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Spence M, Rull-Garza M, Roba YT, Konow N. Do salamanders chew? An X-ray reconstruction of moving morphology analysis of ambystomatid intraoral feeding behaviours. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220540. [PMID: 37839445 PMCID: PMC10577041 DOI: 10.1098/rstb.2022.0540] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 08/02/2023] [Indexed: 10/17/2023] Open
Abstract
Chewing is widespread across vertebrates, including mammals, lepidosaurs, and ray-finned and cartilaginous fishes, yet common wisdom about one group-amphibians-is that they swallow food whole, without processing. Earlier salamander studies lacked analyses of internal kinematics of the tongue, analyses of muscle function, and sampled few individuals, which may have caused erroneous conclusions. Specifically, without tongue and food kinematics, intraoral behaviours are difficult to disambiguate. We hypothesized that ambystomatid salamanders use diverse intraoral behaviours, including chewing, and tested this hypothesis with biplanar videofluoroscopy, X-ray reconstruction of moving morphology, and fluoromicrometry. We generated musculoskeletal kinematic profiles for intraoral behaviours in Axolotls (Ambystoma mexicanum), including three-dimensional skeletal kinematics associated with feeding, for gape, cranial and pectoral girdle rotations, and tongue translations. We also measured muscle fibre and muscle-tendon unit strains for six muscles involved in generating skull, jaw and tongue kinematics (adductor mandibulae, depressor mandibulae, geniohyoid, sternohyoid, epaxialis and hypaxialis). A principal component analysis recovered statistically significant differences between behaviour cycles, classified based on food movements as either chewing or transport. Thus, our data suggest that ambystomatid salamanders use a previously unrecognized diversity of intraoral behaviours, including chewing. Combined with existing knowledge, our data suggest that chewing is a basal trait for tetrapods and jaw-bearing vertebrates. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.
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Affiliation(s)
- Meghan Spence
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA 01854, USA
| | - Mateo Rull-Garza
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA 01854, USA
| | - Yonas Tolosa Roba
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA 01854, USA
| | - Nicolai Konow
- Department of Biological Sciences, University of Massachusetts Lowell, Lowell, MA 01854, USA
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2
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Hovorakova M, Zahradnicek O, Bartos M, Hurnik P, Stransky J, Stembirek J, Tucker AS. Reawakening of Ancestral Dental Potential as a Mechanism to Explain Dental Pathologies. Integr Comp Biol 2021; 60:619-629. [PMID: 32492167 DOI: 10.1093/icb/icaa053] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
During evolution, there has been a trend to reduce both the number of teeth and the location where they are found within the oral cavity. In mammals, the formation of teeth is restricted to a horseshoe band of odontogenic tissue, creating a single dental arch on the top and bottom of the jaw. Additional teeth and structures containing dental tissue, such as odontogenic tumors or cysts, can appear as pathologies. These tooth-like structures can be associated with the normal dentition, appearing within the dental arch, or in nondental areas. The etiology of these pathologies is not well elucidated. Reawakening of the potential to form teeth in different parts of the oral cavity could explain the origin of dental pathologies outside the dental arch, thus such pathologies are a consequence of our evolutionary history. In this review, we look at the changing pattern of tooth formation within the oral cavity during vertebrate evolution, the potential to form additional tooth-like structures in mammals, and discuss how this knowledge shapes our understanding of dental pathologies in humans.
