Functional Morphology of Animal Feeding Apparata

[Supercommunist]

Could be that false gharials only deathroll to get themselves out of sticky situations but don't actually do it when biting prey.

Of course, it is also possible that the researchers were a bit too conservative and underestimated the strength of a sarcho's jaws.

It seems a lot of paleontologist kind of underestimate extinct animals, seeing as we had people arguing that tyrannosaurus was a scavenger, giant pterosaurs were too heavy to fly, and that large multi ton theropods rarely attacked and hunted fully grown animals.

[Infinity Blade]

Info dump incoming. All citations below are hyperlinked.

Felids and canids have different skull shape patterns for specializing on small versus large prey (Slater, 2009).

Carnivorans (Carnivora, Mammalia) exhibit a wide range of skull shapes. In this dissertation, I quantified patterns of skull shape variation in dogs (Canidae), cats (Felidae) and extinct, cat-like carnivorans (Nimravidae) using traditional and geometric morphometric methods. I then used Finite Element Analysis (FEA) to investigate the biomechanical consequences of skull shape variation in canids and felids. Canids are social pursuit predators, relying on their skulls and teeth to apprehend prey. Felids are solitary ambush predators that use suffocating bites to kill restrained prey. Patterns of skull shape variation in canids and felids are associated with these differences in predatory behavior. In canids, skull shape variation is associated with the size of prey taken. Canids that specialize on small, fast moving prey have long, narrow jaws for increased bite speed. Conversely, canids that specialize on large, thick-skinned prey have short, broad jaws for increasing bite force. The jaws of generalist canids fall intermediate to the two specialized types. Felids exhibit a different pattern of shape variation; small felids take small prey but have short jaws while large felids take large prey and have longer jaws. Prey size in felids is limited by what can be fit between the canine teeth. Longer jaws result in relatively larger gape distances, allowing large felids to access relatively larger prey than small felids. FEA simulations of biting behavior show that the skulls of canids that take small or medium prey are similar in strength. Canids that take large prey have stronger skulls and are better able to resist additional forces, such as those incurred by large, struggling prey. FEA also reveals that large felids produce relatively smaller bite forces than small felids and that their skulls undergo more strain when biting. However, large felid skulls exhibit lower stress values, and are therefore stronger, during biting and prey-driven loads. While cranial strength in canids is increased by changes in skull shape, large felids achieve increased cranial strength by thickening the bones of their skulls. Independent evolution of large prey specialization in canids and felids results in similar biomechanical demands, which are met in different ways.

Corroborated in this book (Castelló, 2020).

The skull in most small cats is rounded, with a domed braincase, and a very short, broad rostrum. Large cats have a more elongated skull, with a more extended muzzle.

And in this biomechanical study (Slater & Van Valkenburgh, 2009).

Variation in bite force among the three FE models is inversely proportional to jaw length and gape distance. The shortest-jawed felid, the wild cat, produced the highest bite forces for the muscle force used, and the longest-jawed felid, the lion, produced the lowest bite forces (Table 3). Overall, however, the absolute differences in bite force magnitudes among the four models were small, with maximum differences of 12 N for bilateral biting and 25 N for unilateral biting.

Our results show that larger felids have both absolutely and relatively larger gape distances than small felids. The importance of gape for predatory performance in felids relates directly to the mode of prey capture in these carnivores. As predominantly solitary ambush predators, felids kill their prey using a single bite either to the nape, throat or muzzle (Ewer, 1973; Leyhausen, 1979), and are therefore restricted to prey with throats or necks that can fit between the canine teeth (Kiltie, 1984, 1988). Larger gape distances should increase the range of prey sizes that can be taken by large felids. This is corroborated by field studies of predatory behaviour. Although large carnivores do not focus exclusively on large prey, they do take a wider range of prey sizes (Radloff & Du Toit, 2004) and prefer larger prey (Hayward & Kerley, 2005). This predatory strategy contrasts with other hypercarnivorous carnivorans such as canids or hyaenids, which use multiple shallow, tearing bites in combination with pack hunting to subdue and kill large prey, and therefore exhibit different patterns of cranial shape variation (Slater et al., 2009).

Large cat skulls are stronger, though, even when scaled to the same surface area.

Large cat skulls appear to be overbuilt with respect to the intrinsic loads that they generate while biting. However, other forces act on the skulls of predators during the act of prey killing, and these forces offer an explanation for our results. Maximum prey size increases with body size among felids, and large felids regularly take prey much larger than themselves (Van Valkenburgh & Hertel, 1998; Radloff & Du Toit, 2004; Hayward & Kerley, 2005; Meachen-Samuels & Van Valkenburgh, 2009). Even moderately sized prey can generate considerable forces when struggling in a predator’s jaws (Preuschoft and Witzel, 2005). Large prey can take up to 10 min to kill (Schaller, 1972) and are therefore likely to pose a significant challenge to the skulls of large felids. FE models of the large cat crania performed substantially better than the small cat under all extrinsic loading conditions. This finding suggests that strengthening the cranium in response to extrinsic loads incurred by struggling prey, rather than to those incurred by intrinsic forces, may be more important in the evolution of cranial strength in felids.

A note on big cat and bear canine teeth (Christiansen, 2008).

Ursid canines are moderate in size relative to those of more specialized carnivores such as most canids and felids. Despite being the largest extant carnivores, the upper canines of large male polar bears and big brown bears rarely exceed 50–55 mm in vertical crown height. In contrast, many male tigers and some lions less than half this size often have 55–60 mm long canines, sometimes even exceeding 70 mm (not 45 mm, as per Gittleman and Van Valkenburgh, 1997), reaching extremes as high as 90 mm (Mazák, 1983). Thus, ursids appear not to follow the trend among derived carnivorous carnivorans of relying on proportionally large canines for prey capture (Biknevicius and Van Valkenburgh, 1996).

So the longest canine crowns for tigers (the citation is of a book about tigers specifically, not sure about lions) can be 9 cm (~3.5 inches) long. At first glance, this sounds impressive and horrifying. However, I don't think canines this long (compared to more reasonably sized ones) are necessarily an advantage. If anything, having canines this long could very well be disadvantageous, as canines that are too long would be more fragile. This would not be completely balanced out by the cross sectional area of the tooth (Freeman & Lemen, 2006).

