Functional Morphology of Animal Feeding Apparata

[theropod]

As I wrote, the comparison is complicated due to most figures for crocodilians being based on in vivo measurements, so this isn’t the best situation for comparison. But Bates & Falkingham provided estimates using their methodology for an Alligator with a 53 cm skull: 5.7 kN (posterior). If we follow Randomdinos, Deinosuchus skulls can reach 153 cm, so isometric scaling would indicate about 47.5 kN for such a specimen, slightly lower than T. rex (the equivalent T. rex figure was 57.2 kN). But of course this is extrapolating very far in terms of body size range.

Purussaurus is even more problematic because its skull morphology is very different. I’ll wager we should expect a proportionately (to skull or body size) harder bite from it due to how massively it is constructed, but that isn’t quantifiable or verifiable without a proper analysis, which hasn’t been done so far. Most of the other giant crocodilians are relatively slender-snouted and probably wouldn’t be serious contenders, even if their bite forces were still respectable.

Livyatan would of course bite harder than T. rex pretty much certainly, and by a significant margin, even if there is currently no basis for anything but a ballpark estimate for it.

Some giant temnodontosaurine ichthyosaurs, as has been briefly discussed to before, were likely also serious contenders (if not for the hardest bite force in the animal kingdom, then at least for bite forces exceeding that of T. rex by a significant margin), with a Temnodontosaurus platyodon with a ~2m skull estimated to reach over 30 kN (that is roughly comparable to the giant carcharodontosaurines, or a little over half that of T. rex) and we know there were far larger and more raptorial ichthyosaurs, which would likely have bitten considerably harder. McGowan estimated an isolated quadrate possibly referrable to T. platyodon to have come from a 2.5m skull, which would bring the bite force into a similar territory to Deinosuchus and approach that of T. rex. As I mentioned before, the largest isolated ichthyosaur teeth from the Lower Jurassic are actually twice as large as the largest ones in T. platyodon, which means 4 times the bite force when scaling isometrically. Although of course it would not be prudent to put much weight to estimates only based on isolated teeth, this is in megalodon territory (and of course megalodon’s estimates are also based on isolated teeth, so that is a fair comparison).
That being said, more reliably, the largest temnodontosaurine ichthyosaurs actually known from postcranial material seem to be around 70% larger than the large T. platyodon for which the bite force estimate was made (assuming its skull length when complete was around 2m, it would likely have had a TL of around 9m) in terms of body size, which could imply a bite force 3 times higher. As the likely owners of the large teeth, their skulls might have been proportionately shorter, but more robust, more comparable to T. eurycephalus, just giant-sized, so it seems reasonably conservative to scale bite force isometrically with body size.
This of course remains highly speculative as long as these ichthyosaurs are so fragmentary and understudied, and as long as Moon’s bite force estimate remains unpublished.

[Grey]

Are we hinting at possible macrophagous temnodontosaurids with 4 m long skull ?

[theropod]

Well, no. As I wrote, it would be unwise to attempt scaling up based on isolated teeth. As I also wrote, I would expect cranial morphology more similar to T. eurycephalus which has proportionately larger teeth and a shorter, more robust skull.

[Grey]

Right I missed that part.

Certainly big ichthyosaurs are of equal interest in this department, even if I ve to see an ichthyosaur skull as powerfully built as a pliosaur.

Regarding the capacity to explode and pulverize bones, is this to be expected in other taxa than T. rex. I ve never read such a feeding mechanism description for other carnivorous animals.

[theropod]

→

Capacity to "explode and pulverize" bones? Not sure what exact description you are referring to, but I can think of quite a few animals that are or were very competent bone crushers, and this is certainly widely acknowledged. Hyaenas, Borophagines, quite a few other living and extinct carnivorous mammals, certain mosasaurines, brachyrostrine crocodilians and some other pseudosuchians…Even among theropods, where its morphological adaptations for osteophagy are exceptional, the largest and boniest coprolite known belongs to a jurassic theropod (probably Allosaurus), which shows how widespread bone-feeding behaviour really is, even if it is not strictly "crushing" behaviour.

[Grey]

Yes I know this specimen but it represents a rather moderate sized species.

The description of the effects of impact tootj pressure in T. rex were widely reported around Erickson 2017. I think to remember they make a clear distinction between the crassical bone crushing, piercing bites and the bite of T. rex which pulverizes bones, because of the extremely high pressures at the tip of the teeth.