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Affiliation(s)
- Maria Hovorakova
- Institute of Histology and Embryology, First Faculty of Medicine, Charles University in Prague, Albertov 4, 128 00 Prague 2, Czech Republic.,Institute of Experimental Medicine, Czech Academy of Sciences, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Oldrich Zahradnicek
- Institute of Experimental Medicine, Czech Academy of Sciences, Videnska 1083, 14220 Prague 4, Czech Republic
| | - Martin Bartos
- Department of Stomatology, First Faculty of Medicine, Charles University, General University Hospital in Prague, Katerinska 32, 12801 Prague 2, Czech Republic.,Institute of Anatomy, First Faculty of Medicine, Charles University, U Nemocnice 3, Prague 2, 128 00, Czech Republic
| | - Pavel Hurnik
- Department of Pathology, University Hospital Ostrava, 17. listopadu 1790, Ostrava-Poruba, 708 52, Czech Republic.,Department of Pathology at Faculty of Medicine, University of Ostrava, Syllabova 19, Ostrava-Zabreh, 703 00, Czech Republic
| | - Jiri Stransky
- Department of Oral and Maxillofacial Surgery, University Hospital Ostrava, 17. listopadu 1790, 708 52 Ostrava-Poruba, Czech Republic
| | - Jan Stembirek
- Department of Oral and Maxillofacial Surgery, University Hospital Ostrava, 17. listopadu 1790, 708 52 Ostrava-Poruba, Czech Republic.,Institute of Animal Physiology and Genetics, v.v.i., Czech Academy of Sciences, Veveri 97, 602 00, Brno 2, Czech Republic
| | - Abigail S Tucker
- Centre for Craniofacial and Regenerative Biology, Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, London, SE1 9RT, UK
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3
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Winkler DE, Schulz-Kornas E, Kaiser TM, Tütken T. Dental microwear texture reflects dietary tendencies in extant Lepidosauria despite their limited use of oral food processing. Proc Biol Sci 2020; 286:20190544. [PMID: 31113323 DOI: 10.1098/rspb.2019.0544] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Lepidosauria show a large diversity in dietary adaptations, both among extant and extinct tetrapods. Unlike mammals, Lepidosauria do not engage in sophisticated mastication of their food and most species have continuous tooth replacement, further reducing the wear of individual teeth. However, dietary tendency estimation of extinct lepidosaurs usually rely on tooth shape and body size, which allows only for broad distinction between faunivores and herbivores. Microscopic wear features on teeth have long been successfully applied to reconstruct the diet of mammals and allow for subtle discrimination of feeding strategies and food abrasiveness. Here, we present, to our knowledge, the first detailed analysis of dental microwear texture on extant lepidosaurs using a combination of 46 surface texture parameters to establish a framework for dietary tendency estimation of fossil reptilian taxa. We measured dental surface textures of 77 specimens, belonging to herbivorous, algaevorous, frugivorous, carnivorous, ovivorous, insectivorous, molluscivorous, as well as omnivorous species. Carnivores show low density and shallow depth of furrows, whereas frugivores are characterized by the highest density of furrows. Molluscivores show the deepest wear features and highest roughness, herbivores have lower surface roughness and shallower furrows compared to insectivores and omnivores, which overlap in all parameters. Our study shows that despite short food-tooth interaction, dental surface texture parameters enable discrimination of several feeding strategies in lepidosaurs. This result opens new research avenues to assess diet in a broad variety of extant and extinct non-mammalian taxa including dinosaurs and early synapsids.
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Affiliation(s)
- Daniela E Winkler
- 1 Applied and Analytical Palaeontology, Institute of Geosciences, Johannes Gutenberg University , J.-J.-Becher-Weg 21, 55128 Mainz , Germany
| | - Ellen Schulz-Kornas
- 2 Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology , Leipzig , Germany
| | - Thomas M Kaiser
- 3 Center of Natural History (CeNak), University of Hamburg , Hamburg , Germany
| | - Thomas Tütken
- 1 Applied and Analytical Palaeontology, Institute of Geosciences, Johannes Gutenberg University , J.-J.-Becher-Weg 21, 55128 Mainz , Germany
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4
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Jones MEH, Lucas PW, Tucker AS, Watson AP, Sertich JJW, Foster JR, Williams R, Garbe U, Bevitt JJ, Salvemini F. Neutron scanning reveals unexpected complexity in the enamel thickness of an herbivorous Jurassic reptile. J R Soc Interface 2019; 15:rsif.2018.0039. [PMID: 29899156 PMCID: PMC6030635 DOI: 10.1098/rsif.2018.0039] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 05/18/2018] [Indexed: 11/12/2022] Open
Abstract
Eilenodontines are one of the oldest radiation of herbivorous lepidosaurs (snakes, lizards and tuatara) characterized by batteries of wide teeth with thick enamel that bear mammal-like wear facets. Unlike most reptiles, eilenodontines have limited tooth replacement, making dental longevity particularly important to them. We use both X-ray and neutron computed tomography to examine a fossil tooth from the eilenodontine Eilenodon (Late Jurassic, USA). Of the two approaches, neutron tomography was more successful and facilitated measurements of enamel thickness and distribution. We find the enamel thickness to be regionally variable, thin near the cusp tip (0.10 mm) but thicker around the base (0.15–0.30 mm) and notably greater than that of other rhynchocephalians such as the extant Sphenodon (0.08–0.14 mm). The thick enamel in Eilenodon would permit greater loading, extend tooth lifespan and facilitate the establishment of wear facets that have sharp edges for orally processing plant material such as horsetails (Equisetum). The shape of the enamel dentine junction indicates that tooth development in Eilenodon and Sphenodon involved similar folding of the epithelium but different ameloblast activity.