Results from regression analysis indicate that the relationship between body weight and tooth strength is allometric. Larger species have relatively weaker teeth. The tooth strength (S_A,0.7) of a fox-sized predator could support about
7.3 times its body weight, but for a lion-sized predator this value is about 4.4 times its body weight. Not surprisingly, the saber-toothed Smilodon is the most different species for tooth strength. The long tooth results in a much higher input arm that is not fully compensated for by the large cross-sectional area of the tooth. Our regression analysis predicts that a typical predator of 320 kg has SA,0.7 that could support about four times its body weight. Predictions from FEA for Smilodon indicate its SA,0.7 could only support about 2.2 times its body weight (Fig. 4).

I'm pretty sure I've posted this before somewhere, but interestingly tigers with broken canines actually take prey about the same size as those without. Although they're obviously not as sharp, it could be that the decreased length of the canine crowns makes them more resistant against large prey (Goodrich et al., 2012).

EDIT 5/9/21: also, it appears that despite their relatively short snouts/jaws, cats seem to lose a lot of the muscle force going into the bite. Wroe (2007) shows the results of a finite element analysis on Thylacoleo carnifex in comparison to Panthera leo. The lion specimen used was a particularly large one that they estimated at 267 kg. While total muscle force was estimated at 8880 N (almost 2,000 lbf) for the lion, the actual bite reaction force at the carnassial teeth was 5612 N (~1,262 lbf), which is much less than total jaw muscle force. Bite force at the canines is even less at 2906 N (~653 lbf). In other words, the actual killing bite of the lion has a third of the force of the raw strength of its jaw muscles.

Stephen Wroe has noted before how a lot of the mammalian carnivores he's looked at showed this kind of mechanical inefficiency (with the marsupial lion being one of the more efficient mammalian carnivores he's looked at).

"'I have to say that I am pretty impressed with just how complex and sophisticated the feeding apparatus of the shark is," Wroe added. "With all the mammalian predators I've looked at, a lot of the muscle force going into the bite is actually lost. The shark has a much more efficient lever system going on.'"
www.nbcnews.com/id/wbna26012702

[Supercommunist]

Was looking through this thread and decided to respond to some old posts.

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.

I looked at that study, and I gotta say they seem like overestimates of felid bite force given that, according to their results, the cats would be biting harder than similar sized crocodiles: For instance, the 100 kg jaguar bit harder than a 110 kg morelet's crocodile while a 200 kg tiger would have had a more powerful bite force than a 207 kg mugger crocodile:






Given Erickson figures that most crocodilians bite 3 times harder than cats at equal weights, the top figures are very odd.

3:39



I do see that you very recently provided a quote that suggests cats do not efficiently transfer their full jaw strength into a bite so it could be the case that the 2012 cat study didn't keep that in mind.

According to this recent analysis on Baurusuchus pachecoi, it had a relatively weak bite (~578 N), apparently having significantly less jaw strength than modern crocodylians of similar size. However, the authors state that a crocodylian of similar size to this specimen of B. pachecoi was a 1.5 meter long Chinese alligator, citing Erickson et al.'s 2012 crocodylian bite force paper (it, btw, had a bite force of up to 963 N at the caniniform teeth). That paper states that a Chinese alligator of a mean body length of 1.5 meters is 14 kg, which is by no means a particularly massive animal. So I wonder if part of the reason for the shockingly low bite force figure for this Baurusuchus specimen is simply due to it (possibly) being a small animal (though this would change nothing about bite force corrected for size).

I am not familiar with Baurusuchus' size but assuming that 14 kg specimen is a small animal young, it could be the case the case that young baurusuchus have weaker jaws that become more powerful and robust as they age like modern day crocodilians.

American alligators Alligator mississippiensis undergo major transformations in morphology and ecology during
development. These include several thousand-fold changes in body mass, modified snout and dental proportions,
and shifts in diet from small, delicate foodstuffs to the inclusion of increasingly larger, more robust prey. How
these changes in anatomical form contribute to actual physical performance and niche use is largely unknown. In
the present study, bite-force measurements for 41 specimens of A. mississipiensis, were made throughout ontogeny
(hatchling–older adults) using a series of precision force transducers. How this performance indicator scaled with
respect to cranial and whole-body measurements was determined. Bite-force production throughout development
was contrasted with ontogenetic changes in trophic ecology. The influences of this performance measure on these
changes were then analysed. The results showed a 800-fold range (12–9452 N) of bite forces with values positively
correlating with increases in body size. Scaling of biting forces through ontogeny showed positive allometry with
respect to body mass, head length, jaw length, snout–vent length and total length. These patterns may be attributable
to allometric growth of individual skeletal elements (and associated musculature), and/or progressive fusion and
ossification of skull and jawbones during development. The overall pattern of force increase throughout ontogeny
did not vary in association with major shifts in diet.

www.alligatorfarm.com/images/Research/Erickson%20et%20al.%202003.pdf

[Infinity Blade]

Yeah, I recently looked through the methods of that 2012 paper again, and I don't trust the way it estimated bite force. They calculated leverage purely from lateral photographs of their specimens.

BF at three different points along the tooth row (the tip of the canine, the primary cusp of the third maxillary premolar, and the upper carnassial notch) was then calculated by combining the PCSA data with a constant expressing the load that can be produced by a given cross-section of skeletal muscle (3 kg/cm²; Close, 1972) and the leverages of those muscles. The 3 kg/cm² estimate is from the extensor digitorum longus of a rat at optimum length and is considered a reliable estimate by Close, although estimates for mammalian skeletal muscle vary widely, as much as from 1 to 5 kg/cm². Leverage estimates were gathered from lateral photographs of the crania of each of the dissected specimens with the specimens posed in dental occlusion (Fig. 4). Lateral photographs of the separate crania and mandibles were used to visualize surfaces that overlap when the skull is in occlusion. The load arm is the measurement from the condyle to the bite points for each of the three chosen bite points. The lever arm for each of the muscle groups is the length of a perpendicular line that connects the condyle to the line of action for the muscle group. The line of action is a line connecting the centroid of the origin of the muscle group to the centroid of the insertion of that muscle group. This model assumes that the movement at the condyle is purely rotational and not translational—a fair assumption in felids (Turnbull, 1970; Herring and Herring, 1974; Herring, 1992). It also is also an oversimplification of these masticatory leverages because it does not account for the dynamism of these lever arms at different degrees of gape or the specific orientation of the BF (though we assume it to be perpendicular to the moment). However, since the masticatory muscles were dissected and their fibers measured at near occlusion, when combining these data and the leverage data gathered at occlusion, these estimated BFs can be assumed to represent BFs at occlusion. These BF estimates also assume that all muscles are maximally active at once.

anatomypubs.onlinelibrary.wiley.com/doi/pdf/10.1002/ar.22518

Whereas the study by Stephen Wroe used actual 3D biomechanical models. I think it's pretty obvious which one gives you a more accurate picture of a jaw's lever system.

