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Abstract

The notorious jaws of the white shark Carcharodon carcharias are widely feared, yet poorly understood. Neither its bite force, nor how such force might be delivered using relatively elastic cartilaginous jaws, have been quantified or described. We have digitally reconstructed the jaws of a white shark to estimate maximum bite force and examine relationships among their three-dimensional geometry, material properties and function. We predict that bite force in large white sharks may exceed c. 1.8 tonnes, the highest known for any living species, and suggest that forces may have been an order of magnitude greater still in the gigantic fossil species Carcharodon megalodon. However, jaw adductor-generated force in Carcharodon appears unremarkable when the predator's body mass is considered. Although the shark's cartilaginous jaws undergo considerably greater deformation than would jaws constructed of bone, effective bite force is not greatly diminished.

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... The Young's modulus of the chondrocranium of chondrichthyan fish (tesselated cartilage) varies significantly between taxa (Porter et al., 2013). In some species it may still be less than 50 MPa but in others it may exceed 700 MPa, or even in some regions, and under certain loading conditions, begin to approach the stiffness of bone (Porter et al., 2013;liu et al., 2014;wroe et al., 2008). ...
... In the past, representing the complex three-dimensional shape of the chondrocranium presented a significant challenge (wooD et al., 1991;loZanoFF, et al., 1993;HoF staDlerDeiques et al., 2005): the chondrocranium can be small and delicate, and it lies deep within the skull. However, particularly in the last few years, a wealth of detailed computer models have been successfully built for a range of vertebrate taxa including the hagfish (Eptatretus burger;oisi et al., 2015), lamprey (Lethenteron reissneri;oisi et al., 2015), various sharks (wroe et al., 2008;HowarD et al., 2013;mara et al., 2015;mCquiston, et al., 2017) (KauCKa et al., 2018;Tesařová et al., 2019), and various primates including humans (loZanoFF, et al., 1993;manuel et al., 2014;tse et al., 2015;leary et al., 2015;sHamouelian et al., 2015;HuanG et al., 2018;smitH et al., 2020). ...
... Sutures, if included in a model, are typically given a value of 20 MPa and due to size constraints may be slightly enlarged relative to actual size (KuPCZiK et al., 2007;Jones et al., 2017). Cartilage, when included in models, has been given different values that are generally related to the species and anatomical region being analysed (wroe et al., 2008;lee et al., 2010;leary et al., 2015;Jones et al., 2017). ...
Article
The chondrocranium is the cartilage component of the vertebrate braincase. Among jawed vertebrates it varies greatly in structure, mineralisation, and in the extent to which it is replaced by bone during development. In mammals, birds, and some bony fish, most of the chondrocranium is replaced by bone whereas in lizards, amphibians, and chondrichthyan fish it may remain a significant part of the braincase complex in adulthood. To what extent this variation relates to differences in skull biomechanics is poorly understood. However, there have been examinations of chondrocranium histology, in vivo strain, and impact on rostrum growth following partial removal of the chondrocranium. These studies have led to suggestions that the chondrocranium may provide structural support or serve to dampen external loads. Advances in computing-power have also facilitated an increase in the number of three-dimensional computer-based models. These models can be analysed (in silico) to test specific biomechanical hypotheses under specified loading conditions. However, representing the material properties of cartilage is still problematic because these properties differ according to the speed and direction of loading. The relationship between stress and strain is also non-linear. Nevertheless, analyses to date suggest that the chondrocranium does not provide a vertical support in lizards but it may serve to absorb some loads in humans. We anticipate that future models will include ever more detailed representations of the loading, anatomy, and material properties, in tandem with rigorous forms of model validation. However, comparison among a wider range of vertebrate subjects should also be pursued, in particular larvae, juveniles, and very small adult animals.
... The great white shark is an ideal analogue for Dunkleosteus, being a lamniform shark (the same order as Cetorhinus [47]) with a powerful bite force befitting of an apex predator [48]. The horn shark H. francisci was selected for its durophagous lifestyle [49], making it analogous for the proposed feeding strategy of Tafilalichthys. ...
... This, unfortunately, prevented the incorporation of internal features into the models; therefore, the jaws were treated as homogeneous structures. Doing so has previously yielded differing results to more accurate, heterogeneous models [48]. However, the surface scans should still prove valid for the purely shape-based comparison undertaken in this paper; although CT scanning would be essential for an assessment of the absolute performance of Titanichthys' jaw. ...
... Consequently, the great white shark lower jaw was expected to prove more resistant to stress than the inferognathal of Dunkleosteus-and this may have been seen to a greater extent if cartilaginous properties were applied to the shark. Treating a great white shark jaw as homogeneous bone has previously resulted in underestimated stress resistance [48], and a lower Young's modulus associated with calcified cartilage would result in higher jaw strain. On the other hand, prior research indicating that the bite force : body mass ratio of Dunkleosteus is roughly equivalent to that of the great white shark [29] suggests that similar stress resistances, when scaled to length, are to be expected. ...
Article
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Large nektonic suspension feeders have evolved multiple times. The apparent trend among apex predators for some evolving into feeding on small zooplankton is of interest for understanding the associated shifts in anatomy and behaviour, while the spatial and temporal distribution gives clues to an inherent relationship with ocean primary productivity and how past and future perturbations to these may impact on the different tiers of the food web. The evolution of large nektonic suspension feeders—‘gentle giants’—occurred four times among chondrichthyan fishes (e.g. whale sharks, basking sharks and manta rays), as well as in baleen whales (mysticetes), the Mesozoic pachycormid fishes and at least twice in radiodontan stem group arthropods (Anomalocaridids) during the Cambrian explosion. The Late Devonian placoderm Titanichthys has tentatively been considered to have been a megaplanktivore, primarily due to its gigantic size and narrow, edentulous jaws while no suspension-feeding apparatus have ever been reported. Here, the potential for microphagy and other feeding behaviours in Titanichthys is assessed via a comparative study of jaw mechanics in Titanichthys and other placoderms with presumably differing feeding habits (macrophagy and durophagy). Finite-element models of the lower jaws of Titanichthys termieri in comparison to Dunkleosteus terrelli and Tafilalichthys lavocati reveal considerably less resistance to von Mises stress in this taxon. Comparisons with a selection of large-bodied extant taxa of similar ecological diversity reveal similar disparities in jaw stress resistance. Our results, therefore, conform to the hypothesis that Titanichthys was a suspension feeder with jaws ill-suited for biting and crushing but well suited for gaping ram feeding.
... We chose such gape angles as they were selected for carrying out the FEA analyses on B. isis (ca. 20°, measured from Snively et al. 2015: Figure 1a) and Carcharodon carcharias (35°; Wroe et al. 2008), thus allowing for robust comparisons of bite force values in these marine predator species. As origin of the temporalis muscle, we chose the entire surface of the temporal fossa (Figure 1), following the reconstruction proposed by Lambert et al. (2014) for Acrophyseter robustus and the muscular anatomy of extant odontocetes (Von Schulte and De Forest Smith 1918; Seagars 1982). ...
... In order to compare the bite force of Z. varolai with that exerted by an extant marine apex predator in a comparative palaeoecological framework, we estimated the body mass of a hypothetical great white shark (Carcharodon carcharias) that could generate the same bite forces estimated for Zygophyseter at 35° gape angle by following the equation proposed by Wroe et al. (2008). Furthermore, we applied the equation provided by Kohler et al. (1996) to calculate the total length of such a hypothetical great white shark. ...
... Furthermore, we applied the equation provided by Kohler et al. (1996) to calculate the total length of such a hypothetical great white shark. We did not perform this calculation for the bite force at 20° gape angle because Wroe et al. (2008) proposed their bite force estimation at a gape angle of 35°. Consequently, doing the same calculation with the Z. varolai bite force at 20° would produce misleading data. ...
Article
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Differing from the extant physeteroids, macroraptorial sperm whales are currently regarded as apex predators of the Miocene seas based on several morphofunctional observations. Here, we estimate the bite force of Zygophyseter varolai, a macroraptorial physeteroid from lower upper Miocene strata of the Pietra leccese formation (Apulia, Italy) using the finite element analysis (FEA). To explore multiple bite scenarios, we set four different load cases on a 3D model of the cranium obtained via digital photogram-metry, considering the temporalis and masseter muscles as jaw adductors. Our FEA simulations indicate that Z. varolai exerted an anterior bite force of more than 4000 N and a posterior bite force of more than 10000 N. These values are similar to those estimated for other marine predators known for their powerful bite. This suggests that Z. varolai might have fed upon medium-sized marine vertebrates like other odontocetes. Considering the significant difference observed between the anterior and posterior bite forces, Z. varolai likely fed via 'grip-and-shear' feeding, snapping the food items with an anterior bite and then cutting them with a powerful posterior bite. Other macroraptorial sperm whales such as the roughly coeval Acrophyseter from Peru likely employed the same feeding technique. ARTICLE HISTORY
... Cartilaginous fishes offer an interesting model to investigate bite force owing to the simplicity of their feeding apparatus, a wide range of dietary guilds, and the large range of sizes achieved by this group Motta 2004;Motta and Huber 2012). The study of bite force has been performed through a variety of methods ranging from voluntary in situ measurements and in vivo measurements during tetanic muscle stimulation to theoretical models based on jaw lever mechanics and computational simulations based on finite element analysis (Habegger et al. 2012;Huber and Motta 2004;Huber et al. 2005Huber et al. , 2006Huber et al. , 2008Kolmann et al. 2015a;Mara et al. 2012;Wroe et al. 2008). ...
... Bite forces vary widely among cartilaginous fishes (from 12 N in velvet belly lantern sharks Etmopterus spinax to 6000 N in bull sharks Carcharhinus leucas). Although in some cases extremely high bite forces are more related to large body size than functional necessity (Habegger et al. 2012;Huber et al. 2009;Wroe et al. 2008), other cases demonstrate linkages between biting performance and dietary specialization, such as in durophagous species Kolmann and Huber 2009;Kolmann et al. 2015a). For example, horn sharks Heterodontus francisci, spotted ratfish Hydrolagus colliei, and cownose rays Rhinoptera bonasus produce high mass-specific bite forces in association with reinforced dentition, hypertrophied jaw adductor muscles, and high leverage jaws (i.e., high mechanical advantage) to consume hard prey such as sea urchins, gastropods, and bivalves Kolmann and Huber 2009;Kolmann et al. 2015a;Summers et al. 2004). ...
... GPa, with a median value (0.050 GPa) that is just 0.3% of the stiffness of human Haversian bone (~20 GPa) (Fig. 8.11) (Currey 1998;Ferrara et al. 2013;Jagnandan and Huber 2010;Porter et al. Unpublished;Wroe et al. 2008). Similarly, the ultimate strength (i.e., stress at which complete structural failure occurs) of elasmobranch unmineralized cartilage (range: 0.008-0.042 ...
Chapter
Fishes, and elasmobranchs in particular, are often described as “opportunistic” predators meaning that they will take advantage of feeding opportunities as they arise. The implication of this term is that elasmobranchs are not selective about what they eat, which is a gross oversimplification of the complex interactions that shape diet, many of which are driven by interactions of an organism’s physiology, ecology, and behavior.
... A few studies have investigated the mechanism and force of shark bites over the last 20 years [33][34][35][36]. Throughout these studies, bite force has been measured in various ways, either theoretically through anatomical dissection and subsequent construction of 3D models [37,38] or through measurements taken from transducers gained through voluntary or forced bites, e.g. through stimulation of muscles with electric current [33,39]. Two studies have investigated the bite force of white sharks Carcharodon carcharias using 3D models constructed from a CT scan of a 2.5 m white shark [37,38]. ...
... Throughout these studies, bite force has been measured in various ways, either theoretically through anatomical dissection and subsequent construction of 3D models [37,38] or through measurements taken from transducers gained through voluntary or forced bites, e.g. through stimulation of muscles with electric current [33,39]. Two studies have investigated the bite force of white sharks Carcharodon carcharias using 3D models constructed from a CT scan of a 2.5 m white shark [37,38]. However, studies have shown that theoretical bite force maximums are often higher than bite force recorded from live animals [34,39] and the bite force of white sharks has never been recorded in situ and published in peer-reviewed literature. ...
... where B true is the true bite force value in N, B field is the bite force value recorded from the field, m is the slope of the line calculated from the calibrations (force recorded by pressure exerted) and c is the intercept. These field-based observations were then compared to theoretical maxima calculated from previous studies (Ferrara et al. 2011;Wroe et al. 2008; S1 Table). Field testing of wetsuit fabric. ...
Article
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Increases in the number of shark bites, along with increased media attention on shark-human interactions has led to growing interest in preventing injuries from shark bites through the use of personal mitigation measures. The leading cause of fatality from shark bite victims is blood loss; thus reducing haemorrhaging may provide additional time for a shark bite victim to be attended to by emergency services. Despite previous shark-proof suits being bulky and cumbersome, new technological advances in fabric has allowed the development of lightweight alternatives that can be incorporated onto traditional wetsuits. The ability for these fabrics to withstand shark bites has not been scientifically tested. In this report, we compared two types of recently developed protective fabrics that incorporated ultra-high molecular weight polyethylene (UHMWPE) fibre onto neoprene (SharkStop and ActionTX) and compared them to standard neoprene alternatives. We tested nine different fabric variants using three different tests, laboratory-based puncture and laceration tests, along with field-based trials involving white sharks Carcharodon carcharias. Field-based trials consisted of measuring C. carcharias bite force and quantifying damages to the new fabrics following a bite from 3–4 m total length C. carcharias. We found that SharkStop and ActionTX fabric variants were more resistant to puncture, laceration, and bites from C. carcharias. More force was required to puncture the new fabrics compared to control fabrics (laboratory-based tests), and cuts made to the new fabrics were smaller and shallower than those on standard neoprene for both types of test, i.e. laboratory and field tests. Our results showed that UHMWPE fibre increased the resistance of neoprene to shark bites. Although the use of UHMWPE fibre (e.g. SharkStop and ActionTX) may therefore reduce blood loss resulting from a shark bite, research is needed to assess if the reduction in damages to the fabrics extends to human tissues and decreased injuries.