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Affiliation(s)
- Marc E H Jones
- Department of Earth Sciences, The Natural History Museum, London, UK .,Department of Genetics and Evolution, School of Biological Sciences, The University of Adelaide, North Terrace, Adelaide, South Australia 5005, Australia.,South Australian Museum, North Terrace, Adelaide, South Australia 5001, Australia
| | - Peter W Lucas
- Smithsonian Tropical Research Institute, Balboa, Panama
| | - Abigail S Tucker
- Craniofacial Development and Stem Cell Biology, King's College London, London, UK
| | - Amy P Watson
- Department of Genetics and Evolution, School of Biological Sciences, The University of Adelaide, North Terrace, Adelaide, South Australia 5005, Australia
| | - Joseph J W Sertich
- Department of Earth Sciences, Denver Museum of Nature and Science, Denver, CO, USA
| | | | - Ruth Williams
- Department of Adelaide Microscopy, The University of Adelaide, Adelaide, South Australia 5001, Australia
| | - Ulf Garbe
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Sydney, Australia
| | - Joseph J Bevitt
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Sydney, Australia
| | - Floriana Salvemini
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Sydney, Australia
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5
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Jones MEH, Button DJ, Barrett PM, Porro LB. Digital dissection of the head of the rock dove ( Columba livia) using contrast-enhanced computed tomography. ZOOLOGICAL LETTERS 2019; 5:17. [PMID: 31205748 PMCID: PMC6558907 DOI: 10.1186/s40851-019-0129-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 04/09/2019] [Indexed: 06/09/2023]
Abstract
The rock dove (or common pigeon), Columba livia, is an important model organism in biological studies, including research focusing on head muscle anatomy, feeding kinematics, and cranial kinesis. However, no integrated computer-based biomechanical model of the pigeon head has yet been attempted. As an initial step towards achieving this goal, we present the first three-dimensional digital dissection of the pigeon head based on a contrast-enhanced computed tomographic dataset achieved using iodine potassium iodide as a staining agent. Our datasets enable us to visualize the skeletal and muscular anatomy, brain and cranial nerves, and major sense organs of the pigeon, including very small and fragile features, as well as maintaining the three-dimensional topology of anatomical structures. This work updates and supplements earlier anatomical work on this widely used laboratory organism. We resolve several key points of disagreement arising from previous descriptions of pigeon anatomy, including the precise arrangement of the external adductor muscles and their relationship to the posterior adductor. Examination of the eye muscles highlights differences between avian taxa and shows that pigeon eye muscles are more similar to those of a tinamou than they are to those of a house sparrow. Furthermore, we present our three-dimensional data as publicly accessible files for further research and education purposes. Digital dissection permits exceptional visualisation and will be a valuable resource for further investigations into the head anatomy of other bird species, as well as efforts to reconstruct soft tissues in fossil archosaurs.
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Affiliation(s)
- Marc E. H. Jones
- Department of Earth Sciences, Natural History Museum, London, SW7 5BD UK
| | - David J. Button
- Department of Earth Sciences, Natural History Museum, London, SW7 5BD UK
| | - Paul M. Barrett
- Department of Earth Sciences, Natural History Museum, London, SW7 5BD UK
| | - Laura B. Porro
- Department of Cell and Developmental Biology, UCL, University College London, Gower Street, London, WC1E 6BT UK
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6
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Bertin TJC, Thivichon-Prince B, LeBlanc ARH, Caldwell MW, Viriot L. Current Perspectives on Tooth Implantation, Attachment, and Replacement in Amniota. Front Physiol 2018; 9:1630. [PMID: 30519190 PMCID: PMC6258785 DOI: 10.3389/fphys.2018.01630] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 10/29/2018] [Indexed: 01/03/2023] Open
Abstract
Teeth and dentitions contain many morphological characters which give them a particularly important weight in comparative anatomy, systematics, physiology and ecology. As teeth are organs that contain the hardest mineralized tissues vertebrates can produce, their fossil remains are abundant and the study of their anatomy in fossil specimens is of major importance in evolutionary biology. Comparative anatomy has long favored studies of dental characters rather than features associated with tooth attachment and implantation. Here we review a large part of the historical and modern work on the attachment, implantation and replacement of teeth in Amniota. We propose synthetic definitions or redefinitions of most commonly used terms, some of which have led to confusion and conflation of terminology. In particular, there has long been much conflation between dental implantation that strictly concerns the geometrical aspects of the tooth-bone interface, and the nature of the dental attachment, which mostly concerns the histological features occurring at this interface. A second aim of this work was to evaluate the diversity of tooth attachment, implantation and replacement in extant and extinct amniotes in order to derive hypothetical evolutionary trends in these different dental traits over time. Continuous dental replacement prevails within amniotes, replacement being drastically modified only in Mammalia and when dental implantation is acrodont. By comparison, dental implantation frequently and rapidly changes at various taxonomic scales and is often homoplastic. This contrasts with the conservatism in the identity of the tooth attachment tissues (cementum, periodontal ligament, and alveolar bone), which were already present in the earliest known amniotes. Because the study of dental attachment requires invasive histological investigations, this trait is least documented and therefore its evolutionary history is currently poorly understood. Finally, it is essential to go on collecting data from all groups of amniotes in order to better understand and consequently better define dental characters.
