Ceratopsians Didn't Use Their Horns For Defense

[suspsy]

http://www.greatfallstribune.com/story/news/local/2015/05/28/jack-horner-dinosaurs-likely-behaved-like-birds/28130865/

At least according to our old friend Jack Horner, they didn't. I'd be curious to hear more about this latest theory. Has he published anything on it?

[Kayakasaurus]

It takes five Velociraptors to take down a T-Rex?

[suspsy]

I think it would take at least twice that number.

[stargatedalek]

One, but you'd have to smother the rex throat and nostrils with feathers manually

Oh Horner, you've really already had your time in the spotlight but none of your "recent theories" have ever been anything new...

[Pachyrhinosaurus]

Interesting. Weren't there trike skulls with injuries around their horns, though? I thought they were at least used for intraspecific combat.

[stargatedalek]

Oh they were most certainly used for self defense, as bite marks from large predators show us. The part where it gets tricky is were they really intended for self defense. I would expect to see more ceratopsian species with horns or frills that pointed outwards if this were the case, but rather a number of species have horns and/or frills that would be practically useless for self defense. Triceratops may have simply gotten the luck of the draw with horns intended as species identification that just happened to form in a way that made them good weapons.

[Dinoguy2]

Oh they were most certainly used for self defense, as bite marks from large predators show us. The part where it gets tricky is were they really intended for self defense. I would expect to see more ceratopsian species with horns or frills that pointed outwards if this were the case, but rather a number of species have horns and/or frills that would be practically useless for self defense. Triceratops may have simply gotten the luck of the draw with horns intended as species identification that just happened to form in a way that made them good weapons.

Yeah, this theory isn't new and is pretty widely accepted, it's certainly not just a "Horner thing". If the horns were for defense there's no evolutionary reason for so much variability between species. Huge variation between species means they have primarily a display function, with combat and defense secondary benefits. Like in modern antelope. If the horns were for defense, they certainly wouldn't drastically change their orientation during growth from backward to upward to hooked forward, which is seen in the horns of pretty much all ceratopsids where juveniles are known. The nose horn of Einiosaurus, for example, or the frill horns of Centrosaurus and Kosmoceratops, are utterly useless for defense or combat.

It has also been suggested as part of possible sexual dimorphism in Triceratops. Some Triceratops have upward-pointing horns and some have forward-pointing horns. This goes for Torosaurus too. Some have suggested that the forward horns were more for combat and thus males, and the upward horns were at a better angle for jabbing into a tyrannosaur belly, thus defense/females. I personally think this is just growth trajectory but it's still not what you'd expect in a structure intended to defend against predators.

[Derek.McManus]

They might have used their horns for self-defense but I suspect the most common use was sexual diomorphism.

[Arul]

They might have used their horns for self-defense but I suspect the most common use was sexual diomorphism.

So male and female trike have a different type of horn ?

[Dinoguy2]

They might have used their horns for self-defense but I suspect the most common use was sexual diomorphism.

So male and female trike have a different type of horn ?

Unknown. There are various morphs that need to be sorted chronologically to eliminate the possibility of evolutionary change before we can begin to know what might be dimorphism. Right now the upright vs. forward horn dimorphism thing is just speculation.

[goodlife18]

I get annoyed by this  overemphasis on ceratopsian horns being used for display and species recognition.

Just because defense wasn't their main function, it doesn't mean that ceratopsians CAN'T use them for defense. Modern day animals - Antelopes, Bovines and Rhinos have horns that come in all different shapes and sizes. Yet they were used for display and intraspecific combat but if the need arose, they could be used as defensive weapons.

In a similar vein, the teeth and claws of carnivorous dinosaurs came in different shapes and sizes and some were not very good at tearing up meat e.g. Majungsaurus teeth were better designed to hold on rather than slash through flesh. And yet they were all used to kill prey. Only difference was the killing technique.

Being rhino to elephant sized beasts, Ceratopsians were certainly capable of putting up a fight.

[suspsy]

I take anything Jack Horner says with a heavy dose of salt. From what I've heard, he's become one of those irritating folks who isn't nearly as interested in listening to other people's ideas as he is about telling other people all about his wonderful ideas.

He also relishes any and all media attention.

[goodlife18]

I agree with that media attention part. I don't understand it. There are so many wonderful and equally qualified palaeontologists out there and yet, Jack Horner seems be the one getting all the press.  And with that, his theories get propagated as well.

Like the one about Triceratops and Torosaurus being the same dinosaur but representing different growth rates. That one got so much media attention.

There was subsequent study by the Yale University which  disagreed, saying that they were separate species but that study didn't get much publicity.

[Simon]

Jack Horner making another outrageous, counter-intuitive, illogical statement?  Hmmmm.....

Lessee....

What time is it kids?



That's right.

[Balaur]

Usually, if a display structure were to evolve that would be a disadvantage to an animal, it's for sociosexual display, because you are proving to others of your kind that you can suvive with this disadvantage. Species recognition can be as subtle as a different colouration or smell. And we do have evidence of ceratopsian's using their horns to battle each other, so yeah, they aren't for display. The frill is mainly for display.

[goodlife18]

Usually, if a display structure were to evolve that would be a disadvantage to an animal, it's for sociosexual display, because you are proving to others of your kind that you can suvive with this disadvantage. Species recognition can be as subtle as a different colouration or smell. And we do have evidence of ceratopsian's using their horns to battle each other, so yeah, they aren't for display. The frill is mainly for display.

Exactly. Bearing in mind some dinosaurs might not have had good eyesight and might have relied on their sense of smell,  display structures would not be very useful for species recognition. Species recognition could also come in the form of vocalization as well.

