Functional Morphology of Animal Feeding Apparata

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On the relationship between maxillary molar root shape and jaw kinematics in Australopithecus africanus and Paranthropus robustus

Plio-Pleistocene hominins from South Africa remain poorly understood. Here, we focus on how Australopithecus africanus and Paranthropus robustus exploited and—in part—partitioned their environment. Specifically, we explore the extent to which first maxillary molar roots (M1) are oriented and thus, by proxy, estimate the direction of loads habitually exerted on the chewing surface. Landmark-based shape analysis of M1 root reconstructions of 26 South African hominins and three East African Paranthropus boisei suggest that A. africanus may have been able to dissipate the widest range of laterally directed loads. Paranthropus robustus and P. boisei, despite having overlapping morphologies, differ in aspects of root shape/size, dento-cranial morphologies, microwear textures and C4 food consumption. Hence, while Paranthropus monophyly cannot be excluded, equivalence of dietary niche can. The South African hominins occupied distinct ecological niches, whereby P. robustus appears uniquely adapted to dissipate antero-posteriorly directed loads.

www.ncbi.nlm.nih.gov/pmc/articles/PMC6124107/

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Cerdocyonina is a clade composed by the South-American canids in which the bush dog (Speothos venaticus) is one of the most elusive species. Known for its unique morphology within the group, this small, bear-like faced canid is the only member of the clade adapted to hypercarnivory, an almost exclusively meat-based diet currently present only in usually large, pack-hunting canids such as the grey wolf (Canis lupus). However, much of the biology of the bush dog is poorly understood, and inferences about its ecology, hunting strategies and diet are usually based on observation of captive individuals and anecdotal records, with reduced quantitative data to offer support. Here, we investigated the craniomandibular functional morphology of the bush dog through finite element analysis (FEA). FEA was employed to model the biting behaviour and to create extrinsic and intrinsic functional scenarios with different loads, corresponding to different bites used to subdue and process the prey. For comparison, the same modelling was applied to the skull of a grey wolf and a grey fox (Urocyon cinereoargenteus). Our analysis showed that the bush dog's responses to loading are more similar to the wolf's than to the fox's in most scenarios, suggesting a convergent craniomandibular functional morphology between these two hypercarnivorous species, despite their distinct phylogenetic positions and body sizes. Differences between the three taxa are noteworthy and suggested to be related to the size of the usual prey. The modelled bite force for the bush dog is relatively strong, about half of that estimated for the wolf and about 40% stronger than the fox's bite. The results strengthen with quantitative data the inferences of the bush dog as a pack-hunting predator with prey size similar to its own, such as large rodents and armadillos, being specialised in subduing and killing its prey using multiple bites. Its similarity to the wolf also confirms anecdotal accounts of predation on mammals that are much larger than itself, such as peccaries and tapirs. These data highlight the ecological specialisation of this small canid in a continent where large, pack-hunting canids are absent.

The craziest part about this study is that it found the bush dog to have a bite force half that of a grey wolf, a canid seven times it size.

Our analyses show a strong bite for the bush dog when compared to the other tested species (Table 3). In all tested scenarios, the bush dog exerted a bite force of about half the strength of that of the wolf, a canid about seven times heavier (see Section 4.2). This is likely directly related to the skull morphology of the bush dog, as its short rostrum and deep cranium is linked to a strong bite (Penrose et al., 2020; Slater et al., 2009). In other analyses using the dry-skull methods to calculate bite force in both bush dog and wolf, the results were not so extreme (Table 3). A more similar result was obtained by Penrose et al. (2020), who tested the bite force in canids using reduced physiological cross-sectional area (a methodology that considers the muscle mass and angle of pinnation of the fibres to estimate muscular force; Anapol et al., 2008) instead of the dry-skull method and, in near occlusion scenarios, obtained bite force estimates for the bush dog about half of those of the wolf.

The bush dog's cranium is less suited to dealing with lateral stresses in a head shake scenario. This is probably because the bush dog, with its short legs and interdigital membranes, allow it to hunt prey in water and tight spaces where the prey cannot struggle as much.