[theropod]

Bone will be "pulverized" somewhat sensationalist term, living bone of course having a high moisture content and being very different from dry bone in consistency, this is not a very accurate description of what will happen to it under high compressive loading) at any pressure on excess of its yield strength. And how high a pressure you get depends on how small an area you assume. The initial contact area of any tooth will be very small, but at that tooth penetrates deeper the area will get larger. Refer to the previous discussion I linked in one of my last posts.

[Grey]

The paper itself describes it as such :

"Although not testable in our modelling, catastrophic explosion of some bones, particularly smaller elements or those with thin cortices, may have also occurred due to the introduction of strain energy densities exceeding the limits of bone)."

"Apical tooth pressures (1 mm crown height) range from 718 to 2,974 MPa (104,137 to 431,342 pounds per square inch [psi]) (left M3 of BHI 4100 and right M5 of MOR 980, respectively) (Supplementary Table S2). The larger values are the highest tooth pressures ever estimated (2,473 MPa [358,678 psi] was deduced for a 2.99 m bob-tailed C. porosus 8). Tyrannosaurus rex tooth pressures exceeded the ultimate shear stress of cortical bone (65–71 MPa4, 39[9,427–10,298 psi]) for at least 25 mm of crown height in nearly all maxillary teeth. One of the largest T. rexindividuals (FMNH PR 2081) maintained such pressures up to (and presumably beyond) the 37 mm indentation maximum utilized in this study15."



My understanding is that crocs have a high bite force but their teeth wont allow that.

To me, this really suggests that, in terms of pressure under a single tooth, Tyrannosaurus is the champion.

[theropod]

Such pressures are entirely theoretical. Unless its tooth enamel and dentine had strengths around an order of magnitude higher than those of other animals, such values could never be achieved in reality. What pressure you calculate does not necessarily have anything to do with how powerful the bite is, but with the assumptions you make about tooth contact areas. There simply is no objective basis for comparison, as any animal will generate, at most, the pressure equivalent to the yield strength of bone (you can find that in the study you cite).

That small or thin-walled bones would be destroyed by the kind of force involved in a T. rex bite (a different matter, now we are not talking about pressure, or compression, but bending and shear) is a rather unsurprising prediction, and one that would likewise apply to crocodiles, hyaenas or pliosaurs.

I am not sure what you mean by "crocs have a high bite force but their teeth wont allow that". Crocs do have a high bite force, and their teeth do allow that. Indeed their straight, conical morphology can presumably withstand relatively higher compressive loading than the curved morphology of an equivalent-sized T. rex tooth.

[Infinity Blade]

Also:



compbiomechblog.blogspot.com/p/finite-element-models_7567.html

It turns out Stephen Wroe has done 3D computer FEA on T. rex's skull (like he has done with a bunch of mammalian carnivores, sharks, and hominids). I'm having trouble finding out what study this came from, let alone how much stress the analysis found the skull could take during biting.

After more than a year, I reached out to Dr. Stephen Wroe again. This time he responded.


Off to refer to Snively's reconstruction, then.

[Grey]

What we truly can say about megalodon size from its teeth and associated dentitions is that the largest megalodon teeth are almost 3 times longer than the largest white sharks teeth but the dentitions to which belonged the biggest meg teeth teeth were probably 4 times larger than the dentition of the larger modern white sharks.
We can at very least say that the largest megalodons had probably a dentition (thus the jaws) which was about 4 times larger than in the largest modern sharks dentitions.

From this we can add :
A modern white shark (not particularly large) is said to take 14 kg of flesh in one bite. Translating this bite to the volume of a bite 4 times larger than this makes a bite of almost 900 kg.

Many things about megalodons are hardly verifiable but the teeth and dentitions definitely indicate the larger megalodons had bite size in this region.

Do you simply know another biting carnivore, living or extinct, with a bite that massive ?

The only one I can think of is Livyatan and even this one I m not sure it is as voluminous.

[theropod]

The thing I’ve noted before about badger jaw joints→ also applies to wolverines (Gulo gulo):


It seems that as in badgers, the lower jaw is firmly enclosed at the joint so it remains articulated and the hinge intact even after the whole thing is skeletonized, but this constrains how far the jaw can be opened, in this case around 50° measured with respect to the ends of the jaw margins, around 30° with respect to the canine tips.