... For example, the diet of juvenile sandbar sharks Carcharhinus plumbeus Nardo 1827 is mainly crustaceans and small teleosts, whereas the adult's diet is dominated by cephalopods, teleosts and other elasmobranchs (Grubbs, 2010;McElroy et al., 2006). Similarly, the white shark Carcharodon carcharias Linnaeus 1758 exhibits a paired ontogenetic shift between diet and dentition, transitioning from a primarily piscivorous diet as juveniles to a diet that includes marine mammals as adults (Grainger et al., 2020), with the latter only possible after a change in dentition (French et al., 2017;Grubbs, 2010;Wroe et al., 2008). Juvenile C. carcharias have cuspid teeth which allow them to pierce and hold flesh, while the broader and more serrated teeth of adults enable the gouging of chunks of flesh (Ferrara et al., 2011;French et al., 2017;Wilga & Ferry, 2015). ...
... Juvenile C. carcharias have cuspid teeth which allow them to pierce and hold flesh, while the broader and more serrated teeth of adults enable the gouging of chunks of flesh (Ferrara et al., 2011;French et al., 2017;Wilga & Ferry, 2015). Teeth are not the only ontogenetic change in the feeding apparatus of C. carcharias, as there is also structural reinforcement of the jaw that results from additional mineralization (Ferrara et al., 2011;French et al., 2017;Wroe et al., 2008). ...
Article
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Teeth are an integral component of feeding ecology with a clear link between tooth morphology and diet, as without suitable dentition prey cannot be captured nor broken down for consumption. Bull sharks Carcharhinus leucas undergo an ontogenetic niche shift from freshwater to marine habitats, which raises the question: does tooth morphology change with ontogeny? Tooth shape, surface area and thickness were measured using both morphometrics and an Elliptic Fourier Analysis, to determine if morphology varied with position in the jaw and if there was an ontogenetic change concordant with this niche shift. Significant ontogenetic differences in tooth morphology as a function of position in the jaw and shark total length were found, with upper and lower jaws of bull sharks presenting two different tooth morphologies. Tooth shape and thickness fell into two groupings, anterior and posterior, in both the upper and lower jaws. Tooth surface area, however, indicated three groupings, mesial, intermediate and distal, in both the upper and lower jaws. While tooth morphology changed significantly with size, showing an inflexion at sharks of 135 cm total length, each morphological aspect retained the same tooth groupings throughout. These ontogenetic differences in tooth morphologies reflect tooth strength, prey handling and heterodonty. This article is protected by copyright. All rights reserved.
... For example, a simplified analytical model of the tessellated cartilage cross-section predicted that during compression, stresses will tend to be concentrated in the tessellated layer rather than the unmineralized cartilage ( Liu et al., 2010 ). This hypothesized 'stress-sink' behavior for tesserae was also supported by larger scale computational structural analyses performed on models derived from CT scans of shark jaws and simulating biological loading conditions ( Ferrara et al., 2011 ;Wroe et al., 2008 ). One of these models also showed that stresses would tend to be lower in jaws composed of tessellated cartilage as compared to jaws modeled in bone, although tissue strains were predicted to be higher ( Wroe et al., 2008 ). ...
... This hypothesized 'stress-sink' behavior for tesserae was also supported by larger scale computational structural analyses performed on models derived from CT scans of shark jaws and simulating biological loading conditions ( Ferrara et al., 2011 ;Wroe et al., 2008 ). One of these models also showed that stresses would tend to be lower in jaws composed of tessellated cartilage as compared to jaws modeled in bone, although tissue strains were predicted to be higher ( Wroe et al., 2008 ). Lastly, in the only study to examine the mechanical effects of tesserae properties on the mechanics of the tessellated cartilage composite, parametric, 2D analytical models of tesserae demonstrated that variations in tesserae geometry and material properties should translate into differences in effective modulus of the composite at larger scales, suggesting that emergent skeletal properties can be tuned through local structural/material variations at the tesseral level ( Jayasankar et al., 2017 ). ...
Article
Sharks and rays have distinctive skeletons among vertebrate animals, consisting primarily of unmineralized cartilage wrapped in a surface tessellation of minute polygonal tiles called tesserae, linked by unmineralized collagenous fibers. The discrete combination of hard and soft tissues is hypothesized to enhance the mechanical performance of tessellated cartilage (which performs many of the same functional roles as bone) by providing either rigidity or flexibility, depending on the nature of the applied load. These mechanisms and the effect of tesserae ultrastructure on cartilage mechanics, however, have never been demonstrated in the actual tissue, nor in bio-accurate models. Here, we develop bio-inspired three-dimensional tesserae computer models, incorporating material properties and ultrastructural features from natural tessellated cartilage. The geometries of ultrastructural features were varied parametrically, and the effective modulus of whole tesserae was evaluated using finite element analysis to determine the roles of ultrastructural features in mechanics. Whereas altering some structural features had no effect on the macroscopic in-plane modulus of tesserae, a three-fold increase in the contact surface area between two adjacent tesserae increased the effective modulus of tesserae by 6%. Modeled stress distributions suggest that tesseral ‘spokes’ (distinct hypermineralized features in tesserae) bear maximum stresses in the skeleton and serve to funnel stresses to particular populations of cells in tesserae, while spokes’ lamellated structure likely helps dissipate crack energy, making tesserae more damage-tolerant. Simulations of multi-tesseral arrays showed that maximum stresses in tension and compression are borne by different tissues, supporting hypotheses of multi-functional properties of tessellated cartilage. Further, tesseral array models showed that minor alterations to tesserae/joint shape and/or material properties can be used to tune the mechanical behavior of the whole tiled composite. Our models provide the first functional understanding of the distinct morphologies of spokes and of ‘stellate’ tesserae (a tesseral shape observed first over 150 years ago), while also being useful drivers for hypotheses of growth, mechanics, load management, and the prevention and ‘directing’ of cracks in tessellated cartilage, as well as other biological composites. Additionally, these results establish guidelines and design principles for bio-inspired, tunable tiled materials.
... While there have been numerous studies on tooth structural composition (Enax et al. 2012;Deang et al. 2018), shape (Wautier et al. 2001;Streelman et al. 2003;Jernvall and Thesleff 2012), bite force (Huber et al. 2005;Grubich et al. 2008;Wroe et al. 2008;Mara et al. 2010), bite speed (Porter and Motta 2004;Grubich et al. 2008;Habegger et al. 2011), and sharpness (Freeman and Lemen 2007;Song et al. 2011) there are few published works on tooth size and placement (Trapani 2001;Plikus et al. 2005;Dean et al. 2008;Mihalitsis and Bellwood 2019), and even fewer on tooth occlusion in extant fishes (Dickson 1979;Yamaoka 1983;Bemis 1984;Powlik 1995). Fish teeth may be homodont or heterodont, with some piscivores having a gradient of increasing tooth size anteriorly as in C. limbatus, a tropical shallow water shark (Castro 1996), in the middle of the jaw as in Scomberomorus maculatus, a pelagic fish in tropical and subtropical waters (Ferguson et al. 2015), or with fang-like teeth positioned at various locations on the jaws as in Sphyraena barracuda, a solidary fish in shallow tropical and subtropics waters (Habegger et al. 2011), and Trichiurus lepturus, a benthopelagic eel-like fish found in tropical and temperature waters (Bemis et al. 2019). ...
... With regards to feeding in fishes there are many studies concerning tooth shape (Wautier et al. 2001;Streelman et al. 2003;Jernvall and Thesleff 2012), tooth sharpness (Freeman and Lemen 2007;Song et al. 2011; Anderson and Rayeld 2012; van Casteren and Crofts 2019), bite force and pressure (Huber et al. 2005;Grubich et al. 2008;Wroe et al. 2008;Mara et al. 2010;Ferguson et al. 2015), and prey capture speed (Porter and Motta 2004; Grubich et al. 2008;Habegger et al. 2011). However, tooth size, placement, and particularly tooth occlusion has not been vastly studied (Trapani 2001;Plikus et al. 2005;Dean et al. 2008;Mihalitsis and Bellwood 2019), especially in extant bony fishes (Dickson 1979;Yamaoka 1983;Bemis 1984;Powlik 1995). ...
Article
Full-text available
Fitness is in part determined by the success of prey capture, often achieved in marine piscivores using teeth to capture and process prey. In ram feeding piscivores, a pattern of monognathic heterodonty has been observed where tooth size either increases posteriorly (Scomberomorus maculatus), or anteriorly (Carcharhinus limbatus), with exceptions such as Trichiurus lepturus and Sphyraena barracuda which have large anterior fangs. Tooth size and placement, as related to prey capture, was examined in Atlantic Spanish Mackerel (S. maculatus), Great Barracuda (S. barracuda), Atlantic Cutlassfish (T. lepturus), and the Blacktip shark (C. limbatus) by quantifying tooth occlusion along the jaw. Percent gape at occlusion in S. maculatus decreased anteriorly in a linear fashion, indicating occlusion from posterior to anterior. Therefore, prey initially contact the posterior teeth with high puncture pressure during high velocity strikes, capitalizing the region of greatest bite force. For S. barracuda and T. lepturus, posterior teeth and premaxillary fangs occlude at similar percent gapes (within 10%). The premaxillary fangs are likely used for initial capture due to the high angular velocity of the anterior section of the jaw and then for cutting, due to their laterally compressed shape. In C. limbatus all teeth occluded within a narrow range of 1.4–8.8% gape, indicating that all teeth meet at almost complete jaw closure. Simultaneous puncture of teeth prevents prey escape while maximizing the cutting area during head shaking. Thus, various tooth size and dentition patterns may yield similar success in prey capture, serving the same function.
... In this way, the tessellation can manage bending loads and increase resistance to damage by distributing the highest stresses to the tissues and loading regimes best able to bear them. Stresses may also be mitigated by the properties of the unmineralized cartilage itself, which Wroe et al. (2008) showed would tend to result in considerably lower stresses and higher strains than simulated shark jaws made of bone and subjected to the same bite forces (Figure 8) Seidel et al., 2016Seidel et al., , 2017b, although it is surely loaded a large number of times over an animal's lifetime during cyclical swimming and feeding behaviours (e.g., Dean & Motta, 2004;Laurence-Chasen et al., 2019;Sasko et al., 2006). ...
... Nanoindentation experiments typically involve pushing a very small, hard tip (e.g., with a tip radius of hundreds of nanometres) into a material to examine the hardness and elastic modulus at very small scales. Nonetheless, as the indenter used by Ferrara et al. was comparatively very large (100 μm) andapproached the dimensions of some tesserae(Applegate, 1967;Dean et al., 2009;Seidel et al., 2016), it is believed that their data are more representative of the properties of the composite material (e.g., tesserae and their surrounding soft tissues), given that they report values considerably softer than either the tesserae themselves(Liu et al., 2014;Seidel et al., 2019a;Wroe et al., 2008) or whole skeletal elements(Macesic & Summers, 2012). In fact, recent work has shown that some finescale structural features in tesserae (e.g., the high-mineral-density laminae in spokes) exhibit stiffness and hardness valuesF I G U R E 4 Local variation in tesserae form and suggested relationship to function. ...
Article
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When describing the architecture and ultrastructure of animal skeletons, introductory biology, anatomy and histology textbooks typically focus on the few bone and cartilage types prevalent in humans. In reality, cartilage and bone are far more diverse in the animal kingdom, particularly within fishes (Chondrichthyes and Actinopterygii), where cartilage and bone types exist that are characterized by features that are anomalous or even pathological in human skeletons. Here, we discuss the curious and complex architectures of shark and ray tessellated cartilage, highlighting similarities and differences with their mammalian skeletal tissue counterparts. By synthesizing older anatomical literature with recent high‐resolution structural and materials characterization work, we frame emerging pictures of form‐function relationships in this tissue and of the evolution and true diversity of cartilage and bone. This article is protected by copyright. All rights reserved.
... The shark is further referred to as Carcharodon megalodon, being aware of the taxonomical uncertainty. C. megalodon was one of the most powerful and largest predators ever known in Earth's vertebrate history (Wroe et al., 2008) and may have approached a maximum length of 16 to 20 m (Capetta, 2012;Wroe et al., 2008;Klimley and Ainley, 1996). The cosmopolitan shark may have looked similar to an enlarged great white shark (Carcharodon carcharias) and had a preference for warm waters (Klimley and Ainley, 1996). ...
... The shark is further referred to as Carcharodon megalodon, being aware of the taxonomical uncertainty. C. megalodon was one of the most powerful and largest predators ever known in Earth's vertebrate history (Wroe et al., 2008) and may have approached a maximum length of 16 to 20 m (Capetta, 2012;Wroe et al., 2008;Klimley and Ainley, 1996). The cosmopolitan shark may have looked similar to an enlarged great white shark (Carcharodon carcharias) and had a preference for warm waters (Klimley and Ainley, 1996). ...
Article
Clumped isotope data from carbonated apatite from in vivo and in vitro samples are presented to refine the relationship between mineral growth temperature and carbonate clumped isotopic composition (Δ 47 ). Δ 47 , δ ¹⁸ O and δ ¹³ C data were obtained from phosphoric acid digestion (T = 110 °C) of chemically untreated teeth from an African elephant, Greenland sharks, sand tiger sharks and synthetic apatites. These data cover a temperature range between 1 °C and 80 °C and enlarge the calibration dataset presented in Wacker et al. (2016) by a factor of five. Taxon-specific analyses of tooth enamel(oid) and dentine reveal that both tissues show identical Δ 47 values even though the content of organic matter differs by an order of magnitude. The following Δ 47 temperature calibration for (bio)apatite is derived (R ² = 0.9924, p-value < 0.0001, n = 122; 8 samples): Δ 47CDES110 =0.0325(±0.0012)×10 ⁶ /T ² +0.2137(±0.0124)(withTinKandΔ 47 in‰) This calibration becomes indistinguishable from a reprocessed empirical calibration of calcite made in the same laboratory if a difference of the acid fractionation factors (AFF) of 0.110‰ between 25 °C and 110 °C is considered. The measured AFF for bioapatite matches the one that is extrapolated from experimental data on calcite and aragonite. The oxygen isotope fractionation between structural carbonate in the synthesized carbonated hydroxylapatites (CHAP) and water between 7 °C and 80 °C closely follows the temperature dependence for the calcite-water system. It is described by the following (CHAP-water) equation (R ² = 0.997, p-value < 0.04, n = 17; 3 samples): 1000ln(α CHAP-water )=17.23±0.59×10 ³ ×T ⁻¹ -27.28(±1.73)(withTinK) Both calibrations are applied to shark teeth from a modern Greenland shark and a fossil megatooth shark (Carcharodon megalodon) specimen to reconstruct the apparent Δ 47 -based habitat temperature of C. megalodon (19 ± 4 °C) and the oxygen isotopic compositions of seawater.
