Dinosaur had a 'motorcycle helmet' skull for head-butting love rivals

Scarinae

This is an article that went up on the Guardian website yesterday:

A small, two-legged dinosaur that browsed leaves and berries in the forests of the late Cretaceous fought off rivals by unleashing some of the most formidable head butts ever seen, say scientists.

Stegoceras validum, a beast no bigger than a goat, was engaging in head-to-head combat to overpower its sexual competitors 72m years ago in what is now North America.

Brain scans of skulls belonging to Stegoceras and modern animals that practise head-ramming, such as bighorn sheep and musk ox, revealed that they share cranial features that allowed the animals to withstand eye-watering clashes.

The bony anatomy of the Stegoceras head would have been particularly effective at absorbing heavy blows, and better able to protect the animal's brain than that of any living creature that embraces head-butting as a mate-winning strategy.

"The Stegoceras skull is almost like an enhanced motorcycle helmet. It has a stiff outer shell and a compliant layer beneath, and then another really stiff layer over the brain," said Eric Snively a co-author on the study at Ohio University.

X-ray scans of the skulls of giraffes and llamas, which don't engage in cranial combat, suggested the animals would sustain life-threatening injuries to their heads if they tried, according to the report in the journal PLoS One.

Snively and Jessica Theodor at the University of Calgary in Alberta used a hospital CT (computed tomography) scanner and collision simulation software to investigate the controversial role of the thick, bony domes that characterise pachycephalosaurs such as Stegoceras. An alternative theory has it that the domes were purely for sexual display, like a peacock's tail.

The scans showed that both Stegoceras and modern head-butting animals have relatively large neck muscles and a dense dome of cortical bone above a spongier layer of cancellous bone. The living animal whose skull most closely ressembled Stegoceras was the common duiker, a small antelope that is native to sub-Saharan Africa.

Using a technique called finite element analysis, Snively and Theodor modelled the stresses and strains on the animals' skulls during virtual head-on-head collisions, which allowed them to calculate the violence they could survive. The Stegoceras used in the study had a bony dome some 9cm thick, though some relatives boasted skulls more than 20cm thick.

"It is 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," Theodor said.

It might seem to be something that we all know already, but I thought that the paper itself (PloS ONE, so open access!) was interesting; they did CT scans of the skulls of some artiodactyls and pachycephalosaurs (not sure why the Guardian article focused so much on Stegoceras validum) to look at the stress on the cranium from repeated impacts.

Adam Khor

So they did headbutt. I knew it. It was just stupid to think that those domes were for display. Why the thickness then? It is much easier to develop a thin crest or a fan of feathers or a skin flap or whatever.

Galvasean

In other news, scientists confirm the long standing theory that a species of dinosaur with legs was capable of walking.

Adam Khor

Galvasean wrote: »

In other news, scientists confirm the long standing theory that a species of dinosaur with legs was capable of walking.

I wish I was THAT smart.

Galvasean

I mean, it was pretty obvious that the thick dome of Stegoceras was for fighting. However, I'm not entirely convinced that they would butt head on as often portrayed in artwork as even the slightest miscalculation would bring about serious injury to the face. More likely I'd say they butted each other's flanks

Urquell

I absolutely love the thread title !

Adam Khor

Galvasean wrote: »

I mean, it was pretty obvious that the thick dome of Stegoceras was for fighting. However, I'm not entirely convinced that they would butt head on as often portrayed in artwork as even the slightest miscalculation would bring about serious injury to the face. More likely I'd say they butted each other's flanks

But the face was covered by thick skin and scales/osteoderms, wasn´t it?

Monty Burnz

I take it that they've ruled out the the possibility that the 'motorcycle helmet' head was to protect them while riding motorbikes?

Adam Khor

Monty Burnz wrote: »

I take it that they've ruled out the the possibility that the 'motorcycle helmet' head was to protect them while riding motorbikes?

XD

But really, think about it: would it really be so incredible if Stegoceras fought with the actual intention of hurting each other? I mean, yes, some animals fight so that injury is minimal, but others are much more violent. Rhinos and buffalo can injure each other very seriously and even kill each other during duels; same goes for elephants.

