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Mitchell DR, Sherratt E, Weisbecker V. Facing the facts: adaptive trade-offs along body size ranges determine mammalian craniofacial scaling. Biol Rev Camb Philos Soc 2024; 99:496-524. [PMID: 38029779 DOI: 10.1111/brv.13032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2023] [Revised: 11/12/2023] [Accepted: 11/14/2023] [Indexed: 12/01/2023]
Abstract
The mammalian cranium (skull without lower jaw) is representative of mammalian diversity and is thus of particular interest to mammalian biologists across disciplines. One widely retrieved pattern accompanying mammalian cranial diversification is referred to as 'craniofacial evolutionary allometry' (CREA). This posits that adults of larger species, in a group of closely related mammals, tend to have relatively longer faces and smaller braincases. However, no process has been officially suggested to explain this pattern, there are many apparent exceptions, and its predictions potentially conflict with well-established biomechanical principles. Understanding the mechanisms behind CREA and causes for deviations from the pattern therefore has tremendous potential to explain allometry and diversification of the mammalian cranium. Here, we propose an amended framework to characterise the CREA pattern more clearly, in that 'longer faces' can arise through several kinds of evolutionary change, including elongation of the rostrum, retraction of the jaw muscles, or a more narrow or shallow skull, which all result in a generalised gracilisation of the facial skeleton with increased size. We define a standardised workflow to test for the presence of the pattern, using allometric shape predictions derived from geometric morphometrics analysis, and apply this to 22 mammalian families including marsupials, rabbits, rodents, bats, carnivores, antelopes, and whales. Our results show that increasing facial gracility with size is common, but not necessarily as ubiquitous as previously suggested. To address the mechanistic basis for this variation, we then review cranial adaptations for harder biting. These dictate that a more gracile cranium in larger species must represent a structural sacrifice in the ability to produce or withstand harder bites, relative to size. This leads us to propose that facial gracilisation in larger species is often a product of bite force allometry and phylogenetic niche conservatism, where more closely related species tend to exhibit more similar feeding ecology and biting behaviours and, therefore, absolute (size-independent) bite force requirements. Since larger species can produce the same absolute bite forces as smaller species with less effort, we propose that relaxed bite force demands can permit facial gracility in response to bone optimisation and alternative selection pressures. Thus, mammalian facial scaling represents an adaptive by-product of the shifting importance of selective pressures occurring with increased size. A reverse pattern of facial 'shortening' can accordingly also be found, and is retrieved in several cases here, where larger species incorporate novel feeding behaviours involving greater bite forces. We discuss multiple exceptions to a bite force-mediated influence on facial proportions across mammals which lead us to argue that ecomorphological specialisation of the cranium is likely to be the primary driver of facial scaling patterns, with some developmental constraints as possible secondary factors. A potential for larger species to have a wider range of cranial functions when less constrained by bite force demands might also explain why selection for larger sizes seems to be prevalent in some mammalian clades. The interplay between adaptation and constraint across size ranges thus presents an interesting consideration for a mechanistically grounded investigation of mammalian cranial allometry.
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Affiliation(s)
- D Rex Mitchell
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia
- Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage, Wollongong, New South Wales, 2522, Australia
| | - Emma Sherratt
- School of Biological Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia
- South Australian Museum, Adelaide, South Australia, 5000, Australia
| | - Vera Weisbecker
- College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, 5001, Australia
- Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage, Wollongong, New South Wales, 2522, Australia
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2
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Ruiz JV, Ferreira GS, Lautenschlager S, de Castro MC, Montefeltro FC. Different, but the same: Inferring the hunting behaviour of the hypercarnivorous bush dog (Speothos venaticus) through finite element analysis. J Anat 2023; 242:553-567. [PMID: 36485003 PMCID: PMC10008295 DOI: 10.1111/joa.13804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 11/23/2022] [Accepted: 11/25/2022] [Indexed: 12/13/2022] Open
Abstract
Cerdocyonina is a clade composed by the South-American canids in which the bush dog (Speothos venaticus) is one of the most elusive species. Known for its unique morphology within the group, this small, bear-like faced canid is the only member of the clade adapted to hypercarnivory, an almost exclusively meat-based diet currently present only in usually large, pack-hunting canids such as the grey wolf (Canis lupus). However, much of the biology of the bush dog is poorly understood, and inferences about its ecology, hunting strategies and diet are usually based on observation of captive individuals and anecdotal records, with reduced quantitative data to offer support. Here, we investigated the craniomandibular functional morphology of the bush dog through finite element analysis (FEA). FEA was employed to model the biting behaviour and to create extrinsic and intrinsic functional scenarios with different loads, corresponding to different bites used to subdue and process the prey. For comparison, the same modelling was applied to the skull of a grey wolf and a grey fox (Urocyon cinereoargenteus). Our analysis showed that the bush dog's responses to loading are more similar to the wolf's than to the fox's in most scenarios, suggesting a convergent craniomandibular functional morphology between these two hypercarnivorous species, despite their distinct phylogenetic positions and body sizes. Differences between the three taxa are noteworthy and suggested to be related to the size of the usual prey. The modelled bite force for the bush dog is relatively strong, about half of that estimated for the wolf and about 40% stronger than the fox's bite. The results strengthen with quantitative data the inferences of the bush dog as a pack-hunting predator with prey size similar to its own, such as large rodents and armadillos, being specialised in subduing and killing its prey using multiple bites. Its similarity to the wolf also confirms anecdotal accounts of predation on mammals that are much larger than itself, such as peccaries and tapirs. These data highlight the ecological specialisation of this small canid in a continent where large, pack-hunting canids are absent.
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Affiliation(s)
- Juan V Ruiz
- Laboratório de Paleontologia e Evolução de Ilha Solteira, UNESP, Ilha Solteira, Brazil.,Programa de Pós-Graduação em Biodiversidade, UNESP, São José do Rio Preto, Brazil.,Eberhard Karls University of Tübingen, Tübingen, Germany.,Senckenberg Centre for Human Evolution and Palaeoenvironment, Tübingen, Germany
| | - Gabriel S Ferreira
- Eberhard Karls University of Tübingen, Tübingen, Germany.,Senckenberg Centre for Human Evolution and Palaeoenvironment, Tübingen, Germany
| | - Stephan Lautenschlager
- School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
| | - Mariela C de Castro
- Laboratório de Biologia Integrativa e Conservação, Universidade Federal de Catalão, Catalão, Brazil
| | - Felipe C Montefeltro
- Laboratório de Paleontologia e Evolução de Ilha Solteira, UNESP, Ilha Solteira, Brazil
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3
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Rajmil J, Velazco PM, Giannini NP. Growing apart: comparative cranial ontogeny in the myrmecophagous aardwolf (Proteles cristata) and the bone-cracking spotted hyaena (Crocuta crocuta). J MAMM EVOL 2023. [DOI: 10.1007/s10914-023-09653-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/19/2023]
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4
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Sellers KC, Nieto MN, Degrange FJ, Pol D, Clark JM, Middleton KM, Holliday CM. The effects of skull flattening on suchian jaw muscle evolution. Anat Rec (Hoboken) 2022; 305:2791-2822. [PMID: 35661427 DOI: 10.1002/ar.24912] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 02/28/2022] [Accepted: 03/02/2022] [Indexed: 12/20/2022]
Abstract
Jaw muscles are key features of the vertebrate feeding apparatus. The jaw musculature is housed in the skull whose morphology reflects a compromise between multiple functions, including feeding, housing sensory structures, and defense, and the skull constrains jaw muscle geometry. Thus, jaw muscle anatomy may be suboptimally oriented for the production of bite force. Crocodylians are a group of vertebrates that generate the highest bite forces ever measured with a flat skull suited to their aquatic ambush predatory style. However, basal members of the crocodylian line (e.g., Prestosuchus) were terrestrial predators with plesiomorphically tall skulls, and thus the origin of modern crocodylians involved a substantial reorganization of the feeding apparatus and its jaw muscles. Here, we reconstruct jaw muscles across a phylogenetic range of crocodylians and fossil suchians to investigate the impact of skull flattening on muscle anatomy. We used imaging data to create 3D models of extant and fossil suchians that demonstrate the evolution of the crocodylian skull, using osteological correlates to reconstruct muscle attachment sites. We found that jaw muscle anatomy in early fossil suchians reflected the ancestral archosaur condition but experienced progressive shifts in the lineage leading to Metasuchia. In early fossil suchians, musculus adductor mandibulae posterior and musculus pterygoideus (mPT) were of comparable size, but by Metasuchia, the jaw musculature is dominated by mPT. As predicted, we found that taxa with flatter skulls have less efficient muscle orientations for the production of high bite force. This study highlights the diversity and evolution of jaw muscles in one of the great transformations in vertebrate evolution.