... Considering absolute bite force as a measure of predator's maximal performance, blue marlin and white marlin stand out among billfishes. Posterior bite force was 1359 N in the 2.6 m TL blue marlin; this magnitude is similar to other top predators such as a 2.5 m TL white shark Carcharodon carcharias (Wroe et al., 2008). When comparing anterior bite force among species, rankings can vary substantially with regards to relative or absolute values as seen in other studies where small often durophagous species are compared Grubich et al., 2012). ...
... In swordfish, the teeth are reduced to almost absent, making the most posterior position difficult to determine. However, this variability does not prevent further comparisons in overall biting performance, given that most comparative analyses in fishes, both theoretically and experimentally, are more likely to use ABF over PBF due to its accessibility Huber et al., 2009, Wroe, McHenry & Thomason, 2005Wroe et al., 2008;Mara, Motta & Huber, 2010;Grubich et al., 2012). ...
Article
Bite force is one of the most utilized performance measures due to its association with feeding and consequently fitness. Due to their large size and the concomitant increase in the adductor muscles it is expected that apex predators may rely on high biting performance allowing for increased dietary breadth. Billfish are apex marine predators characterized by the extreme elongation of the upper jaw bones forming a rostrum. This structure has been shown to facilitate prey capture and processing, but little is known as to whether this elongated structure has had an effect on biting performance in this group of enigmatic fishes. The goal of this study was to investigate bite force among five billfish species differing in size and rostrum morphology, and to determine the relationship between bite force and cranial anatomy. Because prey processing is partially decoupled from the oral jaws in these fishes, we hypothesized that bite force will be relatively low in billfishes compared to other fish, and that mass specific bite force will be inversely proportional to rostrum length. Anterior and posterior values of bite force ranged from 29 to 330 N and 99 to 1361 N, respectively among billfish species. Although absolute bite forces reached high values, mass specific bite force was among the lowest recorded for cartilaginous and bony fishes. Contrary to our hypothesis, rostrum length was not a predictor of bite force. The evolution of this novel structure, however, has been demonstrated to have a role in feeding, and the relatively low bite force in billfishes may indicate a lack of dependence on this performance metric for prey capture and processing.
... Modeling has become a powerful tool in understanding the physical forces in biological systems. A small sample of the organisms modeled shows a wide variety of topics, including the human knee [17], insect locomotion [18,19], unicellular mechanics [20], plant growth [21], neurulation [22], gastrulation [23], heart development [24], and many evolutionary studies focus on the skull and feeding apparatus [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42]. A fundamental problem with creating physical models of developing elements is that the irregularly curved and complex threedimensional structures found in living organisms do not easily translate to mathematical computation. ...
... This involves a wide variety of subjects such as plant seeds [43], dinosaur tails [44,45], gastropod shells [46], and insect wings [19]. Vertebrate skulls are typical structures that are frequently studied [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42], particularly as they relate to stresses on the bones during feeding. FEA is most often used to study a single species, though a few studies have used inter-and intraspecific specimens for a comparative analysis [26,27,31,41,47]. ...
Article
Full-text available
Advances in imaging and modeling facilitate the calculation of biomechanical forces in biological specimens. These factors play a significant role during ontogenetic development of cichlid pharyngeal jaws, a key innovation responsible for one of the most prolific species diversifications in recent times. MicroCT imaging of radiopaque-stained vertebrate embryos were used to accurately capture the spatial relationships of the pharyngeal jaw apparatus in two cichlid species (Haplochromis elegans and Amatitlania nigrofasciata) for the purpose of creating a time series of developmental stages using finite element models, which can be used to assess the effects of biomechanical forces present in a system at multiple points of its ontogeny. Changes in muscle vector orientations, bite forces, force on the neurocranium where cartilage originates, and stress on upper pharyngeal jaws are analyzed in a comparative context. In addition, microCT scanning revealed the presence of previously unreported cement glands in A. nigrofasciata. The data obtained provide an underrepresented dimension of information on physical forces present in developmental processes and assist in interpreting the role of developmental dynamics in evolution.
... We have found in this species of shark several intrinsic traits that inspired us to develop the proposed WSO. White sharks, also known as white pointers or great white sharks, are some of the strongest and most hazardous predacious sharks in the world [104]. White sharks are highly acclimatized predators and stunning hunters, armed with powerful muscles, sturdy eyesight for well-contrasted vision, and a keen sense of smell. ...
... White sharks are streamlined, torpedo-shaped swimmers with mighty tails that can impel them in the water. They swim toward prey with undulating motion, and can even leave the water completely, and explode like whales when attacking prey from underneath [104]. The most interesting facts of the collective conduct of great white sharks are their way of catching prey using their method of swimming as well as their uncommon senses of hearing and smelling the scent of prey. ...
Article
Full-text available
This paper presents a novel meta-heuristic algorithm so-called White Shark Optimizer (WSO) to solve optimization problems over a continuous search space. The core ideas and underpinnings of WSO are inspired by the behaviors of great white sharks, including their exceptional senses of hearing and smell while navigating and foraging. These aspects of behavior are mathematically modeled to accommodate a sufficiently adequate balance between exploration and exploitation of WSO and to assist search agents to explore and exploit each potential area of the search space in order to achieve optimization. The search agents of WSO randomly update their position in connection with best-so-far solutions, to eventually arrive at the optimal outcome. The performance of WSO was comprehensively benchmarked on a set of 29 test functions from the CEC-2017 test suite for several dimensions. WSO was further applied to solve the benchmark problems of the CEC-2011 evolutionary algorithm competition to prove its reliability and applicability to real-world problems. A thorough analysis of computational and convergence results was presented to shed light on the efficacy and stability levels of WSO. The performance score of WSO in terms of several statistical methods was compared with 9 well-established meta-heuristics based on the solutions generated. Friedman’s and Holm’s tests of the results showed that WSO revealed reasonable solutions, in terms of global optimality, avoidance of local minima and solution quality, compared to other existing meta-heuristics.
... El diagnóstico de las lesiones dentales que figuran en la Tabla I, todavía deja espacio a diferentes interpretaciones por la ausencia de un registro fósil paleopatológico de comparación, así como por los reducidos conocimientos sobre la biología y fisiología de C. megalodon (derivados casi exclusivamente de los dientes y pocos centros vertebrales hallados), y de los estudios de fisiopatología comparada (principalmente en el gran tiburón blanco Carcharodon carcharias) (Hubbell;Renz;Wroe et al., 2008). ...
Article
Full-text available
Paleopathology is the science that studies the origin and evolution of diseases. The interest in this discipline derives from the fact that the frequency and distribution of the pathologies that have affected the extinct species, correlate with their ecology and ethology. This assumption is also valid in the case of Carcharocles megalodon, the largest shark that ever existed, located at the top of the food chain and that lived in temperate seas from the middle Miocene to the Pliocene periods (15.9-2.6 My). In the present article we present the pathological alterations of the teeth of Carcharocles megalodon housed in the University Museum of Chieti (Italy). The collection consists of nine teeth of the upper arch, all of them with pathological alterations corresponding to developmental defects and crown trauma. A particular tooth (specimen #165) presents an anomalous apposition of the enamel on the labial surface, a condition not yet described in the literature. The collection of the University Museum of Chieti enriches the existing relatively poor paleopathological record, and could improve the knowledge of the paleobiology of Carcharocles megalodon.
... El diagnóstico de las lesiones dentales que figuran en la Tabla I, todavía deja espacio a diferentes interpretaciones por la ausencia de un registro fósil paleopatológico de comparación, así como por los reducidos conocimientos sobre la biología y fisiología de C. megalodon (derivados casi exclusivamente de los dientes y pocos centros vertebrales hallados), y de los estudios de fisiopatología comparada (principalmente en el gran tiburón blanco Carcharodon carcharias) (Hubbell;Renz;Wroe et al., 2008). ...
Article
Paleopathology is the science that studies the origin and evolution of diseases. The interest in this discipline derives from the fact that the frequency and distribution of the pathologies that have affected the extinct species, correlate with their ecology and ethology. This assumption is also valid in the case of Carcharocles megalodon, the largest shark that ever existed, located at the top of the food chain and that lived in temperate seas from the middle Miocene to the Pliocene periods (15.9-2.6 My). In the present article we present the pathological alterations of the teeth of Carcharocles megalodon housed in the University Museum of Chieti (Italy). The collection consists of nine teeth of the upper arch, all of them with pathological alterations corresponding to developmental defects and crown trauma. A particular tooth (specimen #165) presents an anomalous apposition of the enamel on the labial surface, a condition not yet described in the literature. The collection of the University Museum of Chieti enriches the existing relatively poor paleopathological record, and could improve the knowledge of the paleobiology of Carcharocles megalodon.
... These include techniques like high-speed cinematography (Bemis and Lauder 1986;Konow and Bellwood 2005;Konow et al. 2008), electromyography (Bemis and Lauder 1986;Habegger et al. 2010), digital particle image velocimetry (Ferry- Graham et al. 2003), bioelectricity studies (Watt et al. 1999) and use of bite meters . Other methods can be applied to both fossil and extant taxa however, such as simple lever mechanics (Barel 1983;Wainwright and Richard 1995;Bellwood 2003;Westneat 2004;Davis et al. 2010), more complex lever mechanics such as 4-bar linkage systems (Wainwright et al. 2004;Westneat 2007, 2009), or finite element analysis (FEA) (Rayfield 2007; Wroe et al. 2007Wroe et al. , 2008Moreno et al. 2008). FEA is an engineering principle where the strength of the material (e.g. ...
Thesis
The modem Australian fauna includes one of the most enduring extant vertebrate lineages, the Dipnoi, and this body of work examines their anatomy, evolution and relationships, with insights from the Australian lungfish, Neoceratodus forsteri. Through application of modern technology and techniques, this thesis provides comparative, ontogenetic, phylogenetic and functional insights into both fossil and extant lungfishes. Three recently discovered fossil taxa are discussed. These include the first Gondwanan species of a European genus (Rhinodipterus kimberleyensis, Clement 2012), and a primitive genus belonging to the holodontid family (Xeradipterus hatcheri, Clement and Long 2010b), both from the Late Devonian Gogo Formation of Western Australia. Also, a Middle Devonian genus from central Australia (Harajicadipterus youngi, Clement 2009) and a detailed examination of the postcranial anatomy of two lungfishes from Victoria (Howidipterus donnae and Barwickia downunda, Long 1992a) is included. Key findings include the first unequivocal marine lungfish with air-breathing adaptations, possible examples ofsympatric speciation driven by competition for trophic resources, and some of the earliest dipnoans to make the transition to freshwater in Australia. Cladistic analysis was employed to examine dipnoan interrelationships, with special emphasis on early Australian forms. The analysis suggests there were significant adaptive radiations of lungfishes in Devonian reefs, with three locally-evolving clades identified; the chirodipterids, holodontids and dipnorhynchids. The monophyly ofa number ofgenera found in Australian deposits, namely Chirodipterus and Griphognathus is not supported, whereas, the monophyly of Rhinodipterus is confirmed. The analysis suggests that air-breathing probably evolved only once within the Dipnoi. Partition homogeneity tests and Farris' successive weighting provide support for the hypothesis that anatomical characters relating to feeding, such as those of the dentition, jaw and palate, may be less reliable than some other, less convergence-prone traits. Basic jaw lever mechanics in conjunction with 3D bite-modelling software were used to estimate bite force and velocity in extant and fossil genera. Neoceratodus was shown to have a mid level mechanical advantage for its bite compared to earlier fossil forms, implying it has neither a particularly strong nor fast bite. The two main adductor mandibulae muscle portions, the temporalis and masseter, contribute similar forces, and effective mechanical advantage remains constant throughout ontogeny despite an observable shift in diet. Analysis of functional morphology illustrates a large variety of feeding ecomorphologies, and thus, inferred behaviours of Devonian lungfishes. Early members of this lineage were evidently capable of eating diverse prey types, and likely filled a wide range of ecological roles. An inherent ability to remodel plastic dental morphologies is supported as a mechanism by which the early lungfishes were able to evolve, adapt and exploit new niches throughout their long history.
... In carcharinids (including the bull shark C. leucas), heterodonty is characterized by triangular and serrated teeth on the upper jaw aiming at cutting, while teeth from the lower jaw are slender and smoother (see Section 3.4), acting as puncturing/holding devices before the shark starts moving the head laterally for cutting the tissues. Whatever their sharpness and shape, these jaws and teeth constitute a potential threat to humans, also considering that certain species, such as the tiger shark, may produce biting forces of up to 3300 kg/cm 2 [14][15][16]. ...
... The black piranha, Serrasalmus rhombeus, may hold the record for relative bite force among extant vertebrate taxa (Grubich et al., 2012). The force of its jaws is, proportionally to body size, up to three times stronger than the bite force for a great white shark (Wroe et al., 2008;Ferrara et al., 2011) or an adult alligator (Erickson et al., 2003). In addition to an extreme jaw force, the black piranha has a single row of highly specialized sharp and triangular teeth on each jaw allowing it to cut small pieces of flesh from larger animals (Shellis & Berkovitz, 1976;Jégu, 2003). ...
... The black piranha, Serrasalmus rhombeus, may hold the record for relative bite force among extant vertebrate taxa (Grubich et al., 2012). The force of its jaws is, proportionally to body size, up to three times stronger than the bite force for a great white shark (Wroe et al., 2008;Ferrara et al., 2011) or an adult alligator (Erickson et al., 2003). In addition to an extreme jaw force, the black piranha has a single row of highly specialized sharp and triangular teeth on each jaw allowing it to cut small pieces of flesh from larger animals (Shellis & Berkovitz, 1976;Jégu, 2003). ...
Article
Serrasalmid fishes form a highly specialized group of biters that show a large trophic diversity, ranging from pacus able to crush seeds to piranhas capable of cutting flesh. Their oral jaw system has been hypothesized to be forceful, but variation in bite performance and morphology with respect to diet has not previously been investigated. We tested whether herbivorous species have higher bite forces, larger jaw muscles and more robust jaws than carnivorous species. We measured in vivo and theoretical bite forces in 27 serrasalmid species. We compared the size of the adductor mandibulae muscle, the jaw mechanical advantages, the type of jaw occlusion, and the size and shape of the lower jaw. We also examined the association between bite performance and functional morphological traits of the oral jaw system. Contrary to our predictions, carnivorous piranhas deliver stronger bites than their herbivorous counterparts. The size of the adductor mandibulae muscle varies with bite force and muscles are larger in carnivorous species. Our study highlights an underestimated level of functional morphological diversity in a fish group of exclusive biters. We provide evidence that the trophic specialization towards carnivory in piranhas results from changes in the configuration of the adductor mandibulae muscle and the lower jaw shape, which have major effects on bite performance and bite strategy.
