1
|
Marghoub A, Kéver L, Williams CJA, Abzhanov A, Vickaryous M, Herrel A, Evans SE, Moazen M. The role of cranial osteoderms on the mechanics of the skull in scincid lizards. Anat Rec (Hoboken) 2023; 306:2415-2424. [PMID: 36748783 DOI: 10.1002/ar.25168] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 01/04/2023] [Accepted: 01/04/2023] [Indexed: 02/08/2023]
Abstract
Osteoderms (ODs) are calcified organs formed directly within the skin of most major extant tetrapod lineages. Lizards possibly show the greatest diversity in ODs morphology and distribution. ODs are commonly hypothesized to function as a defensive armor. Here we tested the hypothesis that cranial osteoderms also contribute to the mechanics of the skull during biting. A series of in vivo experiments were carried out on three specimens of Tiliqua gigas. Animals were induced to bite a force plate while a single cranial OD was strain gauged. A finite element (FE) model of a related species, Tiliqua scincoides, was developed and used to estimate the level of strain across the same OD as instrumented in the in vivo experiments. FE results were compared to the in vivo data and the FE model was modified to test two hypothetical scenarios in which all ODs were (i) removed from, and (ii) fused to, the skull. In vivo data demonstrated that the ODs were carrying load during biting. The hypothetical FE models showed that when cranial ODs were fused to the skull, the overall strain across the skull arising from biting was reduced. Removing the ODs showed an opposite effect. In summary, our findings suggest that cranial ODs contribute to the mechanics of the skull, even when they are loosely attached.
Collapse
Affiliation(s)
- Arsalan Marghoub
- Department of Mechanical Engineering, University College London, London, UK
| | - Loïc Kéver
- Département Adaptations du Vivant, Bâtiment, UMR 7179 MECADEV C.N.R.S/M.N.H.N, d'Anatomie Comparée, Paris, France
| | - Catherine J A Williams
- Department of Biology, Aarhus University, Aarhus C, Denmark
- Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Arkhat Abzhanov
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, Silkwood Park Campus, Berkshire, UK
| | - Matthew Vickaryous
- Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Anthony Herrel
- Département Adaptations du Vivant, Bâtiment, UMR 7179 MECADEV C.N.R.S/M.N.H.N, d'Anatomie Comparée, Paris, France
| | - Susan E Evans
- Centre for Integrative Anatomy, Department of Cell and Developmental Biology, University College London, London, UK
| | - Mehran Moazen
- Department of Mechanical Engineering, University College London, London, UK
| |
Collapse
|
2
|
Sharp AC, Dutel H, Watson PJ, Gröning F, Crumpton N, Fagan MJ, Evans SE. Assessment of the mechanical role of cranial sutures in the mammalian skull: Computational biomechanical modelling of the rat skull. J Morphol 2023; 284:e21555. [PMID: 36630615 PMCID: PMC10107956 DOI: 10.1002/jmor.21555] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 01/03/2023] [Accepted: 01/05/2023] [Indexed: 01/13/2023]
Abstract
Cranial sutures are fibrocellular joints between the skull bones that are progressively replaced with bone throughout ontogeny, facilitating growth and cranial shape change. This transition from soft tissue to bone is reflected in the biomechanical properties of the craniofacial complex. However, the mechanical significance of cranial sutures has only been explored at a few localised areas within the mammalian skull, and as such our understanding of suture function in overall skull biomechanics is still limited. Here, we sought to determine how the overall strain environment is affected by the complex network of cranial sutures in the mammal skull. We combined two computational biomechanical methods, multibody dynamics analysis and finite element analysis, to simulate biting in a rat skull and compared models with and without cranial sutures. Our results show that including complex sutures in the rat model does not substantially change overall strain gradients across the cranium, particularly strain magnitudes in the bones overlying the brain. However, local variations in strain magnitudes and patterns can be observed in areas close to the sutures. These results show that, during feeding, sutures may be more important in some regions than others. Sutures should therefore be included in models that require accurate local strain magnitudes and patterns of cranial strain, particularly if models are developed for analysis of specific regions, such as the temporomandibular joint or zygomatic arch. Our results suggest that, for mammalian skulls, cranial sutures might be more important for allowing brain expansion during growth than redistributing biting loads across the cranium in adults.
