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Butler RJ, Meade LE, Cleary TJ, McWhirter KT, Brown EE, Kemp TS, Benito J, Fraser NC. Hwiccewyrm trispiculum gen. et sp. nov., a new leptopleuronine procolophonid from the Late Triassic of southwest England. Anat Rec (Hoboken) 2024; 307:1390-1420. [PMID: 37735997 DOI: 10.1002/ar.25316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 08/16/2023] [Accepted: 08/22/2023] [Indexed: 09/23/2023]
Abstract
The fissure fill localities of southwest England and South Wales are well-known for preserving rich assemblages of predominantly small-bodied Late Triassic to Early Jurassic tetrapods, but many aspects of these assemblages remain contentious. The age of the Late Triassic fissures is disputed, with some lines of argument suggesting a latest Triassic (Rhaetian) age, whereas other evidence suggests they may be as old as Carnian. The fissures have been hypothesized by some workers to have formed on an archipelago, with island effects invoked to explain aspects of the assemblages such as the abundance of small-bodied species. Procolophonids were a successful group of Triassic parareptiles, best known from Early to early Late Triassic assemblages, but have only recently been described from one of the fissure fill sites (Ruthin) based upon fragmentary remains. Here, we describe new procolophonid specimens from another fissure (Cromhall) that represent at least six individuals of different sizes, with much of the skeleton represented including well-preserved skull material. The Cromhall procolophonid shows strong similarities to Late Triassic procolophonids from Scotland, Brazil and North America, but both autapomorphies and a unique character combination demonstrate that it represents a new species, which we name as Hwiccewyrm trispiculum gen. et sp. nov. Phylogenetic analysis places Hwiccewyrm in a derived clade within Leptopleuroninae, together with Leptopleuron, Hypsognathus, and Soturnia. The largest specimens of Hwiccewyrm demonstrate a body size that is similar to Leptopleuron and Hypsognathus, supporting other recent work that has questioned the insular dwarfism hypothesis for the fissure fill assemblages.
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Affiliation(s)
- Richard J Butler
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK
| | - Luke E Meade
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK
| | - Terri J Cleary
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK
| | - Kai T McWhirter
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK
| | - Emily E Brown
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, UK
- Fossil Reptiles, Amphibians and Birds Section, Natural History Museum, London, UK
| | - Tom S Kemp
- St John's College, University of Oxford, Oxford, UK
| | - Juan Benito
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Nicholas C Fraser
- Department of Natural Sciences, National Museums Scotland, Edinburgh, Scotland
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2
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Mueller BD, Small BJ, Jenkins X, Huttenlocker AK, Chatterjee S. Cranial anatomy of Libognathus sheddi Small, 1997 (Parareptilia, Procolophonidae) from the Upper Triassic Dockum Group of West Texas, USA. Anat Rec (Hoboken) 2024; 307:1421-1441. [PMID: 38071453 DOI: 10.1002/ar.25364] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 11/27/2023] [Accepted: 11/28/2023] [Indexed: 03/16/2024]
Abstract
Libognathus sheddi, a leptopleuronine procolophonid from the Upper Triassic Cooper Canyon Formation, Dockum Group, West Texas, was based on an isolated left dentary and partial coronoid. New material referable to Libognathus sheddi, from the Cooper Canyon Formation, provides new information on the cranial anatomy. This new cranial material includes the antorbital portion of a skull, a left maxilla and premaxilla, quadratojugals, and dentaries, including intact tooth rows in the upper and lower jaws. Libognathus shows autapomorphies including; dentary deep with ventral margin oblique to tooth row immediately from the symphysis at ≥23°; anterior projecting coronoid contacting the lingual surface of the dentary underlying the last two dentary teeth; reduced contact between the lacrimal and the nasal; suborbital foramen formed by the maxilla and ectopterygoid, excluding the palatine; a posterior supralabial foramen shared by the maxilla and jugal; a Y-shaped antorbital pillar formed by the palatine, and massive orbitonasale and facial foramina (shared with unnamed southwest USA leptopleuronines). Phylogenetic analysis indicates that Libognathus is a highly derived leptopleuronine procolophonid, closely related to Hypsognathus fenneri and other southwest USA Revueltian leptopleuronines, which fall out as sister taxa to Hypsognathus, a relationship supported by a maxillary dentition restricted anterior to the orbital margin, a possibly synapomorphic orbitonasale septum in the form of an "antorbital pillar" created by the palatine, an anteroventral process of the jugal, and the presence of a small diastema between the first dentary tooth and the more posterior dentition. Libognathus exhibits a possible ankylosed protothecodont tooth implantation with frequent replacement, differing from some other proposed procolophonid implantation and replacement models. Chinle Formation and Dockum Group leptopleuronines are restricted to the Revueltian teilzone/holochronozone, making them possible Revueltian index taxa.
