Functional Morphology of Animal Feeding Apparata

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CORTICAL VS TRABECULAR BONE AND THE SPECIALIZED KILLING BITE OF SABER-TOOTHS
FIGUEIRIDO, Borja, University of Málaga, Málaga, Spain; PÉREZ-RAMOS, Alejandro, University of Málaga, Málaga, Spain; VAN VALKENBURGH, Blaire, university of California Los Angeles, Los Angeles, CA, United States of America

"The repeated evolution of elongate and laterally compressed (saber-like) canine teeth in different lineages of carnivorous mammals is one of the most spectacular cases of convergent evolution towards a specialized killing behavior. Although scimitar-toothed and dirk-toothed sabertooths have been traditionally identified as different ecomorphs, it is not clear whether these morphs deployed different killing bites. Here we use histologically-based algorithms to quantify the volume of cortical and trabecular bone in coronal sections of complete skulls to create biomechanical profiles of the ‘scimitar toothed’ Homotherium serum and in the ‘dirk-toothed’ Smilodon fatalis, as well as in a comparative sample of living carnivores, including the ‘conical-toothed’ Panthera leo. Whereas trabecular bone is well suited to deal with continuous and repetitive loads, cortical bone is better able to dissipate larger, more localized stresses. Our data indicate that Smilodon has much thicker cortical bone in its rostrum than other taxa. In the posterior region of the skull, cortical bone thickness is similar in Homotherium and Smilodon, but greater than in P. leo. In the same region, the trabecular bone in Homotherium is thicker than in Smilodon but thinner than in P. leo. Our results suggest that the two ecomorphs of saber-tooths differ in the distribution and quantity of cortical and trabecular bone across their skulls, reflecting different behaviors during prey dispatch. The thickened rostrum of Smilodon suggests that it deployed one or two very strong killing bites with its canines, whereas Homotherium might have used multiple, less forceful slashing bites. This suggests that the saber-tooth killing repertoire was more complex than previously suspected."

Grant Information:
Spanish MINNECO (Grants CGL2012-37866; CGL2015-68300P).
Technical Session XIX (Saturday, August 26, 2017, 3:45 PM)

vertpaleo.org/Annual-Meeting/Annual-Meeting-Home/SVP-2017-program-book-7-20-17a-(1).aspx

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New Reconstruction of Cranial Musculature in Ceratopsian Dinosaurs: Implications for Jaw Mechanics and ‘Cheek’ Anatomy
Ali Nabavizadeh

Abstract:

For over a century, researchers have attempted to reconstruct cranial musculature in the horned ceratopsian dinosaurs, like Triceratops, in order to elucidate feeding behavior and mechanics in this important group of large herbivores. Here I present a new interpretation of muscle architecture in ceratopsian crania redefining the jaw mechanics of these animals. Muscular anatomy is interpreted through in-depth observation of muscle scarring and osteological correlates in taxa spanning the entire clade. M. adductor mandibulae externus (mAME), the main adductor muscle group originating within the supratemporal fenestra, has conservatively been reconstructed as inserting along the apex and caudal aspect of the tall coronoid process. The jugal flares out laterally, allowing communication between the caudal aspect of the maxilla and the endocranial adductor chamber. Accordingly, a large pocket is created allowing one enlarged muscular layer of mAME to exit the adductor chamber rostroventrally and extend much farther rostrally than previously proposed, inserting fibers all along the prominent lateral dentary ridge characteristic of ceratopsians. This lateral dentary ridge has traditionally been suspected as insertion of a novel, buccinator-like ‘cheek’ muscle. This new mAME reconstruction discounts the necessity of this type of novel musculature and, in turn, repurposes mAME as both a major jaw adductor as well as a secondarily functional ‘cheek’ containing food within the oral cavity. MAME then also creates a direct line of action between the rostral extent of the lateral dentary ridge and the origin of the muscle within the frill, lining up directly through the jugal opening and creating a massive palinal feeding stroke of the mandible. This corroborates with previous microwear studies while cradling the entire lower jaw around the sides, ideal for withstanding a much larger bite force. M. pterygoideus ventralis (mPTV), originating ventrally on the pterygoid flange and traditionally wrapping ventral to and laterally on the retroarticular process of the mandible, is now reconstructed to insert more rostrally on the lateral aspect of the dentary. The lack of a prominent retroarticular process in ceratopsians and the presence of a large depression just ventral to the coronoid process indicate this architecture. This creates a vertical line of action of mPTV for a powerful, orthal feeding stroke compensating for mAME creating a much more palinal vector. M. pterygoideus dorsalis (mPTD), originating on the dorsum of the pterygoid flange and inserting medially on the retroarticular process, is now reconstructed as extending its origin rostrolaterally onto the lateral aspect of the maxilla resting in a clear depression. The laterally flaring jugals create a continuous surface between the dorsum of the pterygoid phalange and the caudal aspect of the lateral surface of the maxilla, which is indicative of this reconstruction. MPTD in this orientation creates a rostrally-oriented vector, compensating for the vector of mPTV becoming more vertical. These newly reconstructed muscle configurations hold many important implications for the future of studies of feeding mechanics in these massive herbivores through computer modeling methodologies, among others.