... Additionally, our values for stiffness and hardness of dry tesserae are also at least an order of magnitude larger than those reported for both wet-and dry-indented, non-sectioned shark and ray tesserae examined in other studies [16,18]. Discrepancies between our measurements and those of other studies are surely partly a function of differences in tissue hydration due to sample preparation (see Methods: Nanoindentation above). ...
Article
Skeletal tissues are built and shaped through complex, interacting active and passive processes. These spatial and temporal variabilities make interpreting growth mechanisms from morphology difficult, particularly in bone, where the remodeling process erases and rewrites local structural records of growth throughout life. In contrast to the majority of bony vertebrates, the elasmobranch fishes (sharks, rays, and their relatives) have skeletons made of cartilage, reinforced by an outer layer of mineralized tiles (tesserae), which are believed to grow only by deposition, without remodeling. We exploit this structural permanence, performing the first fine-scale correlation of structure and material properties in an elasmobranch skeleton. Our characterization across an age series of stingray tesserae allows unique insight into the growth processes and mechanical influences shaping the skeleton. Correlated quantitative backscattered electron imaging (qBEI) and nanoindentation measurements show a positive relationship between mineral density and tissue stiffness/hardness. Although tessellated cartilage as a whole (tesserae plus unmineralized cartilage) is considerably less dense than bone, we demonstrate that tesserae have exceptional local material properties, exceeding those of (mammal) bone and calcified cartilage. We show that the finescale ultrastructures recently described in tesserae have characteristic material properties suggesting distinct mechanical roles and that regions of high mineral density/stiffness in tesserae are confined predominantly to regions expected to bear high loads. In particular, tesseral spokes (laminated structures flanking joints) exhibit particularly high mineral densities and tissue material properties, more akin to teeth than bone or calcified cartilage. We conclude that these spokes toughen tesserae and reinforce points of contact between them. These toughening and reinforcing functions are supported by finite element simulations incorporating our material data. The high stresses predicted for spokes, and evidence we provide that new spoke laminae are deposited according to their local mechanical environment, suggest tessellated cartilage is both mutable and responsive, despite lacking remodeling capability. STATEMENT OF SIGNIFICANCE: The study of vertebrate skeletal materials is heavily biased toward mammal bone, despite evidence that bone and cartilage are extremely diverse. We broaden the perspective on vertebrate skeleton materials and evolution in an investigation of stingray tessellated cartilage, a curious type of unmineralized cartilage with a shell of mineralized tiles (tesserae). Combining high-resolution imaging and material testing, we demonstrate that tesserae have impressive local material properties for a vertebrate skeletal tissue, arguing for unique tissue organization relative to mammalian calcified cartilage and bone. Incorporating our materials data into mechanical models, we show that finescale material arrangements allow this cartilage to act as a functional and responsive alternative to bone, despite lacking bone's ability to remodel. These results are relevant to a diversity of researchers, from skeletal, developmental, and evolutionary biologists, to materials scientists interested in high-performance, low-density composites.
... In general, the small size of the larvae, as well as the rapid ossification of the larval skeleton after hatching, often impedes studying stress and strain in the larval cartilaginous elements. For the modelled cartilage in this study, the mechanical properties that are most commonly used on FEA models of cartilaginous fishes are used (Wroe et al., 2008). ...
... Studies of feeding performance among sharks often fall into one of two general categories: kinematic studies of feeding (Ferry-Graham, 1998;Motta et al., 1997;Motta & Wilga, 1999;Wilga & Motta, 1998, 2000 or computational studies of bite strength as a metric of performance (Ferrara et al., 2011;Huber et al., 2005Huber et al., , 2008Wroe et al., 2008). Logistical hurdles traditionally associated with studies of bite kinematics of large sharks include access to study animals and stationary high-speed cameras that require sharks to swim past a viewing window at the exact moment of prey capture. ...
Article
This study examines the feeding behaviour and kinematics of three sub‐adult sand tiger sharks Carcharias taurus on display at Mystic Aquarium (Mystic, Connecticut, USA). Using high‐speed video data from 52 bites, we identify kinematic variables associated with the expansive and compressive phases of the bite. The mean bite duration from the onset of the expansive phase to the conclusion of the compressive phase is mean (± SD) 0.14 ± 0.01 s and across the ten fastest bites of each individual, the maximum performance average is 0.13 ± 0.01 s. Values of maximum performance do not vary significantly among individuals. When compared with kinematic bite data from species studied previously, these results indicate that body size is not the only determinant factor of bite duration. This study also provides detailed descriptions of feeding behaviours in C. taurus and presents documentation of tooth loss both prior to and during feeding, suggesting that there are multiple mechanisms of tooth loss and use in C. taurus. Finally, we discuss the behavioural and ecological components of prey capture in C. taurus and suggest points of consideration to facilitate interspecific comparisons of prey capture performance in ram‐feeding macrophagous elasmobranchs. This article is protected by copyright. All rights reserved.
... Research examining the force required of teeth to penetrate and puncture prey raises the question of why high bite force is generated in sharks, when force to penetrate is generally low (Huber et al., 2006Whitenack & Motta, 2010;Galloway et al., 2016). The excessively high bite forces of shark species suggests an over-development of the feeding mechanism in that they generate forces higher than necessary for puncture (Habegger et al., 2012), with some carcharhinid species generating kN bite forces greater than those required by the prey tissues (Huber et al., 2006Wroe et al., 2008;Mara et al., 2009). This study focused on investigating the minimum force required to pierce two species of teleosts in the fleshy epaxial region and did not incorporate additional force required to catch and consume shelled prey, hold struggling prey, or sever tough integument and skeletal elements of larger prey items like turtles, large teleosts, elasmobranchs and marine mammals. ...
Article
Full-text available
This study examined the minimum force required of functional teeth and replacement teeth in the tiger shark Galeocerdo cuvier and the sandbar shark Carcharhinus plumbeus to penetrate the scales and muscle of sheepshead Archosargus probatocephalus and pigfish Orthopristis chrysoptera. Penetration force ranged from 7·7-41·9 and 3·2-26·3 N to penetrate A. probatocephalus and O. chrysoptera, respectively. Replacement teeth required significantly less force to penetrate O. chrysoptera for both shark species, most probably due to microscopic wear of the tooth surfaces supporting the theory shark teeth are replaced regularly to ensure sharp teeth that are efficient for prey capture.
... The black piranha, Serrasalmus rhombeus, may hold the record for relative bite force among extant vertebrate taxa (Grubich et al., 2012). The force of its jaws is, proportionally to body size, up to three times stronger than the bite force for a great white shark (Wroe et al., 2008;Ferrara et al., 2011) or an adult alligator (Erickson et al., 2003). In addition to an extreme jaw force, the black piranha has a single row of highly specialized sharp and triangular teeth on each jaw allowing it to cut small pieces of flesh from larger animals (Shellis & Berkovitz, 1976;Jégu, 2003). ...
Presentation
Serrasalmidae are mainly known for “piranhas” and their negative reputation of ferocious predatory fishes. A recent study demonstrated that the piranha Serrasalmus rhombeus had an extreme bite force that is even proportionally greater than that of the white shark. However, these sharp teeth fishes represent only a minority of Serrasalmidae. Other serrasalmid species (pacus and myleus) feed on plants, fruits or seeds and their bite force and feeding capacities are still uninvestigated. In the present research, in vivo bite forces were measured and compared according to jaw morphology in ten species of Serrasalmidae including six herbivorous and four carnivorous species. The Bite Force Quotient (BFQ) was calculated for each individual to compare the jaw strength across species. The results of the analysis showed that species feeding on fins and fish flesh have a significant greater bite force than species feeding on plants, fruits or seeds. This difference can be explained by the larger adductor mandibulae muscle in carnivorous species which have comparatively longer and higher skull than herbivorous species. In addition, there is a significant difference in the lower jaw morphology between piranhas and pacus and relatives. The piranha species have longer lower jaws than pacus and myleus species which have shorter and higher lower jaws. This study shows that the Serrasalmidae family regroups remarkable biters whose bite performance is mostly related to diet.
... The extinct 'megalodon' shark (Megaselachus megalodon) is widely considered to be the largest chondrichthyan ever to have existed, based on size comparisons with teeth of the modern great white shark, Carcharodon carcharias (maximum length estimates range between 15 and 24 m; Randall, 1973Randall, , 1987Gottfried et al., 1996;Wroe et al., 2008). Megaselachus and other members of the lamniform family Otodontidae have a widespread fossil record that extends back into the lower Paleocene, suggesting that many of these taxa were itinerant, transoceanic epipelagic swimmers (Cappetta, 2012). ...
Article
The occipital regions of the braincases of two gigantic ctenacanthiform sharks are described from the Finis Shale (Virgilian, Upper Pennsylvanian, ca. 300 Ma) of Texas. Their original braincase lengths are estimated to have been 42.8–68.2 and 33.9–64.8 cm, based on comparison with smaller, more complete ctenacanthiform specimens (e.g., Tamiobatis). In complete ctenacanthiform body fossils (e.g., Goodrichthys), braincase length represents approximately 10% of total body length. This suggests that the Finis Shale sharks attained lengths up to 7 m (as large as modern great white sharks and Cretaceous cardabiodontids) and body weights of 1500–2500 kg. As apex predators, such large sharks probably maintained a high hepatosomatic index and may even have utilized lamnid-like heat exchange retia in critical parts of the body (e.g., brain, eyes, stomach). Citation for this article: Maisey, J. G., A. W. Bronson, R. R. Williams, and M. Mckinzie. 2017. A Pennsylvanian ‘supershark’ from Texas. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1325369.
... A diving cage shall withstand bites from sharks, the pitch of the bars as well as their rigidity are important in avoiding contact between a shark and the humans inside the cage. An analysis was run using a white shark biting force of 18,216 N, which was quantified in another study [18], assuming a maximum bite or gape angle of 55͒ [19] and a mandible length of 50 cm. The results depicted in Figure 4a showed that for metallic cage under the specified loading conditions a shark could permanently deform/bend the bars at a stress of 1.17 GPa. ...
Technical Report
Full-text available
Great white sharks have been a source of fascination to humans for a very long time. It has been furthered by popular culture movies based on sharks such as Jaws (1975) that portray them as ruthless apex predators or killing machines. This drives a desire amongst many shark enthusiasts to view them up-close by undertaking cage diving to swim with sharks in their natural habitat within the safety of the metallic cage. However, overly adventurous tourists have been reported reaching their hands or heads out of the wide 'viewing gallery' of the shark cage as well as incidents where relatively smaller species of sharks have entered these cages through that gap leading to injuries to both the shark and tourists. In light of this, the authors have redesigned the shark cage with a transparent polymer, i.e. Polymethyl methacrylate (PMMA), improving visibility as the bars and underlying mesh in metallic cages are completely discarded. The polymeric cage has been modelled and the simulation results demonstrated safety under biting and lifting conditions. Moreover, the proposed design is more eco-friendly as it is lighter, which translates to reduced fuel consumption for the boat as well as the crane. The report qualitatively and quantitatively asserts why the proposed material is better than the current one based on parameters such as enhanced visibility, improved safety and reduced carbon footprint, while discussing the associated development and challenges.
... For the last decade or so, the boundaries of FEA have been pushed towards more accurate modeling of bone structures to better understand skeletal form and function (Rayfield, 2007;Bourke et al., 2008;Wroe et al., 2008;Strait et al., 2010). Still, porous structures like trabecular bone and other complex biological geometries remain problematic in FE modeling given their internal complexity, and the conversion from 2D to 3D of intricate structures that frequently generate errors in elemental overlaps and highly skewed elemental shapes in small anatomical regions. ...
Article
Full-text available
Finite element analysis has been an increasingly widely applied biomechanical modeling method in many different science and engineering fields over the last decade. In the biological sciences, there are many examples of FEA in areas such as paleontology and functional morphology. Despite this common use, the modeling of trabecular bone remains a key issue because their highly complex and porous geometries are difficult to replicate in the solid mesh format required for many simulations. A common practice is to assign uniform model material properties to whole or portions of models that represent trabecular bone. In this study we aimed to demonstrate that a physical, element reduction approach constitutes a valid protocol for addressing this problem in addition to the wholesale mathematical approach. We tested a customized script for element reduction modeling on five exemplar trabecular geometry models of carnivoran temporomandibular joints, and compared stress and strain energy results of both physical and mathematical trabecular modeling to models incorporating actual trabecular geometry. Simulation results indicate that that the physical, element reduction approach generally outperformed the mathematical approach: physical changes in the internal structure of experimental cylindrical models had a major influence on the recorded stress values throughout the model, and more closely approximates values obtained in models containing actual trabecular geometry than solid models with modified trabecular material properties. In models with both physical and mathematical adjustments for bone porosity, the physical changes exhibit more weight than material properties changes in approximating values of control models. Therefore, we conclude that maintaining or mimicking the internal porosity of a trabecular structure is a more effective method of approximating trabecular bone behavior in finite element models than modifying material properties.
... This method allows for a complex three-dimensional (3D) structure to be broken down into a finite number of elements of known material properties, size and shape whose response to a force can be readily quantified [1][2][3]. In vertebrates, FEA has mainly been used to assess feeding behaviour and mechanical performance of the skull in a wide array of groups, including cartilaginous fish [4], ray-finned fish [5], crocodilians [6], non-avian dinosaurs [7], birds [8], mammaliaforms [9], rodents [10,11], primates [12][13][14], bats [15], ungulates [16] and carnivorous mammals [17][18][19][20]. To a lesser extent it has been used in the study of locomotion and behaviour, for example, to assess the loading regime of the metatarsus in a theropod dinosaur [21], to study the mechanical potential of the manual ungual of dromaeosaurids in prey dispatching [22], to simulate sauropod trackway formation [23] and theropod dinosaur locomotion [24,25]. ...