Additionally, one of the other papers I cited estimated how much force it would take to fracture the canine teeth of various carnivores.

On the basis of FEA, we estimated the strength of the canines (of several species) that we never broke: lion 8243 N, tiger 7440 N, leopard 2483 N, puma 2840 N, clouded leopard 1229 N, gray wolf 2660 N and the sabertooth 7000 N.

For perspective I bolded and underlined two species that appear in both this paper and Hartstone-Rose et al. (2012). The canine bite force figure for the tiger in the latter study is equivalent to 6901 N, while the canine bite force figure for the clouded leopard is equivalent to 1068 N. These bite force figures would have us believe that the tiger and clouded leopard bite with almost the amount of force needed to break their own canine teeth, which is ridiculous. Cats, especially those that prey on large prey, need strong canines not just for biting hard, but also to be able to withstand the forces from large, violently struggling prey (this is why their canines are relatively rounded in cross section). If, for example, a tiger bites with nearly 7000 N of force at its canines, those teeth would be subjected to forces close to what they can withstand. Now imagine if whatever sambar deer, wild boar, or (even worse) gaur it's biting into decides to struggle: the cat's teeth would snap off. It makes no sense for cat canines to have such low safety factors.


EDIT: As for Baurusuchus, I found what appears to be a more complete and cleaned up version of the paper I posted (link->). They mention that this specimen of Baurusuchus they used had a skull 33.10 cm in basal length (the lion used in Wroe's 2007 study probably had a skull of similar length*), with an estimated total body length of about 170 cm, which would make it, in their words, a medium-sized baurusuchid. No idea on body mass, but I can't imagine it would have been all that enormous.

*The lion used in Wroe (2007) had a skull that was said to be almost 52% longer than the marsupial lion skull in the same study. That marsupial lion had a skull that was 213 mm (or 21.3 cm) in length (Wroe et al., 1999). A skull that's 52% longer is ~32 cm long.

[Verdugo]

May 15, 2021 3:39:37 GMT 5 Infinity Blade said:

Yeah, I recently looked through the methods of that 2012 paper again, and I don't trust the way it estimated bite force. They calculated leverage purely from lateral photographs of their specimens.

Whereas the study by Stephen Wroe used actual 3D biomechanical models. I think it's pretty obvious which one gives you a more accurate picture of a jaw's lever system.

Hartstone-Rose et al. (2012) is one a few modelled bite force studies, in which the muscles architecture of animals were dissected and examined. This allows them to actually observe many variables that previously could only be assumed or estimated based on osteology. The variables are:

. Muscle volume/mass or anatomical cross sectional area (ACSA): this variable was actually measured in Hartstone-Rose et al. (2012). In studies do not involve dissecting animals (which are most studies in extant and all studies on extinct, duh), muscle mass/volume or ACSA can only be estimated based on the attachment areas on the skull.

. Fibre length/pennation/physiological cross sectional area (PCSA): there are no reliable ways i know to determine or estimate this variable based on osteology alone. This variable is, therefore, almost always assumed in studies in which muscles are not dissected.

Wroe (2008) paper allows for more accurate in-level arms modelling thanks to 3D FEA. However, the two variables i mentioned above were either estimated or assumed, not observed and measured as in Hartstone-Rose et al. (2012). Wroe (2008) only worked with 'dry skull' and did not dissect any specimens.

Actually, Wroe (2008) used the total muscle force data from his earlier 'dry-skull' 2D paper, which is Wroe et al (2005)

Calculation of maximal muscle forces was based on 2-D estimates of the cross-sectional area (Thomason, 1991;Wroe et al., 2005; Christiansen & Wroe, 2007).

Wroe et al (2005) did not take into account in pennation and PCSA. In fact, they assumed the fibre to be parallel, hence PCSA = ACSA (anatomical cross sectional area). Wroe et al (2005) assumption is intuitive for comparative purposes, especially to extinct animals, but it is not appropriate when it comes to estimating realistic bite force. Also, ACSA in Wroe et al (2005) was estimated using Thompson 'dry skull' method, not examined and measured as in Hartstone-Rose et al. (2012). See their Supplementary for description of the methodology:

The ‘dry-skull’ method assumes that bite force
correlates with muscle cross-sectional areas and lever arm lengths, and does not take
into account any interspecific differences in jaw muscle pennation. We have not applied
correction factors to account for underestimations because these make additional
assumptions and, as the focus of our study is comparative, it is relative not absolute
values that are important.

Hartstone-Rose et al. (2012) while still used 2D level arm method, the level arms are based on the orientation of the jaw muscles. The orientation and direction of jaw muscles were determined by connecting the centroid of muscle origin to the centroid of muscle insertion:

Leverage measurements for the (I) lever arms and working‐side load arms and (II) the balancing‐side load arms. The red lines represent the line of action of mandibular adductors (solid = temporalis, dashed = masseter, dotted = medial pterygoid). These lines connect the centroids (red circles) of the origin areas to the centroids of the insertion areas. The lever arm (yellow lines) for each mandibular adductor are the lines connecting the temporomandibular joint perpendicularly to the red lines.

The origins and insertions of these jaw muscles were dissected and determined, not estimated or assumed.

Mandibular adductor origins (o) and insertions (i), lateral view. Muscle abbreviations are the same as those in Fig. 1. Note: from lateral view some origins (i.e., ZM, MP) and insertions (i.e., MP, DT) cannot be viewed. Male P. onca from study. Scale is in centimeters.

[Infinity Blade]

Hartstone-Rose et al. (2012) is one a few modelled bite force studies, in which the muscles architecture of animals were dissected and examined. This allows them to actually observe many variables that previously could only be assumed or estimated based on osteology.