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Affiliation(s)
- Thomas J. C. Bertin
- Team Evolution of Vertebrate Dentition, Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Béatrice Thivichon-Prince
- Team Evolution of Vertebrate Dentition, Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Lyon, France
- Faculte d’Odontologie, Université Claude Bernard Lyon 1, Lyon, France
- Service d’Odontologie, Hospices Civils de Lyon, Lyon, France
| | - Aaron R. H. LeBlanc
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Michael W. Caldwell
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Laurent Viriot
- Team Evolution of Vertebrate Dentition, Institut de Génomique Fonctionnelle de Lyon, Université de Lyon, CNRS UMR 5242, Ecole Normale Supérieure de Lyon, Université Claude Bernard Lyon 1, Lyon, France
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7
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Puncture-and-Pull Biomechanics in the Teeth of Predatory Coelurosaurian Dinosaurs. Curr Biol 2018; 28:1467-1474.e2. [PMID: 29706515 DOI: 10.1016/j.cub.2018.03.042] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2017] [Revised: 02/22/2018] [Accepted: 03/20/2018] [Indexed: 11/20/2022]
Abstract
The teeth of putatively carnivorous dinosaurs are often blade-shaped with well-defined serrated cutting edges (Figure 1). These ziphodont teeth are often easily differentiated based on the morphology and density of the denticles [1, 2]. A tearing function has been proposed for theropod denticles in general [3], but the functional significance of denticle phenotypic variation has received less attention. In particular, the unusual hooked denticles found in troodontids suggest a different feeding strategy or diet compared to other small theropods. We used a two-pronged approach to investigate the function of denticle shape variation across theropods with both congruent body shapes and sizes (e.g., dromaeosaurids versus troodontids) and highly disparate body shapes and sizes (e.g., troodontids versus tyrannosaurids), using microwear and finite element analyses (Figure 1). We found that many toothed coelurosaurian theropods employed a puncture-and-pull feeding movement, in which parallel scratches form while biting down into prey and oblique scratches form as the head is pulled backward with the jaws closed. In finite element simulations, theropod teeth had the lowest stresses when bite forces were aligned with the oblique family of microwear scratches. Different denticle morphologies performed differently under a variety of simulated biting angles: Dromaeosaurus and Saurornitholestes were well-adapted for handling struggling prey, whereas troodontid teeth were more likely to fail at non-optimal bite angles. Troodontids may have favored softer, smaller, or immobile prey.
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Jones MEH, Gröning F, Dutel H, Sharp A, Fagan MJ, Evans SE. The biomechanical role of the chondrocranium and sutures in a lizard cranium. J R Soc Interface 2017; 14:20170637. [PMID: 29263126 PMCID: PMC5746569 DOI: 10.1098/rsif.2017.0637] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 11/28/2017] [Indexed: 11/30/2022] Open
Abstract
The role of soft tissues in skull biomechanics remains poorly understood. Not least, the chondrocranium, the portion of the braincase which persists as cartilage with varying degrees of mineralization. It also remains commonplace to overlook the biomechanical role of sutures despite evidence that they alter strain distribution. Here, we examine the role of both the sutures and the chondrocranium in the South American tegu lizard Salvator merianae We use multi-body dynamics analysis (MDA) to provide realistic loading conditions for anterior and posterior unilateral biting and a detailed finite element model to examine strain magnitude and distribution. We find that strains within the chondrocranium are greatest during anterior biting and are primarily tensile; also that strain within the cranium is not greatly reduced by the presence of the chondrocranium unless it is given the same material properties as bone. This result contradicts previous suggestions that the anterior portion (the nasal septum) acts as a supporting structure. Inclusion of sutures to the cranium model not only increases overall strain magnitudes but also leads to a more complex distribution of tension and compression rather than that of a beam under sagittal bending.