m.fasebj.org/content/30/1_Supplement/lb27.short

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The basal cross section of many theropod lateral teeth is more rectangular than elliptical

...

With a rectangular model (Figures 9 and 10), theropod teeth have bending strength indices that fall within the scatter for, or are greater than, those calculated for mammalian carnivore canines using the elliptical model; the appearance of greater strength is reduced, but not eliminated, if theropod tooth bending strength is calculated using an elliptical model for tooth base shape. Van Valkenburgh and Ruff (1987) noted that living canids have canines that are basally more mediolaterally compressed than those of living felids, particularly at large tooth sizes. Theropod lateral teeth likewise tend to be flatter than canines of extant felids, although there is much overlap in their relationships between BW and FABL (Figure 11); theropod teeth have considerably greater basal widths than sabercat canines, however. Small theropod teeth tend to be more mediolaterally compressed at their bases than canid teeth, again with overlap in the relationships, but large theropod teeth are less compressed than dog canines of comparable size. The canine teeth of hyaenids plot within the scatter of theropod teeth for both bending strength indices and the relationship between BW and FABL.

link

So, if I'm interpreting the above correctly, theropod teeth, even the ones often thought of as blade-like, were just as resistant to bending, if not more so, than the canines of mammalian carnivores in both the anteroposterior and mediolateral planes.

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Here may be an idea of just how much bite force estimation methods that do not actually look at the actual jaw muscles (e.g. the dry skull method) can underestimate actual bite force, either that calculated in vivo or calculated from the actual muscle tissue.

Rose et al. (2012) did the latter and calculated that a 100 kilogram jaguar would be able to bite with a force of 503.57 kilograms at the canines. That's 4,938.33 Newtons. Christiansen & Wroe (2007) used the dry skull method to deduce that a 95.5 kilogram jaguar would bite with a force of 887 Newtons at the canines. If scaled up to exactly to the slightly larger size of the jaguar specimen in Rose et al. (2012), this would be increased to 914.65 Newtons. The value obtained by analyzing the masticatory muscles of dissected felids is about 5.4 times greater than that predicted by the dry skull method. I wonder if bite force estimations for at least some extinct animals, whose muscle tissue is impossible to analyze (for obvious reasons), are similarly underestimated.

Obviously, however, if someone can demonstrate that a jaguar would not actually be able to bite that hard at the aforementioned body mass, I'll be willing to listen.

References:

Hartstone-Rose, A., Perry, J. M. G. and Morrow, C. J. (2012), Bite Force Estimation and the Fiber Architecture of Felid Masticatory Muscles. Anat Rec, 295: 1336–1351. doi:10.1002/ar.22518

Christiansen, P., Wroe, S. (2007), Bite Forces and Evolutionary Adaptations to Feeding Ecology in Carnivores. Ecology, 88(2): 347-358.

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An important bit from Snively et al. (2011).