Collapse
Affiliation(s)
- Alana C Sharp
- Department of Musculoskeletal and Ageing Sciences, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK.,Department of Cell and Developmental Biology, University College London, London, UK
| | - Hugo Dutel
- Department of Engineering, University of Hull, Hull, UK.,Faculty of Science, School of Earth Sciences, University of Bristol, Bristol, UK
| | | | - Flora Gröning
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, UK
| | - Nick Crumpton
- Department of Cell and Developmental Biology, University College London, London, UK
| | | | - Susan E Evans
- Department of Cell and Developmental Biology, University College London, London, UK
| |
Collapse
|
3
|
Deeming DC. Inter‐relationships among body mass, body dimensions, jaw musculature and bite force in reptiles. J Zool (1987) 2022. [DOI: 10.1111/jzo.12981] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- D. C. Deeming
- Joseph Banks Laboratories Department of Life Sciences School of Life and Environmental Sciences University of Lincoln Lincoln UK
| |
Collapse
|
4
|
Dickinson E, Davis JS, Deutsch AR, Patel D, Nijhawan A, Patel M, Blume A, Gannon JL, Turcotte CM, Walker CS, Hartstone-Rose A. Evaluating bony predictors of bite force across the order Carnivora. J Morphol 2021; 282:1499-1513. [PMID: 34313337 DOI: 10.1002/jmor.21400] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 06/30/2021] [Accepted: 07/18/2021] [Indexed: 12/28/2022]
Abstract
In carnivorans, bite force is a critical and ecologically informative variable that has been correlated with multiple morphological, behavioral, and environmental attributes. Whereas in vivo measures of biting performance are difficult to obtain in many taxa-and impossible in extinct species-numerous osteological proxies exist for estimating masticatory muscle size and force. These proxies include both volumetric approximations of muscle dimensions and direct measurements of muscular attachment sites. In this study, we compare three cranial osteological techniques for estimating muscle size (including 2D-photographic and 3D-surface data approaches) against dissection-derived muscle weights and physiological cross-sectional area (PCSA) within the jaw adductor musculature of 40 carnivoran taxa spanning eight families, four orders of magnitude in body size, and the full dietary spectrum of the order. Our results indicate that 3D-approaches provide more accurate estimates of muscle size than do surfaces measured from 2D-lateral photographs. However, estimates of a muscle's maximum cross-sectional area are more closely correlated with muscle mass and PCSA than any estimates derived from muscle attachment areas. These findings highlight the importance of accounting for muscle thickness in osteological estimations of the masticatory musculature; as muscles become volumetrically larger, their larger cross-sectional area does not appear to be associated with a proportional increase in the attachment site area. Though volumetric approaches approximate muscle dimensions well across the order as a whole, caution should be exercised when applying any single method as a predictor across diverse phylogenies.
Collapse
Affiliation(s)
- Edwin Dickinson
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Jillian S Davis
- Pathology, Anatomy, and Laboratory Medicine Department, West Virginia University School of Medicine, Morgantown, West Virginia, USA
| | - Ashley R Deutsch
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Dhuru Patel
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Akash Nijhawan
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Meet Patel
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Abby Blume
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Jordan L Gannon
- Biology Department, High Point University, High Point, North Carolina, USA
| | - Cassandra M Turcotte
- Department of Anthropology, New York University, New York, New York, USA.,New York Consortium in Evolutionary Primatology, New York, New York, USA
| | - Christopher S Walker
- Department of Molecular Biomedical Sciences, North Carolina State University, Raleigh, North Carolina, USA
| | - Adam Hartstone-Rose
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina, USA
| |
Collapse
|
5
|
Computational biomechanical modelling of the rabbit cranium during mastication. Sci Rep 2021; 11:13196. [PMID: 34162932 PMCID: PMC8222361 DOI: 10.1038/s41598-021-92558-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 06/08/2021] [Indexed: 11/08/2022] Open
Abstract
Although a functional relationship between bone structure and mastication has been shown in some regions of the rabbit skull, the biomechanics of the whole cranium during mastication have yet to be fully explored. In terms of cranial biomechanics, the rabbit is a particularly interesting species due to its uniquely fenestrated rostrum, the mechanical function of which is debated. In addition, the rabbit processes food through incisor and molar biting within a single bite cycle, and the potential influence of these bite modes on skull biomechanics remains unknown. This study combined the in silico methods of multi-body dynamics and finite element analysis to compute musculoskeletal forces associated with a range of incisor and molar biting, and to predict the associated strains. The results show that the majority of the cranium, including the fenestrated rostrum, transmits masticatory strains. The peak strains generated over all bites were found to be attributed to both incisor and molar biting. This could be a consequence of a skull shape adapted to promote an even strain distribution for a combination of infrequent incisor bites and cyclic molar bites. However, some regions, such as the supraorbital process, experienced low peak strain for all masticatory loads considered, suggesting such regions are not designed to resist masticatory forces.