Article
Full-text available
Finite-element (FE) analysis has been used in palaeobiology to assess the mechanical performance of the jaw. It uses two types of models: tomography-based three-dimensional (3D) models (very accurate, not always accessible) and two-dimensional (2D) models (quick and easy to build, good for broad-scale studies, cannot obtain absolute stress and strain values). Here, we introduce extruded FE models, which provide fairly accurate mechanical performance results, while remaining low-cost, quick and easy to build. These are simplified 3D models built from lateral outlines of a relatively flat jaw and extruded to its average width. There are two types: extruded (flat mediolaterally) and enhanced extruded (accounts for width differences in the ascending ramus). Here, we compare mechanical performance values resulting from four types of FE models (i.e. tomography-based 3D, extruded, enhanced extruded and 2D) in Morganucodon and Kuehneotherium. In terms of absolute values, both types of extruded model perform well in comparison to the tomography-based 3D models, but enhanced extruded models perform better. In terms of overall patterns, all models produce similar results. Extruded FE models constitute a viable alternative to the use of tomography-based 3D models, particularly in relatively flat bones.
... Six gill [8] Great White [5,9,15] Dogfish [8,10] Lemon [11] Nurse [12] Method • Artificial damping energies such (ALLVD), artificial strain energy (ALLAE) and mass scaling work (ALLWM) must be negligible compared to (ALLKE). ...
Article
In the search for new subsea oil fields, geologists use vessels to tow streamer cables, which collects seismic data. This activity attracts bull sharks to the magnetic streamer fields causing shark attacks and hence losses and delays. This paper discusses how shark attacks on streamer cables can be modelled and simulated in cable design and optimization processes. In order to generate a representative simulation model, a large and authentic bull shark jaw was 3D-scanned. The shark jaw was converted to a CAD-model utilizing reverse engineering applications. Numerical models of the streamer cables, capturing the response with respect to friction properties and failure criteria’s, were benchmarked using quasi-static compression tests. Additionally, dynamic bite and impact simulations replicating the shark attack on streamer cables have been conducted. The physical compression tests and simulations show that the streamer cable FE-models are valid. The results indicate that a shark bite can be sufficient to critically damage the cable, but the bite resilience of the streamer cable is strongly correlated to the shark speed upon impact.
... Maximum bite force (Table 9.1) varies greatly among taxa, although few have been measured to date. The difficulties in gathering data on the maximum bite force of wild species have been reported frequently (Binder and Van Valkenburgh 2000;Erickson et al. 1996Erickson et al. , 2004Lindner et al. 1995;Wroe et al. 2008). In comparison, among the greatest bite force for an extant predator species is that of the great white shark (Carcharodon carcharias), although this force is applied over multiple shearing teeth instead of concentrated on chisel-shaped teeth anchored in bony jaws, as is the case with spotted hyena (Crocuta crocuta). ...
Chapter
Gnawing from animal species is a common alteration to human bones and comes under frequent forensic analysis in order to separate these effects from human-caused trauma and to understand the context and postdepositional history of a set of remains. This chapter examines the motivations for (predation, defleshing, fat extraction, incisor sharpening, etc.) and mechanisms of bone gnawing, the typical sequences of body part consumption and long bone destruction, and defines tooth mark types and other bone damage, including pits, scores/striations, punctures, furrows, edge wear, crenellation, peeling, scalloping, and gastric corrosion. This chapter also examines bone dispersal by carnivores and how this common behavior impacts subsequent scene dimensions and searching methods; reconcentration of bones by some species into dens; and distinguishing among size class of carnivores that created tooth marks. The modifications by rodents gnawing on wet or dry bone are also examined, along with modifications made by pigs, other large ungulates (osteophagia), and humans. The overall patterns of skeletal modification by taxon are also examined.
... Great white, tiger, and bull sharks grow to relatively large sizes, making their feeding behavior inherently more damaging and less survivable. Great white sharks are among the largest predators known, and their maximum bite force of approximately 4000 lb may be the highest of any extant species (Wroe et al. 2008;Chapter 9). Shark teeth among all predatory species, however, are relatively fragile and grow in multiple lines (series) attached to the mandibles by flexible tissues. ...
Chapter
Marine environments and coastal areas are a frequent source of remains undergoing forensic investigation, given the frequency of remains introduced from homicide, suicide, and accidents, and the concentration of human activity along coastlines. This chapter examines the many types of taphonomic effects accrued in marine environments. These include (1) alterations by scavengers, including sharks and arthropods, (2) colonization/bioerosion by organisms, including algae/kelp, barnacles, mollusks, Osedax worms, coral, sponges, and bryozoans, (3) sediment abrasion, battering, rounding, windowing, and embedding and salt crystal formation, (4) marine bleaching and mineral staining, and (5) more general changes including fat leaching and overall bone preservation. The propensity for remains to be transported and the factors that increase this likelihood, including decompositional bloating, are also examined. In addition, this chapter presents methods of estimating the postmortem submergence interval (PMSI) in these environments, including degree of decomposition and the stage of marine abrasion and other accrued taphonomic effects on exposed bones.
... Here, we used a different method to incorporate the muscular action on the FEm. This method consists of the creation of a contractile bars system (attached to the bone surfaces) that mirror muscle morphology (e.g., Wroe et al., 2008Wroe et al., , 2013McCurry et al., 2015;Attard et al., 2016;Taborda, 2016). We named this system "muscular action bars" (MAB) (Taborda, 2016). ...
Article
Aetosaurs are an archosaur group with a worldwide distribution during the Late Triassic. They were quadrupedal amniotes, had small heads relative to their body size, and had a long tail. Characterized by a dorsal and ventral carapace formed by ornamented and articulated osteoderms, aetosaur feeding ecology is poorly understood. Although aetosaurs are historically considered as the only herbivore among early pseudosuchian archosaurs, some authors have proposed omnivorous and/or scavengers habits for this group. Neoaetosauroides engaeus Bonaparte, 1969, an aetosaur from Late Triassic known from three relatively well preserved skulls (from the Los Colorados Formation, La Rioja, Argentina), is an excellent taxon to make biomechanics models of feeding to decipher the feeding ecology of this clade. We applied the Finite Element Method (FEM) for estimating the bite force and evaluated the structural response of the skull at different positions during the food processing. Our results show that the skull of N. engaeus generated a bite force of 3.6kN (magnitude comparable with the measurement made in Alligator mississippiensis) and could resist lateral and longitudinal forces during feeding. This indicates that these animals were capable of hunting of small living prey with their jaws (e.g. cynodonts), and/or drag carcasses of larger sizes (e.g. dicynodont). These results support possible zoophagy or omnivory for N. engaeus, and thus expanding the potential ecological roles of aetosaurs.
... 1993;Quillin 2000;Che and Dorgan 2010). Descriptions of animal and plant morphology are facilitated by imaging technology such as X-ray computed tomography (CT), magnetic resonance imaging and laser and white light scanning(Huising and Gomes Pereira 1998;Dean et al. 2007;Wroe et al. 2008;Gignac and Kley 2014;Bot and Irschick 2019). For example, X-ray CT scans have revealed the skeleton shape of sand lance fishes along with the kinematics they use to rapidly penetrate sandy soils to hide from predators(Bizarro 2016) (Figure 5a). ...
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A broad diversity of biological organisms and systems interact with soil in ways that facilitate their growth and survival. These interactions are made possible by strategies that enable organisms to accomplish functions that can be analogous to those required in geotechnical engineering systems. Examples include anchorage in soft and weak ground, penetration into hard and stiff subsurface materials and movement in loose sand. Since the biological strategies have been “vetted” by the process of natural selection, and the functions they accomplish are governed by the same physical laws in both the natural and engineered environments, they represent a unique source of principles and design ideas for addressing geotechnical challenges. However, prior to implementation as engineering solutions, the differences in spatial and temporal scales and material properties between the biological environment and engineered system must be addressed. Bio-inspired geotechnics research is addressing topics such as soil excavation and penetration, soil–structure interface shearing, load transfer between foundation and anchorage elements and soils, and mass and thermal transport, having gained inspiration from organisms such as worms, clams, ants, termites, fishes, snakes and plant roots. This work highlights the potential benefits to both geotechnical engineering through new or improved solutions and biology through understanding of mechanisms as a result of cross-disciplinary interactions and collaborations.
... For these validation analyses, all models were constrained at the jaw joint and a force applied to the mesialmost tooth. A profile model of T. rex FMNH PR 2081 was compared with a 3D representation after methods of Wroe et al. (2008) and Moreno et al. (2008). Results for a 2D mandible model of Carnosaurus sastrei (MACN CH 894) were compared with those for the 3D model by Mazzetta et al. (2005), using their data for material properties and forces of an anterior bite. ...
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The tyrannosaurids are among the most well‐studied dinosaurs described by science, and analysis of their feeding biomechanics allows for comparison between established tyrannosaurid genera and across ontogeny. We used 3D finite element analysis (FEA) to model and quantify the mechanical properties of the mandibles (lower jaws) of three tyrannosaurine tyrannosaurids of different sizes. To increase evolutionary scope and context for 3D tyrannosaurine results, a broader sample of validated 2D mandible FEA enabled comparisons between ontogenetic stages of Tyrannosaurus rex and other large theropods. We found that mandibles of small juvenile and large subadult tyrannosaurs experienced lower stress overall because muscle forces were relatively lower, but experienced greater simulated stresses at decreasing sizes when specimen muscle force or surface area is normalized. Strain on post‐dentary ligaments decreases stress and strain in the posterior region of the dentary and where teeth impacted food. Tension from the lateral insertion of the looping m. ventral pterygoid muscle increases compressive stress on the angular but may decrease anterior bending stress on the mandible. Low mid‐mandible bending stresses are congruent with ultra‐robust teeth and high anterior bite force in adult Tyrannosaurus rex. Mandible strength increases with size through ontogeny in T. rex and phylogenetically among other tyrannosaurids, in addition to that tyrannosaurid mandibles exceed mandible strength of other theropods at equivalent ramus length. These results may indicate separate predatory strategies used by juvenile and mature tyrannosaurids; juvenile tyrannosaurids lacked the bone‐crunching bite of adult specimens and hunted smaller prey, while adult tyrannosaurids fed on larger prey.
... Dorsal images. Figures 18,19,20,21,22,23. ...
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Due to their important phylogenetic position among extant vertebrates, sharks are an invaluable group in evolutionary developmental biology studies. A thorough understanding of shark anatomy is essential to facilitate these studies and documentation of this iconic taxon. With the increasing availability of cross-sectional imaging techniques, the complicated anatomy of both cartilaginous and soft tissues can be analyzed non-invasively, quickly, and accurately. The aim of this study is to provide a detailed anatomical description of the normal banded houndshark ( Triakis scyllium ) using computed tomography (CT) and magnetic resonance imaging (MRI) along with cryosection images. Three banded houndsharks were scanned using a 64-detector row spiral CT scanner and a 3 T MRI scanner. All images were digitally stored and assessed using open-source Digital Imaging and Communications in Medicine viewer software in the transverse, sagittal, and dorsal dimensions. The banded houndshark cadavers were then cryosectioned at approximately 1-cm intervals. Corresponding transverse cryosection images were chosen to identify the best anatomical correlations for transverse CT and MRI images. The resulting images provided excellent detail of the major anatomical structures of the banded houndshark. The illustrations in the present study could be considered as a useful reference for interpretation of normal and pathological imaging studies of sharks.
... the assumption that bite force increases at 0.67 the power of body mass 65 . Estimations were made presuming isometry from values obtained in a jaw model of a 240 kg great white shark specimen (i.e., anterior and posterior bite forces of 1602 N and 3131 N, respectively) 66 . The arithmetic average of anterior and posterior force values was considered as the force exerted by the lateral region of the jaw. ...
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The evolution of gigantism in extinct otodontid sharks was paralleled by a series of drastic modifications in their dentition including widening of the crowns, loss of lateral cusplets, and acquisition of serrated cutting edges. These traits have generally been interpreted as key functional features that enabled the transition from piscivory to more energetic diets based on marine mammals, ultimately leading to the evolution of titanic body sizes in the most recent forms (including the emblematic Otodus megalodon). To investigate this hypothesis, we evaluate the biomechanics of the anterior, lateral, and posterior teeth of five otodontid species under different loading conditions by using two-dimensional finite element analysis. Stress distribution patterns are remarkably similar among all models under puncture and draw (i.e., when subjected to vertical and lateral forces, respectively). Contrary to expectation, higher average stress values are detected under both loading scenarios in more recent species. Altogether, this suggests little correlation between tooth morphology and key aspects of biomechanical behaviour in otodontids, making it difficult to frame the morphological trend of their dentitions within an adaptive scenario. We propose that this pattern most likely emerged as a non-functional by-product of heterochronic processes driven by selection towards larger body sizes.
... These metallic devices exhibit a significantly higher stiffness than soft tissue, which enables the animals to develop higher bite forces. Similar bite forces have been predicted in numerical studies based on muscular and bone structure analysis of Carcharodon carcharias [19,20]. In addition, the exerted bite force will likely be distributed amongst multiple teeth and thus be spread over a larger surface area. ...
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The number of shark attacks resulting in fatalities and severe injuries has increased steadily over recent years. This is mainly attributed to a growing population participating in ocean sports such as swimming, diving, and surfing. To mitigate the severity of shark attacks, the current study presents a novel fibre-reinforced composite for bite protection. This material is intended for integration into neoprene wetsuits, e.g., in the form of protective pads. A suitable material must be able to withstand significant bite forces, which are concentrated within a small contact area at the tips of the shark teeth. At the same time, the material should not hinder the complex motion sequences of aquatic sports. To this end, a novel fibre-reinforced composite was created by integrating Kevlar fibres into an elastic matrix. Uni-axial testing using shark teeth replicas was conducted on a specially designed test rig to quantify the effectiveness of the novel protective material.
... However, some species, such as the bull shark, great white shark and tiger shark have a strong bite force able to even crack shells of sea turtles (e.g. Wroe et al., 2008;Habegger, 2009;Ferrara et al., 2011;Ferrara, 2012), which leads, at Table 5 Significant DMT parameters (confirmed by Cliff's method) for the analysis of diet-related wear parameters of the modern wild sharks. Fig. 5. Boxplots for Asfcfractal complexity, Sqstandard deviation of height distribution (μm) and Vm material volume (μm 3 /μm 2 ). ...