The short legs of the bush dog also allow it to hunt in narrow spaces, where the movements of its prey are also limited. It is known by the Matse people of north-eastern Peru that the bush dog actively hunts the long-nosed armadillo (Dasypus kappleri) by entering the armadillo's burrow, capturing it in the tunnels and dragging it to the entrance of the burrow, where it is finally consumed (Fleck & Voss, 2016). Some authors suggest that its interdigital membranes are also helpful while digging (Chavez et al., 2022), and its robust forelimbs are distinct to the slender bones of cursorial Carnivora, being more similar—although not as robust—to those of the Canadian river otter (Lontra canadensis) and European badger (Meles meles), mustelids of aquatic and burrowing habits respectively (Martín-Serra et al., 2014). These behaviour and anatomic adaptations could help the bush dogs since, presumably, prey movements become reduced in the water and in narrow space, and also may be related to the bush dog's cranium being less suited to deal with lateral movements, as seen in the head shaking scenarios (Figure 5). Once in the water or inside a burrow, the bush dog is much more apt to apply its powerful bite (see Section 4.2) in conditions where the prey would be slower and struggling less than if it were on land surface.

www.researchgate.net/profile/Juan-Ruiz-81/publication/366163105_Different_but_the_same_Inferring_the_hunting_behaviour_of_the_hypercarnivorous_bush_dog_Speothos_venaticus_through_finite_element_analysis/links/63973e5d095a6a777424ead0/Different-but-the-same-Inferring-the-hunting-behaviour-of-the-hypercarnivorous-bush-dog-Speothos-venaticus-through-finite-element-analysis.pdf

[creature386]

I'm currently busy with the feeding apparata of a hedgehog and a shrew (master thesis stuff and all; I'm way too slow with this), so just let me share some papers I've found that are interesting.

This one is on soricids in general:

Dietary adaptations have often been associated with heightened taxonomic diversity. Yet, one of the most species-rich mammalian families, the Soricidae, is often considered to be ecologically and morphologically relatively homogenous. Here, we use geometric morphometrics to capture skull and dentary morphology in a broad sample of shrew species and test the hypothesis that morphological variation among shrew species reflects adaptations to food hardness. Our analyses demonstrate that morphology is associated with dietary ecology. Species that consume hard food items are larger and have specific morphological adaptions including an anteroposteriorly expanded parietal, an anteroposteriorly short and dorsoventrally tall rostrum, a mediolaterally wide palate, buccolingually wide cheek teeth, a large coronoid process and a dorsoventrally short jaw joint. The masseter muscle does not appear to play an important role in the strong bite force of shrews and the dentary is a better indicator of ecology than the skull.Our phylogenetic flexible discriminant function analysis suggests that the evolutionary history of shrews has shaped their morphology, canalizing dietary adaptations and enabling functional equivalence whereby different morphologies achieve similar dietary performances. Our work makes possible future studies of niche partitioning among sympatric species as well as the investigation of the diet of extinct soricids.

academic.oup.com/biolinnean/article/133/1/28/6160485

I haven't found anything on hedgehogs though from what I can tell, their jaw adductor musculature is pretty generic by mammal standards.

If you're interested in the jaw adductor musculature on mammals as a whole, how and when it evolved, and what makes it special, this paper by Lautenschlager and friends is highly recommended:

The evolution of the mammalian jaw during the transition from non-mammalian synapsids to crown mammals is a key event in vertebrate history and characterised by the gradual reduction of its individual bones into a single element and the concomitant transformation of the jaw joint and its incorporation into the middle ear complex. This osteological transformation is accompanied by a rearrangement and modification of the jaw adductor musculature, which is thought to have allowed the evolution of a more-efficient masticatory system in comparison to the plesiomorphic synapsid condition. While osteological characters relating to this transition are well documented in the fossil record, the exact arrangement and modifications of the individual adductor muscles during the cynodont–mammaliaform transition have been debated for nearly a century.

We review the existing knowledge about the musculoskeletal evolution of the mammalian jaw adductor complex and evaluate previous hypotheses in the light of recently documented fossils that represent new specimens of existing species, which are of central importance to the mammalian origins debate. By employing computed tomography (CT) and digital reconstruction techniques to create three-dimensional models of the jaw adductor musculature in a number of representative non-mammalian cynodonts and mammaliaforms, we provide an updated perspective on mammalian jaw muscle evolution.