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Affiliation(s)
- Kaleb C Sellers
- Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, Missouri, USA.,Department of Clinical Anatomy and Osteopathic Principles and Practice, Rocky Vista University, Parker, Colorado, USA
| | - Mauro Nicolas Nieto
- Centro de Investigaciones en Ciencias de la Tierra (CICTERRA), UNC, CONICET, Córdoba, Argentina
| | - Federico J Degrange
- Centro de Investigaciones en Ciencias de la Tierra (CICTERRA), UNC, CONICET, Córdoba, Argentina
| | - Diego Pol
- CONICET, Museo Paleontológico Egidio Feruglio, Trelew, Argentina
| | - James M Clark
- Department of Biological Sciences, The George Washington University, Washington, District of Columbia, USA
| | - Kevin M Middleton
- Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, Missouri, USA
| | - Casey M Holliday
- Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, Missouri, USA
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6
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Tong H, Chen X, Zhang B, Rothschild B, White S, Balisi M, Wang X. Hypercarnivorous teeth and healed injuries to Canis chihliensis from Early Pleistocene Nihewan beds, China, support social hunting for ancestral wolves. PeerJ 2020; 8:e9858. [PMID: 33194358 PMCID: PMC7485486 DOI: 10.7717/peerj.9858] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 08/11/2020] [Indexed: 11/23/2022] Open
Abstract
Collaborative hunting by complex social groups is a hallmark of large dogs (Mammalia: Carnivora: Canidae), whose teeth also tend to be hypercarnivorous, specialized toward increased cutting edges for meat consumption and robust p4-m1 complex for cracking bone. The deep history of canid pack hunting is, however, obscure because behavioral evidence is rarely preserved in fossils. Dated to the Early Pleistocene (>1.2 Ma), Canis chihliensis from the Nihewan Basin of northern China is one of the earliest canines to feature a large body size and hypercarnivorous dentition. We present the first known record of dental infection in C. chihliensis, likely inflicted by processing hard food, such as bone. Another individual also suffered a displaced fracture of its tibia and, despite such an incapacitating injury, survived the trauma to heal. The long period required for healing the compound fracture is consistent with social hunting and family care (food-sharing) although alternative explanations exist. Comparison with abundant paleopathological records of the putatively pack-hunting Late Pleistocene dire wolf, Canis dirus, at the Rancho La Brea asphalt seeps in southern California, U.S.A., suggests similarity in feeding behavior and sociality between Chinese and American Canis across space and time. Pack hunting in Canis may be traced back to the Early Pleistocene, well before the appearance of modern wolves, but additional evidence is needed for confirmation.
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Affiliation(s)
- Haowen Tong
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Life and Paleoenvironment, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Xi Chen
- Nanjing Normal University, Nanjing, Jiangsu, China
| | - Bei Zhang
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.,CAS Center for Excellence in Life and Paleoenvironment, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Bruce Rothschild
- Department of Vertebrate Paleontology, Carnegie Museum of Natural History, Pittsburgh, PA, United States of America
| | - Stuart White
- School of Dentistry, University of California, Los Angeles, Los Angeles, CA, United States of America
| | - Mairin Balisi
- Natural History Museum of Los Angeles County, Los Angeles, CA, United States of America
| | - Xiaoming Wang
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China.,Natural History Museum of Los Angeles County, Los Angeles, CA, United States of America
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7
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Fontoura E, Ferreira JD, Bubadué J, Ribeiro AM, Kerber L. Virtual brain endocast of Antifer (Mammalia: Cervidae), an extinct large cervid from South America. J Morphol 2020; 281:1223-1240. [PMID: 32815595 DOI: 10.1002/jmor.21243] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 06/23/2020] [Accepted: 07/17/2020] [Indexed: 01/22/2023]
Abstract
A diverse fossil record of Cervidae (Mammalia) has been documented in the South American Pleistocene, when these animals arrived during the Great American Biotic Interchange. Using computed tomography-scanning techniques, it is possible to access the endocranial morphology of extinct species. Here, we studied the brain endocast of the extinct late Pleistocene cervid Antifer ensenadensis from southern Brazil, one of the largest forms that lived on this continent, using comparative morphology, geometric morphometrics, and encephalization quotients. The analyzed endocasts demonstrate that A. ensenadensis had a gyrencephalic brain, showing a prominent longitudinal sinus (=sagittal superior sinus), which is also observed in the large South American cervid Blastocerus dichotomus. The encephalization quotient is within the variation of extant cervids, suggesting maintenance of the pattern of encephalization from at least the late Pleistocene. Geometric morphometric analysis suggested a clear and linear allometric trend between brain endocast size and shape, and highlights A. ensenadensis as an extreme form within the analyzed cervids regarding brain morphology.
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Affiliation(s)
- Emmanuelle Fontoura
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, São João do Polêsine, Brazil
| | - José Darival Ferreira
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, São João do Polêsine, Brazil
| | - Jamile Bubadué
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Laboratório de Ciências Ambientais, Universidade Estadual do Norte Fluminense, Campos dos Goytacazes, Brazil
| | - Ana Maria Ribeiro
- Seção de Paleontologia, Museu de Ciências Naturais, Secretaria do Meio Ambiente e Infraestrutura, Porto Alegre, Brazil
| | - Leonardo Kerber
- Programa de Pós-Graduação em Biodiversidade Animal, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil.,Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, São João do Polêsine, Brazil.,Museu Paraense Emílio Goeldi, Coordenação de Ciências da Terra e Ecologia, Belém, Brazil
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8
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Esteban JM, Martín-Serra A, Varón-González C, Pérez-Ramos A, Velasco D, Pastor FJ, Figueirido B. Morphological evolution of the carnivoran sacrum. J Anat 2020; 237:1087-1102. [PMID: 32654137 DOI: 10.1111/joa.13272] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 06/13/2020] [Accepted: 06/15/2020] [Indexed: 12/19/2022] Open
Abstract
The sacrum is a key piece of the vertebrate skeleton, since it connects the caudal region with the presacral region of the vertebral column and the hind limbs through the pelvis. Therefore, understanding its form and function is of great relevance in vertebrate ecomorphology. However, it is striking that morphometric studies that quantify its morphological evolution in relation to function are scarce. The main goal of this study is to investigate the morphological evolution of the sacrum in relation to its function in the mammalian order Carnivora, using three-dimensional (3D) geometric morphometrics. Principal component analysis under a phylogenetic background indicated that changes in sacrum morphology are mainly focused on the joint areas where it articulates with other parts of the skeleton allowing resistance to stress at these joints caused by increasing muscle loadings. In addition, we demonstrated that sacrum morphology is related to both the length of the tail relativised to the length of the body, and the length of the body relativised to body mass. We conclude that the sacrum in carnivores has evolved in response to the locomotor requirements of the species analysed, but in locomotion, each family has followed alternative morphological solutions to address the same functional demands.