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Affiliation(s)
- Marc E H Jones
- School of Biological Sciences, The University of Adelaide, North Terrace, Adelaide, South Australia 5005, Australia
- South Australian Museum, North Terrace, Adelaide, South Australia 5001, Australia
| | - Flora Gröning
- School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Aberdeen AB25 2ZD, UK
| | - Hugo Dutel
- School of Engineering and Computer Science, Medical and Biological Engineering Research Group, University of Hull, Hull HU6 7RX, UK
| | - Alana Sharp
- Research Department of Cell and Developmental Biology, UCL, University College London, Anatomy Building, Gower Street, London WCIE 6BT, UK
| | - Michael J Fagan
- School of Engineering and Computer Science, Medical and Biological Engineering Research Group, University of Hull, Hull HU6 7RX, UK
| | - Susan E Evans
- Research Department of Cell and Developmental Biology, UCL, University College London, Anatomy Building, Gower Street, London WCIE 6BT, UK
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9
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Ma W, Wang J, Pittman M, Tan Q, Tan L, Guo B, Xu X. Functional anatomy of a giant toothless mandible from a bird-like dinosaur: Gigantoraptor and the evolution of the oviraptorosaurian jaw. Sci Rep 2017; 7:16247. [PMID: 29176627 PMCID: PMC5701234 DOI: 10.1038/s41598-017-15709-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 10/31/2017] [Indexed: 12/26/2022] Open
Abstract
The Oviraptorosauria are a group of theropod dinosaurs that diverged from the typical carnivorous theropod diet. It includes two main lineages – Caenagnathidae and Oviraptoridae – that display a number of differences in mandibular morphology, but little is known about their functional consequences, hampering our understanding of oviraptorosaurian dietary evolution. This study presents the first in-depth description of the giant toothless mandible of Gigantoraptor, the only well-preserved stemward caenagnathid mandible. This mandible shows the greatest relative beak depth among caenagnathids, which is an adaptation seen in some modern birds for processing harder seeds. The presence of a lingual triturating shelf in caenagnathids more crownward than Gigantoraptor suggests a possible increased specialization towards shearing along this lineage. Like other oviraptorosaurs, the possession of a dorsally convex articular glenoid in Gigantoraptor indicates that propalinal jaw movement was probably an important mechanism for food processing, as in Sphenodon and dicynodonts. Oviraptorid mandibles were more suited for producing powerful bites (e.g. crushing-related) compared to caenagnathids: oviraptorids generally possess a deeper, more downturned beak, a taller coronoid process prominence and a larger medial mandibular fossa. This disparity in caenagnathid and oviraptorid mandible morphology potentially suggests specialization towards two different feeding styles – shearing and crushing-related mechanisms respectively.
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Affiliation(s)
- Waisum Ma
- Vertebrate Palaeontology Laboratory, Department of Earth Sciences, University of Hong Kong, Pokfulam, Hong Kong, China
| | - Junyou Wang
- Longhao Institute of Geology and Paleontology, Hohhot, Nei Mongol, 010011, China
| | - Michael Pittman
- Vertebrate Palaeontology Laboratory, Department of Earth Sciences, University of Hong Kong, Pokfulam, Hong Kong, China.
| | - Qingwei Tan
- Nei Mongol Museum of Nature, Hohhot, Nei Mongol, 010011, China
| | - Lin Tan
- Longhao Institute of Geology and Paleontology, Hohhot, Nei Mongol, 010011, China
| | - Bin Guo
- Nei Mongol Museum of Nature, Hohhot, Nei Mongol, 010011, China
| | - Xing Xu
- Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China.
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10
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Melstrom KM. The relationship between diet and tooth complexity in living dentigerous saurians. J Morphol 2017; 278:500-522. [PMID: 28145089 DOI: 10.1002/jmor.20645] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 11/28/2016] [Accepted: 12/09/2016] [Indexed: 11/07/2022]
Abstract
Living saurian reptiles exhibit a wide range of diets, from carnivores to strict herbivores. Previous research suggests that the tooth shape in some lizard clades correlates with diet, but this has not been tested using quantitative methods. I investigated the relationship between phenotypic tooth complexity and diet in living reptiles by examining the entire dentary tooth row in over 80 specimens comprising all major dentigerous saurian clades. I quantified dental complexity using orientation patch count rotated (OPCR), which discriminates diet in living and extinct mammals, where OPCR-values increase with the proportion of dietary plant matter. OPCR was calculated from high-resolution CT-scans, and I standardized OPCR-values by the total number of teeth to account for differences in tooth count across taxa. In contrast with extant mammals, there appears to be greater overlap in tooth complexity values across dietary groups because multicusped teeth characterize herbivores, omnivores, and insectivores, and because herbivorous skinks have relatively simple teeth. In particular, insectivorous lizards have dental complexities that are very similar to omnivores. Regardless, OPCR-values for animals that consume significant amounts of plant material are higher than those of carnivores, with herbivores having the highest average dental complexity. These results suggest reptilian tooth complexity is related to diet, similar to extinct and extant mammals, although phylogenetic history also plays a measurable role in dental complexity. This has implications for extinct amniotes that display a dramatic range of tooth morphologies, many with no modern analogs, which inhibits detailed dietary reconstructions. These data demonstrate that OPCR, when combined with additional morphological data, has the potential to be used to reconstruct the diet of extinct amniotes. J. Morphol. 278:500-522, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Keegan M Melstrom
- Department of Geology and Geophysics, University of Utah, 115 S 1460 E, Salt Lake City, Utah, 84112-0102
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11
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Matsumoto R, Evans SE. The palatal dentition of tetrapods and its functional significance. J Anat 2017; 230:47-65. [PMID: 27542892 PMCID: PMC5192890 DOI: 10.1111/joa.12534] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/13/2016] [Indexed: 11/30/2022] Open
Abstract
The presence of a palatal dentition is generally considered to be the primitive condition in amniotes, with each major lineage showing a tendency toward reduction. This study highlights the variation in palatal tooth arrangements and reveals clear trends within the evolutionary history of tetrapods. Major changes occurred in the transition between early tetrapods and amphibians on the one hand, and stem amniotes on the other. These changes reflect the function of the palatal dentition, which can play an important role in holding and manipulating food during feeding. Differences in the arrangement of palatal teeth, and in their pattern of loss, likely reflect differences in feeding strategy but also changes in the arrangement of cranial soft tissues, as the palatal dentition works best with a well-developed mobile tongue. It is difficult to explain the loss of palatal teeth in terms of any single factor, but palatal tooth patterns have the potential to provide new information on diet and feeding strategy in extinct taxa.
