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Abd-Elhafeez HH, Massoud D, Mahmoud MS, Abdellah N, Salah AS, Mohamed NE, Sayed MAA, Shaalan M, Rutland CS, Abu-ELhamed AS, Soliman SA, Mustafa FEZA. Microstructural architecture of the bony scutes, spine, and rays of the bony fins in the common pleco (Hypostomus plecostomus). Int J Vet Sci Med 2024; 12:101-124. [PMID: 39239634 PMCID: PMC11376312 DOI: 10.1080/23144599.2024.2374201] [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: 01/31/2024] [Revised: 06/17/2024] [Accepted: 06/24/2024] [Indexed: 09/07/2024] Open
Abstract
Studying scute and fin morphology are advantageous approaches for phylogenetic identification and provide information on biological linkages and evolutionary history that are essential for deciphering the fossil record. Despite this, no prior research has precisely characterized the histological structures of scutes in the common pleco. Therefore, this research investigated the microstructure and organization of bone tissue within the dermal skeleton, including the scutes and fins, in the common pleco, using light microscopy, stereomicroscopy, and scanning electron microscopy. The dermal scutes were organized in a pentagonal shape with denticular coverage and were obliquely aligned with the caudal portion pointing dorsally. The dermal scutes consisted of three distinct portions: the central, preterminal, and terminal portions. Each portion comprised three layers: a superficial bony plate, a basal bony plate, and a mid-plate. Both the superficial and basal bony plates were composed of lamellar bone and lamellar zonal bone, whilst the mid-plate consisted of secondary osteons and woven bone. In the terminal portion, the superficial and basal bony plates became thinner. The pectoral fin consists of spines and rays composed of lepidotrichium (two symmetrical hemi-rays). The spine contained centrifugal and centripetal lamellar and trabecular bones. A centripetal fibrous bone was implanted between the lamellar bones. Besides being oriented in a V shape, the hemi-rays were also composed of thin centrifugal and centripetal lamellar bones and trabecular bones. A fibrous bone was identified between the centrifugal and centripetal bones. The trabecular bone and lamellar bone were made up of bone spicules.
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Affiliation(s)
- Hanan H Abd-Elhafeez
- Department of Cell and Tissues, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt
| | - Diaa Massoud
- Department of Biology, College of Science, Jouf University, Sakaka, Saudi Arabia
- Department of Zoology, Faculty of Science, Fayoum University, Fayoum, Egypt
| | - Mohammed S Mahmoud
- Department of Zoology, Faculty of Science, Fayoum University, Fayoum, Egypt
| | - Nada Abdellah
- Department of Histology, Faculty of Veterinary Medicine, Sohag University, Sohag, Egypt
- Department of Histology and Anatomy, School of Veterinary Medicine, Badr University in Assiut, New Nasser City, Egypt
| | - Abdallah S Salah
- Institute of Aquaculture, University of Stirling, Stirling, UK
- Department of Aquaculture, Faculty of Aquatic and Fisheries Sciences, Kafrelsheikh University, Kafrelsheikh, Egypt
| | - Nor-Elhoda Mohamed
- Faculty of Science, Biomedicine Branch, University of Science & Technology, Zewail, Egypt
| | | | - Mohamed Shaalan
- Department of Pathology, Faculty of Veterinary Medicine, Caio University, Giza, Egypt
- Polymer Institute, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Catrin S Rutland
- School of Veterinary Medicine and Science, University of Nottingham, Nottingham, UK
| | - Alaa Sayed Abu-ELhamed
- Department of Cell and Tissues, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt
- Department of Respiratory Therapy, Faculty of Applied Medical Sciences, Jazan University, Jazan, Saudi Arabia
| | - Soha A Soliman
- Department of Histology, Faculty of Veterinary Medicine, South Valley University, Qena, Egypt
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Miller E, Lee HW, Abzhanov A, Evers SW. The topological organization of the turtle cranium is constrained and conserved over long evolutionary timescales. Anat Rec (Hoboken) 2024; 307:2713-2748. [PMID: 38102921 DOI: 10.1002/ar.25356] [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: 09/13/2023] [Revised: 10/30/2023] [Accepted: 11/14/2023] [Indexed: 12/17/2023]
Abstract
The cranium of turtles (Testudines) is characterized by the secondary reduction of temporal fenestrae and loss of cranial joints (i.e., characteristics of anapsid, akinetic skulls). Evolution and ontogeny of the turtle cranium are associated with shape changes. Cranial shape variation among Testudines can partially be explained by dietary and functional adaptations (neck retraction), but it is unclear if cranial topology shows similar ecomorphological signal, or if it is decoupled from shape evolution. We assess the topological arrangement of cranial bones (i.e., number, relative positioning, connections), using anatomical network analysis. Non-shelled stem turtles have similar cranial arrangements to archosauromorph outgroups. Shelled turtles (Testudinata) evolve a unique cranial organization that is associated with bone losses (e.g., supratemporal, lacrimal, ectopterygoid) and an increase in complexity (i.e., densely and highly interconnected skulls with low path lengths between bones), resulting from the closure of skull openings and establishment of unusual connections such as a parietal-pterygoid contact in the secondary braincase. Topological changes evolutionarily predate many shape changes. Topological variation and taxonomic morphospace discrimination among crown turtles are low, indicating that cranial topology may be constrained. Observed variation results from repeated losses of nonintegral bones (i.e., premaxilla, nasal, epipterygoid, quadratojugal), and changes in temporal emarginations and palate construction. We observe only minor ontogenetic changes. Topology is not influenced by diet and habitat, contrasting cranial shape. Our results indicate that turtles have a unique cranial topology among reptiles that is conserved after its initial establishment, and shows that cranial topology and shape have different evolutionary histories.