As an emerging consensus, current evidence suggests that the mammal-like division of the jaw adductor musculature (into deep and superficial components of the m. masseter, the m. temporalis and the m. pterygoideus) was completed in Eucynodontia. The arrangement of the jaw adductor musculature in a mammalian fashion, with the m. pterygoideus group inserting on the dentary was completed in basal Mammaliaformes as suggested by the muscle reconstruction of Morganucodon oehleri. Consequently, transformation of the jaw adductor musculature from the ancestral (‘reptilian’) to the mammalian condition must have preceded the emergence of Mammalia and the full formation of the mammalian jaw joint. This suggests that the modification of the jaw adductor system played a pivotal role in the functional morphology and biomechanical stability of the jaw joint.

onlinelibrary.wiley.com/doi/full/10.1111/brv.12314

(Also, that's some really beautiful figures in the Lautenschlager paper. I had no idea of the awesomeness of Avizo before I got into that stuff, lol).

[Supercommunist]

Robert Irwin measures a great white shark bite. Peak force was 14,000 newtons/

10:00

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^That's roughly similar to a maximum bite force estimate estimated by computer models. In a 3,324 kg individual, bite force was estimated at 18,216 N at a gape angle of 35^o.

Assuming isometry, scaling the 351 gape angle data for a 6.4 m, 3324 kg white shark yields maximum anterior and posterior bite forces of 9320 and 18 216 N, respectively (Table 2).

www.bio-nica.info/Biblioteca/Wroe2008GreatWhiteSharkBiteForce.pdf

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This study on Mesozoic mammal jaws found that most were insectivores, but some were carnivores or herbivores.

The Mesozoic mammals included in our sample have largely been considered faunivorous and the results of the phylo FDA (Fig. 4b) corroborate this hypothesis. The majority of them are classified as insectivorous, including most stem mammals, australophenidans, “symmetrodontans” and eutherians, among others. Among the eutriconodontans, Argentoconodon, Gobiconodon, Repenomamus, and Trioracodon, are classified as carnivores, Triconodon and Yanoconodon are classified as insectivores, but with moderate support (posterior probabilities: 48% and 52%, respectively), and Phascolotherium and Volaticotherium are more confidently classified as insectivores (posterior probabilities: 60% and 73%, respectively). Among the metatherians, Didelphodon and Eodelphis are classified as carnivores, while Alphadon and Deltatheridium are classified as insectivores with moderate support (posterior probabilities: 54% and 52%, respectively). The stem mammals, Haramiyavia, Sinoconodon, and Docofossor are all confidently classified as carnivores (posterior probabilities over 80%), and the crown mammals Crusafontia and Kennalestes are also classified as carnivores, but with moderate support (posterior probabilities: 54% and 52%, respectively). Two taxa in the analysis are classified as herbivores, because of their relatively tall ascending rami: Vincelestes (#29) and Haldanodon (#6). The dental morphology of Vincelestes points to a primarily faunivorous diet, but it has been previously noted that its jaw morphology is indicative of a forceful bite; Rougier suggested that this jaw morphology might have enabled Vincelestes to incorporate tough plant matter into its diet, but it might also be indicative of durophagy. The dental morphology and body size of Haldanodon point towards an insectivorous diet; in this analysis, the posterior probability of Haldanodon being a herbivore is not high (only 40.3%). The evidence thus far suggests Haldanodon had a faunivorous diet; its jaw morphology might be indicative of the incorporation of tougher food sources into its diet.

www.nature.com/articles/s42003-021-01757-3

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Functional tests of the competitive exclusion hypothesis for multituberculate extinction

Results from functional tests provide apparently conflicting evidence for the CE hypothesis. Masticatory stress and skull strength results refute, while bite force results support, our initial hypotheses (see Introduction).