I knew this. It's not like I conveniently glossed over the crux of their methods and somehow skipped straight over to their talk on leverage (I knew this before I ever realized it was a 2D model). The problem is, as you yourself stated, it's still a two-dimensional lever model. The data you plug in for muscle insertion, origin, fiber length, mass, etc. can be spot on, but are you actually arguing that it gives you as full of a picture of the muscle lever system as an actual three-dimensional model, assuming these same factors aren't also drastically removed from reality (a bit more on that below)?

Yes, the insertions and origins of the jaw muscles in Wroe's biomechanical models are estimates. Is there an actual, specific problem with where some of the muscles were arranged in his models? Is the muscle mapping in that study actually that far off from reality?

Yes, pennate muscles allow for greater force production, more so than when every muscle fiber is assumed to be parallel. But if you correct for size, the tiger's canine bite force as estimated by Hartstone-Rose et al. (2012) would be nearly three times greater than the bite force of the lion as per Wroe's methods (and still well over twice the force at actual body masses, where the lion is a third heavier). It is also, as I've already said, almost the maximum amount of force that the teeth can withstand.



Hartstone-Rose et al. also mention that their specimens were dissected and their fibers measured at near occlusion, and thus that their bite force estimates can be considered to be bite forces at occlusion. They admit that they don't account for different degrees of gape. I wonder if this helps explain why their force estimates are so high.

This model assumes that the movement at the condyle is purely rotational and not translational—a fair assumption in felids (Turnbull, 1970; Herring and Herring, 1974; Herring, 1992). It also is also an oversimplification of these masticatory leverages because it does not account for the dynamism of these lever arms at different degrees of gape or the specific orientation of the BF (though we assume it to be perpendicular to the moment). However, since the masticatory muscles were dissected and their fibers measured at near occlusion, when combining these data and the leverage data gathered at occlusion, these estimated BFs can be assumed to represent BFs at occlusion. These BF estimates also assume that all muscles are maximally active at once.

[Supercommunist]

It's worth noting on carnivora, when they were a bunch of threads comparing reptile strength to mammal strength, one guy posted this study that measured dog bite force via electric muscle stiumlation and produced some rather absurd figures:

The measured value ranged from 147 ± 6.9 to 926 ± 8.1 N on the canine teeth, and from 574 ± 83.2 to 3,417 ± 43.1 N on the carnassial teeth (26).

www.ncbi.nlm.nih.gov/pmc/articles/PMC5932386/

The largest dog in the study was 55 kg, and I assume it it the one that produced a bite of 3417 newtons, which higher than a 100 kg morolets crocodile. There's no way that is accurate.

en.wikipedia.org/wiki/Morelet%27s_crocodile


I am not as well studied as some other guys in thread, so I am sorry if I throw out some speculation that sounds like psuedo science, but maybe these bite force studies are just as flawed as dry skull bite forces, as it measures the absolute maximum theoretical limits of an animal's jaw strength rather than a hard bite they would realistically employ.

For instance, you occasionally hear stories of human's performing superhuman feats of strengths in desperate situations and in the rare cases these occur, usually the person injures themselves.

en.wikipedia.org/wiki/Hysterical_strength

Maybe a tiger could bite with a force with a 7000 newtons if it was pumped full of adrenaline but it'd probably break its teeth and tear its own jaw muscles doing so.

But I, really, really, really doubt, cat's can normally produce bite forces that high. If a lion had a bite force comparable to a similar sized crocodile's we should see them demolishing hyena skulls/necks left and right, and they would make short work of tortoises and pangolins but that doesn't occur.

[Verdugo]

May 16, 2021 1:00:32 GMT 5 Infinity Blade said:

I knew this. It's not like I conveniently glossed over the crux of their methods and somehow skipped straight over to their talk on leverage (I knew this before I ever realized it was a 2D model). The problem is, as you yourself stated, it's still a two-dimensional lever model. The data you plug in for muscle insertion, origin, fiber length, mass, etc. can be spot on, but are you actually arguing that it gives you as full of a picture of the muscle lever system as an actual three-dimensional model, assuming these same factors aren't also drastically removed from reality (a bit more on that below)?

The main difference between 2D model and 3D model is only in the muscle in-level arms actually. The other factors that i mentioned earlier (fibre length, PCSA, muscle volume, etc) appears irrelevant to which models you choose.

You could calculate Bite Force using the following:
Bite Force = Total Muscle Force * Muscle In-Level Arms / Bite Position Out-Level Arm

Out-level: the distance between the position at which you wish to obtain the bite force to articular condyle. We just ignore it for our purpose since it is irrelevant to whether your models are 2D or 3D


Total Muscle Force = PCSA (or ACSA) * Specific Tension

Specific tension: researchers usually use a value around 30 N/cm^2. It's an arbitrary constant, and irrelevant to your muscle modelling method. For instance, Hartstone-Rose et al. (2012) used value of 3 kg/cm^2. Wroe (2008) used 30 N/cm^2 since he used muscle force value from Wroe et al (2005)

PCSA (or ACSA if you assume no-pennation, parallel-fibre muscle model): this variable could only be obtained through either dissection of the muscles itself or estimated based on the muscle attachment areas on the skull. This is variable is irrelevant to your the muscle modelling techniques you choose later. For instance, Hartstone-Rose et al. (2012) obtained this variable PCSA through dissection but decided to model the muscle in-level arms as 2D. Wroe (2008) on the other hand, used total muscle force data from Wroe et al(2005), in which the ACSA was estimated using Thompson's 'dry skull' method.


So only Muscle In-Level Arms variable has relevancy to whether your model is 2D or 3D. 2D muscle in-level arms methods are not as realistic as 3D ones but they are not counter-intuitive nor prone to overestimation either. If anything, 2D level arms tend to have lower result than 3D ones when keeping every other variables equal. The more realistic 3D level arm methods appear to have more advantageous in-levels in comparison to 2D ones. You can see McHenry's Kronosaurus paper, in which his 3D results are higher than his 2D, despite keeping all other variables equal. Or Wroe (2008) also has higher bite force results despite using same Total Muscle Force as Wroe et al (2005)

May 16, 2021 1:00:32 GMT 5 Infinity Blade said:

Hartstone-Rose et al. also mention that their specimens were dissected and their fibers measured at near occlusion, and thus that their bite force estimates can be considered to be bite forces at occlusion. They admit that they don't account for different degrees of gape. I wonder if this helps explain why their force estimates are so high.