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Affiliation(s)
| | | | - Xavier Jenkins
- Department of Biological Sciences, Idaho State University, Pocatello, ID, USA
| | - Adam K Huttenlocker
- Department of Integrative Anatomical Sciences, University of Southern California, Los Angeles, CA, USA
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3
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Freisem LS, Müller J, Sues HD, Sobral G. A new sphenodontian (Diapsida: Lepidosauria) from the Upper Triassic (Norian) of Germany and its implications for the mode of sphenodontian evolution. BMC Ecol Evol 2024; 24:35. [PMID: 38493125 PMCID: PMC10944618 DOI: 10.1186/s12862-024-02218-1] [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: 11/03/2023] [Accepted: 02/27/2024] [Indexed: 03/18/2024] Open
Abstract
The Arnstadt Formation of Saxony-Anhalt, Germany has yielded some of Germany's most substantial finds of Late Triassic tetrapods, including the sauropodomorph Plateosaurus and the stem-turtle Proganochelys quenstedti. Here, we describe an almost complete skull of a new sphenodontian taxon from this formation (Norian, 227-208 Ma), making it the oldest known articulated sphenodontian skull from Europe and one of the oldest in the world. The material is represented by the dermal skull roof and by the complete maxilla and temporal region, as well as parts of the palate, braincase, and lower jaw. A phylogenetic assessment recovers it as a basal sphenodontian closely related to Planocephalosaurus robinsonae and to Eusphenodontia, making it the earliest-diverging sphenodontian known with an articulated skull. Its cranial anatomy is generally similar to the well-known Diphydontosaurus avonis from the Rhaetian of England, showing that this successful phenotype was already established in the clade around 10 myr earlier than assumed. An analysis of evolutionary change rates recovers high rates of evolution in basal sphenodontians, with decreasing rates throughout the evolution of the group. However, contrary to previous studies, reversals in this trend were identified, indicating additional peaks of evolutionary change. These results improve our understanding of the early sphenodontian diversity in Europe, providing critical information on evolutionary trends throughout the history of the clade and sparking renewed interest in its evolution.
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Affiliation(s)
- Lisa S Freisem
- Department of Earth and Planetary Sciences, Yale University, New Haven, CT, 06520, USA.
| | - Johannes Müller
- Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions- Und Biodiversitätsforschung, Invalidenstraße 43, Berlin, 10115, Germany
| | - Hans-Dieter Sues
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121, Washington, DC, USA
| | - Gabriela Sobral
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, Stuttgart, 70191, Germany.
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4
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Salomies L, Eymann J, Ollonen J, Khan I, Di-Poï N. The developmental origins of heterodonty and acrodonty as revealed by reptile dentitions. SCIENCE ADVANCES 2021; 7:eabj7912. [PMID: 34919438 PMCID: PMC8682985 DOI: 10.1126/sciadv.abj7912] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 11/01/2021] [Indexed: 06/14/2023]
Abstract
Despite the exceptional diversity and central role of dentitions in vertebrate evolution, many aspects of tooth characters remain unknown. Here, we exploit the large array of dental phenotypes in acrodontan lizards, including EDA mutants showing the first vertebrate example of positional transformation in tooth identity, to assess the developmental origins and evolutionary patterning of tooth types and heterodonty. We reveal that pleurodont versus acrodont dentition can be determined by a simple mechanism, where modulation of tooth size through EDA signaling has major consequences on dental formula, thereby providing a new flexible tooth patterning model. Furthermore, such implication of morphoregulation in tooth evolution allows predicting the dental patterns characterizing extant and fossil lepidosaurian taxa at large scale. Together, the origins and diversification of tooth types, long a focus of multiple research fields, can now be approached through evo-devo approaches, highlighting the importance of underexplored dental features for illuminating major evolutionary patterns.