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Affiliation(s)
- Eve Miller
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Berkshire, UK
- Natural History Museum, London, UK
| | - Hiu Wai Lee
- Department of Earth Sciences, The University of Hong Kong, Hong Kong SAR, China
| | - Arkhat Abzhanov
- Department of Life Sciences, Imperial College London, Silwood Park Campus, Berkshire, UK
- Natural History Museum, London, UK
| | - Serjoscha W Evers
- Department of Geosciences, University of Fribourg, Fribourg, Switzerland
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3
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Pol D, Baiano MA, Černý D, Novas FE, Cerda IA, Pittman M. A new abelisaurid dinosaur from the end Cretaceous of Patagonia and evolutionary rates among the Ceratosauria. Cladistics 2024; 40:307-356. [PMID: 38771085 DOI: 10.1111/cla.12583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 04/24/2024] [Accepted: 04/24/2024] [Indexed: 05/22/2024] Open
Abstract
Gondwanan dinosaur faunae during the 20 Myr preceding the Cretaceous-Palaeogene (K/Pg) extinction included several lineages that were absent or poorly represented in Laurasian landmasses. Among these, the South American fossil record contains diverse abelisaurids, arguably the most successful groups of carnivorous dinosaurs from Gondwana in the Cretaceous, reaching their highest diversity towards the end of this period. Here we describe Koleken inakayali gen. et sp. n., a new abelisaurid from the La Colonia Formation (Maastrichtian, Upper Cretaceous) of Patagonia. Koleken inakayali is known from several skull bones, an almost complete dorsal series, complete sacrum, several caudal vertebrae, pelvic girdle and almost complete hind limbs. The new abelisaurid shows a unique set of features in the skull and several anatomical differences from Carnotaurus sastrei (the only other abelisaurid known from the La Colonia Formation). Koleken inakayali is retrieved as a brachyrostran abelisaurid, clustered with other South American abelisaurids from the latest Cretaceous (Campanian-Maastrichtian), such as Aucasaurus, Niebla and Carnotaurus. Leveraging our phylogeny estimates, we explore rates of morphological evolution across ceratosaurian lineages, finding them to be particularly high for elaphrosaurine noasaurids and around the base of Abelisauridae, before the Early Cretaceous radiation of the latter clade. The Noasauridae and their sister clade show contrasting patterns of morphological evolution, with noasaurids undergoing an early phase of accelerated evolution of the axial and hind limb skeleton in the Jurassic, and the abelisaurids exhibiting sustained high rates of cranial evolution during the Early Cretaceous. These results provide much needed context for the evolutionary dynamics of ceratosaurian theropods, contributing to broader understanding of macroevolutionary patterns across dinosaurs.
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Affiliation(s)
- Diego Pol
- Museo Argentino de Ciencias Naturales Bernardino Rivadavia, Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Mattia Antonio Baiano
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
- Área Laboratorio e Investigación, Museo Municipal Ernesto Bachmann, Villa El Chocón, Neuquén, Argentina
- Universidad Nacional de Río Negro (UNRN), General Roca, Río Negro, Argentina
| | - David Černý
- Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
| | - Fernando E Novas
- Museo Argentino de Ciencias Naturales Bernardino Rivadavia, Buenos Aires, Argentina
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Ignacio A Cerda
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
- Universidad Nacional de Río Negro (UNRN), General Roca, Río Negro, Argentina
- Instituto de Investigación en Paleobiología y Geología (IIPG), General Roca, Río Negro, Argentina
- Museo Provincial Carlos Ameghino, Cipolletti, Río Negro, Argentina
| | - Michael Pittman
- School of Life Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China
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Scheyer TM. The pseudosuchian record in paleohistology: A small review. Anat Rec (Hoboken) 2024. [PMID: 38655735 DOI: 10.1002/ar.25455] [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: 01/05/2024] [Revised: 03/25/2024] [Accepted: 03/30/2024] [Indexed: 04/26/2024]
Abstract
Archosauria originated around the Earth's largest biotic crisis that severely affected all ecosystems globally, the Permotriassic Mass extinction event, and comprises two crown-group lineages: the bird-lineage and the crocodylian lineage. The bird lineage includes the iconic pterosaurs, as well as dinosaurs and birds, whereas the crocodylian lineage includes clades such as aetosaurs, poposaurs, "rauisuchians," as well as Crocodylomorpha; the latter being represented today only by less than 30 extant species of Crocodylia. Despite playing important roles during Mesozoic and Cenozoic ecosystems, both on land and in water, Pseudosuchia received far less attention compared to the bird-lineage, which is also reflected in number and scope of histological studies so far. Lately, the field has seen a shift of focus toward pseudosuchians, however, and the symposium on "Paleohistological Inferences of Paleobiological Traits in Pseudosuchia" held during the International Congress of Vertebrate Morphology 2023 in Cairns, Queensland, Australia, is the latest proof of that. To put these novel aspects of paleohistological and paleobiological research into context, an overview of the non-extant pseudosuchian taxa whose postcranial bones were studied so far is provided here (c. 80 species out of a total of more than 700 extinct species described) and recent trends in pseudosuchian osteohistology are highlighted. In addition, histological studies on cranial and dental material and other potential hard tissues, such as eggshells and otoliths, are briefly reviewed as well.
