1
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Cox PG, Watson PJ. Masticatory biomechanics of red and grey squirrels ( Sciurus vulgaris and Sciurus carolinensis) modelled with multibody dynamics analysis. ROYAL SOCIETY OPEN SCIENCE 2023; 10:220587. [PMID: 36816846 PMCID: PMC9929510 DOI: 10.1098/rsos.220587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 01/26/2023] [Indexed: 06/18/2023]
Abstract
The process of feeding in mammals is achieved by moving the mandible relative to the cranium to bring the teeth into and out of occlusion. This process is especially complex in rodents which have a highly specialized configuration of jaw adductor muscles. Here, we used the computational technique of multi-body dynamics analysis (MDA) to model feeding in the red (Sciurus vulgaris) and grey squirrel (Sciurus carolinensis) and determine the relative contribution of each jaw-closing muscle in the generation of bite forces. The MDA model simulated incisor biting at different gapes. A series of 'virtual ablation experiments' were performed at each gape, whereby the activation of each bilateral pair of muscles was set to zero. The maximum bite force was found to increase at wider gapes. As predicted, the superficial and anterior deep masseter were the largest contributors to bite force, but the temporalis had only a small contribution. Further analysis indicated that the temporalis may play a more important role in jaw stabilization than in the generation of bite force. This study demonstrated the ability of MDA to elucidate details of red and grey squirrel feeding biomechanics providing a complement to data gathered via in vivo experimentation.
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Affiliation(s)
- Philip G. Cox
- Department of Cell and Developmental Biology, University College London, London, UK
- Department of Archaeology, University of York, York, UK
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2
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Functional morphology of the jaw adductor muscles in the Canidae. Anat Rec (Hoboken) 2020; 303:2878-2903. [DOI: 10.1002/ar.24391] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 01/18/2020] [Accepted: 01/25/2020] [Indexed: 12/17/2022]
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3
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Zherebtsova OV, Potapova EG. Pathways and Level of Morphological Adaptations in Modern Diatomyidae and Ctenodactylidae (Rodentia). BIOL BULL+ 2020. [DOI: 10.1134/s1062359019070124] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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4
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Álvarez A, Ercoli MD, Verzi DH. Integration and diversity of the caviomorph mandible (Rodentia: Hystricomorpha): assessing the evolutionary history through fossils and ancestral shape reconstructions. Zool J Linn Soc 2019. [DOI: 10.1093/zoolinnean/zlz071] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
AbstractCaviomorph rodents constitute a highly diverse clade of Neotropical mammals. They are recorded since at least the late Middle Eocene and have a long and complex evolutionary history. Using geometric morphometric data, we analysed the variation in mandibular shape of this clade through integration analyses, allometry and shape optimizations onto a phylogenetic tree of 104 extant and extinct species. The analyses of shape variation revealed a strong influence of phylogenetic structure and life habits. A remarkable allometric effect was observed for specific mandibular traits. Morphological changes occurring in the alveolar and muscular functional units were moderately associated. Interestingly, the coordinated evolution of these two functional units was decoupled in the clade of extant abrocomids. A sequential and nearly synchronic acquisition of convergent traits has occurred in chinchillids and derived cavioids since at least the early Middle Oligocene, probably derived from grass-feeding habits or similar adaptations to other abrasive items. Convergences between fossorial taxa evolved in two main events through the Oligocene and middle Late Miocene. Morphological analysis of the fossil representatives allowed a better understanding of the timing of trait acquisitions during the evolutionary history of caviomorphs and its relationship with global and regional palaeoenvironmental changes.