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Affiliation(s)
- Juan Miguel Esteban
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - Alberto Martín-Serra
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - Ceferino Varón-González
- Évolution, Biodiversité, ISYEB - UMR 7205 -CNRS, MNHN, UMPC, EPHE, Muséum National d'Histoire naturelle, Institut de Systématique, Sorbonne Universités, Paris, France
| | - Alejandro Pérez-Ramos
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - David Velasco
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
| | - Francisco J Pastor
- Departamento de Anatomía y Radiología, Universidad de Valladolid, Valladolid, Spain
| | - Borja Figueirido
- Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
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9
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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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10
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Santaella BL, Tseng ZJ. Hole in One: an element reduction approach to modeling bone porosity in finite element analysis. PeerJ 2019; 7:e8112. [PMID: 31875143 PMCID: PMC6925947 DOI: 10.7717/peerj.8112] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/28/2019] [Indexed: 11/20/2022] Open
Abstract
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.
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Affiliation(s)
- Beatriz L Santaella
- Department of Pathology and Anatomical Sciences, Jacobs School of Medicine and Biomedical Sciences, State University of New York, Buffalo, NY, United States of America
| | - Z Jack Tseng
- Department of Pathology and Anatomical Sciences, Jacobs School of Medicine and Biomedical Sciences, State University of New York, Buffalo, NY, United States of America.,Department of Integrative Biology and Museum of Paleontology, University of California, Berkeley, CA, United States of America.,Division of Paleontology, American Museum of Natural History, New York, NY, United States of America
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11
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Mitchell DR. The anatomy of a crushing bite: The specialised cranial mechanics of a giant extinct kangaroo. PLoS One 2019; 14:e0221287. [PMID: 31509570 PMCID: PMC6738596 DOI: 10.1371/journal.pone.0221287] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 08/02/2019] [Indexed: 11/28/2022] Open
Abstract
The Sthenurinae were a diverse subfamily of short-faced kangaroos that arose in the Miocene and diversified during the Pliocene and Pleistocene. Many species possessed skull morphologies that were relatively structurally reinforced with bone, suggesting that they were adapted to incorporate particularly resistant foods into their diets. However, the functional roles of many unique, robust features of the sthenurine cranium are not yet clearly defined. Here, the finite element method is applied to conduct a comprehensive analysis of unilateral biting along the cheek tooth battery of a well-represented sthenurine, Simosthenurus occidentalis. The results are compared with those of an extant species considered to be of most similar ecology and cranial proportions to this species, the koala (Phascolarctos cinereus). The simulations reveal that the cranium of S. occidentalis could produce and withstand comparatively high forces during unilateral biting. Its greatly expanded zygomatic arches potentially housed enlarged zygomaticomandibularis muscles, shown here to reduce the risk of dislocation of the temporomandibular joint during biting with the rear of a broad, extensive cheek tooth row. This may also be a function of the zygomaticomandibularis in the giant panda (Ailuropoda melanoleuca), another species known to exhibit an enlarged zygomatic arch and hypertrophy of this muscle. Furthermore, the expanded frontal plates of the S. occidentalis cranium form broad arches of bone with the braincase and deepened maxillae that each extend from the anterior tooth rows to their opposing jaw joints. These arches are demonstrated here to be a key feature in resisting high torsional forces during unilateral premolar biting on large, resistant food items. This supports the notion that S. occidentalis fed thick, lignified vegetation directly to the cheek teeth in a similar manner to that described for the giant panda when crushing mature bamboo culms.
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Affiliation(s)
- D. Rex Mitchell
- Zoology Division, School of Environmental and Rural Sciences, University of New England, Armidale, New South Wales, Australia
- Department of Anthropology, University of Arkansas, Fayetteville, Arkansas, United States of America
- * E-mail:
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12
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Rutledge KM, Summers AP, Kolmann MA. Killing them softly: Ontogeny of jaw mechanics and stiffness in mollusk-feeding freshwater stingrays. J Morphol 2019; 280:796-808. [PMID: 30950541 DOI: 10.1002/jmor.20984] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 03/15/2019] [Accepted: 03/16/2019] [Indexed: 12/17/2022]
Abstract
Durophagous predators consume hard-shelled prey such as bivalves, gastropods, and large crustaceans, typically by crushing the mineralized exoskeleton. This is costly from the point of view of the bite forces involved, handling times, and the stresses inflicted on the predator's skeleton. It is not uncommon for durophagous taxa to display an ontogenetic shift from softer to harder prey items, implying that it is relatively difficult for smaller animals to consume shelled prey. Batoid fishes (rays, skates, sawfishes, and guitarfishes) have independently evolved durophagy multiple times, despite the challenges associated with crushing prey harder than their own cartilaginous skeleton. Potamotrygon leopoldi is a durophagous freshwater ray endemic to the Xingu River in Brazil, with a jaw morphology superficially similar to its distant durophagous marine relatives, eagle rays (e.g., Aetomylaeus, Aetobatus). We used second moment of area as a proxy for the ability to resist bending and analyzed the arrangement of the mineralized skeleton of the jaw of P. leopoldi over ontogeny using data from computed tomography (CT) scans. The jaws of P. leopoldi do not resist bending nearly as well as other durophagous elasmobranchs, and the jaws are stiffest nearest the joints rather than beneath the dentition. While second moment has similar material distribution over ontogeny, mineralization of the jaws under the teeth increases with age. Neonate rays have low jaw stiffness and poor mineralization, suggesting that P. leopoldi may not feed on hard-shelled prey early in life. These differences in the shape, stiffness and mineralization of the jaws of P. leopoldi compared to its durophagous relatives show there are several solutions to the problem of crushing shelled prey with a compliant skeleton.
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Affiliation(s)
- Kelsi M Rutledge
- Department of Biology, Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington.,Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California
| | - Adam P Summers
- Department of Biology, Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington
| | - Matthew A Kolmann
- Department of Biology, Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington.,Department of Biological Sciences, George Washington University, Washington, D.C.,Department of Ichthyology, Royal Ontario Museum, Toronto, Ontario
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13
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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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14
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Wang X, White SC, Balisi M, Biewer J, Sankey J, Garber D, Tseng ZJ. First bone-cracking dog coprolites provide new insight into bone consumption in Borophagus and their unique ecological niche. eLife 2018; 7:34773. [PMID: 29785931 PMCID: PMC5963924 DOI: 10.7554/elife.34773] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 04/16/2018] [Indexed: 11/13/2022] Open
Abstract
Borophagine canids have long been hypothesized to be North American ecological 'avatars' of living hyenas in Africa and Asia, but direct fossil evidence of hyena-like bone consumption is hitherto unknown. We report rare coprolites (fossilized feces) of Borophagus parvus from the late Miocene of California and, for the first time, describe unambiguous evidence that these predatory canids ingested large amounts of bone. Surface morphology, micro-CT analyses, and contextual information reveal (1) droppings in concentrations signifying scent-marking behavior, similar to latrines used by living social carnivorans; (2) routine consumption of skeletons; (3) undissolved bones inside coprolites indicating gastrointestinal similarity to modern striped and brown hyenas; (4) B. parvus body weight of ~24 kg, reaching sizes of obligatory large-prey hunters; and (5) prey size ranging ~35-100 kg. This combination of traits suggests that bone-crushing Borophagus potentially hunted in collaborative social groups and occupied a niche no longer present in North American ecosystems.