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Affiliation(s)
- Torsten M Scheyer
- Department of Paleontology, University of Zurich, Zurich, Switzerland
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Parker WG, Reyes WA, Marsh AD. Incongruent ontogenetic maturity indicators in a Late Triassic archosaur (Aetosauria: Typothorax coccinarum). Anat Rec (Hoboken) 2024; 307:1254-1270. [PMID: 37937738 DOI: 10.1002/ar.25343] [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: 07/19/2023] [Revised: 09/13/2023] [Accepted: 10/13/2023] [Indexed: 11/09/2023]
Abstract
Maximum individual body size in pseudosuchian archosaurs is not well constrained in the fossil record, but it may be influenced by a variety of factors including basal metabolic rate, evolutionary relationships, and environmental conditions. Body size varies among the Aetosauria in which estimated total length ranges between 1 m (e.g., Coahomasuchus kahleorum) and 5 m (e.g., Desmatosuchus spurensis). A new, very large specimen of the aetosaurian Typothorax coccinarum from Petrified Forest National Park in northeastern Arizona is nearly twice the size of all other known specimens of Typothorax and is the largest aetosaur specimen currently known worldwide. The specimen lacks co-ossified neurocentral sutures in the trunk vertebrae which may suggest that the individual had not yet reached skeletal maturity, yet smaller specimens of T. coccinarum exhibit partially or fully co-ossified neurocentral sutures in the same region. If body size correlates with skeletal maturity in aetosaurs, this discrepancy warns that timing of neurocentral suture co-ossification in aetosaurs may not be a reliable indicator of ontogenetic stage. Osteohistological observations of a trunk rib demonstrate that although PEFO 42506 shows a large body size, the specimen did not deposit an external fundamental system despite depositing as many as 19 growth lines, further indicating that it had not yet reached skeletal maturity. Thus, at least within Aetosauria, neurocentral suture co-ossification and skeletal maturity may correlate, whereas body size can be incongruent in comparison. Furthermore, this specimen indicates that non-desmatosuchin aetosaurs could exhibit large body sizes and suggests that some aetosaurs may have experienced indeterminate growth.
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Affiliation(s)
- William G Parker
- Department of Science and Resource Management, Petrified Forest National Park, Petrified Forest, USA
| | - William A Reyes
- Department of Science and Resource Management, Petrified Forest National Park, Petrified Forest, USA
- Jackson School of Geosciences, University of Texas, Austin, Texas, USA
| | - Adam D Marsh
- Department of Science and Resource Management, Petrified Forest National Park, Petrified Forest, USA
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Maden M, Polvadore T, Polanco A, Barbazuk WB, Stanley E. Osteoderms in a mammal the spiny mouse Acomys and the independent evolution of dermal armor. iScience 2023; 26:106779. [PMID: 37378333 PMCID: PMC10291248 DOI: 10.1016/j.isci.2023.106779] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 02/06/2023] [Accepted: 04/25/2023] [Indexed: 06/29/2023] Open
Abstract
Osteoderms are bony plates found in the skin of vertebrates, mostly commonly in reptiles where they have evolved independently multiple times, suggesting the presence of a gene regulatory network that is readily activated and inactivated. They are absent in birds and mammals except for the armadillo. However, we have discovered that in one subfamily of rodents, the Deomyinae, there are osteoderms in the skin of their tails. Osteoderm development begins in the proximal tail skin and is complete 6 weeks after birth. RNA sequencing has identified the gene networks involved in their differentiation. There is a widespread down-regulation of keratin genes and an up-regulation of osteoblast genes and a finely balanced expression of signaling pathways as the osteoderms differentiate. Future comparisons with reptilian osteoderms may allow us to understand how these structures have evolved and why they are so rare in mammals.