Article
Sharks are apex-predators that play an important role in past and present aquatic food webs. However, their diet - especially in extinct species - is often not well constrained. Dental microwear texture analysis (DMTA) has been successfully applied to reconstruct diet and feeding behaviours of different aquatic and terrestrial vertebrates. However, unlike in mammals, food-to-tooth contact in sharks is rather limited because only larger prey is manipulated before swallowing. Together with a fast tooth replacement rate, this reduces wear on individual teeth. Here, we present an explorative study of dental microwear texture on extant and extinct sharks to test whether ante-mortem wear is related to ingested diet or habitat preferences and resistant to post-mortem alteration processes. Shark teeth from 24 modern species and 12 fossil species from different localities were measured. As an additional comparison, extant shark teeth of Carcharhinus plumbeus were tumbled in sediment-water suspensions to simulate post-mortem mechanical alteration by sediment transport. Only three of the twelve extant shark species with three or more specimens had significantly different dental surface textures. Furthermore, no clear relation between food or habitat preferences and ante-mortem dental wear features was detected for this sample set. Tumbling modern shark teeth with siliciclastic sediment of four different grain size fractions led to increasing complexity of the dental surface. Fossil specimens resemble these experimentally altered shark teeth more in complexity and roughness. Thus, fossil shark teeth seem to display either very different (e.g. harder) diet-related wear or a strong degree of post-mortem alteration. Based on our restricted sample size, dental wear of shark teeth does overall not seem to simply reflect dietary differences; hence, it is difficult to use DMTA as reliable dietary reconstruction, in either extant nor extinct sharks.
... Once the jaws closed, this muscle is thought to be also involved in the dorsal retraction of the whole mandibular arch against the CR, assisting the Levator hyomandibularis in that task (Motta, 1997). Among the group of mandibular muscles involved in adduction: QV, multiple bodies of QD, POD and POV (Motta et al., 1997;Wilga & Motta, 2000), the QV is the most powerful instead the QD is less powerful as smaller (Huber et al., 2006;Mara et al., 2009;Wroe et al., 2008). We assume that the QD complex of H. elongata is relatively shallower than in H. australiensis and C. melanopterus because of the compressed and straightened anatomy of its quadrate process and the absence of a marked developed quadrate ridge. ...
Article
The anatomy of the feeding apparatus of the snaggletooth shark, Hemipristis elongata (Klunzinger, 1871) is illustrated in detail from the dissection of three heads. Two new muscles are described: the Adductor mandibularis internus and the Levator mandibularis. A subdivision of the Levator palatoquadrati is described and named the Pronator subdivision of the Levator palatoquadrati. Also, eight new anatomical features associated with the mandibular arch and with the chondrocranium (CR) are described. Three are cartilages: the suprapalatine cartilages, the craniopalatoquadrate cartilage and the calcified Meckelian dental fold. The remaining five features are processes: the Pronator process of the palatoquadrate (PQ), the Levator palatoquadrati alpha process, the proquadrate process, the ectorbital process (ECP) and the Meckelian Intermandibularis ridge. Some of them are not restricted to H. elongata. The function of these new muscles and anatomical features is discussed and a hypothesis about the functional morphology of the feeding apparatus of the snaggletooth shark is proposed. The extent and the assumptive importance of the pronation of the mandibular arch in the snaggletooth shark feeding behaviour is described and discussed. An alternative for the main function of the Levator palatoquadrati as hypothesized by Motta et al. (1997) and Wilga et al. (2001) is proposed for the families Hemigaleidae, Carcharhinidae and Sphyrnidae. We anticipate this muscle is more involved in the pronation rather than in the protrusion of the mandibular arch.
... This agrees with the previous suggestion that †O. megalodon had a much greater bite force than that of C. carcharias, and perhaps the greatest bite force of any marine predator known throughout geological time 40 . Finally, based on the external colouring of extant macropredatory sharks 41 , we propose that †O. ...
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Inferring the size of extinct animals is fraught with danger, especially when they were much larger than their modern relatives. Such extrapolations are particularly risky when allometry is present. The extinct giant shark †Otodus megalodon is known almost exclusively from fossilised teeth. Estimates of †O. megalodon body size have been made from its teeth, using the great white shark (Carcharodon carcharias) as the only modern analogue. This can be problematic as the two species likely belong to different families, and the position of the †Otodus lineage within Lamniformes is unclear. Here, we infer †O. megalodon body dimensions based on anatomical measurements of five ecologically and physiologically similar extant lamniforms: Carcharodon carcharias, Isurus oxyrinchus, Isurus paucus, Lamna ditropis and Lamna nasus. We first assessed for allometry in all analogues using linear regressions and geometric morphometric analyses. Finding no evidence of allometry, we made morphological extrapolations to infer body dimensions of †O. megalodon at different sizes. Our results suggest that a 16 m †O. megalodon likely had a head ~ 4.65 m long, a dorsal fin ~ 1.62 m tall and a tail ~ 3.85 m high. Morphometric analyses further suggest that its dorsal and caudal fins were adapted for swift predatory locomotion and long-swimming periods.
... Interestingly, elasmobranch feeding morphologists seem to have found means of studying some of the largest and most experimentally intractable species, such as the planktivorous Megamouth Shark (Megachasma pelagios), Whale Shark (Rhincodon typus), and mobulid rays (Tomita et al., 2011;Motta et al., 2010;Paig-Tran et al., 2013). Scientists have also studied jaw protrusion in deep-water species such as the Goblin Shark (Mitsukurina owstoni; Nakaya et al., 2016) and cranial biomechanics of the White Shark (Wroe et al., 2008). AES authors also have conducted research in comparing the functional ecology of extant and extinct taxa, i.e. representing not just current trends in biodiversity but historical ones as well (Whitenack and Motta, 2010;Whitenack et al., 2011). ...
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Given the conservation status and ecological, cultural, and commercial importance of chondrichthyan fishes, it is valuable to evaluate the extent to which research attention is spread across taxa and geographic locations and to assess the degree to which scientific research is appropriately addressing the challenges they face. Here we review trends in research effort over three decades (1985–2016) through content analysis of every abstract (n = 2,701) presented at the annual conference of the American Elasmobranch Society (AES), the oldest and largest professional society focused on the scientific study and management of these fishes. The most common research areas of AES abstracts were reproductive biology, movement/telemetry, age and growth, population genetics, and diet/feeding ecology, with different areas of focus for different study species or families. The most commonly studied species were large and charismatic (e.g., White Shark, Carcharodon carcharias), easily accessible to long-term established field research programs (e.g., Lemon Shark, Negaprion brevirostris, and Sandbar Shark, Carcharhinus plumbeus), or easily kept in aquaria for lab-based research (e.g., Bonnethead Shark, Sphyrna tiburo). Nearly 90% of all described chondrichthyan species have never been mentioned in an AES abstract, including some of the most threatened species in the Americas. The proportion of female* first authors has increased over time, though many current female* Society members are graduate students. Nearly half of all research presented at AES occurred in the waters of the United States rather than in the waters of developing nations where there are more threatened species and few resources for research or management. Presentations based on research areas such as paleontology and aquarium-based research have declined in frequency over time, and identified research priorities such as social science and interdisciplinary research are poorly represented. Possible research gaps and future research priorities for the study of chondrichthyan fishes are also discussed.
... The extinct 'megalodon' shark (Megaselachus megalodon) is widely considered to be the largest chondrichthyan ever to have existed, based on size comparisons with teeth of the modern great white shark, Carcharodon carcharias (maximum length estimates range between 15 and 24 m; Randall, 1973Randall, , 1987Gottfried et al., 1996;Wroe et al., 2008). Megaselachus and other members of the lamniform family Otodontidae have a widespread fossil record that extends back into the lower Paleocene, suggesting that many of these taxa were itinerant, transoceanic epipelagic swimmers (Cappetta, 2012). ...
Article
The occipital regions of the braincases of two gigantic ctenacanthiform sharks are described from the Finis Shale (Virgilian, Upper Pennsylvanian, ca. 300 Ma) of Texas. Their original braincase lengths are estimated to have been 42.8–68.2 and 33.9–64.8 cm, based on comparison with smaller, more complete ctenacanthiform specimens (e.g., Tamiobatis). In complete ctenacanthiform body fossils (e.g., Goodrichthys), braincase length represents approximately 10% of total body length. This suggests that the Finis Shale sharks attained lengths up to 7 m (as large as modern great white sharks and Cretaceous cardabiodontids) and body weights of 1500–2500 kg. As apex predators, such large sharks probably maintained a high hepatosomatic index and may even have utilized lamnid-like heat exchange retia in critical parts of the body (e.g., brain, eyes, stomach).
Chapter
When describing the architecture and ultrastructure of animal skeletons, introductory biology, anatomy and histology textbooks typically focus on the few bone and cartilage types prevalent in humans. In reality, cartilage and bone are far more diverse in the animal kingdom, particularly within fishes, where cartilage and bone types exist that are characterized by features that are anomalous or even pathological in human skeletons. Here, we discuss the curious and complex architectures of fish bone and shark and ray cartilage, highlighting similarities and differences with their mammalian skeletal tissue counterparts. By synthesizing older anatomical literature with recent high-resolution structural and materials characterization work, we frame emerging pictures of form-function relationships in these tissues and of the evolution and true diversity of cartilage and bone.
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An accepted uniting character of modern cartilaginous fishes (sharks, rays, chimaera) is the presence of a mineralized, skeletal crust, tiled by numerous minute plates called tesserae. Tesserae have, however, never been demonstrated in modern chimaera and it is debated whether the skeleton mineralizes at all. We show for the first time that tessellated cartilage was not lost in chimaera, as has been previously postulated, and is in many ways similar to that of sharks and rays. Tesserae in Chimaera monstrosa are less regular in shape and size in comparison to the general scheme of polygonal tesserae in sharks and rays, yet share several features with them. For example, Chimaera tesserae, like those of elasmobranchs, possess both intertesseral joints (unmineralized regions, where fibrous tissue links adjacent tesserae) and recurring patterns of local mineral density variation (e.g. Liesegang lines, hypermineralized ‘spokes’), reflecting periodic accretion of mineral at tesseral edges as tesserae grow. Chimaera monstrosa 's tesserae, however, appear to lack the internal cell networks that characterize tesserae in elasmobranchs, indicating fundamental differences among chondrichthyan groups in how calcification is controlled. By compiling and comparing recent ultrastructure data on tesserae, we also provide a synthesized, up-to-date and comparative glossary on tessellated cartilage, as well as a perspective on the current state of research into the topic, offering benchmark context for future research into modern and extinct vertebrate skeletal tissues.
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Chondrichthyians (sharks, ratfish, and rays) can function at extremes (growing big, swimming fast, and eating hard-prey) suggesting their skeletons are experiencing loading regimes equal to or greater than those of other fishes. In most vertebrates, cartilage is a soft connective tissue serving two purposes; a low-friction bearing surface and contour filler; however, cartilaginous fishes maintain a skeleton made of cartilage throughout life. We examined material properties and biochemical components of cartilage from the jaws and/or chondrocranium of seven species of shark. For each species cylindrical plugs were drilled from the specimen, mineralized tesserae were removed, and plugs tested in compression to ten percent of initial thickness (ε=0.10) at 2mm/sec. Stiffness and strength varied significantly among species and in both cases the chondrocranial properties were greater than those of the jaws. After materials testing, cartilage plugs were lyophilized to obtain water content; then collagen and proteoglycan was measured with hydroxyproline and DMMB assays, respectively. Water content was greatest in the chondrocranial cartilage while collagen content was consistent between the jaws and chondrocrania. However, proteoglycan content was greater in the jaw cartilage. The average values for water and proteoglycan content were consistent with mammalian cartilage, while collagen content was much lower than mammalian cartilage. Material properties and biochemical components were also similar to the mineralized cartilage found in elasmobranch vertebral cartilage.
Chapter
Reports of marine injuries have increased in recent years as water sports and recreation grow in popularity. Eels, wolf-herring, barracuda, triggerfish, and ribbonfish frequently cause trauma. Sharks play an important role in the animal–human attack game and can render land-based, bipedal primates easy prey. The term shark attack has been considered to be any forceful or injurious exchange between a human and any shark. This frightening incident has always been one of the more thoroughly examined issues of the challenge between human and shark. Because of their feeding mechanisms, including sharp teeth and powerful jaws, and because they can attain very large sizes, sharks are considered to be the top predators of the marine world. Regardless of its size, any shark having both opportunity and physical capacity for injuring humans can be considered dangerous. The incidence of shark attacks in the world could not be said to merit the degree of apprehension or antipathy often expressed towards sharks, but when a shark attack does occur, it is often with an impressive efficiency.
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Morphological shifts observed in the fossil record of a lineage potentially indicate concomitant shifts in ecology of that lineage. Mekosuchine crocodiles of Cenozoic Australia display departures from the typical eusuchian body-plan both in the cranium and postcranium. Previous qualitative studies have suggested that these crocodiles had a more terrestrial habitus than extant crocodylians, yet the capacity of mekosuchine locomotion remains to be tested. Limb bone shape, such as diaphyseal cross-section and curvature, has been related to habitual use and locomotory function across a wide variety of taxa. Available specimens of mekosuchine limbs, primarily humeri, are distinctly columnar compared with those of extant crocodylians. Here we apply a quantitative approach to biomechanics in mekosuchine taxa using both geomorphic morphometric and finite element methods to measure bone shape and estimate locomotory stresses in a comparative context. Our results show mekosuchines appear to diverge from extant semi-aquatic saltwater and freshwater crocodiles in cross-sectional geometry of the diaphysis and generate different structural stresses between models that simulate sprawling and high-walk gaits. The extant crocodylians display generally rounded cross-sectional diaphyseal outlines, which may provide preliminary indication of resistance to torsional loads that predominate during sprawling gait, whereas mekosuchine humeri appear to vary between a series of elliptical outlines. Mekosuchine structural stresses are comparatively lower than those of the extant crocodylians and reduce under high-walk gait in some instances. This appears to be a function of bending moments induced by differing configurations of diaphyseal curvature. Additionally, the neutral axis of structural stresses is differently oriented in mekosuchines. This suggests a shift in the focus of biomechanical optimisation, from torsional to axial loadings. Our results lend quantitative support to the terrestrial habitus hypothesis in so far as they suggest that mekosuchine humeri occupied a different morphospace than that associated with the semi-aquatic habit. The exact adaptational trajectory of mekosuchines, however, remains to be fully quantified. Novel forms appear to emerge among mekosuchines during the late Cenozoic. Their adaptational function is considered here; possible applications include navigation of uneven terrain and burrowing.
