek bones and isolated jaw bones … cutting them open to see if I could find any evidence in the internal structure of the bone.”

Muscles and tendons are soft tissue, meaning they would have been long gone a long, long time ago. However, Sharpe said, they leave enough of a mark to see millions of years later in large animals like dinosaurs.

“Connective tissues, like muscles and ligaments, will insert fibres, collagen fibres, into the bone itself,” he said. “When the muscle degrades and all that stuff falls away … the fibres will still be in the bone.”

Sharpe said the more he looked at similarly shaped jaw bones, the more he found the fibre marks. When he shared his research with other paleontologists, they started finding the same thing.

“We brought all our findings together, we mapped it out in the dinosaur family tree, and we just found it was the same everywhere,” he added.

“It was a bit of a ‘eureka’ moment.”

• Get the latest Edmonton updates right to your inbox

The discovery, Sharpe said, helps better understand how dinosaurs ate and calls into question the long-standing practice of modeling dino musculature after their closest living relatives.

“It’s supposed to be you only reconstruct a muscle in dinosaurs if it’s present in birds and present in crocodiles,” Sharpe said.

“We’ve provided an example of the traditional way of doing it, maybe not being so accurate, and we need to be a little bit more creative in how we go about reconstructing these things, because it has implications for not only what they looked like, but how they were going about chewing.”

Sharpe and his peers had their findings published in a scientific journal.

While it’s a big breakthrough, the cheek muscle is more a passion project for Sharpe as he works on his master’s thesis on underwater reptiles.

He hopes the research inspires more paleontologists to follow up on the findings – and perhaps consider there could be other similar discoveries ready to be found in dino remains.

“We want to make sure we’re not missing anything because we’re trying to be too restrictive with how we reconstruct (musculature and ligaments),” he said. “We have to be more creative.

“We have to start looking at the bones first, and our modern relatives maybe second, because it’s the bones that tell us the stories.”

With files from CTV News Edmonton’s Jeremy Thompson