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Lafuma F, Corfe IJ, Clavel J, Di-Poï N. Multiple evolutionary origins and losses of tooth complexity in squamates. Nat Commun 2021; 12:6001. [PMID: 34650041 PMCID: PMC8516937 DOI: 10.1038/s41467-021-26285-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 09/27/2021] [Indexed: 11/21/2022] Open
Abstract
Teeth act as tools for acquiring and processing food, thus holding a prominent role in vertebrate evolution. In mammals, dental-dietary adaptations rely on tooth complexity variations controlled by cusp number and pattern. Complexity increase through cusp addition has dominated the diversification of mammals. However, studies of Mammalia alone cannot reveal patterns of tooth complexity conserved throughout vertebrate evolution. Here, we use morphometric and phylogenetic comparative methods across fossil and extant squamates to show they also repeatedly evolved increasingly complex teeth, but with more flexibility than mammals. Since the Late Jurassic, multiple-cusped teeth evolved over 20 times independently from a single-cusped common ancestor. Squamates frequently lost cusps and evolved varied multiple-cusped morphologies at heterogeneous rates. Tooth complexity evolved in correlation with changes in plant consumption, resulting in several major increases in speciation. Complex teeth played a critical role in vertebrate evolution outside Mammalia, with squamates exemplifying a more labile system of dental-dietary evolution.
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Affiliation(s)
- Fabien Lafuma
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, FI-00014, Helsinki, Finland.
| | - Ian J Corfe
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, FI-00014, Helsinki, Finland.
- Geological Survey of Finland, FI-02150, Espoo, Finland.
| | - Julien Clavel
- Department of Life Sciences, The Natural History Museum, London, SW7 5BD, UK
- Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 LEHNA, F-69622, Villeurbanne, France
| | - Nicolas Di-Poï
- Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, FI-00014, Helsinki, Finland.
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6
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Georgalis GL, Scheyer TM. Lizards and snakes from the earliest Miocene of Saint-Gérand-le-Puy, France: an anatomical and histological approach of some of the oldest Neogene squamates from Europe. BMC Ecol Evol 2021; 21:144. [PMID: 34256702 PMCID: PMC8278609 DOI: 10.1186/s12862-021-01874-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 06/28/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The earliest Miocene (Aquitanian) represents a crucial time interval in the evolution of European squamates (i.e., lizards and snakes), witnessing a high diversity of taxa, including an array of extinct forms but also representatives of extant genera. We here conduct a taxonomical survey along with a histological/microanatomical approach on new squamate remains from the earliest Miocene of Saint-Gérand-le-Puy, France, an area that has been well known for its fossil discoveries since the nineteenth century. RESULTS We document new occurrences of taxa, among which, the lacertid Janosikia and the anguid Ophisaurus holeci, were previously unknown from France. We provide a detailed description of the anatomical structures of the various cranial and postcranial remains of lizards and snakes from Saint-Gérand-le-Puy. By applying micro-CT scanning in the most complete cranial elements of our sample, we decipher previously unknown microanatomical features. We report in detail the subsurface distribution and 3D connectivity of vascular channels in the anguid parietal. The fine meshwork of channels and cavities or sinuses in the parietal of Ophisaurus could indicate some thermoregulatory function, as it has recently been demonstrated for other vertebrate groups, providing implications for the palaeophysiology of this earliest Miocene anguine lizard. CONCLUSIONS A combination of anatomical and micro-anatomical/histological approach, aided by micro-CT scanning, enabled the documentation of these new earliest Miocene squamate remains. A distinct geographic expansion is provided for the extinct anguine Ophisaurus holeci and the lacertid Janosikia (the closest relative of the extant insular Gallotia from the Canary Islands).