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Finite element analysis has been an increasingly widely used tool in many different science and engineering fields over the last decade. In the biological sciences, there are many examples of its use in areas as paleontology and functional morphology. Despite this common use, the modeling of porous structures such as trabecular bone remains a key issue because of the difficulty of meshing such highly complex geometries during the modeling process. A common practice is to mathematically adjust the boundary conditions (i.e. model material properties) of whole or portions of models that represent trabecular bone. In this study we aimed to demonstrate that a physical, element reduction approach constitutes a valid protocol to this problem in addition to the mathematical approach. We tested a new element reduction modeling script on five exemplar trabecular geometry models of carnivoran temporomandibular joints, and compared stress results of both physical and mathematical approaches to trabecular modeling to models incorporating actual trabecular geometry. Simulation results indicate that that the physical, element reduction approach generally outperformed the mathematical approach. Physical changes in the internal structure of experimental cylindrical models had a major influence on the recorded stress values throughout the model, and more closely approximates values obtained in models containing actual trabecular geometry than solid models with modified trabecular material properties. Therefore, we conclude that for modeling trabecular bone in finite element simulations, maintaining or mimicking the internal porosity of a trabecular structure is recommended as a fast and effective method in place of, or alongside, modification of material property parameters to better approximate trabecular bone behavior observed in models containing actual trabecular geometry.
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It has been suggested that the large theropod dinosaur Tyrannosaurus rex was capable of producing extremely powerful bite forces and resisting multi-directional loading generated during feeding. Contrary to this suggestion is the observation that the cranium is composed of often loosely articulated facial bones, although these bones may have performed a shock-absorption role. The structural analysis technique finite element analysis (FEA) is employed here to investigate the functional morphology and cranial mechanics of the T. rex skull. In particular, I test whether the skull is optimized for the resistance of large bi-directional feeding loads, whether mobile joints are adapted for the localized resistance of feeding-induced stress and strain, and whether mobile joints act to weaken or strengthen the skull overall. The results demonstrate that the cranium is equally adapted to resist biting or tearing forces and therefore the 'puncture-pull' feeding hypothesis is well supported. Finite-element-generated stress-strain patterns are consistent with T. rex cranial morphology: the maxilla-jugal suture provides a tensile shock-absorbing function that reduces localized tension yet 'weakens' the skull overall. Furthermore, peak compressive and shear stresses localize in the nasals rather than the fronto-parietal region as seen in Allosaurus, offering a reason why robusticity is commonplace in tyrannosaurid nasals.
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Vertebrate microfossils provide data for potential origination, range and distribution of taxa, for phylogeny of organisms and for assessing response of taxa to events. Isolated vertebrate microremains (microvertebrates, ichthyoliths), such as thelodont and "shark" scales and "shark" teeth can and do provide evidence about the functional morphology and relationships of higher taxa such as the Thelodonti and Chondrichthyes. Vertebrate microfossils can also provide evidence for at least the earliest occurrences of various morphological features characteristic of taxa. Specialized sensory scales related to free neuromasts are identified from a loganellidid thelodont from the Lower Silurian of Devon Island, Nunavut, Canada. New material of early "shark" remains, scales and teeth from the Devonian of Australia and Canada, including the Early Devonian (Emsian) taxon, Emsolepis hanspeteri n. gen. et sp., from the Receptaculites and Jesse limestones of NSW and Doliodus problematicus (WOODWARD), from the Campbellton Formation of northern New Brunswick, add insights into the earliest stages of chondrichthyans. Doliodus, most recently regarded as a member of the Omalodontida, exhibits the earliest fossil record of the chondrichthyan teeth in situ.
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Inertial suction feeding is known to occur in some sharks, but the sequence and temporal kinematics of head and jaw movements have not been defined. We inves- tigated the feeding kinematics of a suction feeding shark, the nurse shark Gingly- mostoma cirratum, to test for differences in the timing and magnitude of feeding components with other shark taxa when sharks were fed pieces of bony fish. Thir- teen kinematic variables were measured from high-speed video recordings. Food capture in this species consists of expansive, compressive, and recovery phases, as in most other sharks, but there is little or no cranial elevation. Mean time to maxi- mum gape (32 msec) is the fastest recorded for an elasmobranch fish. Other rela- tively rapid events include mandibular depression (26 msec), elevation (66 msec), and total bite time (100 msec). Buccal valves assist the unidirectional flow of water into the mouth and out of the gill chambers. Food capture under these experimental conditions appears to be a stereotyped modal action pattern but with significant interindividual variability in timing of kinematic events. Ginglymostoma cirratum ex- hibits a suite of specializations for inertial suction feeding that include (1) the for- mation of a small, anteriorly directed mouth that is approximately round and lat- erally enclosed by modified labial cartilages; (2) small teeth; (3) buccal valves to prevent the backflow of water; and (4) extremely rapid buccal expansion. Sharks that capture food by inertial suction have faster and more stereotyped capture be- havior than sharks that primarily ram feed. Inertial suction feeding, which has evolved multiple times in sharks, represents an example of functional convergence with inertial suction feeding bony fishes.
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Finite element analysis (FEA)1 is used by industrial designers and biomechanicists to estimate the performance of engineered structures or human skeletal and soft tissues subjected to varying regimes of stress and strain2-4. FEA is rarely applied to problems of biomechanical design in animals, despite its potential to inform structure-function analysis. Non-invasive techniques such as computed tomography scans can be used to generate accurate three-dimensional images of structures, such as skulls, which can form the basis of an accurate finite element model. Here we have applied this technique to the long skull of the large carnivorous theropod dinosaur Allosaurus fragilis5. We have generated the most geometrically complete and complex FEA model of the skull of any extinct or extant organism and used this to test its mechanical properties and examine, in a quantitative way, long-held hypotheses concerning overall shape and function6-8. The combination of a weak muscle-driven bite force, a very 'light' and 'open' skull architecture and unusually high cranial strength, suggests a very specific feeding behaviour for this animal. These results demonstrate simply the inherent potential of FEA for testing mechanical behaviour in fossils in ways that, until now, have been impossible.
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2006. Fused and vaulted nasals of tyrannosaurid dinosaurs: Implications for cranial strength and feeding mechanics. Acta Palaeontologica Polonica 51 (3): 435–454. Tyrannosaurid theropods display several unusual adaptations of the skulls and teeth. Their nasals are fused and vaulted, suggesting that these elements braced the cranium against high feeding forces. Exceptionally high strengths of maxillary teeth in Tyrannosaurus rex indicate that it could exert relatively greater feeding forces than other tyrannosaurids. Areas and second moments of area of the nasals, calculated from CT cross−sections, show higher nasal strengths for large tyrannosaurids than for Allosaurus fragilis. Cross−sectional geometry of theropod crania reveals high second moments of area in tyrannosaurids, with resulting high strengths in bending and torsion, when compared with the crania of similarly sized theropods. In tyrannosaurids trends of strength increase are positively allomeric and have similar allometric expo− nents, indicating correlated progression towards unusually high strengths of the feeding apparatus. Fused, arched nasals and broad crania of tyrannosaurids are consistent with deep bites that impacted bone and powerful lateral movements of the head for dismembering prey.
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Models of the mammalian jaw have predicted that bite force is intimately linked to jaw gape and to tooth position. Despite widespread use, few empirical studies have provided evidence to validate these models in non-human mammals and none have considered the influence of gape angle on the distribution of stress. Here using a multi-property finite element (FE) model of Canis lupus dingo, we examined the influence of gape angle and bite point on both bite force and cranial stress. Bite force data in relation to jaw gape and along the tooth row, are in broad agreement with previously reported results. However stress data showed that the skull of C. l. dingo is mechanically suited to withstand stresses at wide gapes; a result that agreed well with previously held views regarding carnivoran evolution. Stress data, combined with bite force information, suggested that there is an optimal bite angle of between 25u and 35u in C. l. dingo. The function of these rather small bite angles remains unclear.
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As top predators in many oceanic communities, sharks are known to eat large prey and are supposedly able to generate high bite forces. This notion has, however, largely gone untested due to the experimental intractability of these animals. For those species that have been investigated, it remains unclear whether their high bite forces are simply a consequence of their large body size or the result of diet-related adaptation. As aquatic poikilotherms, sharks can grow very large, making them ideal subjects with which to investigate the effects of body size on bite force. Relative bite-force capacity is often associated with changes in head shape because taller or wider heads can, for example, accommodate larger jaw muscles. Constraints on bite force in general may also be released by changes in tooth shape. For example, more pointed teeth may allow a predator to penetrate prey more effectively than blunt, pavementlike teeth. Our analyses show that large sharks do not bite hard for their body size, but they generally have larger heads. Head width is the best predictor of bite force across the species included in our study as indicated by a multiple regression model. Contrary to our predictions, sharks with relatively high bite forces for their body size also have relatively more pointed teeth at the front of the tooth row. Moreover, species including hard prey in their diet are characterized by high bite forces and narrow and pointed teeth at the jaw symphysis.
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Computer tomographic (CT) scans are used to correct for tissue inhomogeneities in radiotherapy treatment planning. In order to guarantee a precise treatment, it is important to obtain the relationship between CT Hounsfield units and electron densities (or proton stopping powers for proton radiotherapy), which is the basic input for radiotherapy planning systems which consider tissue heterogeneities. A method is described to determine improved CT calibrations for biological tissue (a stoichiometric calibration) based on measurements using tissue equivalent materials. The precision of this stoichiometric calibration and the more usual tissue substitute calibration is determined by a comparison of calculated proton radiographic images based on these calibrations and measured radiographs of a biological sample. It has been found that the stoichiometric calibration is more precise than the tissue substitute calibration.
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Until the advent of electronic tagging technology, the inherent difficulty of studying swift and powerful marine animals made ecological information about sharks of the family Lamnidae difficult to obtain. Here we report the tracking of movements of white sharks by using pop-up satellite archival tags, which reveal that their migratory movements, depth and ambient thermal ranges are wider than was previously thought.
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Many studies have identified relationships between the forces generated by the cranial musculature during feeding and cranial design. Particularly important to understanding the diversity of cranial form amongst vertebrates is knowledge of the generated magnitudes of bite force because of its use as a measure of ecological performance. In order to determine an accurate morphological proxy for bite force in elasmobranchs, theoretical force generation by the quadratomandibularis muscle of the spiny dogfish Squalus acanthias was modeled using a variety of morphological techniques, and lever-ratio analyses were used to determine resultant bite forces. These measures were compared to in vivo bite force measurements obtained with a pressure transducer during tetanic stimulation experiments of the quadratomandibularis. Although no differences were found between the theoretical and in vivo bite forces measured, modeling analyses indicate that the quadratomandibularis muscle should be divided into its constituent divisions and digital images of the cross-sections of these divisions should be used to estimate cross-sectional area when calculating theoretical force production. From all analyses the maximum bite force measured was 19.57 N. This relatively low magnitude of bite force is discussed with respect to the ecomorphology of the feeding mechanism of S. acanthias to demonstrate the interdependence of morphology, ecology, and behavior in organismal design.
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We provide the first predictions of bite force (BS) in a wide sample of living and fossil mammalian predators. To compare between taxa, we calculated an estimated bite force quotient (BFQ) as the residual of BS regressed on body mass. Estimated BS adjusted for body mass was higher for marsupials than placentals and the Tasmanian devil (Sarcophilus harrisii) had the highest relative BS among extant taxa. The highest overall BS was in two extinct marsupial lions. BFQ in hyaenas were similar to those of related, non-osteophagous taxa challenging the common assumption that osteophagy necessitates extreme jaw muscle forces. High BFQ in living carnivores was associated with greater maximal prey size and hypercarnivory. For fossil taxa anatomically similar to living relatives, BFQ can be directly compared, and high values in the dire wolf (Canis dirus) and thylacine (Thylacinus cynocephalus) suggest that they took relatively large prey. Direct inference may not be appropriate where morphologies depart widely from biomechanical models evident in living predators and must be considered together with evidence from other morphological indicators. Relatively low BFQ values in two extinct carnivores with morphologies not represented among extant species, the sabrecat, Smilodon fatalis, and marsupial sabretooth, Thylacosmilus atrox, support arguments that their killing techniques also differed from extant species and are consistent with 'canine-shear bite' and 'stabbing' models, respectively. Extremely high BFQ in the marsupial lion, Thylacoleo carnifex, indicates that it filled a large-prey hunting niche.
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Three-dimensional static equilibrium analysis of the forces generated by the jaw musculature of the horn shark Heterodontus francisci was used to theoretically estimate the maximum force distributions and loadings on its jaws and suspensorium during biting. Theoretical maximum bite force was then compared with bite forces measured (1) voluntarily in situ, (2) in restrained animals and (3) during electrical stimulation of the jaw adductor musculature of anesthetized sharks. Maximum theoretical bite force ranged from 128 N at the anteriormost cuspidate teeth to 338 N at the posteriormost molariform teeth. The hyomandibula, which connects the posterior margin of the jaws to the base of the chondrocranium, is loaded in tension during biting. Conversely, the ethmoidal articulation between the palatal region of the upper jaw and the chondrocranium is loaded in compression, even during upper jaw protrusion, because H. francisci's upper jaw does not disarticulate from the chondrocranium during prey capture. Maximum in situ bite force averaged 95 N for free-swimming H. francisci, with a maximum of 133 N. Time to maximum force averaged 322 ms and was significantly longer than time away from maximum force (212 ms). Bite force measurements from restrained individuals (187 N) were significantly greater than those from free-swimming individuals (95 N) but were equivalent to those from both theoretical (128 N) and electrically stimulated measurements (132 N). The mean mass-specific bite of H. francisci was greater than that of many other vertebrates and second highest of the cartilaginous fishes that have been studied. Measuring bite force on restrained sharks appears to be the best indicator of maximum bite force. The large bite forces and robust molariform dentition of H. francisci correspond to its consumption of hard prey.
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Placoderms are a diverse group of armoured fishes that dominated the aquatic ecosystems of the Devonian Period, 415-360 million years ago. The bladed jaws of predators such as Dunkleosteus suggest that these animals were the first vertebrates to use rapid mouth opening and a powerful bite to capture and fragment evasive prey items prior to ingestion. Here, we develop a biomechanical model of force and motion during feeding in Dunkleosteus terrelli that reveals a highly kinetic skull driven by a unique four-bar linkage mechanism. The linkage system has a high-speed transmission for jaw opening, producing a rapid expansion phase similar to modern fishes that use suction during prey capture. Jaw closing muscles power an extraordinarily strong bite, with an estimated maximal bite force of over 4400 N at the jaw tip and more than 5300 N at the rear dental plates, for a large individual (6 m in total length). This bite force capability is the greatest of all living or fossil fishes and is among the most powerful bites in animals.