The skull (both cranium and hemimandible) of Kryptobaatar was not under higher stress than the extant rodents, in fact only the hystricomorph (guinea pig) produced consistently lower average stresses. The multituberculate skull was therefore better able to withstand feeding-induced stresses than several extant rodents, refuting our first hypothesis. Similarly, the myomorph (mouse and rat) rostra showed significantly less resistance to bending and torsion than that of the multituberculate with only the sciuromorph (squirrel) having significantly higher resistance. Analysis of the hemimandibles revealed minimal differences in bending and torsion resistance between rodents and multituberculates. Together these results refute our third hypothesis. Support for the CE hypothesis is only found from comparison of bite force metrics, with higher ME and BFQ values among all rodents, as predicted by our second hypothesis. Despite this mixed support, if these patterns extend to Paleogene rodents and multituberculates more broadly, optimization for higher bite force at the cost of higher stress may have given rodents a selective advantage over multituberculates, providing tentative support for a model of competitive exclusion.

royalsocietypublishing.org/doi/10.1098/rsos.181536#:~:text=Multituberculate%20mammals%20thrived%20during%20the,multituberculate%20extinction%20through%20competitive%20exclusion.

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The biting performance of Homo sapiens and Homo heidelbergensis

Modern humans have smaller faces relative to Middle and Late Pleistocene members of the genus Homo. While facial reduction and differences in shape have been shown to increase biting efficiency in Homo sapiens relative to these hominins, facial size reduction has also been said to decrease our ability to resist masticatory loads. This study compares crania of Homo heidelbergensis and H. sapiens with respect to mechanical advantages of masticatory muscles, force production efficiency, strains experienced by the cranium and modes of deformation during simulated biting. Analyses utilize X-ray computed tomography (CT) scan-based 3D models of a recent modern human and two H. heidelbergensis. While having muscles of similar cross-sectional area to H. heidelbergensis, our results confirm that the modern human masticatory system is more efficient at converting muscle forces into bite forces. Thus, it can produce higher bite forces than Broken Hill for equal muscle input forces. This difference is the result of alterations in relative in and out-lever arm lengths associated with well-known differences in midfacial prognathism. Apparently at odds with this increased efficiency is the finding that the modern human cranium deforms more, resulting in greater strain magnitudes than Broken Hill when biting at the equivalent tooth. Hence, the facial reduction that characterizes modern humans may not have evolved as a result of selection for force production efficiency. These findings provide further evidence for a degree of uncoupling between form and function in the masticatory system of modern humans. This may reflect the impact of food preparation technologies. These data also support previous suggestions that differences in bite force production efficiency can be considered a spandrel, primarily driven by the midfacial reduction in H. sapiens that occurred for other reasons. Midfacial reduction plausibly resulted in a number of other significant changes in morphology, such as the development of a chin, which has itself been the subject of debate as to whether or not it represents a mechanical adaptation or a spandrel.

repositorio.uchile.cl/bitstream/handle/2250/151384/The-biting-performance-of-Homo-sapiens.pdf?sequence=1

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New paper on the skull of Irritator. Lots of things consistent with things we know about spinosaur anatomy (weak but fast bite, robust teeth), but the most surprising thing is that the posterior halves of the lower jaws expanded outward as it opened its mouth!

palaeo-electronica.org/content/2023/3821-the-osteology-of-irritator

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First, felid incisors are aligned in a straight row in such a way that adjacent teeth buttress one another against mediolateral forces. Canids, in contrast, have more parabolic incisor arches, perhaps reflecting their more omnivorous diet. This arch shape gives dog incisors some independence from one another and from the canines for selective feeding on plant parts or invertebrates. Canid incisors, especially the more medial ones, are also relatively larger and broader than those of felids, perhaps for increased strength, given their more vulnerable, archlike positioning (see Fig. 4.1). This configuration allows the incisors of canids to help the canines inflict shallow, slashing wounds in prey. It has also been suggested that larger incisors can reflect larger prey (Van Valkenburgh and Koepfli 1993). Smaller incisors in felids also make sense in this light, given that killing bites involve mostly the canines.

www.google.com/books/edition/Mammal_Teeth/BGGTYS2AgncC?hl=en&gbpv=1&dq=canids+shallow+slashing+bites&pg=PA41&printsec=frontcover

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We have now found what basically amounts to a dolphin trying to be a sawfish.