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Affiliation(s)
- Georgios L Georgalis
- University of Zurich, Palaeontological Institute and Museum, Karl Schmid-Strasse 4, 8006, Zurich, Switzerland.
| | - Torsten M Scheyer
- University of Zurich, Palaeontological Institute and Museum, Karl Schmid-Strasse 4, 8006, Zurich, Switzerland
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7
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Witzmann F, Haridy Y, Hilger A, Manke I, Asbach P. Rarity of congenital malformation and deformity in the fossil record of vertebrates - A non-human perspective. INTERNATIONAL JOURNAL OF PALEOPATHOLOGY 2021; 33:30-42. [PMID: 33647859 DOI: 10.1016/j.ijpp.2020.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 12/23/2020] [Accepted: 12/24/2020] [Indexed: 06/12/2023]
Abstract
OBJECTIVE A malformed pectoral joint of the middle Devonian antiarch fish Asterolepis ornata is described, and a survey of congenital malformations in the fossil record is provided. MATERIALS The specimen of A. ornata (MB.f.73) from Ehrman in Latvia, stored at the Museum für Naturkunde Berlin, Germany. METHODS A. ornata was macroscopically and radiologically investigated, and the overview on congenital malformation was based on an extensive literature survey. RESULTS In the deformed joint of A. ornata, the articular surfaces and muscle attachment sites are greatly reduced, indicating restricted mobility. Congenital malformations can be found since the middle Silurian and affect all groups of vertebrates, but they are rare. Teeth and the vertebral column are the most commonly affected anatomical regions, and the mechanisms causing these malformations probably remained the same through geological time. CONCLUSIONS Micro-CT of the deformed joint shows no disturbance of the normal trabecular pattern and no evidence of trauma or disease, suggesting a congenital hypoplasia, although an acquired deformity cannot be ruled out completely. SIGNIFICANCE Congenital malformations, even those that are rare, were part of the common history of vertebrates for more than 400 million years. LIMITATIONS Epidemiologic measures like incidence and prevalence usually cannot be applied to define rare diseases in the fossil record. SUGGESTIONS FOR FURTHER RESEARCH A broadly based analysis of species of fossil vertebrates with numerus recovered specimens (e.g. many bony fishes, amphibians, certain dinosaurs) might statistically affirm the occurrence of malformations and possible correlations with the paleoenvironment.
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Affiliation(s)
- Florian Witzmann
- Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, 10115 Berlin, Germany.
| | - Yara Haridy
- Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Invalidenstraße 43, 10115 Berlin, Germany.
| | - André Hilger
- Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
| | - Ingo Manke
- Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
| | - Patrick Asbach
- Department of Radiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Hindenburgdamm 30, 12203 Berlin, Germany.
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8
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LeBlanc ARH, Paparella I, Lamoureux DO, Doschak MR, Caldwell MW. Tooth attachment and pleurodont implantation in lizards: Histology, development, and evolution. J Anat 2020; 238:1156-1178. [PMID: 33372719 PMCID: PMC8053593 DOI: 10.1111/joa.13371] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 11/10/2020] [Accepted: 11/10/2020] [Indexed: 01/13/2023] Open
Abstract
Squamates present a unique challenge to the homology and evolution of tooth attachment tissues. Their stereotypically pleurodont teeth are fused in place by a single "bone of attachment", with seemingly dubious homology to the three-part tooth attachment system of mammals and crocodilians. Despite extensive debate over the interpretations of squamate pleurodonty, its phylogenetic significance, and the growing evidence from fossil amniotes for the homology of tooth attachment tissues, few studies have defined pleurodonty on histological grounds. Using a sample of extant squamate teeth that we organize into three broad categories of implantation, we investigate the histological and developmental properties of their dental tissues in multiple planes of section. We use these data to demonstrate the specific soft- and hard-tissue features of squamate teeth that produce their disparate tooth implantation modes. In addition, we describe cementum, periodontal ligaments, and alveolar bone in pleurodont squamates, dental tissues that were historically thought to be restricted to extant mammals and crocodilians. Moreover, we show how the differences between pleurodonty and thecodonty do not relate to the identity of the tooth attachment tissues, but rather the arrangements of homologous tissues around the teeth.