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Affiliation(s)
- Xiaoming Wang
- Department of Vertebrate Paleontology, Natural History Museum of Los Angeles County, Los Angeles, United States.,Department of Vertebrate Paleontology, American Museum of Natural History, New York, United States.,Department of Ecology and Evolutionary Biology, University of California, Los Angeles, United States
| | - Stuart C White
- School of Dentistry, University of California, Los Angeles, United States
| | - Mairin Balisi
- Department of Vertebrate Paleontology, Natural History Museum of Los Angeles County, Los Angeles, United States.,Department of Ecology and Evolutionary Biology, University of California, Los Angeles, United States
| | - Jacob Biewer
- Department of Geological Sciences, California State University, Fullerton, United States.,Department of Geology, California State University Stanislaus, Turlock, United States
| | - Julia Sankey
- Department of Geology, California State University Stanislaus, Turlock, United States
| | - Dennis Garber
- Department of Vertebrate Paleontology, Natural History Museum of Los Angeles County, Los Angeles, United States
| | - Z Jack Tseng
- Department of Vertebrate Paleontology, Natural History Museum of Los Angeles County, Los Angeles, United States.,Department of Vertebrate Paleontology, American Museum of Natural History, New York, United States.,Department of Pathology and Anatomical Sciences, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo, Buffalo, United States
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15
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Balisi M, Casey C, Van Valkenburgh B. Dietary specialization is linked to reduced species durations in North American fossil canids. ROYAL SOCIETY OPEN SCIENCE 2018; 5:171861. [PMID: 29765649 PMCID: PMC5936914 DOI: 10.1098/rsos.171861] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 03/19/2018] [Indexed: 05/10/2023]
Abstract
How traits influence species persistence is a fundamental question in ecology, evolution and palaeontology. We test the relationship between dietary traits and both species duration and locality coverage over 40 million years in North American canids, a clade with considerable ecomorphological disparity and a dense fossil record. Because ecomorphological generalization-broad resource use-may enable species to withstand disturbance, we predicted that canids of average size and mesocarnivory would exhibit longer durations and wider distributions than specialized larger or smaller species. Second, because locality coverage might reflect dispersal ability and/or survivability in a range of habitats, we predicted that high coverage would correspond with longer durations. We find a nonlinear relationship between species duration and degree of carnivory: species at either end of the carnivory spectrum tend to have shorter durations than mesocarnivores. Locality coverage shows no relationship with size, diet or duration. To test whether generalization (medium size, mesocarnivory) corresponds to an adaptive optimum, we fit trait evolution models to previously generated canid phylogenies. Our analyses identify no single optimum in size or diet. Instead, the primary model of size evolution is a classic Cope's Rule increase over time, while dietary evolution does not conform to a single model.
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Affiliation(s)
- Mairin Balisi
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
- Vertebrate Paleontology Department, Natural History Museum of Los Angeles County, Los Angeles, CA, USA
- Author for correspondence: Mairin Balisi e-mail:
| | - Corinna Casey
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
| | - Blaire Van Valkenburgh
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA, USA
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16
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Curtis AA, Orke M, Tetradis S, van Valkenburgh B. Diet-related differences in craniodental morphology between captive-reared and wild coyotes, Canis latrans (Carnivora: Canidae). Biol J Linn Soc Lond 2018. [DOI: 10.1093/biolinnean/blx161] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Abigail A Curtis
- Department of Biology, University of Washington, Seattle, WA, USA
| | - Mathew Orke
- Department of Ecology and Evolutionary Biology, UCLA, Los Angeles, CA, USA
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17
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Constantino PJ, Bush MB, Barani A, Lawn BR. On the evolutionary advantage of multi-cusped teeth. J R Soc Interface 2017; 13:rsif.2016.0374. [PMID: 27558851 DOI: 10.1098/rsif.2016.0374] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 07/28/2016] [Indexed: 11/12/2022] Open
Abstract
A hallmark of mammalian evolution is a progressive complexity in postcanine tooth morphology. However, the driving force for this complexity remains unclear: whether to expand the versatility in diet source, or to bolster tooth structural integrity. In this study, we take a quantitative approach to this question by examining the roles of number, position and height of multiple cusps in determining sustainable bite forces. Our approach is to use an extended finite-element methodology with due provision for step-by-step growth of an embedded crack to determine how fracture progresses with increasing occlusal load. We argue that multi-cusp postcanine teeth are well configured to withstand high bite forces provided that multiple cusps are contacted simultaneously to share the load. However, contact on a single near-wall cusp diminishes the strength. Location of the load points and cusp height, rather than cusp number or radius, are principal governing factors. Given these findings, we conclude that while complex tooth structures can enhance durability, increases in cusp number are more likely to be driven by the demands of food manipulation. Structural integrity of complex teeth is maintained when individual cusps remain sufficiently distant from the side walls and do not become excessively tall relative to tooth width.
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Affiliation(s)
- Paul J Constantino
- Department of Biology, Saint Michael's College, Colchester, VT 05439, USA
| | - Mark B Bush
- School of Mechanical and Chemical Engineering, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Amir Barani
- School of Mechanical and Chemical Engineering, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Brian R Lawn
- Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
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18
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Wilson GP, Ekdale EG, Hoganson JW, Calede JJ, Vander Linden A. A large carnivorous mammal from the Late Cretaceous and the North American origin of marsupials. Nat Commun 2016; 7:13734. [PMID: 27929063 PMCID: PMC5155139 DOI: 10.1038/ncomms13734] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 10/28/2016] [Indexed: 12/26/2022] Open
Abstract
Marsupial mammal relatives (stem metatherians) from the Mesozoic Era (252-66 million years ago) are mostly known from isolated teeth and fragmentary jaws. Here we report on the first near-complete skull remains of a North American Late Cretaceous metatherian, the stagodontid Didelphodon vorax. Our phylogenetic analysis indicates that marsupials or their closest relatives evolved in North America, as part of a Late Cretaceous diversification of metatherians, and later dispersed to South America. In addition to being the largest known Mesozoic therian mammal (node-based clade of eutherians and metatherians), Didelphodon vorax has a high estimated bite force and other craniomandibular and dental features that suggest it is the earliest known therian to invade a durophagous predator-scavenger niche. Our results broaden the scope of the ecomorphological diversification of Mesozoic mammals to include therian lineages that, in this case, were linked to the origin and evolution of marsupials.
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Affiliation(s)
- Gregory P. Wilson
- Department of Biology and Burke Museum, University of Washington, Seattle, Washington 98195, USA
| | - Eric G. Ekdale
- Department of Biology, San Diego State University, San Diego, California 92182, USA
- Department of Paleontology, San Diego Natural History Museum, San Diego, California 92101, USA
| | - John W. Hoganson
- North Dakota Geological Survey, Bismarck, North Dakota 58505, USA
| | - Jonathan J. Calede
- Department of Biology and Burke Museum, University of Washington, Seattle, Washington 98195, USA
| | - Abby Vander Linden
- Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA
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19
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Penrose F, Kemp GJ, Jeffery N. Scaling and Accommodation of Jaw Adductor Muscles in Canidae. Anat Rec (Hoboken) 2016; 299:951-66. [PMID: 27103346 PMCID: PMC5084800 DOI: 10.1002/ar.23355] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 03/02/2016] [Accepted: 03/03/2016] [Indexed: 01/21/2023]
Abstract
The masticatory apparatus amongst closely related carnivoran species raises intriguing questions about the interplay between allometry, function, and phylogeny in defining interspecific variations of cranial morphology. Here we describe the gross structure of the jaw adductor muscles of several species of canid, and then examine how the muscles are scaled across the range of body sizes, phylogenies, and trophic groups. We also consider how the muscles are accommodated on the skull, and how this is influenced by differences of endocranial size. Data were collected for a suite of morphological metrics, including body mass, endocranial volume, and muscle masses and we used geometric morphometric shape analysis to reveal associated form changes. We find that all jaw adductor muscles scale isometrically against body mass, regardless of phylogeny or trophic group, but that endocranial volume scales with negative allometry against body mass. These findings suggest that head shape is partly influenced by the need to house isometrically scaling muscles on a neurocranium scaling with negative allometry. Principal component analysis suggests that skull shape changes, such as the relatively wide zygomatic arches and large sagittal crests seen in species with higher body masses, allow the skull to accommodate a relative enlargement of the jaw adductors compared with the endocranium. Anat Rec, 299:951-966, 2016. © 2016 The Authors The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology Published by Wiley Periodicals, Inc.