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Affiliation(s)
- Malcolm Maden
- Department of Biology & UF Genetics Institute, University of Florida, Gainesville, FL 32611, USA
| | - Trey Polvadore
- Department of Biology & UF Genetics Institute, University of Florida, Gainesville, FL 32611, USA
| | - Arod Polanco
- Department of Biology & UF Genetics Institute, University of Florida, Gainesville, FL 32611, USA
| | - W. Brad Barbazuk
- Department of Biology & UF Genetics Institute, University of Florida, Gainesville, FL 32611, USA
| | - Edward Stanley
- Florida Museum of Natural History, University of Florida, Museum Road, Gainesville, FL 32611, USA
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7
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Frýdlová P, Janovská V, Mrzílková J, Halašková M, Riegerová M, Dudák J, Tymlová V, Žemlička J, Zach P, Frynta D. The first description of dermal armour in snakes. Sci Rep 2023; 13:6405. [PMID: 37076516 PMCID: PMC10115820 DOI: 10.1038/s41598-023-33244-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Accepted: 04/10/2023] [Indexed: 04/21/2023] Open
Abstract
Osteoderms, also called dermal armour, often play a role in predator defence. The presence of osteoderms is highly irregularly distributed across the squamate phylogeny and they have not been found in snakes. In this study, we searched for candidate snake species that would benefit from such armour to protect their body, focusing primarily on fossorial species with defensive tail displays. We examined the tail morphology of 27 snake species from different families using micro-computed tomography (µCT) and micro- radiography. We discovered dermal armour in four species of sand boas (Erycidae) that also feature enlarged and highly modified caudal vertebrae. This is the first description of dermal armour in snakes. Ancestral state reconstructions revealed that osteoderms likely evolved once or multiple times in Erycidae. We have not found osteoderms in any other examined snake species. Nevertheless, similar structures are known from unrelated squamate clades, such as gerrhosaurids and geckos. This supports the idea of underlying deep developmental homology. We propose the hypothesis that osteoderms protect sand boas like the "brigandine armour" of medieval warriors. We interpret it as another component of the sand boas' rich defence strategy.
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Affiliation(s)
- Petra Frýdlová
- Department of Zoology, Faculty of Science, Charles University, 128 43, Prague, Czech Republic
- Department of Anatomy, Third Faculty of Medicine, Charles University, 100 00, Prague, Czech Republic
| | - Veronika Janovská
- Department of Zoology, Faculty of Science, Charles University, 128 43, Prague, Czech Republic
| | - Jana Mrzílková
- Department of Anatomy, Third Faculty of Medicine, Charles University, 100 00, Prague, Czech Republic
| | - Milada Halašková
- Department of Histology and Embryology, Third Faculty of Medicine, Charles University, 100 00, Prague, Czech Republic
| | - Markéta Riegerová
- Department of Histology and Embryology, Third Faculty of Medicine, Charles University, 100 00, Prague, Czech Republic
| | - Jan Dudák
- Institute of Experimental and Applied Physics, Czech Technical University in Prague, 110 00, Prague, Czech Republic
| | - Veronika Tymlová
- Institute of Experimental and Applied Physics, Czech Technical University in Prague, 110 00, Prague, Czech Republic
| | - Jan Žemlička
- Institute of Experimental and Applied Physics, Czech Technical University in Prague, 110 00, Prague, Czech Republic
| | - Petr Zach
- Department of Anatomy, Third Faculty of Medicine, Charles University, 100 00, Prague, Czech Republic
| | - Daniel Frynta
- Department of Zoology, Faculty of Science, Charles University, 128 43, Prague, Czech Republic.
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8
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Pochat-Cottilloux Y, Martin JE, Amiot R, Cubo J, de Buffrénil V. A survey of osteoderm histology and ornamentation among Crocodylomorpha: A new proxy to infer lifestyle? J Morphol 2023; 284:e21542. [PMID: 36533737 PMCID: PMC10108047 DOI: 10.1002/jmor.21542] [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: 07/26/2022] [Revised: 11/29/2022] [Accepted: 11/30/2022] [Indexed: 12/23/2022]
Abstract
Osteoderms of eight extant and extinct species of crocodylomorphs are studied histologically and morphologically. Most osteoderms display the typical "crocodilian" structure with a woven-fibered matrix surrounded by an upper and a lower parallel fibered matrix. The dorsal ornamentation of those specimens consists of a pit-and-ridge structure, with corresponding remodeling mechanisms. However, an osteoderm of Iberosuchus, studied here for the first time, differs in being nearly devoid of ornamentation; moreover, it shows strong bundles of straight Sharpey's fibers perpendicular to the surface in its lateral and dorsal walls, along with a rough plywood-like structure in its basal plate. This suggests that this osteoderm was more deeply anchored within the dermis than the other osteoderms studied hitherto. This peculiar structure might have been linked to a terrestrial ecology and a specific thermoregulation strategy. Some other notosuchians in our sample do not exhibit ornamentation on their osteoderms, as opposed to neosuchians. Considering current interpretations of osteoderm function(s) in crocodilians, our observations are discussed in reference to possible ecophysiological peculiarities of Notosuchia in general, and Iberosuchus in particular.