Collapse
|
6
|
Dutel H, Gröning F, Sharp AC, Watson PJ, Herrel A, Ross CF, Jones MEH, Evans SE, Fagan MJ. Comparative cranial biomechanics in two lizard species: impact of variation in cranial design. J Exp Biol 2021; 224:jeb.234831. [PMID: 33504585 PMCID: PMC7970069 DOI: 10.1242/jeb.234831] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 01/18/2021] [Indexed: 12/19/2022]
Abstract
Cranial morphology in lepidosaurs is highly disparate and characterised by the frequent loss or reduction of bony elements. In varanids and geckos, the loss of the postorbital bar is associated with changes in skull shape, but the mechanical principles underlying this variation remain poorly understood. Here, we sought to determine how the overall cranial architecture and the presence of the postorbital bar relate to the loading and deformation of the cranial bones during biting in lepidosaurs. Using computer-based simulation techniques, we compared cranial biomechanics in the varanid Varanus niloticus and the teiid Salvator merianae, two large, active foragers. The overall strain magnitude and distribution across the cranium were similar in the two species, despite lower strain gradients in V. niloticus. In S. merianae, the postorbital bar is important for resistance of the cranium to feeding loads. The postorbital ligament, which in varanids partially replaces the postorbital bar, does not affect bone strain. Our results suggest that the reduction of the postorbital bar impaired neither biting performance nor the structural resistance of the cranium to feeding loads in V. niloticus. Differences in bone strain between the two species might reflect demands imposed by feeding and non-feeding functions on cranial shape. Beyond variation in cranial bone strain related to species-specific morphological differences, our results reveal that similar mechanical behaviour is shared by lizards with distinct cranial shapes. Contrary to the situation in mammals, the morphology of the circumorbital region, calvaria and palate appears to be important for withstanding high feeding loads in these lizards. Summary:In vivo measurements and computer-based simulations of the cranial mechanics of two large lizards indicate that similar mechanical behaviour is shared by lizards with distinct cranial architecture, and show the importance of the postorbital bar in resisting the feeding loads.
Collapse
Affiliation(s)
- Hugo Dutel
- School of Earth Sciences, University of Bristol, Bristol, BS8 1TQ, UK .,Department of Engineering, Medical and Biological Engineering Research Group, University of Hull, Hull, HU6 7RX, UK
| | - Flora Gröning
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen, AB25 2ZD, UK
| | - Alana C Sharp
- Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, L7 8TX, UK.,Centre for Integrative Anatomy, Research Department of Cell and Developmental Biology, University College London, Anatomy Building, Gower Street, London, WCIE 6BT, UK
| | - Peter J Watson
- Department of Engineering, Medical and Biological Engineering Research Group, University of Hull, Hull, HU6 7RX, UK
| | - Anthony Herrel
- UMR 7179 MECADEV, MNHN - CNRS, Département Adaptations du Vivant, Muséum national d'Histoire naturelle, 75005 Paris, France
| | - Callum F Ross
- Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA
| | - Marc E H Jones
- Centre for Integrative Anatomy, Research Department of Cell and Developmental Biology, University College London, Anatomy Building, Gower Street, London, WCIE 6BT, UK
| | - Susan E Evans
- Centre for Integrative Anatomy, Research Department of Cell and Developmental Biology, University College London, Anatomy Building, Gower Street, London, WCIE 6BT, UK
| | - Michael J Fagan
- Department of Engineering, Medical and Biological Engineering Research Group, University of Hull, Hull, HU6 7RX, UK
| |
Collapse
|
7
|
Wilken AT, Middleton KM, Sellers KC, Cost IN, Holliday CM. The roles of joint tissues and jaw muscles in palatal biomechanics of the savannah monitor ( Varanus exanthematicus) and their significance for cranial kinesis. ACTA ACUST UNITED AC 2019; 222:jeb.201459. [PMID: 31481636 DOI: 10.1242/jeb.201459] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Accepted: 08/23/2019] [Indexed: 12/16/2022]
Abstract
Numerous vertebrates exhibit cranial kinesis, or movement between bones of the skull and mandible other than at the jaw joint. Many kinetic species possess a particular suite of features to accomplish this movement, including flexible cranial joints and protractor musculature. Whereas the musculoskeletal anatomy of these kinetic systems is well understood, how these joints are biomechanically loaded, how different soft tissues affect joint loading and kinetic capacity, and how the protractor musculature loads the skull remain poorly understood. Here, we present a finite element model of the savannah monitor, Varanus exanthematicus, a modestly kinetic lizard, to better elucidate the roles of soft tissue in mobile joints and protractor musculature in cranial loading. We describe the 3D resultants of jaw muscles and the histology of palatobasal, otic and jaw joints. We tested the effects of joint tissue type, bite point and muscle load to evaluate the biomechanical role of muscles on the palate and braincase. We found that the jaw muscles have significant mediolateral components that can impart stability across palatocranial joints. Articular tissues affect the magnitude of strains experienced around the palatobasal and otic joints. Without protractor muscle loading, the palate, quadrate and braincase experience higher strains, suggesting this muscle helps insulate the braincase and palatoquadrate from high loads. We found that the cross-sectional properties of the bones of V. exanthematicus are well suited for performing under torsional loads. These findings suggest that torsional loading regimes may have played a more important role in the evolution of cranial kinesis in lepidosaurs than previously appreciated.