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Affiliation(s)
- Alicia Álvarez
- Instituto de Ecorregiones Andinas (INECOA), Universidad Nacional de Jujuy, CONICET, IdGyM, San Salvador de Jujuy, Jujuy, Argentina
| | - Marcos D Ercoli
- Instituto de Ecorregiones Andinas (INECOA), Universidad Nacional de Jujuy, CONICET, IdGyM, San Salvador de Jujuy, Jujuy, Argentina
| | - Diego H Verzi
- Sección Mastozoología, Museo de La Plata, CONICET, La Plata, Buenos Aires, Argentina
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5
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D’Elía G, Fabre PH, Lessa EP. Rodent systematics in an age of discovery: recent advances and prospects. J Mammal 2019. [DOI: 10.1093/jmammal/gyy179] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Affiliation(s)
- Guillermo D’Elía
- Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile
| | - Pierre-Henri Fabre
- Institut des Sciences de l’Evolution (ISEM, UMR 5554 CNRS-UM2-IRD), Université Montpellier, Montpellier Cedex 5, France
| | - Enrique P Lessa
- Departamento de Ecología y Evolución, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
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6
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Adams NF, Rayfield EJ, Cox PG, Cobb SN, Corfe IJ. Functional tests of the competitive exclusion hypothesis for multituberculate extinction. ROYAL SOCIETY OPEN SCIENCE 2019; 6:181536. [PMID: 31032010 PMCID: PMC6458384 DOI: 10.1098/rsos.181536] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 02/21/2019] [Indexed: 05/08/2023]
Abstract
Multituberculate mammals thrived during the Mesozoic, but their diversity declined from the mid-late Paleocene onwards, becoming extinct in the late Eocene. The radiation of superficially similar, eutherian rodents has been linked to multituberculate extinction through competitive exclusion. However, characteristics providing rodents with a supposed competitive advantage are currently unknown and comparative functional tests between the two groups are lacking. Here, a multifaceted approach to craniomandibular biomechanics was taken to test the hypothesis that superior skull function made rodents more effective competitors. Digital models of the skulls of four extant rodents and the Upper Cretaceous multituberculate Kryptobaatar were constructed and used (i) in finite-element analysis to study feeding-induced stresses, (ii) to calculate metrics of bite force production and (iii) to determine mechanical resistances to bending and torsional forces. Rodents exhibit higher craniomandibular stresses and lower resistances to bending and torsion than the multituberculate, apparently refuting the competitive exclusion hypothesis. However, rodents optimize bite force production at the expense of higher skull stress and we argue that this is likely to have been more functionally and selectively important. Our results therefore provide the first functional lines of evidence for potential reasons behind the decline of multituberculates in the changing environments of the Paleogene.
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Affiliation(s)
- Neil F. Adams
- School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK
- Author for correspondence: Neil F. Adams e-mail:
| | - Emily J. Rayfield
- School of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK
- Author for correspondence: Emily J. Rayfield e-mail:
| | - Philip G. Cox
- Department of Archaeology, University of York, York YO1 7EP, UK
- Centre for Anatomical and Human Sciences, Hull York Medical School, University of York, York YO10 5DD, UK
| | - Samuel N. Cobb
- Department of Archaeology, University of York, York YO1 7EP, UK
- Centre for Anatomical and Human Sciences, Hull York Medical School, University of York, York YO10 5DD, UK
| | - Ian J. Corfe
- Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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7
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Carvalhaes JG, Cordeiro-Estrela P, Hohl LSL, Vilela RV, D'Andrea PS, Rocha-Barbosa O. Variation in the skull morphometry of four taxonomic units of Thrichomys (Rodentia: Echimyidae), from different Neotropical biomes. J Morphol 2019; 280:436-445. [PMID: 30747455 DOI: 10.1002/jmor.20955] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 01/04/2019] [Accepted: 01/08/2019] [Indexed: 11/10/2022]
Abstract
The echimyid rodents of the genus Thrichomys vary considerably in their behavior and feeding ecology, reflecting their occurrence in environments as different as the Caatinga, Cerrado, Pantanal, and Chaco biomes. While the genus was originally classified as monospecific, a number of Thrichomys species have been recognized in recent decades, based on morphometric, cytogenetic, and molecular analyses. While Thrichomys is well studied, the variation found in its cranial morphology is poorly understood, given the taxonomic and ecological complexities of the genus. Using a geometric morphometric approach, we characterized the differences found in the cranial morphology of four Thrichomys taxonomic units, including three established species, Thrichomys apereoides, Thrichomys fosteri, and Thrichomys laurentius, and one operational taxonomic unit (OTU), Thrichomys aff. laurentius. No significant differences were found among these units in cranium size, but significant variation was found in skull shape. The Procrustes distances provided a quantification of the differences in the shape of the skull, with the largest distances being found between T. aff. laurentius and T. fosteri in the dorsal view, and between T. aff. laurentius and T. apereoides in the ventral view. A Discriminant Function Analysis (DFA) with cross-validation determined that the pairings with the highest correct classification were T. aff. laurentius vs. T. apereoides and T. aff. laurentius vs. T. fosteri, in both views. The principal variation in skull shape was found in the posterior region and the zygomatic arch, which may be related to differences in diet.