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Affiliation(s)
- Fay Penrose
- Institute of Ageing and Chronic DiseaseDepartment of Musculoskeletal Biology and the MRCArthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA)University of LiverpoolLiverpoolUnited Kingdom
- School of Veterinary ScienceDepartment of Veterinary Preclinical ScienceUniversity of LiverpoolLiverpoolUnited Kingdom
| | - Graham J. Kemp
- Institute of Ageing and Chronic DiseaseDepartment of Musculoskeletal Biology and the MRCArthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA)University of LiverpoolLiverpoolUnited Kingdom
| | - Nathan Jeffery
- Institute of Ageing and Chronic DiseaseDepartment of Musculoskeletal Biology and the MRCArthritis Research UK Centre for Integrated Research into Musculoskeletal Ageing (CIMA)University of LiverpoolLiverpoolUnited Kingdom
- Human Anatomy Resource CentreUniversity of LiverpoolLiverpoolUnited Kingdom
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20
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Skamniotis CG, Patel Y, Charalambides MN, Elliott M. Fracture investigation in starch-based foods. Interface Focus 2016; 6:20160005. [PMID: 27274805 DOI: 10.1098/rsfs.2016.0005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The study of oral processing and specifically cutting of the food piece during mastication can lead towards optimization of products for humans or animals. Food materials are complex biocomposites with a highly nonlinear constitutive response. Their fracture properties have not been largely investigated, while the need for models capable of predicting food breakdown increases. In this study, the blade cutting and the essential work of fracture (EWF) methodologies assessed the fracture behaviour of starch-based pet food. Tensile tests revealed rate-dependent stiffness and stress softening effects, attributed to viscoplasticity and micro-cracking, respectively. Cutting data were collected for 5, 10 and 30 mm s(-1) sample feed rates, whereas the EWF tests were conducted at 1.7, 3.3 and 8.3 mm s(-1) crosshead speeds corresponding to average crack speeds of 4, 7 and 15 mm s(-1), respectively. A reasonable agreement was achieved between cutting and EWF, reporting 1.26, 1.78, 1.76 kJ m(-2) and 1.52, 1.37, 1.45 kJ m(-2) values, respectively, for the corresponding crack speeds. These toughness data were used in a novel numerical model simulating the 'first' bite mastication process. A viscoplastic material model is adopted for the food piece, combined with a damage law that enabled predicting fracture patterns in the product.
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Affiliation(s)
- C G Skamniotis
- Department of Mechanical Engineering , Imperial College London , London SW7 2AZ , UK
| | - Y Patel
- Department of Mechanical Engineering , Imperial College London , London SW7 2AZ , UK
| | - M N Charalambides
- Department of Mechanical Engineering , Imperial College London , London SW7 2AZ , UK
| | - M Elliott
- Mars Petcare UK Ltd , Leicestershire , UK
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21
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Sharp AC, Rich TH. Cranial biomechanics, bite force and function of the endocranial sinuses in Diprotodon optatum, the largest known marsupial. J Anat 2016; 228:984-95. [PMID: 26939052 DOI: 10.1111/joa.12456] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/25/2016] [Indexed: 11/27/2022] Open
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 of the cranium, mandible and jaw adductor muscles were produced. In addition, manipulations to the Diprotodon cranial model were performed to investigate changes in skull and sinus structure, including a model with no sinuses (sinuses 'filled' with bone) and a model with a midsagittal crest. Results indicate that the cranial sinuses in Diprotodon significantly lighten the skull while still providing structural support, a high bite force and low stress, indicating the cranium may have been able to withstand higher loads than those generated during feeding. Data from this study support the hypothesis that pneumatisation is driven by biomechanical loads and occurs in areas of low stress. The presence of sinuses is likely to be a byproduct of the separation of the outer surface of the skull from the braincase due to the demands of soft tissue including the brain and the large jaw adductor musculature, especially the temporalis. In very large species, such as Diprotodon, this separation is more pronounced, resulting in extensive cranial sinuses due to a relatively small brain compared with the size of the skull.
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Affiliation(s)
- Alana C Sharp
- School of Science and Technology, University of New England, Armidale, New South Wales, Australia.,School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria, Australia
| | - Thomas H Rich
- Sciences Department, Museum Victoria, Melbourne, Australia
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22
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Martín-Serra A, Figueirido B, Palmqvist P. In the Pursuit of the Predatory Behavior of Borophagines (Mammalia, Carnivora, Canidae): Inferences from Forelimb Morphology. J MAMM EVOL 2016. [DOI: 10.1007/s10914-016-9321-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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23
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Therrien F, Quinney A, Tanaka K, Zelenitsky DK. Accuracy of mandibular force profiles for bite force estimation and feeding behavior reconstruction in extant and extinct carnivorans. J Exp Biol 2016; 219:3738-3749. [DOI: 10.1242/jeb.143339] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 09/08/2016] [Indexed: 11/20/2022]
Abstract
Mandibular force profiles apply the principles of beam theory to identify mandibular biomechanical properties that reflect the bite force and feeding strategies of extant and extinct predators. While this method uses external dimensions of the mandibular corpus to determine its biomechanical properties, more accurate results could potentially be obtained by quantifying its internal cortical bone distribution. To test this possibility, mandibular force profiles were calculated using both external mandibular dimensions (‘solid mandible model’) and quantification of internal bone distribution of the mandibular corpus obtained from CT scans (‘hollow mandible model’) for five carnivorans (Canis lupus, Crocuta crocuta, Panthera leo, Neofelis nebulosa, and the extinct Canis dirus). Comparison reveals that the solid model slightly overestimates mandibular biomechanical properties, but the pattern of change in biomechanical properties along the mandible remains the same. As such, feeding behavior reconstructions are consistent between the two models and are not improved by computed tomography. Bite force estimates produced by the two models are similar, except for Crocuta where the solid model underestimates bite force by 10%-14%. This discrepancy is due to the more solid nature of the Crocuta mandible relative to other carnivorans. Therefore, computed tomography improves bite force estimation accuracy for taxa with thicker mandibular corpora, but not significantly so otherwise. Bite force estimates derived from mandibular force profiles are far closer to empirically-measured bite force than those inferred from jaw musculature dimension. Consequently, bite force estimates derived from this method can be used to calibrate finite-element analysis models.