While I agree that the frill is mainly for display, there might still be a chance that it could have (unexpectedly) acted as a shield. Yes one could argue that many ceratopsians except for Triceratops and Eotriceratops had holes in their frills which would make them unsuitable as a shield.

But the point is that having an obstacle helps prevent a theropod from getting to the vulnerable neck at the first shot. The frill will be damaged but by taking the brunt of the attack, it could distract the predator long enough for the ceratopsian to shake off the attack and bring its horns into play.
Distracting a predator even for a few seconds makes a difference between life and death.

[Balaur]

Yeah, I think that the thicker frills of Triceratops evolved to protect the animals neck, but the ones with holes inside were probably not so good for that, because they were not as well adapted to take the bite of a predator.

[Dinoguy2]

I get annoyed by this  overemphasis on ceratopsian horns being used for display and species recognition.

Just because defense wasn't their main function, it doesn't mean that ceratopsians CAN'T use them for defense.

If Horner is right about the vascularization and lack of strength in the horn core, than he's right, but we'll have to see when it's published.

Just because an idea is counter-intuitive or uncool doesn't make it wrong. Why should we assume horns are for defense and competition? Nobody assumes that about hadrosaur horns. Because we call them crests? There's no reason to call one thing a horn and one thing a crest unless you're making a basic underlying assumption about its use and biasing the debate. Why is the thing on top of a Lambeosaurus head a crest but the thing on the nose of an Einiosaurus or Wendiceratops a horn? They're all big broad flat rounded bits of bone with some pointy bits behind them. Calling one a horn and one a crest implies that we know its use and prevents us from questioning that.

Yeah, I think that the thicker frills of Triceratops evolved to protect the animals neck, but the ones with holes inside were probably not so good for that, because they were not as well adapted to take the bite of a predator.

Which studies say any of the frills were strong enough to protect against a bite or a puncture? I don't know of any that have ever been done. Except apparently this new one which says they couldn't (in Triceratops at least). Science isn't about just going with whatever seems to make sense, its about trying to prove things wrong. If somebody proves wrong the idea that frills are strong enough for defense then we have to throw that idea in the garbage.

Most ceratopsian frills are thin struts of bone covered in skin and muscle. Using them for defense would be like using a paper shield. Not even a paper shield... like using your own chest as a shield for yourself! It never made any sense and I'm not sure why anybody ever thought it, other than it makes for cool pictures If frills were used for defense, we would expect to observe armor or osteoderms and lack of blood vessels, but we don't. They were covered in skin and full of blood, like stegosaur plates. Obviously, Triceratops frills were different as they were solid. So we need to study them to see what the reason for being solid was. Were they solid enough for defense? Maybe, gotta test it. If Horner did, gotta read his methods and see if they check out before judging.

Usually, if a display structure were to evolve that would be a disadvantage to an animal, it's for sociosexual display, because you are proving to others of your kind that you can suvive with this disadvantage. Species recognition can be as subtle as a different colouration or smell. And we do have evidence of ceratopsian's using their horns to battle each other, so yeah, they aren't for display. The frill is mainly for display.

Exactly. Bearing in mind some dinosaurs might not have had good eyesight and might have relied on their sense of smell,  display structures would not be very useful for species recognition. Species recognition could also come in the form of vocalization as well.

Which dinosaurs didn't have good eyesight? All living dinosaurs are famous for having the best eyesight of any vertebrate group except some kinds of fish, and can generally see father, sharper, better, and in hundreds more colors than mammals or other reptiles. Modern dinosaurs are also famous for being colorful and for having often very elaborate and complex displays, both as part of their anatomy and in their behavior. Almost every group of extinct dinosaurs, from enantiornithines to hadrosaurs to stegosaurs to ceratopsians to tyrannosaurs to deinonychosaurs to ceratosaurs to oviraptorosaurs, all of them also have many members with some kind of crest or frill or horn (and the ones that don't probably had the equivalent as soft tissue). I could easily imagine ceratopsians using their huge variety of horns, crests, and frills in some pretty crazy mating dances.

That doesn't mean they couldn't ALSO use them occasionally in a fight, if it came to that, but we're talking about primary use here, the use that was being driven by evolution. As I said above, the variety of horns means that the primary use was display. If it wasn't then there would be no reason to evolve such a variety. The fact that frills also have huge variety in shape size and ornamentation also means they were primarily for display.

Another overlooked function may be fitness signal (a form of display). Deer often use their antlers in combat, but the reason they are so big and elaborate is to prove their level of physical fitness and ability to find resources to their potential mates. In some deer species only the males grow antlers or horns, but in other both male and female have them, depending on the social structure and mating strategies of each species.

[suspsy]

Dinoguy2 makes some excellent points. It will indeed be worth reading any and all formal publications of this hypothesis. My issue with Horner stems from the fact that he just loves to phrase his hypotheses as absolute facts. Instead of T. rex being a scavenger whenever the opportunity arose, it HAD be an obligate scavenger. Triceratops and Torosaurus HAD to be one and the same. Ceratopsians NEVER employed their horns for defence. And so on.

[Simon]

There is no known herding animal that I know of, that has horns that doesn't use them for defense/interspecies "dominance conflict".

You don't grow one-metre long bone-core, keratin-covered horns for purely ornamental purposes.  Not in an environment populated by TRexes that can outrun you.  The horns of a Triceratops are PLENTY STRONG ENOUGH to impale a TRex's soft underbelly that gets too close, with a straight-up thrust of the head powered by those gigantic front legs.  And plenty strong enough to engage in instinct-driven and controlled "interspecies dominance determination".