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Affiliation(s)
- Jeiel G Carvalhaes
- Laboratório de Biologia e Parasitologia de Mamíferos Silvestres Reservatórios, Instituto Oswaldo Cruz/Fiocruz, Rio de Janeiro, RJ, Brazil.,Programa de Pós-graduação Stricto sensu em Biodiversidade e Saúde, Instituto Oswaldo Cruz/Fiocruz, Rio de Janeiro, RJ, Brazil
| | - Pedro Cordeiro-Estrela
- Laboratório de Mamíferos, Departamento de Sistemática e Ecologia, CCEN, Universidade Federal da Paraíba, Joáo Pessoa, PB, Brazil
| | - Leandro S L Hohl
- Laboratório de Zoologia de Vertebrados Tetrapoda - LAZOVERTE, Departamento de Zoologia, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brazil.,Coordenação de Biologia, Centro Federal de Educação Tecnológica Celso Suckow da Fonseca - CEFET/RJ, Rio de Janeiro, RJ, Brazil
| | - Roberto V Vilela
- Laboratório de Biologia e Parasitologia de Mamíferos Silvestres Reservatórios, Instituto Oswaldo Cruz/Fiocruz, Rio de Janeiro, RJ, Brazil
| | - Paulo S D'Andrea
- Laboratório de Biologia e Parasitologia de Mamíferos Silvestres Reservatórios, Instituto Oswaldo Cruz/Fiocruz, Rio de Janeiro, RJ, Brazil
| | - Oscar Rocha-Barbosa
- Laboratório de Zoologia de Vertebrados Tetrapoda - LAZOVERTE, Departamento de Zoologia, Instituto de Biologia Roberto Alcantara Gomes, Universidade do Estado do Rio de Janeiro, Rio de Janeiro, RJ, Brazil
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8
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9
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Cox PG. The jaw is a second-class lever in Pedetes capensis (Rodentia: Pedetidae). PeerJ 2017; 5:e3741. [PMID: 28875081 PMCID: PMC5581530 DOI: 10.7717/peerj.3741] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 08/05/2017] [Indexed: 11/23/2022] Open
Abstract
The mammalian jaw is often modelled as a third-class lever for the purposes of biomechanical analyses, owing to the position of the resultant muscle force between the jaw joint and the teeth. However, it has been proposed that in some rodents the jaws operate as a second-class lever during distal molar bites, owing to the rostral position of the masticatory musculature. In particular, the infraorbital portion of the zygomatico-mandibularis (IOZM) has been suggested to be of major importance in converting the masticatory system from a third-class to a second-class lever. The presence of the IOZM is diagnostic of the hystricomorph rodents, and is particularly well-developed in Pedetes capensis, the South African springhare. In this study, finite element analysis (FEA) was used to assess the lever mechanics of the springhare masticatory system, and to determine the function of the IOZM. An FE model of the skull of P. capensis was constructed and loaded with all masticatory muscles, and then solved for biting at each tooth in turn. Further load cases were created in which each masticatory muscle was removed in turn. The analyses showed that the mechanical advantage of the springhare jaws was above one at all molar bites and very close to one during the premolar bite. Removing the IOZM or masseter caused a drop in mechanical advantage at all bites, but affected strain patterns and cranial deformation very little. Removing the ZM had only a small effect on mechanical advantage, but produced a substantial reduction in strain and deformation across the skull. It was concluded that the masticatory system of P. capensis acts as a second class lever during bites along almost the entire cheek tooth row. The IOZM is clearly a major contributor to this effect, but the masseter also has a part to play. The benefit of the IOZM is that it adds force without substantially contributing to strain or deformation of the skull. This may help explain why the hystricomorphous morphology has evolved multiple times independently within Rodentia.