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Affiliation(s)
- Aaron R H LeBlanc
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Ilaria Paparella
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | | | - Michael R Doschak
- Faculty of Pharmacy & Pharmaceutical Sciences and Department of Biomedical Engineering, University of Alberta, Edmonton, AB, Canada
| | - Michael W Caldwell
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada.,Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada
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9
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Jenkins KM, Shaw JO. Bite force data suggests relationship between acrodont tooth implantation and strong bite force. PeerJ 2020; 8:e9468. [PMID: 32656000 PMCID: PMC7333653 DOI: 10.7717/peerj.9468] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 06/11/2020] [Indexed: 12/22/2022] Open
Abstract
Extant and extinct reptiles exhibit numerous combinations of tooth implantation and attachment. Tooth implantation ranges from those possessing roots and lying within a socket (thecodonty), to teeth lying against the lingual wall of the jawbone (pleurodonty), to teeth without roots or sockets that are attached to the apex of the marginal jawbones (acrodonty). Attachment may be ligamentous (gomphosis) or via fusion (ankylosis). Generally speaking, adaptative reasonings are proposed as an underlying driver for evolutionary changes in some forms of tooth implantation and attachment. However, a substantiated adaptive hypothesis is lacking for the state of acrodont ankylosis that is seen in several lineages of Lepidosauria, a clade that is plesiomorphically pleurodont. The convergent evolution of acrodont ankylosis in several clades of lepidosaurs suggests a selective pressure shaped the evolution of the trait. We hypothesize that acrodont ankylosis as seen in Acrodonta and Sphenodon punctatus, is an adaptation either resulting from or allowing for a stronger bite force. We analyzed bite force data gathered from the literature to show that those taxa possessing acrodont dentition possess a stronger bite force on average than those taxa with pleurodont dentition. Dietary specialists with pleurodont dentition may also possess relatively high bite forces, though body size may also play a role in their ability to bite hard. Furthermore, our results have implications for the evolution of acrodont ankylosis and potential behaviors related to strong bite force that influenced the evolution of acrodonty within Acrodonta and Rhynchocephalia.
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Affiliation(s)
- Kelsey M Jenkins
- Department of Earth and Planetary Sciences, Yale University, New Haven, United States of America
| | - Jack O Shaw
- Department of Earth and Planetary Sciences, Yale University, New Haven, United States of America
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10
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Hermyt M, Janiszewska K, Rupik W. Squamate egg tooth development revisited using three-dimensional reconstructions of brown anole (Anolis sagrei, Squamata, Dactyloidae) dentition. J Anat 2020; 236:1004-1020. [PMID: 32056203 PMCID: PMC7219623 DOI: 10.1111/joa.13166] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 01/17/2020] [Accepted: 01/20/2020] [Indexed: 02/02/2023] Open
Abstract
The egg tooth is a hatching adaptation, characteristic of all squamates. In brown anole embryos, the first tooth that starts differentiating is the egg tooth. It develops from a single tooth germ and, similar to the regular dentition of all the other vertebrates, the differentiating egg tooth of the brown anole passes through classic morphological and developmental stages named according to the shape of the dental epithelium: epithelial thickening, dental lamina, tooth bud, cap and bell stages. The differentiating egg tooth consists of three parts: the enamel organ, hard tissues and dental pulp. Shortly before hatching, the egg tooth connects with the premaxilla. Attachment tissue of the egg tooth does not undergo mineralization, which makes it different from the other teeth of most squamates. After hatching, odontoclasts are involved in resorption of the egg tooth's remains. This study shows that the brown anole egg tooth does not completely conform to previous reports describing iguanomorph egg teeth and reveals a need to investigate its development in the context of squamate phylogeny.
