(Stegoceras Skull; Credit: Barnum Brown)
Not all dinosaurs had huge teeth and a taste for flesh, but new research suggests that at least one scrappy plant-eating dinosaur was a talented fighter, waging battle with its best weapon: a hard head.
Scientists for years have theorized that certain dinosaurs head butted, with the animals smashing their heads into each other to determine which fighter possessed the best natural crash helmet. Now a new study in PLoS One supports that such behavior did indeed take place.
Eric Snively, a post-doctoral researcher in biomedical engineering at Ohio University, and colleague Jessica Theodor found that the bony anatomy of Stegoceras validum and other pachycephalosaurs would have permitted head butting, allowing the dinosaurs to withstand incredible blows without damaging the brain.
“Pachycephalosaur domes are weird structures not exactly like anything in modern animals,” Snively was quoted as saying in a University of Calgary press release. “We wanted to test the controversial idea that the domes were good for head butting.”
He continued, “Finding out brings us closer to their social lives: were pachycephalosaurs more likely just showing off their domes like peacocks with their tails, or were they also cracking their heads together like musk oxen?”
Snively and Theodor CT scanned the remains of the bony-headed dinosaurs along with the heads of modern hoofed animals that engage in different kinds of combat.
“Our analyses are the closest we can get to observing their behavior,” Snively explained. “In a way, we can get ‘inside their heads’ by colliding them together virtually. We combined anatomical and engineering analyses of all these animals for a pretty thorough approach. We looked at the actual tissue types in the skulls and heads of the animals.”
Theodor shared that head butting is one way that males compete with other males for access to females.
“It’s pretty clear that although the bones are arranged differently in the Stegoceras, it could easily withstand the kinds of forces that have been measured for the living animals that engage in head butting,” she said.
All of these animals possess head protection that the researchers compare to a built-in motorcycle helmet.
“They have a stiff rind on the outside with a sort of a spongy energy absorbing material just beneath it and then a stiff, really dense coat over the brain,” Snively said.
The Stegoceras kicked this usual design up a notch by having an extra layer of dense bone in the middle. This small herbivorous dinosaur was about the same size as a German shepherd. It lived around 72 million years ago.
Many other animals try to head butt and fail. Giraffes, for example, “swing their necks at each other and try to hit each other in the neck or the side,” according to Snively, who added that giraffes can even knock themselves unconscious if they somehow do manage to butt heads.
He said, “Their anatomy isn’t built to absorb the collision as well as something like muskox or big horn sheep.”