Most bite force studies I have come across are either calculated at occlusion or at an 'optimal' gape angle (varied from study to study). I do not think it really matters, and biting at occlusion is not unrealistic as it can simulate a big cat clamping around the throat of a prey animal for instance.

May 16, 2021 1:00:32 GMT 5 Infinity Blade said:

Yes, the insertions and origins of the jaw muscles in Wroe's biomechanical models are estimates. Is there an actual, specific problem with where some of the muscles were arranged in his models? Is the muscle mapping in that study actually that far off from reality?

No, I do not think there are any problems with how the muscles are mapped in Wroe's study. Even if there is, I do not think it is possible for me to tell nor if I think it could affect the bite force results by a significant margin for me to even bother. I just point out that the muscle mapping in Wroe's paper is still an estimation, while Hartstone-Rose et al. (2012) is based on actual dissection of the muscle. If there is a discrepancy to reality, Wroe's paper is just more likely to exhibit them than Hartstone-Rose et al. (2012) (not that I think there are anything wrong with his muscle reconstruction)

May 16, 2021 1:00:32 GMT 5 Infinity Blade said:

Yes, pennate muscles allow for greater force production, more so than when every muscle fiber is assumed to be parallel. But if you correct for size, the tiger's canine bite force as estimated by Hartstone-Rose et al. (2012) would be nearly three times greater than the bite force of the lion as per Wroe's methods (and still well over twice the force at actual body masses, where the lion is a third heavier). It is also, as I've already said, almost the maximum amount of force that the teeth can withstand.

I am doubtful the Lion in Wroe (2008) actually weighs up to 267 kg as suggested by the paper. The Lion's specimen appears to be the same one in McHenry et al (2007). You see Table 1 for detailed measurements of the specimen. It's likely that the regression they used has overestimated the body mass of this specimen. A Total Skull Length of 378 mm and condylobasal length of 332 mm does not seem exceptional for a fully grown male Lion. I prefer using the equation from Christiansen (2007) to estimate body mass in modern Felid. Because:

Body masses were assigned to the specimens based on their skull sizes (premaxilla–occipital condyles), using a sample of 24 specimens, representing 11 different species of felids, in which body masses had been found either shortly prior to or immediately after death.

log(BM) = 2.762*log(CBL) -4.638

When solved using CBL of 332 mm, I got a BM of 212 kg. Frankly, i would not be surprised if the Lion in Wroe (2008) is similar in size to the tiger in Hartstone-Rose et al. (2012). I have seen Lion with significant larger skull, weighing only at 200 kg body mass.

It is possible that the parallel-fibre, no pennation, model in Wroe (2008) has greatly underestimated the bite force of these animals, even as much as two times as you have pointed out.

Wroe (2008) does not provide muscle CSA or muscle volume details of his specimen. I have even looked through Wroe et al (2005) supplementary but still could find the data. However, Wroe (2008) does provide total muscle force data of 8880 N and we know they use specific tension of 30 N/cm^2.

Using the above formula I provided, ACSA can be calculated (in parallel fibre, no pennation model, PCSA = ACSA):
ACSA = 8880 / 30 = 296 cm^2

Hartstone-Rose et al. (2012) provided PCSA for Tiger in Table 2:
PCSA = 622.42 cm^2

The unrealistic, no pennation, parallel-fibre PCSA (PCSA = ACSA in no pennation, parallel-fibre model) in Wroe (2008) is less than half of what observed in a living animal.

I wish I could elaborate more on your points regarding teeth strength but i'm running out of time. I recommend you read Sherman et al (2017). The Alligator tooth failed at only 500 N, not from an adult animal but:

The effectiveness of the gar scale array is demonstrated by experiments
involving the penetration of an alligator tooth shown in Fig. 15.
A foam pad was placed beneath the scales to simulate the flesh of the
fish. Application of pressure caused adjacent scales to hinge on one
another in order to resist from penetration. Small concentric cracks
occurred in the ganoine layer, but were arrested and did not propagate
or cause failure. Eventually, at a force of ~500 N, the alligator tooth
failed, illustrating the capability of the gar scale to withstand the high
forces from the predatory action of an alligator. Tooth failure under the
alligator's biting force is because in an actual bite, the force of up to
10 kN is distributed among the ~80 teeth in an alligator's mouth. The
radius of the adult tooth tip is much larger (~up to 3 mm) and the load
at which the tooth fracture would be significantly increased

In a realistic setting, the bite force would be distributed over 4 Canine teeth in a Tiger.

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The main difference between 2D model and 3D model is only in the muscle in-level arms actually. The other factors that i mentioned earlier (fibre length, PCSA, muscle volume, etc) appears irrelevant to which models you choose.

I never said they were relevant. I literally said the data you put in for those can be spot on, which is great, but you're still not getting a realistic picture of the in-lever arms if it's only two-dimensional. What Wroe's three-dimensional model really shows you is that, in actuality, there's a very marked decrease in bite force in a cat's jaw from total muscle force to the carnassial teeth, and, in turn, from the carnassial teeth to the canines (and unless I've missed something in your posts, you should see this regardless of the data you put in for muscle fiber length, physiological cross section, etc., etc.). This discrepancy in force between the carnassials and canines varies within each species in Hartstone-Rose et al.'s study, but none of them are nearly to the extent shown in Wroe's models.

Most bite force studies I have come across are either calculated at occlusion or at an 'optimal' gape angle (varied from study to study). I do not think it really matters, and biting at occlusion is not unrealistic as it can simulate a big cat clamping around the throat of a prey animal for instance.

Biting at occlusion seems to imply that gape angle is very low. That is, it's opened its mouth, but only just enough for the teeth to be near occlusion, only to bite down again. For example, when a cat is using its carnassial teeth to cut through skin and shear flesh while feeding. An actual killing bite, of course, requires a notably wider gape (and thus, reduced bite force).

Wroe (2008) does not provide muscle CSA or muscle volume details of his specimen. I have even looked through Wroe et al (2005) supplementary but still could find the data. However, Wroe (2008) does provide total muscle force data of 8880 N and we know they use specific tension of 30 N/cm^2.

Using the above formula I provided, ACSA can be calculated (in parallel fibre, no pennation model, PCSA = ACSA):
ACSA = 8880 / 30 = 296 cm^2

Hartstone-Rose et al. (2012) provided PCSA for Tiger in Table 2:
PCSA = 622.42 cm^2

This discrepancy is intriguing. However, a later study (again with Dr. Hartstone-Rose) points out something that may be of interest (Hartstone-Rose et al., 2015).