All extant toothed whales (Cetacea, Odontoceti) are aquatic mammals with homodont dentitions. Fossil evidence from the late Oligocene suggests a greater diversity of tooth forms among odontocetes, including heterodont species with a variety of tooth shapes and orientations. A new fossil dolphin from the late Oligocene of New Zealand, Nihohae matakoigen. et sp. nov., consisting of a near complete skull, earbones, dentition and some postcranial material, represents this diverse dentition. Several preserved teeth are horizon-tally procumbent, including all incisors and canines. These tusk-like teeth suggest adaptive advantages for horizontally procumbent teeth in basal dolphins. Phylogenetic analysis places Nihohae among the poorly constrained basal waipatiid group, many with similarly procumbent teeth. Features of N. matakoi such as its dorsoventrally flattened and long rostrum, long mandibular symphysis, unfused cervical vertebrae, lack of attritional or occlusal wear on the teeth and thin enamel cover suggest the rostrum and horizontally procumbent teeth were used to injure and stun prey though swift lateral head movements, a feeding mode that did not persist in extant odontocetes.

royalsocietypublishing.org/doi/epdf/10.1098/rspb.2023.0873

[theropod]

Mosasaur bite force based on durophagous lizards

This is a bit of fun more than it is hard science, mostly because I got the figures by measuring off of published figures, but it might be a tantalizing indication justifying looking into this further, and I’d be very interesting if anyone can approximately replicate my results

It’s pretty much common knowledge that tegu lizards are some of the most impressive animals for their size in terms of raw bite force, and they are pretty impressively sized compared to many other squamates, making them a potentially interesting analogue for estimating bite forces in durophagous mosasaurs. So I took a study that looked into this (Schaerlaeken et al. 2012) for Salvator merianae and Dracaena guianensis to try and figure out a way to estimate bite forces based on size parameters. Unfortunately Schaerlaeken et al. didn’t publish their dataset anywhere, nor any particularly useful summary statistics (using mean length and mean force to scale something up doesn’t really work well, because maths). So what I did was to try to get the data on the scaling of bite force and head width with SVL from their scatterplots in figures 2 and 3 (using webplotdigitizer: automeris.io/WebPlotDigitizer/).

Because I expect SVL to be less relevant across differently proportioned taxa, I then used the regressions of head width ~ svl for the respective taxa to estimate head width based on svl for each specimen in the svl-bite force dataset, and then ran a regression for the combined dataset of bite force ~ estimated head width and bite force ~ svl.

Here are the results:

All bite forces were measured in vivo and at the tip of the jaws.

On the whole, large, durophagous lizards like tegus are potentially some of the most suitable modern analogues for mosasaurs, specifically durophagous ones such as Globidens or Prognathodon. I would be suspicious about applying this to other forms, but I think for the awesomebro side of me (and probably other people too) Prognathodon is the most interesting taxon in this regard, as it is huge and has a massively robust skull, a good candidate for the strongest bite among mosasaurs.

So for estimating bite force, we have two different approaches:
1) Estimating bite force for a large tegu, then  scaling up to mosasaur size isometrically based on head width (conservative route)

2) Allometric scaling based on  head width (liberal route, likely too liberal, see below)

So how hard does a large tegu bite? Based on my pooled regression for both taxa, a tegu with a head width of 60 mm would be expected to have a bite force of 438 N (90% CI 407–479 N). A tegu with a svl of 400 mm would be expected to bite with about 380 N (90% CI 352–411 N).

1) Isometric estimates

In a 3-dimensionally preserved skull of Prognathodon overtoni, SDSM 3393, the length is approx. 86 cm and the width 35 cm. Large Prognathodon  such as the holotype of P. currii can have a skull approx 1.4 m long and, based on measuring the figure in Christiansen and Bonde (2002), at least 55 cm wide. This is conservative, as the skull seems to be crushed and is preserved in a sort of oblique dorsolateral aspect, but is approximately consistent with what we get from scaling up P. overtoni based on skull length. P. saturator (Dortangs et al. 2002) also seems to have a similarly wide skull, but is similarly crushed. So using this to scale up:

Tegu	60 mm head width	437.6 N
Prognathodon overtoni, SDSM 3393	350 mm head width	e 14.89 kN
Prognathodon currii, HUJ. OR 100	~550 mm head width	e 36.77 kN

2) Allometric estimates

Based on head width, we can estimate bite forces for Prognathodon using the allometric tegu formula (bottom right in the plot above):

Prognathodon overtoni, SDSM 3393	350 mm head width	e 48.77 kN
Prognathodon currii, HUJ. OR 100	~550 mm head width	e 163.24 kN

So estimates diverge widely here. If the higher end is reasonable, this would put large Prognathodon specimens (and even mid-sized ones) among (if not as) the strongest biters ever, with bite forces potentially over 16 tons. However it is quite unexpected to see such strong positive allometry of bite force, especially with regard to skull width; one would expect the two to be fairly closely linked functionally due to the obvious functional coupling between skull width and jaw muscle size. I wonder if a reason could be that large adult tegus get proportionately wider skulls, meaning mechanical advantage increases and causes bite force to increase even at equal muscle size, but I haven’t tested this. Either way extrapolating this allometry far beyond the data range might not be sustainable (for a given skull width, bite force cannot just keep increasing indefinitely). However within the sample the allometry is very well-supported (90% CI for the exponent is 2.56-2.79, so very noticeable allometry is pretty much a given).

If the isometry assumption comes closer, then these are still impressive bite forces, even for modestly-sized skulls when compared to other giant predators.
Large T. rex specimens (Stan and Sue) and large Pliosaurs such as Pliosaurus kevani have both been computationally estimated at a similar bite force to the lower figure for P. currii presented here, both have skulls around 20-30 cm wider than Prognathodon. Zygophyseter was estimated computationally at less than a third of the lower estimate for Prognathodon currii, and also has a considerably wider skull than it (over 70 cm).

Even the smaller specimen still has a minimum bite force estimate of similar magnitudes to the highest bite forces recorded by Erickson et al. (2012) for saltwater crocodiles, which are as of my knowledge the highest bite forces ever actually measured. Granted, they are from a saltie likely around 5 m and 500 kg, so in all likelihood a smaller animal than a Prognathodon with an 85 cm skull would be, but they are also posterior bite forces while the Tegu figures are anterior.
Also, even accepting that the estimates made using the allometric formula are likely too high, the sheer magnitude of the allometry in tegus and the enormous estimates you get from it highlight that the isometric estimates are quite conservative. We don’t know if and how much the bite force would continue to increase allometrically beyond the size range represented in the tegu sample, but we have every reason to suspect that it could do so at least up to a point (it’s quite unlikely that something would scale with such strong positive allometry up to a specific size, and then just suddenly stop. So it’s reasonable to expect the real bite force somewhere in between the two figures, likely closer to the lower one, but quite possible a bit higher than it. Another thing potentially making these estimates conservative is that the regression uses head width (including soft tissues), whereas the fossil data are represented by skull widths (which are naturally a slightly smaller measurement).

So overall, I think Prognathodon definitely needs to be kept in mind when talking about massive bite forces. It would be very interesting to see more work specifically about mosasaur bite mechanics, also looking into the differences between various mosasaurs (as their skull and tooth morphologies are quite disparate) and giving us an insight if this tegu analogue is valid.

Refs:

Christiansen, P. and Bonde, N. 2002. A new species of gigantic mosasaur from the Late Cretaceous of Israel. Journal of Vertebrate Paleontology 22 (3): 629–644.

Dortangs, R.W., Schulp, A.S., Mulder, E.W., Jagt, J.W., Peeters, H.H. and De Graaf, D.T. 2002. A large new mosasaur from the Upper Cretaceous of The Netherlands. Netherlands Journal of Geosciences 81 (1): 1–8.

Erickson, G.M., Gignac, P.M., Steppan, S.J., Lappin, A.K., Vliet, K.A., Brueggen, J.D., Inouye, B.D., Kledzik, D. and Webb, G.J. 2012. Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation. PloS one 7 (3): e31781.
Erickson, G.M., Gignac, P.M., Steppan, S.J., Lappin, A.K., Vliet, K.A., Brueggen, J.D., Inouye, B.D., Kledzik, D. and Webb, G.J. 2012. Insights into the ecology and evolutionary success of crocodilians revealed through bite-force and tooth-pressure experimentation. PloS one 7 (3): e31781.