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Affiliation(s)
- Mateusz Hermyt
- Faculty of Natural SciencesInstitute of Biology, Biotechnology and Environmental ProtectionUniversity of Silesia in KatowiceKatowicePoland
| | | | - Weronika Rupik
- Faculty of Natural SciencesInstitute of Biology, Biotechnology and Environmental ProtectionUniversity of Silesia in KatowiceKatowicePoland
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11
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Unique Tooth Morphology and Prismatic Enamel in Late Cretaceous Sphenodontians from Argentina. Curr Biol 2020; 30:1755-1761.e2. [PMID: 32220319 DOI: 10.1016/j.cub.2020.02.071] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 01/17/2020] [Accepted: 02/24/2020] [Indexed: 02/07/2023]
Abstract
Mammals and reptiles have evolved divergent adaptations for processing abrasive foods. Mammals have occluding, diphyodont dentitions with taller teeth (hypsodonty), more complex occlusal surfaces, continuous tooth eruption, and forms of prismatic enamel that prolong the functional life of each tooth [1, 2]. The evolution of prismatic enamel in particular was a key innovation that made individual teeth more resilient to abrasion in early mammals [2-4]. In contrast, reptiles typically have thin, non-prismatic enamel, and shearing, polyphyodont dentitions with multi-cusped or serrated tooth crowns, multiple tooth rows, rapid tooth replacement rates, or batteries made of hundreds of teeth [5-9]. However, there are rare cases where reptiles have evolved alternative solutions to cope with abrasive diets. Here, we show that the combined effects of herbivory and an ancestral loss of tooth replacement in a lineage of extinct herbivorous sphenodontians, distant relatives of the modern tuatara (Sphenodon punctatus) [10], are associated with the evolution of wear-resistant and highly complex teeth. Priosphenodon avelasi, an extinct sphenodontian from the Cretaceous of Argentina, possesses a unique cone-in-cone dentition with overlapping generations of teeth forming a densely packed tooth file. Each tooth is anchored to its predecessor via a rearrangement of dental tissues that results in a novel enamel-to-bone tooth attachment. Furthermore, the compound occlusal surfaces, thickened enamel, and the first report of prismatic enamel in a sphenodontian are convergent strategies with those in some mammals, challenging the perceived simplicity of acrodont dentitions [11-15] and showcasing the reptilian capacity to produce complex and unusual dentitions.
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12
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Jones MEH, Pistevos JCA, Cooper N, Lappin AK, Georges A, Hutchinson MN, Holleley CE. Reproductive phenotype predicts adult bite-force performance in sex-reversed dragons (Pogona vitticeps). JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2020; 333:252-263. [PMID: 32061035 DOI: 10.1002/jez.2353] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/23/2020] [Accepted: 01/25/2020] [Indexed: 12/21/2022]
Abstract
Sex-related differences in morphology and behavior are well documented, but the relative contributions of genes and environment to these traits are less well understood. Species that undergo sex reversal, such as the central bearded dragon (Pogona vitticeps), offer an opportunity to better understand sexually dimorphic traits because sexual phenotypes can exist on different chromosomal backgrounds. Reproductively female dragons with a discordant sex chromosome complement (sex reversed), at least as juveniles, exhibit traits in common with males (e.g., longer tails and greater boldness). However, the impact of sex reversal on sexually dimorphic traits in adult dragons is unknown. Here, we investigate the effect of sex reversal on bite-force performance, which may be important in resource acquisition (e.g., mates and/or food). We measured body size, head size, and bite force of the three sexual phenotypes in a colony of captive animals. Among adults, we found that males (ZZm) bite more forcefully than either chromosomally concordant females (ZWf) or sex-reversed females (ZZf), and this difference is associated with having relatively larger head dimensions. Therefore, adult sex-reversed females, despite apparently exhibiting male traits as juveniles, do not develop the larger head and enhanced bite force of adult male bearded dragons. This pattern is further illustrated in the full sample by a lack of positive allometry of bite force in sex-reversed females that is observed in males. The results reveal a close association between reproductive phenotype and bite force performance, regardless of sex chromosome complement.