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Affiliation(s)
- Philip G Cox
- Department of Archaeology, University of York, York, UK.,Hull York Medical School, University of York, York, UK
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10
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Smith AL, Grosse IR. The Biomechanics of Zygomatic Arch Shape. Anat Rec (Hoboken) 2017; 299:1734-1752. [PMID: 27870343 DOI: 10.1002/ar.23484] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 06/11/2016] [Accepted: 07/11/2016] [Indexed: 11/05/2022]
Abstract
Mammalian zygomatic arch shape is remarkably variable, ranging from nearly cylindrical to blade-like in cross section. Based on geometry, the arch can be hypothesized to be a sub-structural beam whose ability to resist deformation is related to cross sectional shape. We expect zygomatic arches with different cross sectional shapes to vary in the degree to which they resist local bending and torsion due to the contraction of the masseter muscle. A stiffer arch may lead to an increase in the relative proportion of applied muscle load being transmitted through the arch to other cranial regions, resulting in elevated cranial stress (and thus, strain). Here, we examine the mechanics of the zygomatic arch using a series of finite element modeling experiments in which the cross section of the arch of Pan troglodytes has been modified to conform to idealized shapes (cylindrical, elliptical, blade-like). We find that the shape of the zygomatic arch has local effects on stain that do not conform to beam theory. One exception is that possessing a blade-like arch leads to elevated strains at the postorbital zygomatic junction and just below the orbits. Furthermore, although modeling the arch as solid cortical bone did not have the effect of elevating strains in other parts of the face, as had been expected, it does have a small effect on stress associated with masseter contraction. These results are counterintuitive. Even though the arch has simple beam-like geometry, we fail to find a simple mechanical explanation for the diversity of arch shape. Anat Rec, 299:1734-1752, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Amanda L Smith
- Department of Anthropology, Washington University in St. Louis, One Brookings Drive, St. Louis, Missouri, 63130
| | - Ian R Grosse
- Department of Mechanical & Industrial Engineering, University of Massachusetts, 160 Governor's Drive, Amherst, Massachusetts, 01003-2210
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11
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Fabre PH, Herrel A, Fitriana Y, Meslin L, Hautier L. Masticatory muscle architecture in a water-rat from Australasia (Murinae, Hydromys) and its implication for the evolution of carnivory in rodents. J Anat 2017; 231:380-397. [PMID: 28585258 DOI: 10.1111/joa.12639] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/11/2017] [Indexed: 01/29/2023] Open
Abstract
Murines are well known for their generalist diet, but several of them display specializations towards a carnivorous diet such as the amphibious Indo-Pacific water-rats. Despite the fact that carnivory evolved repeatedly in this group, few studies have investigated associated changes in jaw muscle anatomy and biomechanics. Here, we describe the jaw muscles and cranial anatomy of a carnivorous water-rat, Hydromys chrysogaster. The architecture of the jaw musculature of six specimens captured both on Obi and Papua were studied and described using dissections. We identified the origin and insertions of the jaw muscles, and quantified muscle mass, fiber length, physiological cross-sectional area, and muscle vectors for each muscle. Using a biomechanical model, we estimated maximum incisor and molar bite force at different gape angles. Finally, we conducted a 2D geometric morphometric analyses to compare jaw shape, mechanical potential, and diversity in lever-arm ratios for a set of 238 specimens, representative of Australo-Papuan carnivorous and omnivorous murids. Our study reveals major changes in the muscle proportions among Hydromys and its omnivorous close relative, Melomys. Hydromys was found to have large superficial masseter and temporalis muscles as well as a reduced deep masseter and zygomatico-mandibularis, highlighting major functional divergence among omnivorous and carnivorous murines. Changes in these muscles are also accompanied by changes in jaw shape and the lines of action of the muscles. A more vertically oriented masseter, reduced masseteric muscles, as well as an elongated jaw with proodont lower incisors are key features indicative of a reduced propalinality in carnivorous Hydromys. Differences in the fiber length of the masseteric muscles were also detected between Hydromys and Melomys, which highlight potential adaptations to a wide gape in Hydromys, allowing it to prey on larger animals. Using a biomechanical model, we inferred a greater bite force in Hydromys than in Melomys, implying a functional shift between omnivory and carnivory. However, Melomys has an unexpected greater bite force at large gape compared with Hydromys. Compared with omnivorous Melomys, Hydromys have a very distinctive low mandible with a well-developed coronoid process, and a reduced angular process that projects posteriorly to the ascending rami. This jaw shape, along with our mechanical potential and jaw lever ratio estimates, suggests that Hydromys has a faster jaw closing at the incisor, with a higher bite force at the level of the molars. The narrowing of the Hydromys jaw explains this higher lever advantage at the molars, which constitutes a good compromise between a wide gape, a reduced anterior masseteric mass, and long fiber lengths. Lever arms of the superficial and deep masseter are less favourable to force output of the mandible in Hydromys but more favourable to speed. Compared with the small input lever arm defined between the condyle and the angular process, the relatively longer mandible of Hydromys increases the speed at the expense of the output force. This unique combination of morphological features of the masticatory apparatus possibly has permitted Hydromys to become a highly successful amphibious predator in the Indo-Pacific region.