Schaerlaeken, V., Holanova, V., Boistel, R., Aerts, P., Velensky, P., Rehak, I., Andrade, D.V. and Herrel, A. 2012. Built to Bite: Feeding Kinematics, Bite Forces, and Head Shape of a Specialized Durophagous Lizard, Dracaena guianensis (Teiidae). Journal of Experimental Zoology Part A: Ecological Genetics and Physiology 317 (6): 371–381.

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Jun 15, 2023 18:57:54 GMT 5 theropod said:

Mosasaur bite force based on durophagous lizards

This is a bit of fun more than it is hard science, mostly because I got the figures by measuring off of published figures, but it might be a tantalizing indication justifying looking into this further, and I’d be very interesting if anyone can approximately replicate my results

It’s pretty much common knowledge that tegu lizards are some of the most impressive animals for their size in terms of raw bite force, and they are pretty impressively sized compared to many other squamates, making them a potentially interesting analogue for estimating bite forces in durophagous mosasaurs. So I took a study that looked into this (Schaerlaeken et al. 2012) for Salvator merianae and Dracaena guianensis to try and figure out a way to estimate bite forces based on size parameters. Unfortunately Schaerlaeken et al. didn’t publish their dataset anywhere, nor any particularly useful summary statistics (using mean length and mean force to scale something up doesn’t really work well, because maths). So what I did was to try to get the data on the scaling of bite force and head width with SVL from their scatterplots in figures 2 and 3 (using webplotdigitizer: automeris.io/WebPlotDigitizer/).

Because I expect SVL to be less relevant across differently proportioned taxa, I then used the regressions of head width ~ svl for the respective taxa to estimate head width based on svl for each specimen in the svl-bite force dataset, and then ran a regression for the combined dataset of bite force ~ estimated head width and bite force ~ svl.

Here are the results:

I was interested in this because large, durophagous lizards like tegus are potentially some of the most suitable modern analogues for mosasaurs, specifically durophagous ones such as Globidens or Prognathodon. I would be suspicious about applying this to other forms, but I think for the awesomebro side of me (and probably other people too) Prognathodon is the most interesting taxon in this regard, as it is huge and has a massively robust skull, a good candidate for the strongest bite among mosasaurs.

So for estimating bite force, here are a two different approaches:
1) Estimating bite force for a large tegu, then  scaling up to mosasaur size isometrically based on head width

2) Allometric scaling based on  head width

So how hard does a large tegu bite? Based on my pooled regression for both taxa, a tegu with a head width of 60 mm would be expected to have a bite force of 438 N (90% CI 407–479 N). A tegu with a svl of 400 mm would be expected to bite with about 380 N (90% CI 352–411 N).

1) Isometric estimates

In a 3-dimensionally preserved skull of Prognathodon overtoni, SDSM 3393, the length is approx. 86 cm and the width 35 cm. Large Prognathodon  such as the holotype of P. currii can have a skull approx 1.4 m long and, based on measuring the figure in Christiansen and Bonde (2002), at least 55 cm wide. This is conservative, as the skull seems to be crushed and is preserved in a sort of oblique dorsolateral aspect, but is approximately consistent with what we get from scaling up P. overtoni based on skull length. P. saturator (Dortangs et al. 2002) also seems to have a similarly wide skull, but is similarly crushed. So using this to scale up:

Tegu	60 mm head width	437.6 N
Prognathodon overtoni, SDSM 3393	350 mm head width	e 14.89 kN
Prognathodon currii, HUJ. OR 100	~550 mm head width	e 36.77 kN

2) Allometric estimates

Based on head width, we can estimate bite forces for Prognathodon using the allometric tegu formula (bottom right in the plot above):

Prognathodon overtoni, SDSM 3393	350 mm head width	e 48.77 kN
Prognathodon currii, HUJ. OR 100	~550 mm head width	e 163.24 kN

So estimates diverge widely here. If the higher end is reasonable (though I think it is it is likely too liberal), this would put large Prognathodon specimens (and even mid-sized ones) among the strongest biters ever. If the isometry assumption comes closer, then these are still fairly impressive bite forces for skulls that are not excessively large compared to other giant predators (the 55 cm head width for example is considerably less than large T. rex specimens, that can reach 80-90 cm, and also less than mid-sized raptorial physeteroids like Zygophyseter, at over 70 cm, which was estimated, albeit using a very different methodology, at less than a third of this lower estimate for Prognathodon).