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Affiliation(s)
- Marc E H Jones
- Department of Cell and Developmental Biology, University College London, London, UK.,School of Biological Sciences, University of Adelaide, North Terrace, Adelaide, South Australia, Australia.,Vertebrates, South Australian Museum, North Terrace, Adelaide, South Australia, Australia
| | - Jennifer C A Pistevos
- School of Biological Sciences, University of Adelaide, North Terrace, Adelaide, South Australia, Australia.,Centre de Recherches Insulaires et Observatoire de l'Environnement CRIOBE - USR 3278: PSL Université Paris: EPHE-CNRS-UPVD, Laboratoire d'Excellence "CORAIL", Papetoai, Moorea, Polynésie Française
| | - Natalie Cooper
- Vertebrates, Department of Life Sciences, Natural History Museum, London, UK
| | | | - Arthur Georges
- Institute for Applied Ecology, Canberra, Australian Capital Territory, Australia
| | - Mark N Hutchinson
- School of Biological Sciences, University of Adelaide, North Terrace, Adelaide, South Australia, Australia.,Vertebrates, South Australian Museum, North Terrace, Adelaide, South Australia, Australia
| | - Clare E Holleley
- Institute for Applied Ecology, Canberra, Australian Capital Territory, Australia.,Australian National Wildlife Collection, National Research Collections Australia CSIRO, Canberra, Australian Capital Territory, Australia
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13
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Salomies L, Eymann J, Khan I, Di-Poï N. The alternative regenerative strategy of bearded dragon unveils the key processes underlying vertebrate tooth renewal. eLife 2019; 8:47702. [PMID: 31418691 PMCID: PMC6744223 DOI: 10.7554/elife.47702] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 08/16/2019] [Indexed: 12/24/2022] Open
Abstract
Deep understanding of tooth regeneration is hampered by the lack of lifelong replacing oral dentition in most conventional models. Here, we show that the bearded dragon, one of the rare vertebrate species with both polyphyodont and monophyodont teeth, constitutes a key model for filling this gap, allowing direct comparison of extreme dentition types. Our developmental and high-throughput transcriptomic data of microdissected dental cells unveils the critical importance of successional dental lamina patterning, in addition to maintenance, for vertebrate tooth renewal. This patterning process happens at various levels, including directional growth but also gene expression levels, dynamics, and regionalization, and involves a large number of yet uncharacterized dental genes. Furthermore, the alternative renewal mechanism of bearded dragon dentition, with dual location of slow-cycling cells, demonstrates the importance of cell migration and functional specialization of putative epithelial stem/progenitor niches in tissue regeneration, while expanding the diversity of dental replacement strategies in vertebrates. All multicellular organisms, from lizards to humans, must be able to repair and regrow damaged tissue. This includes not only healing after an injury, but also replacing parts of the body that suffer wear and tear. For example, many animals shed and replace worn out teeth throughout their life, but the number of times this occurs varies greatly between species. Much of the understanding about how teeth grow and develop has come from researching mice. However, mice only develop one set of teeth, making them a poor ‘model’ for studying how species such as fish and reptiles can re-grow and replace their teeth. Recent studies of these species has shown that regenerating teeth relies on a specialised structure known as the dental lamina. In mice, the dental lamina forms but then quickly disappears, preventing new sets of teeth from developing. In most animals that regrow their teeth, however, the dental lamina keeps growing beyond the most recently produced tooth to create an area where its replacement will emerge. Now, Salomies et al. have identified other strategies involved in tooth replacement from studying the bearded dragon lizard, a rare example of an animal that continuously regenerates some, but not all, of its teeth. Analysing the cells in different parts of the re-growing teeth from bearded dragon lizards revealed new features of the dental lamina. Specifically, Salomies et al. found that a previously uncharacterized set of genes within the dental lamina could determine whether or not a tooth will be replaced. Further experiments using microscope imaging revealed that bearded dragon lizards use two distinct groups of stem cells – specialised cells that have the potential to develop into various cell types in the body – to re-grow their teeth. These experiments demonstrate how the bearded dragon lizard uses a previously unknown mechanism to regenerate its teeth, combining elements used by gecko lizards and sharks. These findings are an important step towards understanding the different strategies animals can use to maintain and regenerate their teeth. The knowledge gained could one day help design better therapies for patients suffering from inherited dental disorders or tooth loss.
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Affiliation(s)
- Lotta Salomies
- Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Julia Eymann
- Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Imran Khan
- Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Nicolas Di-Poï
- Program in Developmental Biology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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