However, Allosaurus was probably not limited to a single strategy for removing flesh. Its laterally compressed, ziphodont teeth suggest forceful alternating tugs to either side of the head, as seen in Komodo dragons (Auffenberg, 1981, D’Amore et al., 2011).

link

This means that although Allosaurus' neck musculature was more specialized for striking outwards, powerful ventroflexion, and pulling back (hence feeding more like a hawk), Snively et al. do not think this was the only means through which Allosaurus could deflesh a carcass or victim. They clearly suggest that it could also pull to the sides of the head like a Komodo dragon. To minimize lateral bending stresses to the skull, it could feed in a fashion well illustrated by Fig. 3B in D'Amore & Blumenschine (2009); rotate the head from a position lateral relative to the rest of the body to a more medial position, all while moving the skull caudally. That way, the skull is technically not taking lateral bending stresses, but mostly caudally oriented stress.

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While writing an essay for college and exploring links for references, I eventually found this recent paper.

Puncture-and-Pull Biomechanics in the Teeth of Predatory Coelurosaurian Dinosaurs

Highlights
•Theropods used puncture-and-pull feeding movements, based on microwear analyses
•Troodontid teeth were most likely to fail at non-optimal bite angles
•Troodontids may have favored prey requiring lower bite forces than dromaeosaurids

Summary
The teeth of putatively carnivorous dinosaurs are often blade-shaped with well-defined serrated cutting edges (Figure 1). These ziphodont teeth are often easily differentiated based on the morphology and density of the denticles [1, 2]. A tearing function has been proposed for theropod denticles in general [3], but the functional significance of denticle phenotypic variation has received less attention. In particular, the unusual hooked denticles found in troodontids suggest a different feeding strategy or diet compared to other small theropods. We used a two-pronged approach to investigate the function of denticle shape variation across theropods with both congruent body shapes and sizes (e.g., dromaeosaurids versus troodontids) and highly disparate body shapes and sizes (e.g., troodontids versus tyrannosaurids), using microwear and finite element analyses (Figure 1). We found that many toothed coelurosaurian theropods employed a puncture-and-pull feeding movement, in which parallel scratches form while biting down into prey and oblique scratches form as the head is pulled backward with the jaws closed. In finite element simulations, theropod teeth had the lowest stresses when bite forces were aligned with the oblique family of microwear scratches. Different denticle morphologies performed differently under a variety of simulated biting angles: Dromaeosaurus and Saurornitholestes were well-adapted for handling struggling prey, whereas troodontid teeth were more likely to fail at non-optimal bite angles. Troodontids may have favored softer, smaller, or immobile prey.

www.cell.com/current-biology/fulltext/S0960-9822(18)30371-3

I think this is further evidence against the rubbish notion that these theropods (Troodon excepted) were only hunting relatively small prey.

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Reference

So if I'm interpreting this correctly:

- Theropod teeth tend to be more rectangular than elliptical in cross section, and this would give them stronger bending strength than carnivoran canines of elliptical cross section (though the strength advantage would be reduced under the elliptical model, it would still be there).
- Small theropod teeth tend to be relatively more compressed than dog canines (though with much overlap).
- Large theropod teeth are relatively less compressed than dog canines.
- Relatively speaking the canines of hyenas plot with the teeth of theropods in both bending strength indices.
- Some theropod teeth have much greater anteroposterior and mediolateral bending strength than the canines of any carnivorous mammals sampled.

By no means are dog canines bad at taking stress from struggling prey; in fact, that's what they do. So the way I see it now, if a macropredatory theropod bit into a large prey item that then began to struggle violently, its teeth won't easily break like I used think would happen (or got the impression of).

Someone please fact (or rather, data) check me here.

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Unilateral vs. bilateral biting (I posted this just to shed light on my curiosities about it).

mambobob-raptorsnest.blogspot.com/2007/05/unilateral-vs-bilateral-biting.html

Another one of my introductions into bite force analyses. This time, it's a relatively old but very well cited study by Jeff Thomason et al. (1990). This study is usually cited for the isometric stress values in jaw adductor muscles. What this means, is that when muscles contract, the individual fibres exert a certain amount of stress (force over a unit area). Thomason et al. (1990) showed that the mean muscle stress was 317 kPa which was well within the range of 147 - 392 kPa obtained for other vertebrates in a previous study (Carlson and Wilkie 1974).

The significance of these results is that they allow us to calculate muscular contractile forces from the physiological cross-sectional areas (PCSA) of muslces. Since stress is force over unit area, if the total area is known, then force can be calculated. Now, since stress value seems to be within a known range, we can multiply the stress value (N/m^2) with PCSA (m^2) and get muscle force (N).