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Affiliation(s)
| | - Jeremy E Martin
- Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, Villeurbanne, France
| | - Romain Amiot
- Univ Lyon, Univ Lyon 1, ENSL, CNRS, LGL-TPE, Villeurbanne, France
| | - Jorge Cubo
- Centre de Recherche en Paléontologie-Paris (CR2P), Sorbonne Université, Paris, France
| | - Vivian de Buffrénil
- Centre de Recherche en Paléontologie-Paris (CR2P), Sorbonne Université, Paris, France
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9
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Sena MVDA, Marinho TDS, Montefeltro FC, Langer MC, Fachini TS, Nava WR, Pinheiro AEP, de Araújo EV, Aubier P, de Andrade RCLP, Sayão JM, de Oliveira GR, Cubo J. Osteohistological characterization of notosuchian osteoderms: Evidence for an overlying thick leathery layer of skin. J Morphol 2023; 284:e21536. [PMID: 36394285 PMCID: PMC10107732 DOI: 10.1002/jmor.21536] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 10/12/2022] [Accepted: 11/16/2022] [Indexed: 11/18/2022]
Abstract
Osteoderms are mineralized structures embedded in the dermis, known for nonavian archosaurs, squamates, xenarthrans, and amphibians. Herein, we compared the osteoderm histology of Brazilian Notosuchia of Cretaceous age using three neosuchians for comparative purposes. Microanatomical analyses showed that most of them present a diploe structure similar to those of other pseudosuchians, lizards, and turtles. This structure contains two cortices (the external cortex composed of an outer and an inner layers, and the basal cortex) and a core in-between them. Notosuchian osteoderms show high bone compactness (>0.85) with varying degrees of cancellous bone in the core. The neosuchian Guarinisuchus shows the lowest bone compactness with a well-developed cancellous layer. From an ontogenetic perspective, most tissues are formed through periosteal ossification, although the mineralized tissues observed in baurusuchid LPRP/USP 0634 suggest a late metaplastic development. Histology suggests that the ossification center of notosuchian osteoderm is located at the keel. Interestingly, we identified Sharpey's fibers running perpendicularly to the outer layer of the external cortex in Armadillosuchus arrudai, Itasuchus jesuinoi, and Baurusuchidae (LPRP/USP 0642). This feature indicates a tight attachment within the dermis, and it is evidence for the presence of an overlying thick leathery layer of skin over these osteoderms. These data allow a better understanding of the osteohistological structure of crocodylomorph dermal bones, and highlight their structural diversity. We suggest that the vascular canals present in some sampled osteoderms connecting the inner layer of the external cortex and the core with the external surface may increase osteoderm surface and the capacity of heat transfer in terrestrial notosuchians.
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Affiliation(s)
- Mariana Valéria de Araújo Sena
- Centre de Recherche en Paléontologie Paris (CR2P, UMR 7207), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, Paris, France.,Centro de Ciências Biológicas e da Saúde, Laboratório de Paleontologia da URCA, Universidade Regional do Cariri, Rua Carolino Sucupira-Pimenta, Crato, Ceará, Brazil
| | - Thiago da Silva Marinho
- Centro de Pesquisas Paleontológicas "Llewellyn Ivor Price", Complexo Cultural e Científico Peirópolis, Pró-Reitoria de Extensão Universitária, Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais, Brazil.,Instituto de Ciências Exatas, Naturais e Educação, Universidade Federal do Triângulo Mineiro, Uberaba, Minas Gerais, Brazil
| | - Felipe Chinaglia Montefeltro
- Departamento de Biologia e Zootecnia, Faculdade de Engenharia de Ilha Solteira, Universidade Estadual Paulista, Ilha Solteira, São Paulo, Brazil
| | - Max Cardoso Langer
- Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Laboratório de Paleontologia de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - Thiago Schineider Fachini
- Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Laboratório de Paleontologia de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo, Brazil
| | - William Roberto Nava
- Museu de Paleontologia de Marília, Prefeitura Municipal de Marília, Marília, São Paulo, Brazil
| | | | - Esaú Victor de Araújo
- Museu Nacional do Rio de Janeiro, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Paul Aubier
- Centre de Recherche en Paléontologie Paris (CR2P, UMR 7207), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, Paris, France
| | - Rafael César Lima Pedroso de Andrade
- Centro de Ciências Biológicas e da Saúde, Laboratório de Paleontologia da URCA, Universidade Regional do Cariri, Rua Carolino Sucupira-Pimenta, Crato, Ceará, Brazil
| | - Juliana Manso Sayão
- Museu Nacional do Rio de Janeiro, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Gustavo Ribeiro de Oliveira
- Laboratório de Paleontologia e Sistemática (LAPASI), Departamento de Biologia, Universidade Federal Rural de Pernambuco, Recife, Pernambuco, Brazil
| | - Jorge Cubo
- Centre de Recherche en Paléontologie Paris (CR2P, UMR 7207), Muséum national d'Histoire naturelle, CNRS, Sorbonne Université, Paris, France
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10
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Rehorek SJ, Elsey RM, Smith TV. Ontogeny of the nasolacrimal apparatus and nasal sensory systems of the American alligator (Alligator mississippiensis). J Morphol 2022; 283:1080-1093. [PMID: 35723180 DOI: 10.1002/jmor.21489] [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: 12/15/2021] [Revised: 06/01/2022] [Accepted: 06/04/2022] [Indexed: 11/11/2022]