The analyses of both the linear and three-dimensional data yielded significant results for dividing the sample by species, sex and captivity status. Lions and tigers, though similar in body size and ecology are certainly morphologically distinct and strongly sexually dimorphic [8]; both distinctions were clearly seen in the variables included in our study. However, in the prior research literature, the morphological distinctiveness of captive animals was less certain; although many morphologists have routinely excluded captive specimens from their samples based on qualitative impressions of distinctiveness, few studies have quantified these differences, and those that have, have found only a few significant variables. For the taxa in our study, the previously examined variables that relate to captivity status are most notably foramen magnum constriction in lions (but not tigers; [3], [45]) and wider zygomatic arches and cranial thickness (again described most commonly for lions with less information about other felids [1], [2], [19]). Furthermore, the only study to have examined the effects of captivity on overall three-dimensional skull shape focused on a reptile [38] – the necessity to confirm these effects in mammals was still outstanding.

Whether these differences are due to mechanical properties of diet is a persistent question. The fact that we observe important variation in the shape of the temporalis origin (Fig. 7) seems to support the hypothesis that at least some of the differences between captive and wild animals are due to masticatory factors. So too could the extensively noted differences in zygomatic arch breadth; not only is this the origin on the masseter muscles – the second largest mandibular adductor group, but the temporalis muscles run deep to this anatomy. More greatly flared zygomatic arches might indicate that captive lions and tigers have larger temporalis muscles (i.e., necessitating more space between the zygomatic arches and the neurocranium), though the differences in the shape of the temporalis origin (Fig. 7) seem to contradict this. Likewise, there seems to be a mixed signal in the morphology of the masseter origins: the wider zygomatic arches and the more ventrally flared mandibular angles seem to indicate that the masseter muscles could be more massive in captive animals (i.e., as the difference in these two regions – the origin and insertion – increase then the length and probably the thickness also do), but with increased zygomatic widths, the masseters become more oblique to the sagittal plane and therefore more of the pull of the muscle is out of the plane of the mandibular adduction.

Are the masticatory muscles of captive lions and tigers bigger than those of wild animals? Is the fiber architecture different – e.g., might captive animals have larger, though less pinnate muscles [25]? Because of sampling difficulties (i.e., the prospect of getting a statistical sample of the soft tissue of wild specimens of these taxa) these are difficult questions to answer. However, an examination of another taxon widely represented in captivity and available from the wild (e.g., in North America, otters, bobcats, wolves) might give us an avenue to evaluate the effects of captivity on soft-tissues.

That captive felids might have more massive masticatory muscles than their wild counterparts (accompanied by what are apparently rather important differences in skull shape) may be important to note. Because with the exception of the bobcat and clouded leopard (both of which were wild specimens), the specimens examined in the 2012 study all lived in captivity (and from the same facility). The implication seems to be that it's possible the PCSAs in the jaw muscles of most of the cats in the 2012 study are significantly increased relative to wild specimens (and are therefore not representative of them). The only thing I don't know is if the lion used in Wroe's study was captive or wild.

Lo and behold, if you look at the wild bobcat specimen's PCSA, and compare it to that of their caracal in Table 2 (these two were similar in body mass; 15.5 vs 16.59 kg, respectively), it's significantly less (46.83 cm² vs 62.81 cm²). Even the serval and ocelot, both of which weighed a few kilograms less than the wild bobcat (13.9 and 11.59 kg, respectively), had substantially greater PCSAs than the wild bobcat specimen (61.02 and 67.11 cm², respectively).

In a realistic setting, the bite force would be distributed over 4 Canine teeth in a Tiger.

No, the authors seem to be saying the bite force estimate is concentrated at one particular tooth. They never imply that these forces would be concentrated over several different teeth.

"The working-side BF estimates were then calculated using the following equations:...where WBF_CA, WBF_PM, and WBF_CM, are the working side BFs at the canine, premolar and notch of the lower carnassial (M₁), respectively, c is the force constant of muscle cross-section (3 kg/cm²; Close, 1972)..."

At least from my experience, this is, in fact, what bite force estimates tend to entail: the amount of force at a particular tooth.

I haven't read this last paper of yours fully yet, but if it wasn't an adult like you say, why would they think mentioning a bite force of 10 kN is relevant in this context? I don't imagine an immature individual would bite that hard, and therefore not subject its teeth to a given amount of force.

EDIT: as for the size of the lion in Wroe's study, he claimed that the lion specimen used in his study was a particularly large specimen before providing a weight estimate for it. I don't know if this claim was based on his weight estimate (in which case you'd have a valid point) or if he actually had some information about this specimen during its life. Even if it was "only" 212 kg, scaling the tiger from Hartstone-Rose et al. (2012) up to that size would give us a bite force of ~7174 N. That's still a ~2.5-fold discrepancy with the results of Wroe (2008) when corrected for size.

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This 2017 study said this about the jaw of Psittacosaurus (Taylor et al., 2017).

While the bite force of Psittacosaurus lujiatunensis is greater than that of M. monachus, it should be noted that the difference in body size between psittacosaurs and parrots is great. Psittaciform birds have a bite force to body mass ratio much greater than many other birds, including raptors which have morphologically similar beaks to parrots (Carril et al., 2015). The maximum muscle force exerted by Myiopsitta monachus was calculated at 33.9 N, resulting in a maximum bite force of 16.7 N. This means that approximately 50% of the available muscle force can be transferred into bite force in Myiopsitta monachus. In comparison, of the maximum muscle force of 432.2 N produced by the m. Std muscle arrangement in Psittacosaurus lujiatunensis, less than 20% (74.4 N) is transferred to bite force. The jaw of psittaciform birds is a much more efficient lever than the psittacosaur jaw

However, a more recent study re-estimated the jaw strength and mechanical efficiency of an adult Psittacosaurus (they even used the same specimen), and they got much higher bite forces, and thus what seems to be higher mechanical efficiency than estimated previously (Landi et al., 2021). In Table 6, the ratio of bite force at the tip of the predentary to input force was 0.43, which I think means that 43% of muscle force was transferred to actual bite force at the beak tip. Thus, an adult Psittacosaurus compares much more favorably to parrots in jaw lever efficiency than previously made out to be (bite force at the tip of the lower beak was 82.85 N, btw). It should be worth noting that this study does not account for the pterygoideus muscle either.