Refs:

Christiansen, P. and Bonde, N. 2002. A new species of gigantic mosasaur from the Late Cretaceous of Israel. Journal of Vertebrate Paleontology 22 (3): 629–644.

Dortangs, R.W., Schulp, A.S., Mulder, E.W., Jagt, J.W., Peeters, H.H. and De Graaf, D.T. 2002. A large new mosasaur from the Upper Cretaceous of The Netherlands. Netherlands Journal of Geosciences 81 (1): 1–8.

Schaerlaeken, V., Holanova, V., Boistel, R., Aerts, P., Velensky, P., Rehak, I., Andrade, D.V. and Herrel, A. 2012. Built to Bite: Feeding Kinematics, Bite Forces, and Head Shape of a Specialized Durophagous Lizard, Dracaena guianensis (Teiidae). Journal of Experimental Zoology Part A: Ecological Genetics and Physiology 317 (6): 371–381.

There is an Allopleuron shell fragment with a mosasaur bite mark attributed to either Prognathodon or Mosasaurus. I can't say exactly how much force was required to cause this kind of damage, but it had to have been considerable. I think it's possible all but the ~15 kN bite force figures here could've done the job.



oceansofkansas.com/tylo-prey.html

[elosha11]

Feb 5, 2023 0:15:35 GMT 5 Supercommunist said:

Robert Irwin measures a great white shark bite. Peak force was 14,000 newtons/

10:00

FYI, they stated the bite force was measured at 1400 newtons, not 14,000. Really big difference. Still, a fairly impressive bite for what looks to be a somewhat small female shark.

[theropod]

Jun 16, 2023 5:28:30 GMT 5 elosha11 said:

Feb 5, 2023 0:15:35 GMT 5 Supercommunist said:

Robert Irwin measures a great white shark bite. Peak force was 14,000 newtons/

10:00

FYI, they stated the bite force was measured at 1400 newtons, not 14,000. Really big difference. Still, a fairly impressive bite for what looks to be a somewhat small female shark.

Yes, but less than what Wroe et al. estimated for their 240 kg juvenile Great White (assuming an anterior bite, for a posterior bite it would be less than half). Without knowing the size of the shark, this doesn’t tell us a whole lot (I would not feel very confident about guesstimating it from the video seeing how there’s nothing in the shots that can serve as a scale. The people in the video probably have a better idea of its size, but don’t tell us any specifics ("similar to the crocodile", but how big is the crocodile? And by length, or by weight?). Maybe a decent estimate could be made from the average distance between the tooth marks on the measuring device by using the appropriate formulas, but there are no measurements given.

I also wonder what they mean by "about 2000 Newton of pressure"…which is a phrase that makes literally zero sense. It seems like now we have the inverse of the problem I always like to complain about (the serious failings of an education system producing tons of people making statements along the lines of "bite FORCE of x psi"), now it’s mistaking force for pressure instead of mistaking pressure for force.

Sometimes it can be really frustrating trying to extract scientifically useful data from non-scientific sources that can be deliberately nebulous about what exactly their data even if they give the impression of taking rigorous measurements.

Infinity Blade How big is that turtle? I don’t see a scale bar unfortunately. Anyway, I’m not sure, but even a 15 kn bite force could very well be sufficient to crush bone. That’s still similar to the largest molariform bite forces measured for Crocodylus porosus (i.e. the highest bite forces ever directly measured in anything, if I’m not mistaken), after all.

EDIT: Oh and an important bit of information I neglected to mention: The tegu bite force measurements were all taken at the tip of the jaws, so posterior bite forces would be expected to be considerably higher.