Abstract
The nasolacrimal apparatus (NLA) is a feature common to many sauropsid amniotes. It consists of an orbital Harderian gland (HG)whose secretions drain into the nasal cavity, in the vicinity of the vomeronasal organ (VNO), an accessory olfactory organ derived from the olfactory epithelium, and a connecting nasolacrimal duct (NLD). Though not all features are present in all posthatchling sauropsids (i.e., no VNO in crocodilomorphs), it is not clear if this system either never existed or failed to develop during the embryonic stages. The purpose of this study is to histologically describe the ontogeny of the NLA and the main olfactory organ in Alligator mississippiensis. Alligator specimens, from embryonic stage 9 to hatchling, were serially histologically sectioned, stained, photographed, and segmented into different tissues using Abobe Photoshop and then reconstructed using Amira for 3D analysis and quantitative nasal epithelial distribution. Though there was no evidence of a VNO, the rest of the NLA was present. The development of the NLA could be subdivided into four phases: (1) inception of NLD, (2) establishment of orbitonasal connections of NLD, (3) bone development, and (4) nasal cavity growth. Glands mature during this last phase and the nasal region rapidly grows, rotates, and is displaced anteriorly. The gradual proportional increase in nonolfactory epithelial distribution during ontogeny is consistent with the literature. Alligator embryonic nasal and NLD growth differs from that of mammals and squamates. The NLD is connected to the anterior third of the nasal region during its initial attachment, but as anterior nasal growth exceeds posterior growth, it is gradually displaced into the posterior third of the nasal region by hatching. It is unknown whether this is a derived archosaur condition or just another example of the morphological variation seen within sauropsid amniotes.
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Affiliation(s)
- Susan J Rehorek
- Department of Biology, Slippery Rock University, Slippery Rock, Pennsylvania, USA
| | - Ruth M Elsey
- Louisiana Department of Wildlife and Fisheries, Slippery Rock, Pennsylvania, USA
| | - Timothy V Smith
- School of Physical Therapy, Slippery Rock University, Slippery Rock, Pennsylvania, USA
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11
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Beeching SC, Elsey R, Rehorek SJ. Ontogeny of the American Alligator (
Alligator mississippiensis
) prenatal head: a morphometric approach. J Morphol 2022; 283:805-814. [DOI: 10.1002/jmor.21472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 03/16/2022] [Accepted: 03/22/2022] [Indexed: 11/11/2022]
Affiliation(s)
- S. C. Beeching
- Department of Biology Slippery Rock University, Slippery Rock, PA 16057
| | - R. Elsey
- Department of Wildlife and Fisheries Louisiana
| | - S. J. Rehorek
- Department of Biology Slippery Rock University, Slippery Rock, PA 16057
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12
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Bona P, Fernandez Blanco MV, Ezcurra MD, von Baczko MB, Desojo JB, Pol D. On the homology of crocodylian post-dentary bones and their macroevolution throughout Pseudosuchia. Anat Rec (Hoboken) 2022; 305:2980-3001. [PMID: 35202518 DOI: 10.1002/ar.24873] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 10/29/2021] [Accepted: 11/19/2021] [Indexed: 12/24/2022]
Abstract
The lower jaw of early tetrapods is composed of several intramembranous ossifications. However, a tendency toward the independent reduction of the number of bones has been observed in the mandible of mammals, lepidosaurs, turtles, crocodiles, and birds. Regarding archosaurs, the coronoid and prearticular bones are interpreted to be lost during the evolution of stem-birds and stem-crocodiles, respectively, but the homology of the post-dentary bones retained in living pseudosuchians remains unclear. Here, we combine paleontological and embryological evidence to explore in detail the homology of the crocodylian post-dentary bones. We study the mandible embryogenesis on a sample of 71 embryos of Caiman and compare this pattern with the mandibular transformations observed across pseudosuchian evolution. In the pre-hatching ontogeny of caimans, at least five intramembranous ossification centers are formed along the margins of the internal mandibular fenestra (perifenestral centers) and, subsequently, merge to form the coronoid (three intramembranous centers), angular (one intramembranous center), and articular (one intramembranous and one chondral center). In the fossil record, an independent prearticular is lost around the base of Mesoeucrocodylia (optimized as reappearing in Thalattosuchia if they are placed within Neosuchia), and the coronoid is apomorphically lost in notosuchians. The integration of embryological and paleontological data indicates that most perifenestral centers are involved in the origin of the prearticular of non-mesoeucrocodylian pseudosuchians. These centers are rearranged during the evolution to contribute to different post-dentary bones in mesoeucrocodylians bolstering the idea that the coronoid and the articular of Crocodylia are not completely homologous to those of other diapsids.