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Affiliation(s)
- Ryoko Matsumoto
- Kanagawa Prefectural Museum Natural HistoryOdawaraKanagawaJapan
| | - Susan E. Evans
- Department of Cell and Developmental BiologyUniversity College London (UCL)LondonUK
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12
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Regnault S, Hutchinson JR, Jones MEH. Sesamoid bones in tuatara (Sphenodon punctatus) investigated with X-ray microtomography, and implications for sesamoid evolution in Lepidosauria. J Morphol 2016; 278:62-72. [PMID: 27882577 PMCID: PMC6680162 DOI: 10.1002/jmor.20619] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 09/12/2016] [Accepted: 09/16/2016] [Indexed: 11/08/2022]
Abstract
Sesamoids bones are small intra-tendinous (or ligamentous) ossifications found near joints and are often variable between individuals. Related bones, lunulae, are found within the menisci of certain joints. Several studies have described sesamoids and lunulae in lizards and their close relatives (Squamata) as potentially useful characters in phylogenetic analysis, but their status in the extant outgroup to Squamata, tuatara (Sphenodon), remains unclear. Sphenodon is the only living rhynchocephalian, but museum specimens are valuable and difficult to replace. Here, we use non-destructive X-ray microtomography to investigate the distribution of sesamoids and lunulae in 19 Sphenodon specimens and trace the evolution of these bones in Lepidosauria (Rhynchocephalia + Squamata). We find adult Sphenodon to possess a sesamoid and lunula complement different from any known squamate, but also some variation within Sphenodon specimens. The penultimate phalangeal sesamoids and tibial lunula appear to mineralize prior to skeletal maturity, followed by mineralization of a sesamoid between metatarsal I and the astragalocalcaneum (MTI-AC), the palmar sesamoids, and tibiofemoral lunulae around attainment of skeletal maturity. The tibial patella, ulnar, and plantar sesamoids mineralize late in maturity or variably. Ancestral state reconstruction indicates that the ulnar patella and tibiofemoral lunulae are synapomophies of Squamata, and the palmar sesamoid, tibial patella, tibial lunula, and MTI-AC may be synapomorphies of Lepidosauria. J. Morphol. 278:62-72, 2017. ©© 2016 Wiley Periodicals,Inc.
