Abstract:The giant extinct marsupial Diprotodon optatum has unusual skull morphology for an animal of its size, consisting of very thin bone and large cranial sinuses that occupy most of the internal cranial space. The function of these sinuses is unknown as there are no living marsupial analogues. The finite element method was applied to identify areas of high and low stress, and estimate the bite force of Diprotodon to test hypotheses on the function of the extensive cranial sinuses. Detailed three-dimensional models… Show more
“…This is also the case in T. ornatus, but its values of im∆SEa are only slightly higher than one. This is notable because the main function of the sinuses is thought to be involved in stress dissipation during feeding and to provide skull structural stability (20)(21)(22). However, the analyses of von Mises stress in M. ursinus and U. americanus reveal higher stresses in models with sinuses than in models without sinuses (Figs.…”
Section: Sinus Size and Feeding Biomechanics In Living And Extinct Bearsmentioning
confidence: 98%
“…To test whether the extremely developed sinuses in the cave bear influence its biomechanical performance for feeding behavior, we eliminated virtually the paranasal sinuses by filling the cavities with artificial bone material using Geomagic (21,22). The sinuses have a potential dual effect on feeding biomechanics (i) for having large empty spaces in the paranasal cavities and (ii) for the appearance of a dome as a consequence of sinus inflation on the frontal area.…”
Section: Fea Of the Skull Without Sinusesmentioning
The cave bear is one of the best known extinct large mammals that inhabited Europe during the “Ice Age,” becoming extinct ≈24,000 years ago along with other members of the Pleistocene megafauna. Long-standing hypotheses speculate that many cave bears died during their long hibernation periods, which were necessary to overcome the severe and prolonged winters of the Last Glacial. Here, we investigate how long hibernation periods in cave bears would have directly affected their feeding biomechanics using CT-based biomechanical simulations of skulls of cave and extant bears. Our results demonstrate that although large paranasal sinuses were necessary for, and consistent with, long hibernation periods, trade-offs in sinus-associated cranial biomechanical traits restricted cave bears to feed exclusively on low energetic vegetal resources during the predormancy period. This biomechanical trade-off constitutes a new key factor to mechanistically explain the demise of this dominant Pleistocene megafaunal species as a direct consequence of climate cooling.
“…This is also the case in T. ornatus, but its values of im∆SEa are only slightly higher than one. This is notable because the main function of the sinuses is thought to be involved in stress dissipation during feeding and to provide skull structural stability (20)(21)(22). However, the analyses of von Mises stress in M. ursinus and U. americanus reveal higher stresses in models with sinuses than in models without sinuses (Figs.…”
Section: Sinus Size and Feeding Biomechanics In Living And Extinct Bearsmentioning
confidence: 98%
“…To test whether the extremely developed sinuses in the cave bear influence its biomechanical performance for feeding behavior, we eliminated virtually the paranasal sinuses by filling the cavities with artificial bone material using Geomagic (21,22). The sinuses have a potential dual effect on feeding biomechanics (i) for having large empty spaces in the paranasal cavities and (ii) for the appearance of a dome as a consequence of sinus inflation on the frontal area.…”
Section: Fea Of the Skull Without Sinusesmentioning
The cave bear is one of the best known extinct large mammals that inhabited Europe during the “Ice Age,” becoming extinct ≈24,000 years ago along with other members of the Pleistocene megafauna. Long-standing hypotheses speculate that many cave bears died during their long hibernation periods, which were necessary to overcome the severe and prolonged winters of the Last Glacial. Here, we investigate how long hibernation periods in cave bears would have directly affected their feeding biomechanics using CT-based biomechanical simulations of skulls of cave and extant bears. Our results demonstrate that although large paranasal sinuses were necessary for, and consistent with, long hibernation periods, trade-offs in sinus-associated cranial biomechanical traits restricted cave bears to feed exclusively on low energetic vegetal resources during the predormancy period. This biomechanical trade-off constitutes a new key factor to mechanistically explain the demise of this dominant Pleistocene megafaunal species as a direct consequence of climate cooling.
“…Thus, special attention is needed when trying to predict the biomechanical response of the craniofacial skeleton of extinct species [12]. The individual mechanical properties of the calvarial three-layered system are relevant to understand not only the functional response of the skull, but also its biomechanics, so clinical, functional, and anthropological models of the skull may be evaluated properly [31][32][33]. Additionally, understanding of the mechanical properties of the components of the cranial vault would make possible the development of better synthetic bone substitutes for the cranium [34].…”
Section: Plos Onementioning
confidence: 99%
“…On the other hand, several finite element models (FEM) of the skull have been built using the information available for the engineering sandwich structure and the available mechanical properties. Consequently, most of the FEM of the skull can be grouped into one of four categories: (1) FEM of the skull built using a single isotropic material for an averaged layer in the entire calvarial structure [32]. (2) FEM of the skull including an anisotropic condition of the material for a single layered structure [37].…”
The outer cortical table of the parietal bone has been commonly used as a calvarial bone graft site for the craniofacial reconstruction. However, little is known about how removing the outer table may affect the function and structure of the inner table, and how the knowledge of the biomechanics and material properties of cortical bones will help the calvarial graft to better integrate into the biological and mechanical functions of its surrounding native tissues. In this study, it was hypothesized that there were significant differences in both density and material properties between inner and outer cortical plates in cranial bones. Twelve cylindrical specimens, including inner-outer layers, of cortical parietal bone of a female baboon were collected. Cortical thicknesses and densities were measured, and elastic properties were assessed using an ultrasonic technique. Results demonstrated remarkable difference in both thickness (t = 8.248, p �0.05) and density (t = 4.926, p�0.05) between inner and outer cortical paired samples. Orthotropic characteristics of the cortical plates were detected as well, these findings suggest that there are differences in biomechanical properties between two surfaces of cranial bones at both tissue and organ levels. How these differences are linked to the stress environments of the inner and outer cranial cortical layers awaits further studies. Further study will greatly enhance our ability to address questions derived from both morphological and craniofacial medicine fields about the development and biomechanics of craniofacial skeletons.
“…Yet, typically stress and strain values are only reported and analysed from just a few elements (Porro et al, 2013;Fitton et al, 2012a). Alternatively average or peak stress or strain values can be computed for whole models (Dumont et al, 2011;Cox et al, 2012;Parr et al, 2013;Sharp and Rich, 2016) or selected regions (Wroe et al, 2007a,b;Nakashige et al, 2011).…”
Section: Comparison With Common Techniquesmentioning
Statistical analyses of biomechanical finite element (FE) simulations are frequently conducted on scalar metrics extracted from anatomically homologous regions, like maximum von Mises stresses from demarcated bone areas. Advantages of this approach are numerical tabulability and statistical simplicity, but disadvantages include region demarcation subjectivity, spatial resolution reduction, and results interpretation complexity when attempting to mentally map tabulated results to original anatomy. This study proposes a method which abandons the two aforementioned advantages to overcome these three limitations. The method is inspired by parametric random field theory (RFT), but instead uses a non-parametric analogue to RFT which permits flexible model-wide statistical analyses through non-parametrically constructed probability densities regarding volumetric upcrossing geometry. We illustrate method fundamentals using basic 1D and 2D models, then use a public model of hip cartilage compression to highlight how the concepts can extend to practical biomechanical modeling. The ultimate whole-volume results are easy to interpret, and for constant model geometry the method is simple to implement. Moreover, our analyses demonstrate that the method can yield biomechanical insights which are difficult to infer from single simulations or tabulated multi-simulation results. Generalizability to non-constant geometry including subjectspecific anatomy is discussed.
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