However, there is another important aspect to Thomason et al. (1990) that seems to be overlooked. They actually observe the difference in bite forces between unilateral and bilateral muscular contractions. The jaw adductor muscles in anaesthetized opossums were experimentally stimulated and the resulting bite forces were recorded with a devise clamped between the upper and lower 2nd and 3rd premolars on one side of the jaw (unilateral biting condition). There are two notable experiments, one that stimulated only the muscles on the working side of the jaw (ipsilateral) and another that stimulated both the working and balancing sides (contralateral) of the jaws (bilateral stimulation). The results are very interesting (see figure).



The top graph shows approximately the pattern observed in a unilateral bite force from ipsilateral stimulations of the jaw adductor muscles, again, that's the muscles on the same side of the jaw as the biting point. Two distinct plateaus can be observed. The first is known to be the maximum bite force attained from an ipsilateral muscle stimulation from other experiments. Then what of the second plateau? Now, that's caused by the supposedly unstimulated muscles on the other side actually activating to add to the bite force.

This is really cool as this shows two things. First, it shows that muscle stimulations on the two sides of the skull are somehow linked, and the overstimulation of the ipsilateral muscles actually jumped across and started stimulating the contralateral muscles. This is recognised from the second graph, which shows the pattern in bite force from bilateral stimulations. Note that the value at which bite force plateaus is nearly identical to the second plateau of the top graph.

Second, it shows that bilateral contractions of the muscles actually nearly doubles the unilateral bite force. At least under experimental conditions, it has been shown that when biting on one side of the jaw, as you do when you're trying to crack open some pistachios, you can get twice as much bite force when you use muscles on both sides of the head rather than just the one. This seems really obvious, but it has been a topic of much debate - do muscles on both sides contract in a unilateral bite? At least in some mammals, it has been suggested that the muscles on the balancing side will only contribute to about 30% of the total contractile force (I can't remember the exact reference for this). On the other hand, Compton and Hylander (1986) mention that 'when the tenrec eats hard food, such as bone, there is little or no differential between the active and balancing sides'.

Thomason et al. (1990) also show that some voluntary bites by opossums can reach values obtained as maximal in experiments. This suggests to me that at least in opossums (and tenrecs), unilateral bite forces can employ bilateral muscular contractions to attain maximum bite force. In other words, a unilateral bite can be just as forceful as a bilateral bite.

References:
Carlson, F. D., and Wilke, D. R. 1974. Muscle physiology. Prentice-Hall, Englewood Cliffs.

Crompton, A. W., and W. L. Hylander. 1986. Changes in mandibular function following the acquisition of a dentary-squamosal jaw articulation. Pp. 263-282. In N. I. Hotton, P. D. MacLean, J. J. Roth, and C. Roth, eds. The ecology and biology of mammal-like reptiles. Smithsonian Institute Press, Washington.

Thomason, J. J., A. P. Russell, and M. Morgeli. 1990. Forces of Biting, Body Size, and Masticatory Muscle Tension in the Opossum Didelphis-Virginiana. Canadian Journal of Zoology-Revue Canadienne De Zoologie 68(2):318-324.

So, as I expected, bilateral biting does indeed double unilateral bite force. Except when it doesn't (in certain animals).

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Since theropod is recently posting again, I think I may have some chance to clear something up now (though of course, anyone can feel free to jump in the fray!).

Dec 31, 2017 8:04:22 GMT 5 Infinity Blade said:

Here may be an idea of just how much bite force estimation methods that do not actually look at the actual jaw muscles (e.g. the dry skull method) can underestimate actual bite force, either that calculated in vivo or calculated from the actual muscle tissue.

Rose et al. (2012) did the latter and calculated that a 100 kilogram jaguar would be able to bite with a force of 503.57 kilograms at the canines. That's 4,938.33 Newtons. Christiansen & Wroe (2007) used the dry skull method to deduce that a 95.5 kilogram jaguar would bite with a force of 887 Newtons at the canines. If scaled up to exactly to the slightly larger size of the jaguar specimen in Rose et al. (2012), this would be increased to 914.65 Newtons. The value obtained by analyzing the masticatory muscles of dissected felids is about 5.4 times greater than that predicted by the dry skull method. I wonder if bite force estimations for at least some extinct animals, whose muscle tissue is impossible to analyze (for obvious reasons), are similarly underestimated.