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Affiliation(s)
- Sophie Regnault
- Structure & Motion Lab, Department of Comparative Biomedical Sciences, The Royal Veterinary College, London, United Kingdom
| | - John R Hutchinson
- Structure & Motion Lab, Department of Comparative Biomedical Sciences, The Royal Veterinary College, London, United Kingdom
| | - Marc E H Jones
- Department of Genetics and Evolution, School of Biological Sciences, The University of Adelaide, North Terrace, Adelaide, South Australia, 5005, Australia.,Department of Herpetology, South Australian Museum, North Terrace, Adelaide, South Australia, 5001, Australia
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Nabavizadeh A, Weishampel DB. The Predentary Bone and Its Significance in the Evolution of Feeding Mechanisms in Ornithischian Dinosaurs. Anat Rec (Hoboken) 2016; 299:1358-88. [PMID: 27490958 DOI: 10.1002/ar.23455] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 06/11/2016] [Accepted: 06/16/2016] [Indexed: 11/10/2022]
Abstract
The characteristic predentary bone in ornithischian dinosaurs is a unique, unpaired element located at the midline of the mandibular symphysis. Although traditionally thought to only be a plant "nipping" bone, the true functional significance of this bone among feeding mechanisms of ornithischian dinosaurs is poorly known. Recent studies of a select few ornithischian genera have suggested rotation of the mandibular corpora around their long axes relative to their midline joint articulation with the predentary bone. This study aims to re-evaluate these hypotheses as well as provide in-depth qualitative comparative descriptions of predentary bone morphology in ornithischian genera throughout all subclades, including heterodontosaurids, thyreophorans, ornithopods, and marginocephalians. Descriptions evaluate overall shape of the predentary, its articular surfaces contacting the rostral ends of the dentaries, and the morphology of the rostral extent of the dentaries and their midline symphysis. Functionally relevant morphologies in each predentary morphotype are accentuated for further speculation of feeding mechanisms. Three predentary morphotypes are described throughout ornithischian subclades and each plays a unique role in feeding adaptations. Most notably, the predentary likely evolved as a midline axial point of the mandibular symphysis for simultaneous variable movement or rotation of the mandibular corpora in many, but not all, taxa. This simultaneous movement of the hemimandibles would have aided in feeding on both sides of the jaw at once. The function of the predentary as well as other jaw adaptations is discussed for genera throughout all subclades, focusing on both general shape and joint morphology. Anat Rec, 299:1358-1388, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Ali Nabavizadeh
- Department of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, New Jersey.
| | - David B Weishampel
- Johns Hopkins University School of Medicine, Center for Functional Anatomy and Evolution, Baltimore, Maryland
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Cox PG, Kirkham J, Herrel A. Masticatory biomechanics of the Laotian rock rat, Laonastes aenigmamus, and the function of the zygomaticomandibularis muscle. PeerJ 2013; 1:e160. [PMID: 24058888 PMCID: PMC3775629 DOI: 10.7717/peerj.160] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 08/23/2013] [Indexed: 11/20/2022] Open
Abstract
The Laotian rock rat, Laonastes aenigmamus, is one of the most recently discovered species of rodent, and displays a cranial morphology that is highly specialised. The rostrum of L. aenigmamus is exceptionally elongate and bears a large attachment site for the infraorbital portion of the zygomaticomandibularis muscle (IOZM), which is particularly well-developed in this species. In this study, we used finite element analysis to investigate the biomechanical performance of the Laotian rock rat cranium and to elucidate the function of the IOZM. A finite element model of the skull of L. aenigmamus was constructed and solved for biting on each of the teeth (incisors, premolar and molars). Further load cases were created and solved in which the origin of the IOZM had been moved anteriorly and posteriorly along the rostrum. Finally, a set of load cases were produced in which the IOZM was removed entirely, and its force was redistributed between the remaining masticatory muscles. The analysis showed that, during biting, the most stressed areas of the skull were the zygomatic and orbital regions. Compared to other rodents, L. aenigmamus is highly efficient at incisor gnawing, but less efficient at molar chewing. However, a relatively constant bite force across the molar tooth row may be an adaptation to folivory. Movement of the origin of the IOZM had little on the patterns of von Mises stresses, or the overall stress experienced by the cranium. However, removal of the IOZM had a substantial effect on the total deformation experienced by the skull. In addition, the positioning and presence of the IOZM had large impact on bite force. Moving the IOZM origin to the anterior tip of the rostrum led to a substantially reduced bite force at all teeth. This was hypothesised to be a result of the increasing horizontal component to the pull of this muscle as it is moved anteriorly along the rostrum. Removal of the IOZM also resulted in reduced bite force, even when the total input muscle force was maintained at the same level. It was thus concluded that the function of the IOZM in L. aenigmamus is to increase bite force whilst reducing cranial deformation. If the IOZM can be shown to have this function in other rodent groups, this may help explain the evolution of this muscle, and may also provide an understanding of why it has evolved independently several times within rodents.
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Affiliation(s)
- Philip G Cox
- Centre for Anatomical and Human Sciences, Hull York Medical School , University of Hull, Hull , UK
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Curtis N, Jones MEH, Evans SE, O'Higgins P, Fagan MJ. Cranial sutures work collectively to distribute strain throughout the reptile skull. J R Soc Interface 2013; 10:20130442. [PMID: 23804444 PMCID: PMC3730698 DOI: 10.1098/rsif.2013.0442] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The skull is composed of many bones that come together at sutures. These sutures are important sites of growth, and as growth ceases some become fused while others remain patent. Their mechanical behaviour and how they interact with changing form and loadings to ensure balanced craniofacial development is still poorly understood. Early suture fusion often leads to disfiguring syndromes, thus is it imperative that we understand the function of sutures more clearly. By applying advanced engineering modelling techniques, we reveal for the first time that patent sutures generate a more widely distributed, high level of strain throughout the reptile skull. Without patent sutures, large regions of the skull are only subjected to infrequent low-level strains that could weaken the bone and result in abnormal development. Sutures are therefore not only sites of bone growth, but could also be essential for the modulation of strains necessary for normal growth and development in reptiles.