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Affiliation(s)
- François Therrien
- Royal Tyrrell Museum of Palaeontology, PO Box 7500, Drumheller, AB, T0J 0Y0, Canada
- Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
| | - Annie Quinney
- Arctic Institute of North America, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
| | - Kohei Tanaka
- Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
| | - Darla K. Zelenitsky
- Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N 1N4, Canada
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24
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Sharp AC. Comparative finite element analysis of the cranial performance of four herbivorous marsupials. J Morphol 2015; 276:1230-43. [PMID: 26193997 DOI: 10.1002/jmor.20414] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Revised: 05/19/2015] [Accepted: 05/26/2015] [Indexed: 11/07/2022]
Abstract
Marsupial herbivores exhibit a wide variety of skull shapes and sizes to exploit different ecological niches. Several studies on teeth, dentaries, and jaw adductor muscles indicate that marsupial herbivores exhibit different specializations for grazing and browsing. No studies, however, have examined the skulls of marsupial herbivores to determine the relationship between stress and strain, and the evolution of skull shape. The relationship between skull morphology, biomechanical performance, and diet was tested by applying the finite element method to the skulls of four marsupial herbivores: the common wombat (Vombatus ursinus), koala (Phascolarctos cinereus), swamp wallaby (Wallabia bicolor), and red kangaroo (Macropus rufus). It was hypothesized that grazers, requiring stronger skulls to process tougher food, would have higher biomechanical performance than browsers. This was true when comparing the koala and wallaby (browsers) to the wombat (a grazer). The cranial model of the wombat resulted in low stress and high mechanical efficiency in relation to a robust skull capable of generating high bite forces. However, the kangaroo, also a grazer, has evolved a very different strategy to process tough food. The cranium is much more gracile and has higher stress and lower mechanical efficiency, but they adopt a different method of processing food by having a curved tooth row to concentrate force in a smaller area and molar progression to remove worn teeth from the tooth row. Therefore, the position of the bite is crucial for the structural performance of the kangaroo skull, while it is not for the wombat which process food along the entire tooth row. In accordance with previous studies, the results from this study show the mammalian skull is optimized to resist forces generated during feeding. However, other factors, including the lifestyle of the animal and its environment, also affect selection for skull morphology to meet multiple functional demands.
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Affiliation(s)
- Alana C Sharp
- School of Science and Technology, University of New England, Armidale, New South Wales, Australia.,School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria, Australia
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25
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Curtis AA, Van Valkenburgh B. Beyond the sniffer: frontal sinuses in Carnivora. Anat Rec (Hoboken) 2015; 297:2047-64. [PMID: 25312364 DOI: 10.1002/ar.23025] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Accepted: 06/25/2014] [Indexed: 11/10/2022]
Abstract
Paranasal sinuses are some of the most poorly understood features of mammalian cranial anatomy. They are highly variable in presence and form among species, but their function is not well understood. The best-supported explanations for the function of sinuses is that they opportunistically fill mechanically unnecessary space, but that in some cases, sinuses in combination with the configuration of the frontal bone may improve skull performance by increasing skull strength and dissipating stresses more evenly. We used CT technology to investigate patterns in frontal sinus size and shape disparity among three families of carnivores: Canidae, Felidae, and Hyaenidae. We provide some of the first quantitative data on sinus morphology for these three families, and employ a novel method to quantify the relationship between three-dimensional sinus shape and skull shape. As expected, frontal sinus size and shape were more strongly correlated with frontal bone size and shape than with the morphology of the skull as a whole. However, sinus morphology was also related to allometric differences among families that are linked to biomechanical function. Our results support the hypothesis that frontal sinuses most often opportunistically fill space that is mechanically unnecessary, and they can facilitate cranial shape changes that reduce stress during feeding. Moreover, we suggest that the ability to form frontal sinuses allows species to modify skull function without compromising the performance of more functionally constrained regions such as the nasal chamber (heat/water conservation, olfaction), and braincase (housing the brain and sensory structures).
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Affiliation(s)
- Abigail A Curtis
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, USA
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26
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Are cranial biomechanical simulation data linked to known diets in extant taxa? A method for applying diet-biomechanics linkage models to infer feeding capability of extinct species. PLoS One 2015; 10:e0124020. [PMID: 25923776 PMCID: PMC4414467 DOI: 10.1371/journal.pone.0124020] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 02/24/2015] [Indexed: 11/19/2022] Open
Abstract
Performance of the masticatory system directly influences feeding and survival, so adaptive hypotheses often are proposed to explain craniodental evolution via functional morphology changes. However, the prevalence of "many-to-one" association of cranial forms and functions in vertebrates suggests a complex interplay of ecological and evolutionary histories, resulting in redundant morphology-diet linkages. Here we examine the link between cranial biomechanical properties for taxa with different dietary preferences in crown clade Carnivora, the most diverse clade of carnivorous mammals. We test whether hypercarnivores and generalists can be distinguished based on cranial mechanical simulation models, and how such diet-biomechanics linkages relate to morphology. Comparative finite element and geometric morphometrics analyses document that predicted bite force is positively allometric relative to skull strain energy; this is achieved in part by increased stiffness in larger skull models and shape changes that resist deformation and displacement. Size-standardized strain energy levels do not reflect feeding preferences; instead, caniform models have higher strain energy than feliform models. This caniform-feliform split is reinforced by a sensitivity analysis using published models for six additional taxa. Nevertheless, combined bite force-strain energy curves distinguish hypercarnivorous versus generalist feeders. These findings indicate that the link between cranial biomechanical properties and carnivoran feeding preference can be clearly defined and characterized, despite phylogenetic and allometric effects. Application of this diet-biomechanics linkage model to an analysis of an extinct stem carnivoramorphan and an outgroup creodont species provides biomechanical evidence for the evolution of taxa into distinct hypercarnivorous and generalist feeding styles prior to the appearance of crown carnivoran clades with similar feeding preferences.
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27
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Jones KE, Smaers JB, Goswami A. Impact of the terrestrial-aquatic transition on disparity and rates of evolution in the carnivoran skull. BMC Evol Biol 2015; 15:8. [PMID: 25648618 PMCID: PMC4328284 DOI: 10.1186/s12862-015-0285-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 01/15/2015] [Indexed: 11/25/2022] Open
Abstract
Background Which factors influence the distribution patterns of morphological diversity among clades? The adaptive radiation model predicts that a clade entering new ecological niche will experience high rates of evolution early in its history, followed by a gradual slowing. Here we measure disparity and rates of evolution in Carnivora, specifically focusing on the terrestrial-aquatic transition in Pinnipedia. We analyze fissiped (mostly terrestrial, arboreal, and semi-arboreal, but also including the semi-aquatic otter) and pinniped (secondarily aquatic) carnivorans as a case study of an extreme ecological transition. We used 3D geometric morphometrics to quantify cranial shape in 151 carnivoran specimens (64 fissiped, 87 pinniped) and five exceptionally-preserved fossil pinnipeds, including the stem-pinniped Enaliarctos emlongi. Range-based and variance-based disparity measures were compared between pinnipeds and fissipeds. To distinguish between evolutionary modes, a Brownian motion model was compared to selective regime shifts associated with the terrestrial-aquatic transition and at the base of Pinnipedia. Further, evolutionary patterns were estimated on individual branches using both Ornstein-Uhlenbeck and Independent Evolution models, to examine the origin of pinniped diversity. Results Pinnipeds exhibit greater cranial disparity than fissipeds, even though they are less taxonomically diverse and, as a clade nested within fissipeds, phylogenetically younger. Despite this, there is no increase in the rate of morphological evolution at the base of Pinnipedia, as would be predicted by an adaptive radiation model, and a Brownian motion model of evolution is supported. Instead basal pinnipeds populated new areas of morphospace via low to moderate rates of evolution in new directions, followed by later bursts within the crown-group, potentially associated with ecological diversification within the marine realm. Conclusion The transition to an aquatic habitat in carnivorans resulted in a shift in cranial morphology without an increase in rate in the stem lineage, contra to the adaptive radiation model. Instead these data suggest a release from evolutionary constraint model, followed by aquatic diversifications within crown families. Electronic supplementary material The online version of this article (doi:10.1186/s12862-015-0285-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Katrina E Jones
- Center for Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, MD, USA. .,Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA, 02138, USA.
| | - Jeroen B Smaers
- Department of Anthropology, Stony Brook University, Stony Brook, New York, NY, 11794-4364, USA.
| | - Anjali Goswami
- Department of Genetics, Evolution & Environment, University College London, Gower Street, London, WC1E 6BT, UK. .,Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK.
