Headbutting in tyrannosaurids?

[Infinity Blade]

e.g. in one of the cases where people came up with the idea that T. rex would ram an opponent.

So, this got me thinking about the idea of tyrannosaurids practicing headbutting, and I guess I'll give my $0.02 on it here. I hope I don’t end up coming across as a ridiculous fanboy (I mean, for all I know, I’m about to spew utter hogwash).

Anyway, I found something that had something to say about the idea of tyrannosaurid headbutting.

“The bone surrounding the sinus can be less than a few millimeters thick, and in large individuals like MOR 555 is penetrated by what appear to be small pneumatic foramina. It is unlikely that tyrannosaurs engaged in head butting (Bakker 1986, Bakker et al. 1988), even though the frontals and parietals are disproportionately thick, solid bones.”
www.app.pan.pl/archive/published/app48/app48-191.pdf

So the above says that tyrannosaurid skulls would not have been adapted for headbutting given how the sinus walls were not particularly thick, even though the frontals and parietals were.

But it seems that sinuses aren’t really everything when it comes to shock absorption for headbutts. One study’s findings are only partially consistent with the shock-absorbing hypothesis.

“Frontal sinuses in goats and other mammals have been hypothesized to function as shock absorbers, protecting the brain from blows during intraspecific combat. Furthermore, sinuses are thought to form through removal of `structurally unnecessary' bone. These hypotheses were tested using finite element modeling. Three-dimensional models of domesticated goat (Capra hircus) skulls were constructed, with variable frontal bone and frontal sinus morphology, and loaded to simulate various head-butting behaviors. In general, models with sinuses experienced higher strain energy values (a proxy for shock absorption) than did models with unvaulted frontal bones, and the latter often had higher magnitudes than models with solid vaulted frontal bones. Furthermore, vaulted frontal bones did not reduce magnitudes of principal strain on the surface of the endocranial cavity relative to models with unvaulted frontal bones under most loading conditions. Thus, these results were only partially consistent with sinuses, or the bone that walls the sinuses, acting as shock absorbers. It is hypothesized that the keratinous horn sheaths and cranial sutures are probably more important for absorbing blows to the head. Models with sinuses did exhibit a more `efficient' distribution of stresses, as visualized by histograms in which models with solid frontal bones had numerous unloaded elements. This is consistent with the hypothesis that sinuses result at least in part from the removal of mechanically unnecessary bone.”
jeb.biologists.org/content/211/19/3085

The study’s abstract also says that the keratin sheaths of horns and cranial sutures are likely more important in shock absorption. Now, while tyrannosaurids didn’t really have horns (or at least not horns that are really all that prominent or large), they are apparently considered to have had head bosses (that were even proposed to have been used for intraspecific headbutting; link), which were presumably covered in keratin, in addition to the very thick and solid frontals and parietals, which I think could have absorbed impacts in headbutting.

So whereas I’m obviously open to other ideas, it just really looks/seems to me as if tyrannosaurids had some adaptations for at least SOME form of headbutting.

I really don't know. Thoughts?

[Cross]

This may sound like a really simple response, but given that intraspecific competition within large theropod dinosaurs is performed with their jaws and teeth, I have my doubts. Though Brusatte and Sereno (2008) did mention that carcharodontosaurids had unusually broad and rugose orbital shelves on their crania, and Brusatte even suggested lateral head butting.


Here, from Brusatte and Sereno (2008) :

The texturing of the brow in Eocarcharia and other carcharodontosaurids suggests it was covered in keratin. The large and complex postorbital−frontal suture provides great stability against lateral impact. In advanced carcharodontosaurids, the already elaborated postorbital−lacrimal and postorbital−squamosal sutures, likewise, become even larger and more complex. The head of the laterosphenoid, which braces the postorbital medially, is set in a socket in the postorbital, which is particularly deep in advanced carcharodontosaurids (Fig. 19B2). All of these contacts seem enhanced to handle increased stress (Byron et al. 2004). The brow is clearly overbuilt for were primarily for display. We speculate here that the carcharodontosaurid brow may have been used for intraspecific lateral head−butting. Most large−bodied theropods such as allosauroids and spinosauroids do not have bony orbital swellings, or bosses, on the orbit margin. In those that do, such as abelisaurids and some large tyrannosaurids, the swelling differs in structural detail from that of Eocarcharia and other carcharodontosaurids. Although the swollen postorbital brow in Tyrannosaurus is solid (Brochu 2003: fig. 17), it does not form a prominent lateral feature along the skull margin (Brochu 2003: fig. 3) as in carcharodontosaurids (Fig. 18). In Carcharodontosaurus saharicus, furthermore, there is a nonarticular, pitted pyramidal projection on the lateral aspect of the ventral ramus of the postorbital (Fig. 19B1). Both the brow and this ornamental feature project laterally, and both may have played a role in lateral head−butting.


