Pachycephalosaurus-head butt? flank butt? something else? dome just for display?

[andrewsaurus rex]

so I've been pondering Pachycephalosaurus.  There are very mixed opinions as to why it had its domed head.  The classic interpretation was of course head butting. Naysayers pointing out that rounded domes would mean only glancing blows.......but what's wrong with that?  It would still be jarring, which is the point, but glancing blows would be far less likely to do serious damage. Perfect for intra specific rivalry stuff.

Flank butting has many supporters.  However I think it would be difficult to maneuver to your opponents side and then charge and ram him in the ribs.  The opponent would have to be a bit of an idiot to let that happen, having plenty of time to simply swing around to face his aggressor.  Plus, flank butting could do serious damage and broken ribs could result in punctured heart and lungs.  Not really great behaviour for the survival of the species. 

I think another possibility is that they stood toe to toe and swung their heads like maces, striking each other on the shoulders, sides and head.....much less damaging than head butting and easier to coordinate and still painful enough that one would be overmatched and quit

Of course there are those who think the tall thick dome was merely for display...to intimidate or allure.  There is evidence of healed damage on many pachycephalosaurid skulls, which sort of flies in the face of the display only theory, however.

So what say you all?  What was the big dome used for?

[stargatedalek]

I think you are misunderstanding what "butting" is. It just means whacking the head on something, it doesn't mean charging full speed like some mammals do when they fight. Flank butting wouldn't involve running circles around each other trying to line up shots on each others flank, but rather they would have sized each other up and then while standing in place hit each other until one gave up. Giraffes do something similar.

The argument against head putting isn't that round skulls would mean "glancing blows", quite the opposite. Rather Pachycephalosaurs don't posses any particular shielding to protect their brains from the impact of hitting their heads together. And the round skulls mean repeated smashing blows, not simply lining up and then pushing after the first blow, but repeatedly attacking.

However, there are relatively recently (last ~5 years I think?) found skulls with damage caused by hitting other skulls.

I was fully in favour of flank butting, but it's a settled deal, they butted heads. Whether this means they frequently killed each other while fighting, or fought infrequently, is hard to say, though I'd lean the latter due to how infrequent these heavily damaged skulls are. So probably not fighting frequently over mates but perhaps fighting only for dominance or territory.

[HD-man]

So what say you all?  What was the big dome used for?

"Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae)": https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0068620

[andrewsaurus rex]

 

The evidence for head butting is compelling, and I happen to believe it, but it's still just evidence not proof, and alternate explanations for the skull injuries have been suggested. 

Whether the head butting took the form of big horn sheep style ramming, bison style pushing (which I doubt because in that case the rounded shape of the dome would mean the skulls would constantly be sliding off one another with very little shoving being possible) or coco butting (which I also doubt as the thickest part of the skull is on the top; if coco butting was the contest then one would expect the thickest part to be at the forehead), we can only speculate.

[andrewsaurus rex]

I was watching a show on Musk Ox and suddenly felt that this is how Pachyceph would have behaved as well.  Irritable, grouchy all the time, charging at everything that came near it, hitting them wherever it could.

This would apply to rival males who challenged its dominance, as well.

So the dominant male would be standing off on its own, while the less dominant males would huddle in a group, looking for weakness/illness in the dominant male and otherwise rarely daring to challenge him.

So, no targeted butting with the head.....it would just ram its head into any body part it could, whether it be in intra specific combat, defense from predators or just because it was in a bad mood and didn't like you.

[Carnoking]

I love this topic.