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Tseng ZJ, Flynn JJ. Convergence analysis of a finite element skull model of Herpestes javanicus (Carnivora, Mammalia): Implications for robust comparative inferences of biomechanical function. J Theor Biol 2015; 365:112-48. [DOI: 10.1016/j.jtbi.2014.10.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 09/24/2014] [Accepted: 10/02/2014] [Indexed: 10/24/2022]
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Curtis AA, Lai G, Wei F, Van Valkenburgh B. Repeated loss of frontal sinuses in arctoid carnivorans. J Morphol 2014; 276:22-32. [PMID: 25069818 DOI: 10.1002/jmor.20313] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2013] [Revised: 06/19/2014] [Accepted: 07/01/2014] [Indexed: 11/11/2022]
Abstract
Many mammal skulls contain air spaces inside the bones surrounding the nasal chamber including the frontal, maxilla, ethmoid, and sphenoid, all of which are called paranasal sinuses. Within the Carnivora, frontal sinuses are usually present, but vary widely in size and shape. The causes of this variation are unclear, although there are some functional associations, such as a correlation between expanded frontal sinuses and a durophagous diet in some species (e.g., hyenas) or between absent sinuses and semiaquatic lifestyle (e.g., pinnipeds). To better understand disparity in frontal sinus morphology within Carnivora, we quantified frontal sinus size in relationship to skull size and shape in 23 species within Arctoidea, a clade that is ecologically diverse including three independent invasions of aquatic habitats, by bears, otters, and pinnipeds, respectively. Our sampled species range in behavior from terrestrial (rarely or never forage in water), to semiterrestrial (forage in water and on land), to semiaquatic (forage only in water). Results show that sinuses are either lost or reduced in both semiterrestrial and semiaquatic species, and that sinus size is related to skull size and shape. Among terrestrial species, frontal sinus size was positively allometric overall, but several terrestrial species completely lacked sinuses, including two fossorial badgers, the kinkajou (a nocturnal, arboreal frugivore), and several species with small body size, indicating that factors other than aquatic habits, such as space limitations due to constraints on skull size and shape, can limit sinus size and presence.
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Affiliation(s)
- Abigail A Curtis
- Department of Ecology and Evolutionary Biology, University of California, Los Angeles, California, 90095-1606
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Walmsley CW, McCurry MR, Clausen PD, McHenry CR. Beware the black box: investigating the sensitivity of FEA simulations to modelling factors in comparative biomechanics. PeerJ 2013; 1:e204. [PMID: 24255817 PMCID: PMC3828634 DOI: 10.7717/peerj.204] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 10/14/2013] [Indexed: 11/24/2022] Open
Abstract
Finite element analysis (FEA) is a computational technique of growing popularity in the field of comparative biomechanics, and is an easily accessible platform for form-function analyses of biological structures. However, its rapid evolution in recent years from a novel approach to common practice demands some scrutiny in regards to the validity of results and the appropriateness of assumptions inherent in setting up simulations. Both validation and sensitivity analyses remain unexplored in many comparative analyses, and assumptions considered to be ‘reasonable’ are often assumed to have little influence on the results and their interpretation. Here we report an extensive sensitivity analysis where high resolution finite element (FE) models of mandibles from seven species of crocodile were analysed under loads typical for comparative analysis: biting, shaking, and twisting. Simulations explored the effect on both the absolute response and the interspecies pattern of results to variations in commonly used input parameters. Our sensitivity analysis focuses on assumptions relating to the selection of material properties (heterogeneous or homogeneous), scaling (standardising volume, surface area, or length), tooth position (front, mid, or back tooth engagement), and linear load case (type of loading for each feeding type). Our findings show that in a comparative context, FE models are far less sensitive to the selection of material property values and scaling to either volume or surface area than they are to those assumptions relating to the functional aspects of the simulation, such as tooth position and linear load case. Results show a complex interaction between simulation assumptions, depending on the combination of assumptions and the overall shape of each specimen. Keeping assumptions consistent between models in an analysis does not ensure that results can be generalised beyond the specific set of assumptions used. Logically, different comparative datasets would also be sensitive to identical simulation assumptions; hence, modelling assumptions should undergo rigorous selection. The accuracy of input data is paramount, and simulations should focus on taking biological context into account. Ideally, validation of simulations should be addressed; however, where validation is impossible or unfeasible, sensitivity analyses should be performed to identify which assumptions have the greatest influence upon the results.
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Affiliation(s)
- Christopher W Walmsley
- Department of Anatomy and Developmental Biology, School of Biomedical Sciences, Monash University , Melbourne, Victoria , Australia ; School of Engineering, University of Newcastle , Newcastle, New South Wales , Australia
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Wroe S, Chamoli U, Parr WCH, Clausen P, Ridgely R, Witmer L. Comparative Biomechanical Modeling of Metatherian and Placental Saber-Tooths: A Different Kind of Bite for an Extreme Pouched Predator. PLoS One 2013; 8:e66888. [PMID: 23840547 PMCID: PMC3694156 DOI: 10.1371/journal.pone.0066888] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 05/10/2013] [Indexed: 11/19/2022] Open
Abstract
Questions surrounding the dramatic morphology of saber-tooths, and the presumably deadly purpose to which it was put, have long excited scholarly and popular attention. Among saber-toothed species, the iconic North American placental, Smilodon fatalis, and the bizarre South American sparassodont, Thylacosmilus atrox, represent extreme forms commonly forwarded as examples of convergent evolution. For S. fatalis, some consensus has been reached on the question of killing behaviour, with most researchers accepting the canine-shear bite hypothesis, wherein both head-depressing and jaw closing musculatures played a role in delivery of the fatal bite. However, whether, or to what degree, T. atrox may have applied a similar approach remains an open question. Here we apply a three-dimensional computational approach to examine convergence in mechanical performance between the two species. We find that, in many respects, the placental S. fatalis (a true felid) was more similar to the metatherian T. atrox than to a conical-toothed cat. In modeling of both saber-tooths we found that jaw-adductor-driven bite forces were low, but that simulations invoking neck musculature revealed less cranio-mandibular stress than in a conical-toothed cat. However, our study also revealed differences between the two saber-tooths likely reflected in the modus operandi of the kill. Jaw-adductor-driven bite forces were extremely weak in T. atrox, and its skull was even better-adapted to resist stress induced by head-depressors. Considered together with the fact that the center of the arc described by the canines was closer to the jaw-joint in Smilodon, our results are consistent with both jaw-closing and neck musculature playing a role in prey dispatch for the placental, as has been previously suggested. However, for T. atrox, we conclude that the jaw-adductors probably played no major part in the killing bite. We propose that the metatherian presents a more complete commitment to the already extreme saber-tooth 'lifestyle'.