Collapse
Affiliation(s)
- Alec T Wilken
- Department of Pathology and Anatomical Sciences, University of Missouri, M263, Medical Sciences Building, Columbia, MO 65212, USA
| | - Kevin M Middleton
- Department of Pathology and Anatomical Sciences, University of Missouri, M263, Medical Sciences Building, Columbia, MO 65212, USA
| | - Kaleb C Sellers
- Department of Pathology and Anatomical Sciences, University of Missouri, M263, Medical Sciences Building, Columbia, MO 65212, USA
| | - Ian N Cost
- Department of Pathology and Anatomical Sciences, University of Missouri, M263, Medical Sciences Building, Columbia, MO 65212, USA
| | - Casey M Holliday
- Department of Pathology and Anatomical Sciences, University of Missouri, M263, Medical Sciences Building, Columbia, MO 65212, USA
| |
Collapse
|
8
|
Granatosky MC, McElroy EJ, Laird MF, Iriarte-Diaz J, Reilly SM, Taylor AB, Ross CF. Joint angular excursions during cyclical behaviors differ between tetrapod feeding and locomotor systems. J Exp Biol 2019; 222:jeb.200451. [DOI: 10.1242/jeb.200451] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 04/05/2019] [Indexed: 12/14/2022]
Abstract
Tetrapod musculoskeletal diversity is usually studied separately in feeding and locomotor systems. However, comparisons between these systems promise important insight into how natural selection deploys the same basic musculoskeletal toolkit—connective tissues, bones, nerves and skeletal muscle—to meet the differing performance criteria of feeding and locomotion. In this study, we compare average joint angular excursions during cyclic behaviors– chewing, walking and running–in a phylogenetic context to explore differences in the optimality criteria of these two systems. Across 111 tetrapod species, average limb-joint angular excursions during cyclic locomotion are greater and more evolutionarily labile than those of the jaw joint during cyclic chewing. We argue that these findings reflect fundamental functional dichotomies between tetrapod locomotor and feeding systems. Tetrapod chewing systems are optimized for precise application of force over a narrower, more controlled and predictable range of displacements, the principal aim being to fracture the substrate, the size and mechanical properties of which are controlled at ingestion and further reduced and homogenized (respectively) by the chewing process. In contrast, tetrapod limbed locomotor systems are optimized for fast and energetically efficient application of force over a wider and less predictable range of displacements, the principal aim being to move the organism at varying speeds relative to a substrate whose geometry and mechanical properties need not become more homogenous as locomotion proceeds. Hence, the evolution of tetrapod locomotor systems has been accompanied by an increasing diversity of limb-joint excursions, as tetrapods have expanded across a range of locomotor substrates and environments.
Collapse
Affiliation(s)
- Michael C. Granatosky
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA
| | - Eric J. McElroy
- Department of Biology, College of Charleston, Charleston, SC, USA
| | - Myra F. Laird
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA
| | - Jose Iriarte-Diaz
- Department of Oral Biology, University of Illinois Chicago, Chicago, IL, USA
| | | | | | - Callum F. Ross
- Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL, USA
| |
Collapse
|