--Reference
Sereno, Paul C.; Brusatte, Stephen L. (2008). "Basal abelisaurid and carcharodontosaurid theropods from the Lower Cretaceous Elrhaz Formation of Niger" (pdf). Acta Palaeontologica Polonica 53 (1): 15–46.

[theropod]

@macronectes: Thick frontals and parietals aren’t restricted to tyrannosaurids. If that was all that’s necessary for head butting, we’d have tons of headbutting theropods (e.g. Allosaurus, which has thickened and co-ossified frontoparietals).

I think you are confusing thin-walled sinuses (i.e. in danger of collapse when loaded) with lack of sinuses (i.e. solid bone). Even if they don’t play a role in shock absorption, that doesn’t mean tyrannosaurs have any adaptions for head butting. Thin-walled, delicate sinuses would certainly seem to be an indication against it. So is an s-shaped neck, a long, flat skull (i.e. the axis of force on the skull isn’t in line with, or even parallel to the vertebral collumn) without prominent dorsal domes or horns, and the absence of all evidence for sutures adapted to dissipate stress from dorsal impacts (or even sufficient space for them to do so). Theropod skulls deform precisely in the opposite direction.

I can’t tell you to what extend keratinous growths along the skull roof of tyrannosaurids might have been used in intraspecific combat (but I think a better explanation could be protection during ritualized face-biting behaviour), but nothing suggests they’d be capable of using a ram or head-butt as an effective offensive weapon as some have claimed.

The same of course applies to other theropods, none that I know of seem like they could injure a large opponent with a head-butt without sustaining at least equally severe injuries in the process.

[Infinity Blade]

I guess this would have ended badly for both then.

[theropod]

Nov 10, 2015 5:39:58 GMT 5 Infinity Blade said:

I guess this would have ended badly for both then.

Precisely. One of them would break its neck (and possibly skull) trying to ram its opponent like that, the other one would crush its own ribcage in the fall.

[Cross]

theropod How come carcharodontosaurids seem to be the only large theropods adapted for headbutting, then? With the rugose and keratinous orbital shelves and all.

[creature386]

Looking at Macronectes' depiction and the bones they discussed, it looks like theropod only refuted head-butting where superior/rostral (don't know the correct direction term right now) parts of the skull play a big role while your paper discussed lateral head-butting which appears to be quite a bit less risky.

[theropod]

Nov 26, 2015 13:12:27 GMT 5 Cross said:

theropod How come carcharodontosaurids seem to be the only large theropods adapted for headbutting, then? With the rugose and keratinous orbital shelves and all.

I think they would be just as (or even more) incapable of dealing any significant damage via headbutting without fracturing their own skulls or spines.
The lateral head-butting Brusatte & Sereno proposed doesn't sound like something that would actually cause substantial injuries to a similar-sized animal, but at best like a ritualized fighting behaviour not meant to be dangerous.

[Infinity Blade]

I never necessarily specified the form of headbutting, so intraspecific non-lethal headbutting counts.

Although that raises a question. Would thickened frontals and parietals (which apparently tons of theropods had) help with said non-lethal lateral headbutting?

[theropod]

Not just non-lethal, just not a weapon capable of doing significant damage in general.
Any form of headbutting powerful enough to do so would require adaptions of the head and neck to resist the considerable blunt forces involved, and those simply weren’t present in any known theropod (i.e. a short, straight, thick neck with reduced mobility and increased resistance to compression, an impact point on the head that lies on one straight line with the occipital condyle and cervical vertebrae during headbutting, and specific adaptions to protect the brain during impact).

I guess thickened frontals and parietals wouldn’t hurt, though they were certainly developed in response to stresses incurred during biting accumulating in this region, not as an adaption for headbutting in any direction.

[Infinity Blade]

Apparently, of all theropods, cassowaries seem to be the ones able to headbutt and apparently not injure themselves (check page 4, or 341).

www.qm.qld.gov.au/~/media/Documents/QM/About%20Us/Publications/Memoirs%20-%20Nature/N49-1/n49-1-kofron.pdf