Taylor et al. also say this.

Moreover, the beak shape of parrots is considerably more sharp and pointed than that of psittacosaurs, meaning that the force that could be applied at the beak is concentrated over a smaller area than the rounded, flat beak of psittacosaurs. The beak shape of parrots is in fact more similar to neoceratopsians than to psittacosaurs. It has been suggested that the difference in beak shape between psittacosaurs and basal neoceratopsians could reflect differences in diet, with the narrow, pointed beak of basal neoceratopsians being used to penetrate harder plant material such as stems and large seeds. On the other hand, the relatively wider beak of psittacosaurs was suggested to have been more suitable for plucking large amounts of foliage, fruits and possibly small seeds in a single bite (Tanoue et al., 2009). This pattern is contrary to that hypothesised by Sereno et al. (2010), in which psittacosaurs are using the beak to crush nuts or hard seeds.

But while they address beak morphology, they seem to ignore Sereno et al’s point about the jaw joint of Psittacosaurus that allowed the lower beak to be retracted inside the upper beak to crack nuts.

Upper and lower beaks in psittacosaurs have a semicircular contour of nearly equal size, judging from their supporting bones, the predentary and rostral (figure 4). Neither beak tapers to a recurved median tip as occurs in all other ceratopsians and in most birds including psittaciforms, where the form of the bill is reflected by the underlying bone (figure 7c). The psittacosaur upper and lower beak, which extends onto the premaxilla and dentary from the rostral and predentary, respectively (figure 8b), appears to have had a cropping function when aligned. When the lower beak was retracted and directed inside the upper beak, on the other hand, it appears to have had a shelling or nutcracking function (figure 4c,d).

www.ncbi.nlm.nih.gov/pmc/articles/PMC2842669/

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Mar 6, 2021 20:16:28 GMT 5 Infinity Blade said:

Information on albertosaurines. Proportionately, they bit just as hard as tyrannosaurines. In terms of symphysis strength, T. rex>albertosaurines>most other non-avian theropods.

The albertosaurines Albertosaurus sarcophagus and Gorgosaurus libratus are among the best represented tyrannosaurids, known from nearly complete growth series. These specimens provide an opportunity to study mandibular biomechanical properties and tooth morphology in order to infer changes in feeding behavior and bite force through ontogeny in tyrannosaurids. Mandibular force profiles reveal that the symphyseal region of albertosaurines is consistently stronger in bending than the middentary region, indicating that the anterior extremity of the jaws played an important role in prey capture and handling through ontogeny. The symphyseal region was better adapted to withstand torsional stresses than in most non-avian theropods, but not to the extent seen in Tyrannosaurus rex, suggesting that albertosaurine feeding behavior may have involved less bone crushing or perhaps relatively smaller prey than in T. rex. The constancy of these biomechanical properties at all known growth stages indicates that although albertosaurines maintained a similar feeding strategy through ontogeny, prey size/type had to change between juvenile and mature individuals. This ontogenetic dietary shift likely happened when individuals reached a mandibular length of ~58 cm, a size at which teeth shift from ziphodont to incrassate in shape and bite force begins to increase exponentially. The fact that large albertosaurines were capable of generating bite forces equivalent to similar-sized tyrannosaurines suggests that no significant differences in jaw closing musculature existed between the two clades and that the powerful bite of T. rex is the result of its large body size rather than of unique adaptations related to a specialized ecology.

cdnsciencepub.com/doi/abs/10.1139/cjes-2020-0177

Full open access paper.

tspace.library.utoronto.ca/handle/1807/106568

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This interpretation of diet raises another issue, that of the differing tooth morphologies observed in these predators. As described above, the form seen in Orcinus has robust conical teeth that are frequently broken. This tooth form also is seen in pliosaurs (Massare, 1987). The other form, seen in Squalodon, mosasaurs, the icthyosaurs Leptopterygius and Temnodontosaurus, and some sharks, is laterally compressed and triangular, with serrate cutting edges and typically worn only at the tip. The frequency of breakage in pliosaurs and Orcinus is interesting. The implication is that this tooth form is not a particularly good one for attacking large vertebrates. The triangular serrate tooth seems to withstand damage much better.

An explanation for this distribution of tooth morphologies may lie in the evolutionary histories of the various species involved. Mosasaurs presumably evolved from varanoid lizards that already possessed the triangular serrate tooth form. Squalodonts likewise evolved from some heterodont archaeocete, and retained their primitive dentition, which was well suited to the opportunistic predator lifestyle. Orcinus and pliosaurs have a rather different history. Pliosaurs probably evolved from piscivorous nothosaurs and pleisiosaurs, while Orcinus evolved from the piscivorous dolphins which begin appearing in the Miocene. The Orcinus/pliosaur tooth shape appears to be a suboptimal, if adequate, modification for attacking marine tetrapods of the inherited conical fish-eating tooth morphology.

digitalcommons.lsu.edu/cgi/viewcontent.cgi?article=7824&context=gradschool_disstheses


It's worth noting though, that some pliosaur teeth (namely those of Pliosaurus and Liopleurodon) are actually triangular in cross section with three sharp ridges; those of Liopleurodon and "Pliosaurus" andrewsi are actually equipped with transverse ribs on the cutting edges, effectively making them serrated (Massare, 1987; Sues, 2019). So these teeth aren't completely conical like a dolphin's tooth. Kronosaurus is a pliosaur with teeth that better fit this description (being conical and having no cutting edges).

Also some interesting notes on squalodont teeth: the only teeth that were not laterally compressed were the incisors, which were nearly circular in cross section, so the canines were laterally compressed as well. Even the incisors, though, were still slightly serrated.