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Affiliation(s)
- P-H Fabre
- Institut des Sciences de l'Evolution (ISEM, UMR 5554 CNRS), Universite Montpellier II, Montpellier, France.,National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,Harvard Museum of Comparative Zoology, Cambridge, MA, USA
| | - A Herrel
- Département d'Ecologie et de Gestion de la Biodiversité, UMR 7179 C.N.R.S/M.N.H.N., Paris, France.,Evolutionary Morphology of Vertebrates, Ghent University, Gent, Belgium
| | - Y Fitriana
- Museum Zoologicum Bogoriense, Research Center For Biology, Indonesian Institute of Sciences (LIPI), Cibinong, Indonesia
| | - L Meslin
- Institut des Sciences de l'Evolution (ISEM, UMR 5554 CNRS), Universite Montpellier II, Montpellier, France
| | - L Hautier
- Institut des Sciences de l'Evolution (ISEM, UMR 5554 CNRS), Universite Montpellier II, Montpellier, France
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12
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Tsouknidas A, Jimenez-Rojo L, Karatsis E, Michailidis N, Mitsiadis TA. A Bio-Realistic Finite Element Model to Evaluate the Effect of Masticatory Loadings on Mouse Mandible-Related Tissues. Front Physiol 2017; 8:273. [PMID: 28536534 PMCID: PMC5422518 DOI: 10.3389/fphys.2017.00273] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 04/18/2017] [Indexed: 01/29/2023] Open
Abstract
Mice are arguably the dominant model organisms for studies investigating the effect of genetic traits on the pathways to mammalian skull and teeth development, thus being integral in exploring craniofacial and dental evolution. The aim of this study is to analyse the functional significance of masticatory loads on the mouse mandible and identify critical stress accumulations that could trigger phenotypic and/or growth alterations in mandible-related structures. To achieve this, a 3D model of mouse skulls was reconstructed based on Micro Computed Tomography measurements. Upon segmenting the main hard tissue components of the mandible such as incisors, molars and alveolar bone, boundary conditions were assigned on the basis of the masticatory muscle architecture. The model was subjected to four loading scenarios simulating different feeding ecologies according to the hard or soft type of food and chewing or gnawing biting movement. Chewing and gnawing resulted in varying loading patterns, with biting type exerting a dominant effect on the stress variations experienced by the mandible and loading intensity correlating linearly to the stress increase. The simulation provided refined insight on the mechanobiology of the mouse mandible, indicating that food consistency could influence micro evolutionary divergence patterns in mandible shape of rodents.
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Affiliation(s)
- Alexander Tsouknidas
- Laboratory of Mechanical Engineering Systems, Department of Mechanical Engineering, University of Western MacedoniaKozani, Greece.,Physical Metallurgy Laboratory, Department of Mechanical Engineering, Aristotle University of ThessalonikiThessaloniki, Greece
| | - Lucia Jimenez-Rojo
- Orofacial Development and Regeneration, Institute of Oral Biology, ZZM, University of ZurichZurich, Switzerland
| | | | - Nikolaos Michailidis
- Physical Metallurgy Laboratory, Department of Mechanical Engineering, Aristotle University of ThessalonikiThessaloniki, Greece
| | - Thimios A Mitsiadis
- Orofacial Development and Regeneration, Institute of Oral Biology, ZZM, University of ZurichZurich, Switzerland
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McIntosh AF, Cox PG. The impact of gape on the performance of the skull in chisel-tooth digging and scratch digging mole-rats (Rodentia: Bathyergidae). ROYAL SOCIETY OPEN SCIENCE 2016; 3:160568. [PMID: 27853575 PMCID: PMC5099000 DOI: 10.1098/rsos.160568] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 09/09/2016] [Indexed: 05/24/2023]
Abstract
The African mole-rats (Bathyergidae) are a family of rodents highly adapted for life underground. Previous research has shown that chisel-tooth digging mole-rats (which use their incisors to dig burrows) are clearly distinguishable from scratch diggers (which only use the forelimbs to tunnel) on the basis of morphology of the skull, and that the differences are linked to the production of high bite forces and wide gapes. We hypothesized that the skull of a chisel-tooth digging mole-rat would perform better at wider gapes than that of a scratch digging mole-rat during incisor biting. To test this hypothesis, we created finite-element models of the cranium of the scratch digging Bathyergus suillus and the chisel-tooth digging Fukomys mechowii, and loaded them to simulate incisor bites at different gapes. Muscle loads were scaled such that the ratio of force to surface area was the same in both models. We measured three performance variables: overall stress across the cranium, mechanical efficiency of biting and degree of deformation across the skull. The Fukomys model had a more efficient incisor bite at all gapes, despite having greater average stress across the skull. In addition, the Fukomys model deformed less at wider gapes, whereas the Bathyergus model deformed less at narrower gapes. These properties of the cranial morphology of Fukomys and Bathyergus are congruent with their respective chisel-tooth and scratch digging behaviours and, all other factors being equal, would enable the more efficient production of bite force at wider gapes in Fukomys. However, in vivo measurements of muscle forces and activation patterns are needed to fully understand the complex biomechanics of tooth digging.