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Affiliation(s)
- Paula Bona
- División Paleontología Vertebrados, Anexo II Laboratorios del Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - María Victoria Fernandez Blanco
- División Paleontología Vertebrados, Anexo II Laboratorios del Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Martín Daniel Ezcurra
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Sección Paleontología de Vertebrados, CONICET-Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires, Argentina
| | - María Belén von Baczko
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Sección Paleontología de Vertebrados, CONICET-Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Buenos Aires, Argentina
| | - Julia Brenda Desojo
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,División Paleontología Vertebrados, Museo de La Plata, Universidad Nacional de La Plata, Buenos Aires, Argentina
| | - Diego Pol
- Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Museo Paleontológico Egidio Feruglio, Trelew, Argentina
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13
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Korneisel DE, Vice R, Maddin HC. Anatomy and development of skull-neck boundary structures in the skeleton of the extant crocodylian Alligator mississippiensis. Anat Rec (Hoboken) 2021; 305:3002-3015. [PMID: 34846803 DOI: 10.1002/ar.24834] [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: 06/24/2021] [Revised: 10/05/2021] [Accepted: 10/07/2021] [Indexed: 11/08/2022]
Abstract
A system-by-system approach dominates morphological and evolutionary study; however, some structures that are better understood within the context of an interface between two systems or traditional units remain less well understood. As part of a larger goal to clarify aspects of skull-neck boundary evolution, we herein describe the morphology and development of the occiput and atlas-axis complex in the crocodylian Alligator mississippiensis. We apply micro-computed tomography scanning, clearing and double staining, and histological analyses to skull-neck boundary structures at three stages of development (embryonic stage 22, 23, and hatchling). Regions of ossification that could possibly pertain to a postparietal were found adjacent to the parietal bone and supraoccipital; however, these were not deemed convincing and are considered part of the supraoccipital. Within the atlas-axis complex, the proatlas appears as two discrete cartilaginous elements in Stage 22 that ossify together at Stage 23. Posterior to the proatlas, the atlas-axis complex is composed of two centra, each with cervical ribs ventrally and neural arches dorsally that begin ossifying at Stage 23. Histology and clearing and staining of Stages 22 and 23 embryos reveal a discrete atlas intercentrum applied to the ventral part of the occipital condyle of the skull. Posterior to this is a cartilage that appears to be a co-chondrified atlas pleurocentrum, axis intercentrum, and axis pleurocentrum. Ossification of this cartilaginous structure produces discrete atlas inter- and pleurocentra, as well as a singular axis centrum. Together these data are discussed with reference to clarifying historical discrepancies concerning elements at the crocodylian skull-neck boundary.
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Affiliation(s)
- Dana E Korneisel
- Department of Earth Sciences, Carleton University, Ottawa, Ontario, Canada
| | - Rebekah Vice
- Department of Earth Sciences, Carleton University, Ottawa, Ontario, Canada
| | - Hillary C Maddin
- Department of Earth Sciences, Carleton University, Ottawa, Ontario, Canada
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14
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Gruntmejer K, Bodzioch A, Konietzko-Meier D. Mandible histology in Metoposaurus krasiejowensis (Temnospondyli, Stereospondyli) from the Upper Triassic of Poland. PeerJ 2021; 9:e12218. [PMID: 34703667 PMCID: PMC8487625 DOI: 10.7717/peerj.12218] [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: 06/15/2021] [Accepted: 09/06/2021] [Indexed: 01/10/2023] Open
Abstract
Recent studies that have systematically augmented our knowledge of dermal bones of the Late Triassic temnospondyl amphibian Metoposaurus krasiejowensis have mostly focused on shoulder girdle elements and the skull. So far, histological data on the mandible are still scant. For the present study, two mandibles have been examined, using 50 standard thin sections. Dermal bones of the mandible reveal a uniform diploë structure, with the external cortex consisting of moderately vascularised, parallel-fibred bone, as well as a distinct alternation of thick zones and thinner annuli. Dense bundles of well-mineralised Sharpey's fibres are seen in the external cortex over the entire length of the mandible. The trabecular middle region is highly porous and well vascularised, showing small primary vascular canals and more numerous secondary osteons; irregular erosion spaces occur in large numbers as well. The thin and poorly vascular internal cortex consists of parallel-fibred bone. The articular is not a dermal bone in origin, having been formed of a thin layer of avascular cortex and a very extensive, trabecular middle region. In contrast to the dermal bones of the mandible, the articular developed from a cartilaginous precursor, as evidenced by numerous remains of calcified cartilage in the central parts of the bone. Histological variability is extremely high along the mandible, its anterior part being characterised by high compactness and biomechanically good resistance in contrast to the highly porous posterior parts. Distinct variations of bone thickness and degree of bone porosity in specific areas of the mandible, may be due to local differences in biomechanics during feeding. The microstructure of the mandible corroborates a previous study of the active and ambush predation strategy in metoposaurids.