Squalodont tooth crowns are quite distinctive when compared to those of other primitive odontocetes, and a complete crown is probably sufficient for identifying the family. There is some individual variation in the degree and type of ornamentation, but all the S. calvertensis specimens share certain features. The enamel on the post-canine teeth is heavily ornamented with fine ridges, which extend more or less toward the tip of the crown. The individual ridges up to 5 mm long. Toward the base of the crown, the ornamentation is more in the form of bumps and knobs. This texturing does not extend to the accessory denticles, and the apex of the crown is usually free. The ornamentation becomes finer on the anterior teeth, but it is still present even on the incisors. When not reworked, the crowns are serrate, and sometimes even the accessory denticles are serrate. The post-canine crowns are almost always triangular, with the height-to-length ratio decreasing posteriorly. For example, in USNM 25910, the lower left eighth, ninth, and eleventh buccal teeth have ratios of 1.2, 1.0, and 0.7, respectively. The teeth are often gently recurved. The incisors are nearly circular in cross section, and very large (length about 10% of the overall skull length). The crowns still have a slightly serrate cutting edge. As mentioned above, the incisors are procumbent, with the first pointing almost directly anteriorly, and the posterior teeth progressively directed more laterally and ventrally. This is also the case in at least the mandible of Kelloggia (Mchedlidze, 1976).

While almost all of the buccal alveolae are laterally compressed, they are all much less compressed than the equivalent alveolae in any specimen of S. calvertensis. In USNM 23537 [S. calvertensis] the alveoli for all the maxillary teeth are flattened laterally, including the canines. This is also true of the preserved alveoli in USNM 10484 and USNM 328343 (both S. calvertensis).

Brackets mine.

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Temporomandibular joint and Giant Panda’s (Ailuropoda melanoleuca) adaptation to bamboo diet

Here, we present new evidence that evolutionary adaptation of the Ailuripodinae lineage to bamboo diet has taken place by morphological adaptations in the masticatory system. The giant panda in the wild and in captivity removes without an exception the outer skin of all bamboo shoots, rich in abrasive and toxic compounds, by the highly adapted premolars P3 and P4. The temporomandibular joint (TMJ) allows sidewise movement of the jaw and the premolars can, in a cusp-to-cusp position, remove the poorly digestible outer skin of the bamboo before crushing the bamboo with molars. Based on the evidence presented here, we suggest that adaptation of TMJ to lateral movement for enabling cusp-to-cusp contact of premolars is the crucial evolutionary factor as which we consider the key to understand the Ailuropodinae lineage adaptive pathway to utilize the bamboo resource.

www.nature.com/articles/s41598-021-93808-2

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Unsurprisingly, it looks like extant primates that regularly eat hard food objects show the highest frequencies of tooth chipping.

Species considered hard-object-feeding specialists presented higher rates of chipping, with sakis, mandrills, sooty mangabeys and Raffles' banded langurs having high chipping rates (28.3%, 36.7%, 48.4%, and 34.7% of teeth, respectively). Species that seasonally eat harder foods had intermediate chipping frequencies (e.g., brown woolly monkeys: 18.5%), and those that less commonly consume hard food items had the lowest chipping frequencies (e.g., Kloss gibbon: 7.3%; chimpanzees: 4.4%).

onlinelibrary.wiley.com/doi/10.1002/ajpa.24232

Additionally, certain "functional" cusps are associated with high wear, but low chipping frequencies.

www.sciencedirect.com/science/article/abs/pii/S0047248420301846?via%3Dihub


A recent study on chipping rates in Paranthropus teeth provide further support that it, surprisingly, was not regularly eating hard food objects.

The paranthropines, including Paranthropus boisei and Paranthropus robustus, have often been considered hard-food specialists. The large post-canine teeth, thick enamel, and robust craniofacial features are often suggested to have evolved to cope with habitual mastication of hard foods. Yet, direct evidence for Paranthropus feeding behaviour often challenges these morphological interpretations. The main exception being antemortem tooth chipping which is still regularly used as evidence of habitual mastication of hard foods in this genus. In this study, data were compiled from the literature for six hominin species (including P. boisei and P. robustus) and 17 extant primate species, to analyse Paranthropus chipping patterns in a broad comparative framework. Severity of fractures, position on the dentition, and overall prevalence were compared among species. The results indicate that both Paranthropus species had a lower prevalence of tooth fractures compared to other fossil hominin species (P. boisei: 4%; P. robustus: 11%; Homo naledi: 37%; Australopithecus africanus: 17%; Homo neanderthalensis: 45%; Epipalaeolithic Homo sapiens: 29%); instead, their frequencies are similar to apes that masticate hard items in a non-regular frequency, including chimpanzees, gibbons, and gorillas (4%, 7% and 9% respectively). The prevalence is several times lower than in extant primates known to habitually consume hard items, such as sakis, mandrills, and sooty mangabeys (ranging from 28% to 48%). Comparative chipping analysis suggests that both Paranthropus species were unlikely habitual hard object eaters, at least compared to living durophage analogues.

www.biorxiv.org/content/biorxiv/early/2021/03/27/2021.02.12.431024.full.pdf

[Supercommunist]

Hopefully this hasn't been posted before. Barracuda's don't have powerful bites but do to their momentum and their sharp teeth can slice prey in half:

Computational modeling predicted a maximum staticbite force of 73.1 N at the jaw corners for the largestindividual in our study (Table 1). This is lower than thatof many smaller durophagous fishes, several reptiles,and some mammals of similar and even smaller bodysizes that have been measured or modeled (Herrelet al., 2001;Huber et al., 2005). We suggest that themechanical demands of barracuda teeth to slice throughfish flesh do not require substantially high bite forces, asseen in other mechanical methodologies and configura-tions (e.g.,Dunajski, 1980;Sigurgisladottir et al., 1999;Veland and Torrissen, 1999). Generally, barracuda teethhave a cutting edge or piercing tip that is less than1mm2. It is notable that, with regard to the sharpness ofthe canines (area of the tooth tip:0.54 mm2), adynamic bite force of 33 N at the large canine at theend of the lower jaw can theoretically produce apuncturing bite pressure of over 61 MPa. The abilityof the barracuda to section its prey results from acombination of the biomechanical architecture of thejaws, their force generating capacity (e.g.,Westneat,1994, 2003), and the sharpness and shape of the teeth(Frazzetta, 1988;Osborn, 1996;Korioth et al., 1997;Popowics and Fortelius, 1997;Evans and Sanson, 1998,2003;Shergold and Fleck, 2004;Freeman and Lemen,2006). Thus, with its razor sharp teeth, powerful jaws,and fast swimming speed, the barracuda is literallyable to bite its prey items in half during the initialattack; few other fishes possess this unique ram-bitingfeeding ability

www.researchgate.net/publication/5767030_Functional_morphology_of_bite_mechanics_in_the_great_barracuda_Sphyraena_barracuda