I guess we will never know unless someone finds a pachycephalosaur skull with injuries caused by a particularly violent duel...

Galvasean

Adam Khor wrote: »

But the face was covered by thick skin and scales/osteoderms, wasn´t it?

I don't think that would offer enough protection. However...

Adam Khor wrote: »

But really, think about it: would it really be so incredible if Stegoceras fought with the actual intention of hurting each other?

That's a distinct possibility alright. Maybe they 'played for keeps'.

Alvin T. Grey

Galvasean wrote: »

I mean, it was pretty obvious that the thick dome of Stegoceras was for fighting. However, I'm not entirely convinced that they would butt head on as often portrayed in artwork as even the slightest miscalculation would bring about serious injury to the face. More likely I'd say they butted each other's flanks

I'm not so sure. Deer face (no pun intended) the same problem with big spikey antlers. Elephants the same with their tusks. Mountain goats and water buffalo the same.

Head to head contact would be the safest bet. Head to flank with a helmet like that would invarably end up with one of them dead or seriously injured. Thats not a good thing for the gene pool I reckon.

Galvasean

Alvin T. Grey wrote: »

I'm not so sure. Deer face (no pun intended) the same problem with big spikey antlers. Elephants the same with their tusks. Mountain goats and water buffalo the same.

Head to head contact would be the safest bet. Head to flank with a helmet like that would invarably end up with one of them dead or seriously injured. Thats not a good thing for the gene pool I reckon.

It would weed them out so to speak, leaving only the most over the top fierce ones to reproduce.

Alvin T. Grey

Galvasean wrote: »

It would weed them out so to speak, leaving only the most over the top fierce ones to reproduce.

Animals rarely fight to the death by design. Thats a human trait. If those circumstances were the norm then the number of suitable genetic donors would be severly reduced.
In nature the object isn't to kill the opposition, it's to prevent him from breeding at this time, in this place, with this(these) females. It allows younger less experienced males to grow to maturity.
If death was the desired outcome, not only do you kill off your competition, but your eventual replacement for the next generation too.

I believe that this is the reason that 90% of animal confrontation during the mating season is noise and bluster. Varey rarely does it degenerate into real combat.
At least that what I have observed from watching deer. And it's what I know from training dogs. (did you know you actually have to train a dog to fight?

And then a lot of time training them not to when they are eventually rescued....

Rubecula

Maybe they attacked each other from behind? But, but a butt is not something I would fancy.

Sorry.... I just couldn't resist that......I'll get me coat.

Adam Khor

I insist, there's plenty of animals that kill each other during dominance/mating season duels. Even deer (I've seen deer kill each other myself).
The risk of injury and death is always there; the claim that pachycephalosaurs would avoid head butting because they could be injured seems a little dumb to me. I mean, if these creatures were having highly ritualized, non life-threatening duels, why the enormously reinforced skulls and neck vertebrae?
These things were prepared to fight and hurt and be hurt themselves. I bet they were tough little buggers, able to withstand serious injury and heal very quickly. It actually fits what we know about other kinds of dinosaur, which often survived injury so serious that it would kill a mammal at about the same size.

Alvin T. Grey

Adam Khor wrote: »

I insist, there's plenty of animals that kill each other during dominance/mating season duels. Even deer (I've seen deer kill each other myself).
The risk of injury and death is always there; the claim that pachycephalosaurs would avoid head butting because they could be injured seems a little dumb to me. I mean, if these creatures were having highly ritualized, non life-threatening duels, why the enormously reinforced skulls and neck vertebrae? These things were prepared to fight and hurt and be hurt themselves. I bet they were tough little buggers, able to withstand serious injury and heal very quickly. It actually fits what we know about other kinds of dinosaur, which often survived injury so serious that it would kill a mammal at about the same size.

Because 9 out of 10 times its over before the first blow is struck.
However that leaves the other one time when you need a thick head.

People imagine that during the rutting season animals always fight. - They don't. Most of the conflict is resolved by grunts and or snorts, because the animal equivelant of Peewee Hermann is not going to take on Arnold Sch- you know what I mean...