[Infinity Blade]

That's amazing. 50^o is a bit below an alligator (Lautenschlager, 2015) and I would not have considered a gape of 30^o (with respect to the canine tips) to be sufficient for a lethal killing bite to large animals before this. Yet the wolverine can still very much kill large ungulates (okay, maybe sometimes their health and/or their mobility in deep snow is compromised, but still). And it's not as if its head is so large compared to the rest of its body that it makes up for the limited clearance between its canine tips.

[Infinity Blade]

A few notes on the carnassial teeth of felids, and an apparent idiosyncrasy in their jaw anatomy.

Cats’ teeth have fewer different functions than those of other carnivorans, perhaps reflecting the cats’ obligate carnivory. Canines are clearly important for killing and incisors play an important role in plucking fur and feathers from carcasses prior to feeding, and pulling meat from carcasses during feeding. The carnassials have traditionally been thought of as the principal teeth for slicing through muscle, but studies of feeding in several large African carnivorans, including lion and cheetah, revealed that they were used primarily for slicing through tough skin and pieces of muscle too large to swallow, and that incisors are more important for removing meat from bone (Van Valkenburgh 1996). Mixtures of muscle and bone, for example ribcage or pelvis, were processed using both carnassials and adjacent premolars. To allow the carnassials to engage, the jaws must shift sideways, because the lower tooth rows are narrower and fit between the upper tooth rows. This lateral movement is facilitated by the cylindrical mandibular condyle (Fig. 3.12). When canines are being used, the carnassials do not engage, thereby preventing damage to these important teeth during killing.

Felid form and function

Also, not new info by any means, but, perhaps surprisingly, allosaurs have mechanical advantage profiles similar to those of abelisaurids.

Function space occupation by theropod taxa shows interesting disparity patterns. At the high-efficiency end of the tetanuran function space distribution, tyrannosaurs, allosaurs and ceratosaurs plot out close to each other despite their obviously different cranial morphology. Allosaurs have long been considered to be weak biters (Bakker 1998; Rayfield et al. 2001), but strikingly, their MA profiles are here found to be similar to those of abelisaurid ceratosaurs. Although MA does not take into account the magnitude of muscle forces, previous reconstructions of muscles however have also yielded similar bite forces for Allosaurus and Carnotaurus (Rayfield et al. 2001; Mazzetta et al. 2004, 2009), further supporting functional similarities in these two disparate clades. An extreme case of high-efficiency biting and functional convergence with ceratosaurs can be observed in Carcharodontosaurus, which plots beyond the range of distribution of tetanuran theropods and converges with Ceratosaurus towards the ancestral function space.

royalsocietypublishing.org/doi/full/10.1098/rspb.2010.0794

[Infinity Blade]

The mandible of Gigantoraptor was described in detail for the first time. Its beak has the greatest relative depth among caenagnathids, a parameter that decreases overall along this lineage. This parameter does not appear to be correlated with bite force in the same way as modern animals because Gigantoraptor has a coronoid process prominence that is relatively low rather than high and its height varies among caenagnathids. The possession of the lingual triturating shelf in caenagnathids more crownward than Gigantoraptor (a feature absent in oviraptorids) suggests an increased specialization towards shearing along the caenagnathid lineage, possibly related to a dietary shift. The dorsally convex articular region of Gigantoraptor and other oviraptorosaurs suggests that propalinal jaw movement was likely to be an important part of food processing based on its morphological convergence with that of Sphenodon as well as dicynodonts. In comparison, oviraptorids have more downturned beaks, dorsoventrally taller coronoid process prominences and larger medial mandibular fossae, suggesting specialization towards feeding styles that utilize a stronger bite force e.g. crushing-related feeding. Despite having an unusually large body size, Gigantoraptor displays an intermediate mandibular morphology which suggests rudimentary shearing and crushing-related feeding capabilities when compared to crownward caenagnathids and crownward oviraptorids or perhaps even a unique feeding style related to the energy needs of such a large animal. This study provides new data and functional analogues that reinforce suggestions that the two main oviraptorosaur lineages — Caenagnathidae and Oviraptoridae — had divergent feeding styles likely to be linked with divergent dietary preferences.

www.ncbi.nlm.nih.gov/pmc/articles/PMC5701234/

Is there any information as to what the two small bony projections sticking out from the palates of oviraptorids were for?