Obviously, however, if someone can demonstrate that a jaguar would not actually be able to bite that hard at the aforementioned body mass, I'll be willing to listen.

References:

Hartstone-Rose, A., Perry, J. M. G. and Morrow, C. J. (2012), Bite Force Estimation and the Fiber Architecture of Felid Masticatory Muscles. Anat Rec, 295: 1336–1351. doi:10.1002/ar.22518

Christiansen, P., Wroe, S. (2007), Bite Forces and Evolutionary Adaptations to Feeding Ecology in Carnivores. Ecology, 88(2): 347-358.

So, if we're to go by these figures, a jaguar scaled up to the size of T. rex (let's say 6,160 kilograms) would bite with a force of a little over 77 kN. Scaled up to the largest known Tyrannosaurus specimen (8,400 kilograms) that gives us an animal biting with a force of nearly 95 kN. Keep in mind that these are at the canine teeth.

Some months ago theropod and I corresponded with each other via email and I think he said something like the largest T. rex specimens having a bite force likely in the 60-90 kN range.

That's about the same as our scaled up jaguar. But...something seems off. Even relatively speaking a felid has a relatively much smaller head than does something like Tyrannosaurus. Consequently I'd expect the tyrannosaur to have relatively larger jaw-closing muscles, and therefore to bite relatively harder. Are either one of these bite force estimates off or is my suspicion just not true?

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A second thing is regarding Therrien et al. (2005). With their mandibular bending profiles, they had been able to estimate how hard an animal would bite relative to an American alligator (and a Komodo dragon for further comparison). They predicted an Allosaurus could bite about has hard as an alligator, a Ceratosaurus 36.2% harder, a Majungasaurus almost twice as hard and a Carnotaurus over twice as hard, a Giganotosaurus 5 times harder, a Daspletosaurus over 7 times harder, and a Tyrannosaurus nearly 16 times harder than an alligator (perhaps it is important to know the mandible lengths for each, and if needed I can easily provide them).

I thought "hmm, intuitively this doesn't sound unreasonable".

But then I also realized what this meant with regards to their alligator bite force figure. They had it at 18,912 Newtons; this seems to have been derived from an experimentally measured alligator bite that was then doubled to account for contralateral jaw musculature. This meant that Tyrannosaurus would bite with a force of ~300 kN. Ww...H'WHAT?!

As far as I can tell the methodology seemed to be reasonable, and in some ways produced what might seem like reasonable results (I mean, I can swallow Allosaurus biting with a force roughly equal to that of an alligator, as well as some of the other implied theropod bite force estimates). But then it results in...300 kN??!!

The only person who addressed my bafflement about these ungodly enormous figures was LionClaws back when he was temporarily active again in 2016. And...he didn't seem to think much wrong with the ~235 kN figures for T. rex (and consequently didn't see a problem with Giganotosaurus biting as hard as ~80 kN). And it's not like he's a theropod fanboy either.

But surely this is unreasonably high, right?

[theropod]

Infinity Blade
About the first thing, based on the four P. onca with reported body masses and condylobasal lengths in Maźak et al. 2011, a hypothetical isometric 8.4t jaguar would have a 1.2m skull. I’ve measured a dorsal view picture of a jaguar skull, and based on that, the skull would be over 80cm wide if scaled to that length (), meaning its skull width and space for jaw adductors are probably on par with T. rex at a given body mass.
So I’ve got no problems with the proposition that it would have jaw muscles more or as powerful as T. rex at that size. Also the bite force value for the canines does not seem that unrealistic, considering the shortness of the snout and probable high mechanical advantage in the jaguar jaw.

–––References:
Mazák, J. H., P. Christiansen, and A. C. Kitchener. 2011: Oldest Known Pantherine Skull and Evolution of the Tiger. PLOS ONE 6:e25483.