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Affiliation(s)
- Stephen Wroe
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
- School of Engineering, University of Newcastle, Callaghan, NSW, Australia
- * E-mail:
| | - Uphar Chamoli
- School of Engineering, University of Newcastle, Callaghan, NSW, Australia
- St. George Clinical School, University of New South Wales, Sydney, NSW, Australia
| | - William C. H. Parr
- School of Engineering, University of Newcastle, Callaghan, NSW, Australia
| | - Philip Clausen
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Ryan Ridgely
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, United States of America
| | - Lawrence Witmer
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, United States of America
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Tseng ZJ. Testing adaptive hypotheses of convergence with functional landscapes: a case study of bone-cracking hypercarnivores. PLoS One 2013; 8:e65305. [PMID: 23734244 PMCID: PMC3667121 DOI: 10.1371/journal.pone.0065305] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 04/27/2013] [Indexed: 11/18/2022] Open
Abstract
Morphological convergence is a well documented phenomenon in mammals, and adaptive explanations are commonly employed to infer similar functions for convergent characteristics. I present a study that adopts aspects of theoretical morphology and engineering optimization to test hypotheses about adaptive convergent evolution. Bone-cracking ecomorphologies in Carnivora were used as a case study. Previous research has shown that skull deepening and widening are major evolutionary patterns in convergent bone-cracking canids and hyaenids. A simple two-dimensional design space, with skull width-to-length and depth-to-length ratios as variables, was used to examine optimized shapes for two functional properties: mechanical advantage (MA) and strain energy (SE). Functionality of theoretical skull shapes was studied using finite element analysis (FEA) and visualized as functional landscapes. The distribution of actual skull shapes in the landscape showed a convergent trend of plesiomorphically low-MA and moderate-SE skulls evolving towards higher-MA and moderate-SE skulls; this is corroborated by FEA of 13 actual specimens. Nevertheless, regions exist in the landscape where high-MA and lower-SE shapes are not represented by existing species; their vacancy is observed even at higher taxonomic levels. Results highlight the interaction of biomechanical and non-biomechanical factors in constraining general skull dimensions to localized functional optima through evolution.
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Affiliation(s)
- Zhijie Jack Tseng
- Department of Biological Sciences, University of Southern California, Los Angeles, California, USA.
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Hussein AK, Sullivan M, Penderis J. Effect of brachycephalic, mesaticephalic, and dolichocephalic head conformations on olfactory bulb angle and orientation in dogs as determined by use of in vivo magnetic resonance imaging. Am J Vet Res 2012; 73:946-51. [PMID: 22738044 DOI: 10.2460/ajvr.73.7.946] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To determine the effect of head conformation (brachycephalic, mesaticephalic, and dolichocephalic) on olfactory bulb angle and orientation in dogs by use of in vivo MRI. ANIMALS 40 client-owned dogs undergoing MRI for diagnosis of conditions that did not affect skull conformation or olfactory bulb anatomy. PROCEDURES For each dog, 2 head conformation indices were calculated. Olfactory bulb angle and an index of olfactory bulb orientation relative to the rest of the CNS were determined by use of measurements obtained from sagittal T2-weighted MRI images. RESULTS A significant negative correlation was found between olfactory bulb angle and values of both head conformation indices. Ventral orientation of olfactory bulbs was significantly correlated with high head conformation index values (ie, brachycephalic head conformation). CONCLUSIONS AND CLINICAL RELEVANCE Low olfactory bulb angles and ventral olfactory bulb orientations were associated with brachycephalia. Positioning of the olfactory bulbs, cribriform plate, and ethmoid turbinates was related. Indices of olfactory bulb angle and orientation may be useful for identification of dogs with extremely brachycephalic head conformations. Such information may be used by breeders to reduce the incidence or severity of brachycephalic-associated diseases.
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Affiliation(s)
- Aseel K Hussein
- School of Veterinary Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G61 1QH, Scotland
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Voss RS, Jansa SA. Snake-venom resistance as a mammalian trophic adaptation: lessons from didelphid marsupials. Biol Rev Camb Philos Soc 2012; 87:822-37. [PMID: 22404916 DOI: 10.1111/j.1469-185x.2012.00222.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Mammals that prey on venomous snakes include several opossums (Didelphidae), at least two hedgehogs (Erinaceidae), several mongooses (Herpestidae), several mustelids, and some skunks (Mephitidae). As a group, these taxa do not share any distinctive morphological traits. Instead, mammalian adaptations for ophiophagy seem to consist only in the ability to resist the toxic effects of snake venom. Molecular mechanisms of venom resistance (as indicated by biochemical research on opossums, mongooses, and hedgehogs) include toxin-neutralizing serum factors and adaptive changes in venom-targeted molecules. Of these, toxin-neutralizing serum factors have received the most research attention to date. All of the toxin-neutralizing serum proteins discovered so far in both opossums and mongooses are human α1B-glycoprotein homologs that inhibit either snake-venom metalloproteinases or phospholipase A(2) myotoxins. By contrast, adaptive changes in venom-targeted molecules have received far less attention. The best-documented examples include amino-acid substitutions in mongoose nicotinic acetylcholine receptor that inhibit binding by α-neurotoxins, and amino-acid substitutions in opossum von Willebrand factor (vWF) that are hypothesized to weaken the bond between vWF and coagulopathic C-type lectins. Although multiple mechanisms of venom resistance are known from some species, the proteomic complexity of most snake venoms suggests that the evolved biochemical defences of ophiophagous mammals are likely to be far more numerous than currently recognized. Whereas most previous research in this field has been motivated by the potential for medical applications, venom resistance in ophiophagous mammals is a complex adaptation that merits attention from comparative biologists. Unfortunately, evolutionary inference is currently limited by ignorance about many relevant facts that can only be provided by future research.
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Affiliation(s)
- Robert S Voss
- Department of Mammalogy, American Museum of Natural History, New York, NY 10024, USA.
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Segura V, Prevosti F. A quantitative approach to the cranial ontogeny of Lycalopex culpaeus (Carnivora: Canidae). ZOOMORPHOLOGY 2012. [DOI: 10.1007/s00435-012-0145-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Model sensitivity and use of the comparative finite element method in mammalian jaw mechanics: mandible performance in the gray wolf. PLoS One 2011; 6:e19171. [PMID: 21559475 PMCID: PMC3084775 DOI: 10.1371/journal.pone.0019171] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 03/21/2011] [Indexed: 11/19/2022] Open
Abstract
Finite Element Analysis (FEA) is a powerful tool gaining use in studies of biological form and function. This method is particularly conducive to studies of extinct and fossilized organisms, as models can be assigned properties that approximate living tissues. In disciplines where model validation is difficult or impossible, the choice of model parameters and their effects on the results become increasingly important, especially in comparing outputs to infer function. To evaluate the extent to which performance measures are affected by initial model input, we tested the sensitivity of bite force, strain energy, and stress to changes in seven parameters that are required in testing craniodental function with FEA. Simulations were performed on FE models of a Gray Wolf (Canis lupus) mandible. Results showed that unilateral bite force outputs are least affected by the relative ratios of the balancing and working muscles, but only ratios above 0.5 provided balancing-working side joint reaction force relationships that are consistent with experimental data. The constraints modeled at the bite point had the greatest effect on bite force output, but the most appropriate constraint may depend on the study question. Strain energy is least affected by variation in bite point constraint, but larger variations in strain energy values are observed in models with different number of tetrahedral elements, masticatory muscle ratios and muscle subgroups present, and number of material properties. These findings indicate that performance measures are differentially affected by variation in initial model parameters. In the absence of validated input values, FE models can nevertheless provide robust comparisons if these parameters are standardized within a given study to minimize variation that arise during the model-building process. Sensitivity tests incorporated into the study design not only aid in the interpretation of simulation results, but can also provide additional insights on form and function.
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TSENG ZHIJIEJACK, STYNDER DEANO. Mosaic functionality in a transitional ecomorphology: skull biomechanics in stem Hyaeninae compared to modern South African carnivorans. Biol J Linn Soc Lond 2011. [DOI: 10.1111/j.1095-8312.2010.01602.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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