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The extinct marsupial thylacine (Thylacinus cynocephalus) and placental grey wolf (Canis lupus) are commonly presented as an iconic example of convergence. However, various analyses suggest distinctly different behaviours and specialization towards either relatively small or large prey in the thylacine, bringing the degree of apparent convergence into question. Here we apply a powerful engineering tool, three-dimensional finite element analysis incorporating multiple material properties for bone, to examine mechanical similarity and niche overlap in the thylacine and the wolf subspecies implicated in its extinction from mainland Australia, Canis lupus dingo. Comparisons of stress distributions not only reveal considerable similarity, but also informative differences. The thylacine's mandible performs relatively poorly where only the actions of the jaw muscles are considered, although this must be considered in the light of relatively high bite forces. Stresses are high in the posterior of the thylacine's cranium under loads that simulate struggling prey. We conclude that relative prey size may have been comparable where both species acted as solitary predators, but that the dingo is better adapted to withstand the high extrinsic loads likely to accompany social hunting of relatively large prey. It is probable that there was considerable ecological overlap. As a large mammalian hypercarnivore adapted to taking small-medium sized prey, the thylacine may have been particularly vulnerable to disturbance.
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The American sabercat Smilodon fatalis is among the most charismatic of fossil carnivores. Despite broad agreement that its extraordinary anatomy reflects unique hunting techniques, after >150 years of study, many questions remain concerning its predatory behavior. Were the "sabers" used to take down large prey? Were prey killed with an eviscerating bite to the abdomen? Was its bite powerful or weak compared with that of modern big cats? Here we quantitatively assess the sabercat's biomechanical performance using the most detailed computer reconstructions yet developed for the vertebrate skull. Our results demonstrate that bite force driven by jaw muscles was relatively weak in S. fatalis, one-third that of a lion (Panthera leo) of comparable size, and its skull was poorly optimized to resist the extrinsic loadings generated by struggling prey. Its skull is better optimized for bites on restrained prey where the bite is augmented by force from the cervical musculature. We conclude that prey were brought to ground and restrained before a killing bite, driven in large part by powerful cervical musculature. Because large prey is easier to restrain if its head is secured, the killing bite was most likely directed to the neck. We suggest that the more powerful jaw muscles of P. leo may be required for extended, asphyxiating bites and that the relatively low bite forces in S. fatalis might reflect its ability to kill large prey more quickly, avoiding the need for prolonged bites.
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Models of the mammalian jaw have predicted that bite force is intimately linked to jaw gape and to tooth position. Despite widespread use, few empirical studies have provided evidence to validate these models in non-human mammals and none have considered the influence of gape angle on the distribution of stress. Here using a multi-property finite element (FE) model of Canis lupus dingo, we examined the influence of gape angle and bite point on both bite force and cranial stress. Bite force data in relation to jaw gape and along the tooth row, are in broad agreement with previously reported results. However stress data showed that the skull of C. l. dingo is mechanically suited to withstand stresses at wide gapes; a result that agreed well with previously held views regarding carnivoran evolution. Stress data, combined with bite force information, suggested that there is an optimal bite angle of between 25 degrees and 35 degrees in C. l. dingo. The function of these rather small bite angles remains unclear.
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The Komodo dragon (Varanus komodoensis) displays a unique hold and pull-feeding technique. Its delicate 'space-frame' skull morphology differs greatly from that apparent in most living large prey specialists and is suggestive of a high degree of optimization, wherein use of materials is minimized. Here, using high-resolution finite element modelling based on dissection and in vivo bite and pull data, we present results detailing the mechanical performance of the giant lizard's skull. Unlike most modern predators, V. komodoensis applies minimal input from the jaw muscles when butchering prey. Instead it uses series of actions controlled by postcranial muscles. A particularly interesting feature of the performance of the skull is that it reveals considerably lower overall stress when these additional extrinsic forces are added to those of the jaw adductors. This remarkable reduction in stress in response to additional force is facilitated by both internal and external bone anatomy. Functional correlations obtained from these analyses also provide a solid basis for the interpretation of feeding ecology in extinct species, including dinosaurs and sabre-tooth cats, with which V. komodoensis shares various cranial and dental characteristics.
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Carcharodon carcharias was studied at Dangerous Reef, South Australia. A single bit action is composed of a uniform sequence of jaw and head movements. Various approach behaviors to baits were documented. Small sharks (<3 m) feed primarily on fish prey, while larger sharks feed on marine mammals, especially pinnipeds. Telemetric studies of white shark thermal biology show that they are warm-bodied, c4-5oC above ambient water temperature. -from Sport Fishery Abstracts
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The feeding behavior of the theropod dinosaur Tyrannosaurus rex is investigated through analysis of two variables that are critical to successful predation, bite force and prey body mass, as they scale with the size of the predator. These size-related variables have important deterministic effects on the predator's feeding strategy, through their effects on lethal capacity and choice of prey. Bite force data compiled for extant predators (crocodylians, carnivorans, chelonians and squamates) are used to establish a relationship between bite force and body mass among extant predators. These data are used to estimate the maximum potential bite force of T. rex, which is between about 183,000 and 235,000 N for a bilateral bite. The relationship between maximum prey body mass and predator body mass among the same living vertebrates is used to infer the likely maximum size of prey taken by T. rex in the Late Cretaceous. This makes it possible to arrive at a more rigorous assessment of the role of T. rex as an active predator and/or scavenger than has hitherto been possible. The results of this analysis show that adult Triceratops horridus fall well within the size range of potential prey that are predicted to be available to a solitary, predaceous T. rex. This analysis establishes boundary conditions for possible predator/prey relationships among other dinosaurs, as well as between these two taxa.
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WHETHER tyrannosaurs occupied predatory or scavenging niches has been debated for nearly a century1-5. Palaeontologists have turned to the study of dental morphology to address this question, but the results have been highly disparate. Some contend that the tyrannosaur dentition was very strong and well suited for engaging and killing herbivorous dinosaurs6,7. Others posit that tyrannosaurs ate carrion, because their teeth and/or jaws would fail during struggles with prey2,3. The discovery of skeletal remains with bite marks from Tyrannosaurus rex8makes it possible to estimate, through indentation simulations on bovine ilia, the bite forces produced by T. rexduring feeding. The estimates (6,410 to 13,400 N) rival the largest bite forces determined for any taxon to date and suggest that T. rex had very strong, impact-resistant teeth. Although these data do not prove that T. rex was predominantly predacious, they indicate that its dentition could probably withstand the stresses associated with prey capture.
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A crucial task for paleontologists and paleobiologists is the reconstruction of the appearance, movements, and behavior of extinct vertebrates from studies of their bones or other, more rarely preserved parts. A related issue is the boundary between the scientific evidence for reconstruction and the need to resort to imagination. In this book, sixteen paleontologists and biologists discuss these questions, review the current status of functional studies of extinct vertebrates in the context of similar work on living animals, and present a broad philosophical view of the subject's development within the framework of phylogenetic analysis. The authors describe and debate methods for making realistic inferences of function in fossil vertebrates, and present examples where we may be confident that our reconstructions are both detailed and accurate.
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This chapter reviews the functional capacities of fish skeletal structures and tissues, as those capacities have been determined by the measurement of mechanical properties under life‐like loading conditions. The mechanical workings of fishes have been approached in a two-pronged framework, with (1) muscle as the engine of motion and force and (2) water as the external source of resistance and purchase. The interaction of muscle and water certainly lays the foundation for behaviors as diverse as swimming, breathing, and feeding, but the interaction between them is only part of the picture. Understanding fishes as mechanical actors requires study of a third factor: the skeleton. This chapter defines skeleton broadly to include connective tissues such as tendon, ligament, cartilage, and bone that have a large component of extracellular collagen fibers. By measuring the mechanical properties of skeletal tissue and structures, one can begin modeling a few mechanical behaviors of a few species and understanding the integrated function of muscle, water, and skeleton. Even though the skeletal systems of fishes are complicated, analysis is helped by the often clear connection between skeletal structure and mechanical function, particularly when that correlation has convergently evolved. A clear causal connection is easily seen between the teeth and prey processing in heterodontid sharks and in sparid fish: their robust molariform teeth permit the crushing of hard prey such as mollusks and echinoderms.
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Abstract Few species have generated more or longer running controversy than Australia's extinct marsupial lion Thylacoleo carnifex ( Owen, 1859). Over the last century and a half, feeding behaviours as disparate as osteophagy and specialized herbivory have been suggested and T. carnifex has been placed in both phalangeriform and vombatiform clades. Phylogenetic placement remains uncertain, but broad consensus has been achieved regarding diet, with all recent authors agreeing that T. carnifex was a carnivore. However, the marsupial lion's extraordinary cranial and dental morphologies remain without clear analogy, leaving many questions unanswered regarding how this most atypical mammalian predator killed its prey. Here I apply a rapidly emerging new approach in comparative biology, finite-element analysis, to the examination of cranial mechanics in T. carnifex. Comparisons are made with an extant lion Panthera leo (Linnaeus, 1758) under simulations designed to model stress distributions imposed by biting (intrinsic loads) and interaction with struggling prey (extrinsic loads). Modelling that approximates the 3-D architecture of jaw adductors suggests that both the placental and marsupial lions could generate considerably greater bite forces than has been predicted using 2-D approaches, but with relatively greater forces in the marsupial. The distribution of cranial stress is in many respects similar in both species, but results from simulations of extrinsic forces suggest that the marsupial was particularly well adapted to resist the high stresses that would be expected in dealings with relatively large prey. On the other hand, relatively high stress recorded in the rostrum of T. carnifex under intrinsic loadings suggests that it may have deployed a very different modus operandi, wherein the carnassial teeth played an active role in effecting a kill.
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Mechanical properties of cortical and cancellous bone from eight human subjects were determined using an ultrasonic transmission technique. Raw computerized tomography (CT) values obtained from scans of the bones in water were corrected to Hounsfield units. The correlations between CT numbers and mechanical property estimated from cortical bone were found to be low (r2 < 0.2), while these relationships for cancellous bone were found to be higher (r2 > 0.6). These results suggest that CT values may be useful in predicting mechanical properties only for cancellous bone. Poor correlations were found between modulus in the radial or circumferential direction and modulus in the superior-inferior direction for cortical bone, whereas good correlations were found between modulus in the anterior-posterior direction or medial-lateral direction and modulus in the S-I direction for cancellous bone. These results indicate that modulus in the radial or circumferential direction could not be predicted from modulus in the S-I direction for cortical bone, but could be predicted for cancellous bone. The predictive capabilities of linear and power models evaluated for cancellous bone alone were approximately equal. However, the power function gives a better fit of data at the low and high density values. The specific relationships, depending on the types of bone, that predict elastic modulus from density and CT numbers were suggested for human cortical and cancellous bone. These specific correlations may help a number of researchers develop more accurate models; however, these hypotheses should be proven by further study.
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The stingray family Myliobatidae contains five durophagous (hard prey specialist) genera and two planktivorous genera. A suite of morphological features makes it possible for the hard prey specialists to crush mollusks and crustaceans in their cartilaginous jaws. These include: 1) flat, pavement-like tooth plates set in an elastic dental ligament; 2) multiple layers of calcified cartilage on the surface of the jaws; 3) calcified struts running through the jaws; and 4) a lever system that amplifies the force of the jaw adductors. Examination of a range of taxa reveals that the presence of multiple layers of calcified cartilage, previously described from just a few species, is a plesiomorphy of Chondrichthyes. Calcified struts within the jaw, called "trabecular cartilage," are found only in the myliobatid genera, including the planktivorous Manta birostris. In the durophagous taxa, the struts are concentrated under the area where prey is crushed, thereby preventing local buckling of the jaws. Trabecular cartilage develops early in ontogeny, and does not appear to develop as a direct result of the stresses associated with feeding on hard prey. A "nutcracker" model of jaw function is proposed. In this model, the restricted gape, fused mandibular and palatoquadrate symphyses, and asynchronous contraction of the jaw adductors function to amplify the closing force by 2-4 times.
Article
Maximum isometric tetanic force produced by bundles of red muscle fibres from dogfish, Scyliorhinus canicula (L.), was 142.4+/-10.3 kN m(-2) (N=35 fibre bundles); this was significantly less than that produced by white fibres 289.2+/-8.4 kN m(-2) (N=25 fibre bundles) (means +/- S.E.M.). Part, but not all, of the difference is due to mitochondrial content. The maximum unloaded shortening velocity, 1.693+/-0.108 L(0) s(-1) (N=6 fibre bundles), was measured by the slack-test method. L(0) is the length giving maximum isometric force. The force/velocity relationship was investigated using a step-and-ramp protocol in seven red fibre bundles. The following equation was fitted to the data: [(P/P(0))+(a/P(0))](V+b)=[(P(0)(*)/P(0))+(a/P(0))]b, where P is force during shortening at velocity V, P(0) is the isometric force before shortening, and a, b and P(0)(*) are fitted constants. The fitted values were P(0)(*)/P(0)=1.228+/-0.053, V(max)=1.814+/-0.071 L(0) s(-1), a/P(0)=0.269+/-0.024 and b=0.404+/-0.041 L(0) s(-1) (N=7 for all values). The maximum power was 0.107+/-0.005P(0)V(max) and was produced during shortening at 0.297+/-0.012V(max). Compared with white fibres from dogfish, the red fibres have a lower P(0) (49%) and V(max) (48%), but the shapes of the force/velocity curves are similar. Thus, the white and red fibres have equal capacities to produce power within the limits set by the isometric force and maximum velocity of shortening of each fibre type. A step shortening of 0.050+/-0.003L(0) (N=7) reduced the maximum isometric force in the red fibres' series elasticity to zero. The series elasticity includes all elastic structures acting in series with the attached cross-bridges. Three red fibre bundles were stretched at a constant velocity, and force (measured when length reached L(0)) was 1.519+/-0.032P(0). In the range of velocities used here, -0.28 to -0.63V(max), force varied little with the velocity.
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The cartilaginous endoskeleton of chondrichthyan fishes (sharks, rays, and chimaeras) exhibits complex arrangements and morphologies of calcified tissues that vary with age, species, feeding behavior, and location in the body. Understanding of the development, evolutionary history and function of these tissue types has been hampered by the lack of a unifying terminology. In order to facilitate reciprocal illumination between disparate fields with convergent interests, we present levels of organization in which crystal orientation/size delimits three calcification types (areolar, globular, and prismatic) that interact in two distinct skeletal types, vertebral and tessellated cartilage. The tessellated skeleton is composed of small blocks (tesserae) of calcified cartilage (both prismatic and globular) overlying a core of unmineralized cartilage, while vertebral cartilage usually contains all three types of calcification.