[theropod]

About the second thing, I think not all animals have the same safety factors, for various reasons (for one, an alligator’s head and jaw have to be flat for reasons of camouflage and aquatic locomotion, T. rex is under no such pressure), so mandibular bending strength is not necessarily a reliable proxy for bite force.

EDIT: T. rex also seems to have had muscular arrangements adapted to allow much bigger gape angles than do crocodilians’ (Lautenschlager 2015). In Allosaurus that same trend matches adaptions of the jaw joint to accomodate these gapes without dislocation (Bakker 1998), and hence is probably an accurate representation of the real range of motion, which implies a proportionately weaker musculature than a crocodile. If it turns out that T. rex’ jaw joint was a more limiting factor on its gape, then that would probably imply that T. rex also had more muscle fibre pennation (than Allosaurus), which would increase the physiological cross-section and force output. But the macroscopic muscle arrangements suggest that T. rex’ muscles are not arranged in quite such a motion-constraining but force-optimising fashion as crocodilians’ (though better than Allosaurus, of course).
…Not sure where exactly I was going with this to be honest, this is more relevant when comparing T. rex’ muscle size or head size to crocodiles than it is for comparing its lower jaw strength. I guess an important point is, that bite force in crocodilians may be unexpectedly high given their osteology, due to additional differences in myology and muscle histology, and it’s quite plausible that an alligator simply bites harder for its mandible’s safety factors than a T. rex due to ecomorphological pressures forcing it to have a platyrostral morphology, or conversely that a T. rex’s mandible is overengineered for its bite force for reasons such as peak forces encountered in large prey restraint.

So if you want my opinion, yes I definitely think both Meers’ 2003 18-24t bite force estimates and a hypothetical 30t bite force based on comparing mandible strength to Alligators is unrealistic. But of course on top of that we have to differenciate between peak and sustained bite forces here. Peak bite forces may well be even higher than those 6-9t guesstimates (although I highly doubt they reached the aforementioned figures).


Bakker, R. T. 1998: Brontosaur killers: Late Jurassic allosaurids as sabre-tooth cat analogues. Gaia 15:145–158.
Lautenschlager, S. 2015: Estimating cranial musculoskeletal constraints in theropod dinosaurs. Royal Society open science 2:150495.

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Jun 28, 2018 23:07:03 GMT 5 theropod said:

Infinity Blade
About the first thing, based on the four P. onca with reported body masses and condylobasal lengths in Maźak et al. 2011, a hypothetical isometric 8.4t jaguar would have a 1.2m skull. I’ve measured a dorsal view picture of a jaguar skull, and based on that, the skull would be over 80cm wide if scaled to that length (), meaning its skull width and space for jaw adductors are probably on par with T. rex at a given body mass.
So I’ve got no problems with the proposition that it would have jaw muscles more or as powerful as T. rex at that size. Also the bite force value for the canines does not seem that unrealistic, considering the shortness of the snout and probable high mechanical advantage in the jaguar jaw.

–––References:
Mazák, J. H., P. Christiansen, and A. C. Kitchener. 2011: Oldest Known Pantherine Skull and Evolution of the Tiger. PLOS ONE 6:e25483.

I tried making a hypothetical size comparison of this to the best of my ability on a Word document. I'm an amateur at best, though, so you should take this with a grain of salt.



The jaguar skull is actually be a little oversized (some 125 cm long as opposed to 120), as I used a meter long scale bar divided into quarters and I don't have the skills or equipment to downscale the jaguar a notch. The tyrannosaur should be at about 152 cm long (same as Sue's I believe).

To be fair I do know of published word that's still suggestive of greater jaw power in Tyrannosaurus than what biomechanical models suggest at face value, though it's not ridonkulously high to the extent of Therrien et al. (2005) and not too terribly higher than 90 kN. According to Snively et al. (2015)

"Reptiles have a laterally unconstrained, multi-aponeurosis m. pterygoideus posterior/ventralis that loops around the lower jaw, and pennate temporal muscles with greater forces per ACSA than the 30–37 N/cm2 specific tension (ST) values for mammals. (When isometric ST for Tyrannosaurus is scaled to ST of the tuatara Sphenodon, the tyrannosaur’s posterior bite forces reach the 100,000 N values estimated through structural mechanics [83], and calculated for giant crocodilians.)"