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Affiliation(s)
- Neil Curtis
- Medical and Biological Engineering Research Group, School of Engineering, University of Hull, Hull HU6 7RX, UK.
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Gröning F, Jones MEH, Curtis N, Herrel A, O'Higgins P, Evans SE, Fagan MJ. The importance of accurate muscle modelling for biomechanical analyses: a case study with a lizard skull. J R Soc Interface 2013; 10:20130216. [PMID: 23614944 PMCID: PMC3673157 DOI: 10.1098/rsif.2013.0216] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Computer-based simulation techniques such as multi-body dynamics analysis are becoming increasingly popular in the field of skull mechanics. Multi-body models can be used for studying the relationships between skull architecture, muscle morphology and feeding performance. However, to be confident in the modelling results, models need to be validated against experimental data, and the effects of uncertainties or inaccuracies in the chosen model attributes need to be assessed with sensitivity analyses. Here, we compare the bite forces predicted by a multi-body model of a lizard (Tupinambis merianae) with in vivo measurements, using anatomical data collected from the same specimen. This subject-specific model predicts bite forces that are very close to the in vivo measurements and also shows a consistent increase in bite force as the bite position is moved posteriorly on the jaw. However, the model is very sensitive to changes in muscle attributes such as fibre length, intrinsic muscle strength and force orientation, with bite force predictions varying considerably when these three variables are altered. We conclude that accurate muscle measurements are crucial to building realistic multi-body models and that subject-specific data should be used whenever possible.
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Affiliation(s)
- Flora Gröning
- Department of Engineering, Medical and Biological Engineering Research Group, University of Hull, Hull, UK.
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18
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Jones MEH, Werneburg I, Curtis N, Penrose R, O'Higgins P, Fagan MJ, Evans SE. The head and neck anatomy of sea turtles (Cryptodira: Chelonioidea) and skull shape in Testudines. PLoS One 2012; 7:e47852. [PMID: 23144831 PMCID: PMC3492385 DOI: 10.1371/journal.pone.0047852] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 09/19/2012] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Sea turtles (Chelonoidea) are a charismatic group of marine reptiles that occupy a range of important ecological roles. However, the diversity and evolution of their feeding anatomy remain incompletely known. METHODOLOGY/PRINCIPAL FINDINGS Using computed tomography and classical comparative anatomy we describe the cranial anatomy in two sea turtles, the loggerhead (Caretta caretta) and Kemp's ridley (Lepidochelys kempii), for a better understanding of sea turtle functional anatomy and morphological variation. In both taxa the temporal region of the skull is enclosed by bone and the jaw joint structure and muscle arrangement indicate that palinal jaw movement is possible. The tongue is relatively small, and the hyoid apparatus is not as conspicuous as in some freshwater aquatic turtles. We find several similarities between the muscles of C. caretta and L. kempii, but comparison with other turtles suggests only one of these characters may be derived: connection of the m. adductor mandibulae internus into the Pars intramandibularis via the Zwischensehne. The large fleshy origin of the m. adductor mandibulae externus Pars superficialis from the jugal seems to be a characteristic feature of sea turtles. CONCLUSIONS/SIGNIFICANCE In C. caretta and L. kempii the ability to suction feed does not seem to be as well developed as that found in some freshwater aquatic turtles. Instead both have skulls suited to forceful biting. This is consistent with the observation that both taxa tend to feed on relatively slow moving but sometimes armoured prey. The broad fleshy origin of the m. adductor mandibulae externus Pars superficialis may be linked to thecheek region being almost fully enclosed in bone but the relationship is complex.
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Affiliation(s)
- Marc E H Jones
- Research Department of Cell and Developmental Biology, UCL, University College London, London, England, United Kingdom.
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Meloro C, Jones MEH. Tooth and cranial disparity in the fossil relatives ofSphenodon(Rhynchocephalia) dispute the persistent ‘living fossil’ label. J Evol Biol 2012; 25:2194-209. [DOI: 10.1111/j.1420-9101.2012.02595.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 07/04/2012] [Accepted: 07/09/2012] [Indexed: 11/28/2022]
Affiliation(s)
- C. Meloro
- Hull York Medical School; The University of Hull; Hull; UK
| | - M. E. H. Jones
- Research Department of Cell and Developmental Biology; University College London; London; UK
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