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Affiliation(s)
- Andrew F. McIntosh
- Centre for Anatomical and Human Sciences, Hull York Medical School, University of Hull, Hull, UK
| | - Philip G. Cox
- Centre for Anatomical and Human Sciences, Hull York Medical School, University of York, York, UK
- Department of Archaeology, University of York, York, UK
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14
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Maestri R, Patterson BD, Fornel R, Monteiro LR, de Freitas TRO. Diet, bite force and skull morphology in the generalist rodent morphotype. J Evol Biol 2016; 29:2191-2204. [DOI: 10.1111/jeb.12937] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 06/17/2016] [Accepted: 07/05/2016] [Indexed: 01/23/2023]
Affiliation(s)
- R. Maestri
- Programa de Pós-Graduação em Ecologia; Universidade Federal do Rio Grande do Sul; Porto Alegre RS Brazil
| | - B. D. Patterson
- Integrative Research Center; Field Museum of Natural History; Chicago IL USA
| | - R. Fornel
- Programa de Pós-Graduação em Ecologia; Universidade Regional Integrada do Alto Uruguai e das Missões; Erechim RS Brazil
| | - L. R. Monteiro
- Laboratório de Ciências Ambientais; CBB; Universidade Estadual do Norte Fluminense; Campos dos Goytacazes RJ Brazil
| | - T. R. O. de Freitas
- Programa de Pós-Graduação em Ecologia; Universidade Federal do Rio Grande do Sul; Porto Alegre RS Brazil
- Departamento de Genética; Universidade Federal do Rio Grande do Sul; Porto Alegre RS Brazil
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15
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First Approach to the Paleobiology of Extinct Prospaniomys (Rodentia, Hystricognathi, Octodontoidea) Through Head Muscle Reconstruction and the Study of Craniomandibular Shape Variation. J MAMM EVOL 2015. [DOI: 10.1007/s10914-015-9291-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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Cox PG, Rinderknecht A, Blanco RE. Predicting bite force and cranial biomechanics in the largest fossil rodent using finite element analysis. J Anat 2015; 226:215-23. [PMID: 25652795 DOI: 10.1111/joa.12282] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2015] [Indexed: 11/27/2022] Open
Abstract
Josephoartigasia monesi, from the Pliocene of Uruguay, is the largest known fossil rodent, with an estimated body mass of 1000 kg. In this study, finite element analysis was used to estimate the maximum bite force that J. monesi could generate at the incisors and the cheek teeth. Owing to uncertainty in the model inputs, a sensitivity study was conducted in which the muscle forces and orientations were sequentially altered. This enabled conclusions to be drawn on the function of some of the masticatory muscles. It was found that J. monesi had a bite of 1389 N at the incisors, rising to 4165 N at the third molar. Varying muscle forces by 20% and orientations by 10° around the medio-lateral aspect led to an error in bite force of under 35% at each tooth. Predicted stresses across the skull were only minimally affected by changes to muscle forces and orientations, but revealed a reasonable safety factor in the strength of the skull. These results, combined with previous work, lead us to speculate that J. monesi was behaving in an elephant-like manner, using its incisors like tusks, and processing tough vegetation with large bite forces at the cheek teeth.
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Affiliation(s)
- Philip G Cox
- Department of Archaeology and Hull York Medical School, University of York, York, UK
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