Table 6 (see here) then gives the precise number, which is 105,732 N at the posterior end and 53,593 N at the anterior end. That's three times the force of the conservative end of Bates & Falkingham's figures, mind you (which would be 18,065 N at the anterior end and 35,640 N at the posterior end). The liberal end obviously gives you higher numbers.

[theropod]

Another thing to note is that Bates & Falkinham apparently tested their models at 45° gape angle, which is well above the optimal tension limit of the muscles according to Lautenschlager. Perhaps testing at 30° gape angle instead would have produced higher estimates. EDIT: Nope, sorry. They set the specific tension to a fixed 300kN/m², so that part is taken out of the equation.

[Infinity Blade]

^So...just never mind that?

I also tried to make another Word doc comparison with a skull comp. blaze made a while back with the skulls of a cougar, grey wolf, spotted hyena, and Deinonychus. After conversing with him he seemed to suggest that an isometrically scaled up Deinonychus would have a skull about a fifth (to be more precise ~18%; since my skills aren't that precise I just tried my best making the tyrannosaur skull 4/5ths the length of the raptor's) longer than a Tyrannosaurus would, and I recently concocted another comparison that roughly shows this (again, not an expert size comp. maker; for that reason I recently asked a friend for tyrannosaur and jaguar skulls at what would probably be mass parity).



It’s worth noting that different felid taxa won’t necessarily all be as big (or small) headed as each other. Chui on Carnivora recently showed how leopards are bigger headed than cougars, for instance. So a jaguar might have better odds of rivaling a Tyrannosaurus' bite force than a cougar would (relatively speaking of course).

I remember you once said that at parity (as fantastic, literally fantasy, of a scenario that would be for obvious reasons) a macrophagous tyrannosaur would have a way more damaging bite than a felid (somewhere in the ask a question thread). Do you still think that? I know bite force isn’t everything, although given what I wrote above it seems it's still possible a hard biting tyrannosaurid could bite harder than an equal sized felid could at the canines (and a relatively durophagous one at that; it turned out that the tiger, while it bit absolutely harder than the jaguar, had a bite force proportionately inferior to it).

You know, I was a bit worried I was turning this into more unhealthy, obsessive versus crap, but then I remembered that "This is a place to discuss and compare the potency, strenghts/weaknesses and purpose of feeding apparata among vertebrates", which is exactly what I'm doing here.

[elosha11]

Ausar/Theropod, just wanted to say this is a really interesting conversation and quite illuminating. It boggles the mind how powerful T-Rex could bite under any of the proposed estimates and the jaguar's comparative strength is very impressive.

Reading your comments makes me wish it we could get some real life testing on the bite force of the big marine mammals of today, such as orcas, pseudo orcas, and sperm whales. For orcas at least, I'm quite sure it would be highly impressive. If one could get accurate estimates, I would love to see an extrapolation to Livyatan. Given how much larger its head and overall jaw was in comparison even to T Rex, I think it could quite likely pose the highest known bite force, exceeding Megalodon and the the largest pliosaurs.

[theropod]

While I get that it’s probably a lot more difficult than it sounds, it actually boggles my mind that nobody has as of yet tried to measure and or estimate Orcinus’ bite force. As the largest raptorial predator on the planet, it’s not difficult to justify such an analysis.
I get that captive individuals may be a poor analogue for their wild counterparts, but there are (comparatively) lots of captive orcas and nobody even seems to have tried measuring their bite force. And I get that getting a wild orca to chomp down with full power on a measuring device is pretty unlikely. But the same holds true for great whites, and that didn’t stop Wroe and colleagues from estimating its bite force by other means. Certainly any figure for orca bite force would be interesting, whether it be an in vivo measurement from a captive specimen, or a computional model of its jaw function. If it’s been done on tons of extinct animals, then doing it on an animal with completely known osteology and myology shouldn’t be too challenging.

Also if there was some way of measuring bite forces in wild orcas, that would definitely be intriguing with regards of the vast differences in feeding ecology between the morphotypes, and how it relates to their anatomical differences.

It’s really weird to have a clearer picture of the biting mechanics of Basilosaurus or Pliosaurus than we do of an extant cetacean with a cosmopolitan distribution that’s literally being held in zoos.