Muscle forces for biting load cases were calculated using a version of Thomason’s ‘dry skull’ method modified for crocodilian jaw muscle anatomy  with the ‘temporalis’ and ‘masseter’ groups  adjusted to ‘temporalis’ (adductor externus, adductor posterior, pseudotemporalis) and ‘pterygoid’ (pterygoidus) groups respectively  (Table 7). No, Is the Subject Area "Skull" applicable to this article? AICc score is a measure of the relative amount of information lost when using an explanatory model to approximate reality, taking into account both the number of parameters in the EM and the sample size. What would I have looked like otherwise? Peak strain (95%) values are plotted against morphometric variables in Figure 26. Google search results numbers show a huge preference of using the over a. 152 mm in M. cataphractus). Department of Anatomy and Developmental Biology, School of Biomedical Sciences, Monash University, Melbourne, Victoria, Australia, But I also know that much of my self-esteem issues originate from years of mockery from the boys at school who teased me mercilessly about my "horse face". Specific tension of jaw muscles is not often measured in reptiles but in Sphenodon punctatus is 89 KPa , a figure that is much greater than isometric values used in our models (30 KPa: ), and this may be a source of error which may also contribute to differences in bite force between our results and experimental findings . The general pattern of. X axis plots the ratio of mandibular length to width, giving a size-controlled proxy for the spectrum of brevisrostral to longirostral morphology. Under simulated bite loads, strain in the beam models correlated positively and linearly with length when symphyseal length also varied (CA-CW-VL-VSL), and with length when symphyseal length did not vary (CSL-CW-VA-VL). The mandible was then meshed such that the average size of tetrahedral elements was approximately the same as the cranium, yielding 2.5 million tetrahedra (+/−10%) (Table 3) for the cranium and mandible combined. It was produced by Chris Sheldon and the band. The chart in the centre shows the value of each morphological variable (e.g. Symphyseal length (SL) does affect Iyy; a longer SL means a reduced Iyy, with a change in Iyy at the junction of the symphysis with the rami. Predicted bite force was consistent between volume scaled FEMs, correlating with outlever length. The response to twisting is best predicted by symphyseal length, while beam models predicted inter-rami angle. In the latter case bite force in longirostrine forms decreases as outlever length increases, so the higher strain may indicate a more gracile mandible in these forms in addition to the effects of increased bending moments acting on the jaws. Whilst comparative approaches are of high value to palaeobiology, they tend to use post hoc analysis and are sometimes difficult to conduct in a way that explicitly tests hypotheses of form and function. Jill had such a long face yesterday after she learned that she failed her exam. Like this video? The largest discrepancy between the beam modelling and FE modelling is for twist loads; the beam models found angle to be the best predictor of strain, whilst the complex FEMs found symphyseal length as the best sole predictor. The accuracy of the isosurface model was measured by averaging the difference between isosurface and segmentation mask diameters as measured at 10 locations on the mandible and cranium. Each linear measurement was tested as an explanatory model (EM) and compared using the second-order Akaike’s Information Criterion, AICc, as recommended in the case of small sample sizes , , . T. schlegelii is clearly separated from the other specimens along the PC1 axis, but not on the PC2. Whilst FEA offers many advantages for biomechanical analysis, the gap between the high accuracy of the FE models and the simple geometry explained by beam theory has meant that the results of high resolution biological FEA are rarely discussed with reference to underlying mechanical principles such as beam theory. The Mechanics of Mandibular ... hypotheses of which morphological variables should control the biomechanical response. For twisting, these teeth are all fully fixed. https://doi.org/10.1371/journal.pone.0053873.g002. Well done withy showing this in your pictures! Yes As twisting and shaking behaviours are used by crocodilians to feed on large prey, these results provide direct correlations between simple morphological variables and feeding ecology. The chart in the centre shows the value of each morphological variable (e.g. Her team looked at the response in domestic horses to whinnies (high pitched neighing) from both familiar and unfamiliar conspecifics. https://doi.org/10.1371/journal.pone.0053873.g010. Deformations are exaggerated to emphasize the structural response to each load simulated and the general pattern of stress is characteristic of all beam models. Free body rotation was prevented by restraining nodes on the skull - restraints prevent translation and/or rotations about a given axis. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The third dimension is undoubtedly important in crocodilian skull biomechanics ,  and is here incorporated in the hi-res FE models (see below). For a given section, the mechanical response will depend only on the length of the whole mandible; the proportion of the mandible that is formed by the symphysis will not affect the area moment of inertia in the dorso-ventral direction (Ixx, about the horizontal x axis), and so symphyseal length is irrelevant. The mandible can be viewed as a ‘Y’ shaped beam configuration with uniform sections and X, Y, and Z axes representing the transverse, dorso-ventral, and longitudinal directions respectively (Figure 4). When people can have bona fide medical conditions all their lives and not even know until middle age, then surely that is an indictment on the poor communication channels between academia, medicine and the public. This lack of a theoretical context means that the analyses do not attempt to test hypotheses of structure/function relationships constructed a priori, but are instead used to describe post-hoc patterns of variation from which underlying generalities might be elucidated. In the scaled models, the diameter of all beam elements was standardised. (Table 4 and Figure 9B). For different specimens, a given quality setting gave a wide range of isosurface accuracy values (‘Average Contour Error’ in Table 2); presumably because of the different scan resolutions between specimens. Correlation with symphyseal length was positive and linear for models where symphyseal length varied (CA-CW-VL-VSL), but strain did not vary between models when symphyseal length was constant (CL-CSL-VA-VW, CSL-CW-VA-VL). We therefore created four sets of models, within which two of the measurements were kept constant while two co-varied (Figure 10); Model variations used to explore relationship between strain and linear variables in the first set of beam models. https://doi.org/10.1371/journal.pone.0053873.g027, https://doi.org/10.1371/journal.pone.0053873.t017. Width is inversely correlated with the other variables along PC1, whereas along PC2 changes in SL, W, and A are correlated. While material properties for bone are considerably different to steel, the results indicate relative performance of each beam model; additionally, under assumed linear behaviour, stresses or strains in other materials can easily be calculated from a given result. the simple variables that best explain variation in strain between beam models will also best explain variation in strain between complex FE models. Ruby Hamad, right, flashes her gummy smile. A bad bite results in the wearing away of teeth (which is how mine was finally caught), which can make chewing difficult and lead to costly crowns and bridges. In the plots of strain against length and symphyseal length in twisting, T. schlegelii appears to be an outlier while the data points for the other specimens suggest a negative relationship between length and symphyseal length for strain in twisting, but again these lack explanatory power under Akaike scores. PLOS ONE promises fair, rigorous peer review, How can mouth breathing make the upper jaw grow long? Taxa shown are Caiman latirostris (A), Gavialis gangeticus (B), Feresa attenuata (C), Platanista gangetica (D), Leptocleidus capensis (E), Dolichorhynchops osborni (F), Temnodontosaurus eurycephalus (G), Ophthalmosaurus icenicus (H), Suchodus brachyrhynchus (I), Steneosaurus gracilirostris (J). 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