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Affiliation(s)
- Kamil Gruntmejer
- European Centre of Palaeontology, University of Opole, Opole, Poland
| | - Adam Bodzioch
- European Centre of Palaeontology, University of Opole, Opole, Poland.,Institute of Biology, Laboratory of Palaeobiology, University of Opole, Opole, Poland
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15
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Woodborne S, Botha H, Huchzermeyer D, Myburgh J, Hall G, Myburgh A. Ontogenetic dependence of Nile crocodile (Crocodylus niloticus) isotope diet-to-tissue discrimination factors. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2021; 35:e9159. [PMID: 34224610 DOI: 10.1002/rcm.9159] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 06/25/2021] [Accepted: 06/27/2021] [Indexed: 06/13/2023]
Abstract
RATIONALE The diet of wild Nile crocodiles (Crocodylus niloticus) is difficult to assess because they are cryptic and nocturnal predators that are extremely sensitive to disturbance by observers, and stomach content analysis is challenging, especially in large specimens. Stable light isotope analysis provides a means of assessing their diet, but diet-to-tissue discrimination factors have yet to be established for the species. METHODS Isotope ratio (15 N/14 N and 13 C/12 C expressed as δ15 N and δ13 C) analyses of scutes, claws, and blood of farmed crocodiles of different sizes were compared with the isotope values of their lifelong diet, which comprises chickens from a single supplier. RESULTS Systematic size dependence in the diet-to-tissue discrimination factors for scute collagen, scute keratin, and claw keratin is described in regression relationships against the snout to vent length. Fixed values are presented for erythrocytes and blood plasma because blood was not sampled from juveniles. CONCLUSIONS The diet-to-tissue discrimination factors help assess the diet of wild crocodiles. The diet of crocodiles from Lake Flag Boshielo shows a clear ontogenic shift, as has been seen in other studies, and the results strongly indicate a dependence on the terrestrial food web rather than a fish diet. That this population may exploit a terrestrial diet highlights potential conflicts for conserving Nile crocodiles outside protected areas.
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Affiliation(s)
- Stephan Woodborne
- Tandem & AMS Laboratory, iThemba LABS, Johannesburg, South Africa
- Stable Isotope Laboratory, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Hannes Botha
- Mpumalanga Tourism and Parks Agency, Scientific Services, Nelspruit, South Africa
- Department of Biodiversity, University of Limpopo, Sovenga, South Africa
| | | | - Jan Myburgh
- Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
| | - Grant Hall
- Stable Isotope Laboratory, Mammal Research Institute, University of Pretoria, Pretoria, South Africa
| | - Albert Myburgh
- Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
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16
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Williams C, Kirby A, Marghoub A, Kéver L, Ostashevskaya-Gohstand S, Bertazzo S, Moazen M, Abzhanov A, Herrel A, Evans SE, Vickaryous M. A review of the osteoderms of lizards (Reptilia: Squamata). Biol Rev Camb Philos Soc 2021; 97:1-19. [PMID: 34397141 PMCID: PMC9292694 DOI: 10.1111/brv.12788] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 07/30/2021] [Accepted: 08/03/2021] [Indexed: 12/24/2022]
Abstract
Osteoderms are mineralised structures consisting mainly of calcium phosphate and collagen. They form directly within the skin, with or without physical contact with the skeleton. Osteoderms, in some form, may be primitive for tetrapods as a whole, and are found in representatives of most major living lineages including turtles, crocodilians, lizards, armadillos, and some frogs, as well as extinct taxa ranging from early tetrapods to dinosaurs. However, their distribution in time and space raises questions about their evolution and homology in individual groups. Among lizards and their relatives, osteoderms may be completely absent; present only on the head or dorsum; or present all over the body in one of several arrangements, including non-overlapping mineralised clusters, a continuous covering of overlapping plates, or as spicular mineralisations that thicken with age. This diversity makes lizards an excellent focal group in which to study osteoderm structure, function, development and evolution. In the past, the focus of researchers was primarily on the histological structure and/or the gross anatomy of individual osteoderms in a limited sample of taxa. Those studies demonstrated that lizard osteoderms are sometimes two-layered structures, with a vitreous, avascular layer just below the epidermis and a deeper internal layer with abundant collagen within the deep dermis. However, there is considerable variation on this model, in terms of the arrangement of collagen fibres, presence of extra tissues, and/or a cancellous bone core bordered by cortices. Moreover, there is a lack of consensus on the contribution, if any, of osteoblasts in osteoderm development, despite research describing patterns of resorption and replacement that would suggest both osteoclast and osteoblast involvement. Key to this is information on development, but our understanding of the genetic and skeletogenic processes involved in osteoderm development and patterning remains minimal. The most common proposition for the presence of osteoderms is that they provide a protective armour. However, the large morphological and distributional diversity in lizard osteoderms raises the possibility that they may have other roles such as biomechanical reinforcement in response to ecological or functional constraints. If lizard osteoderms are primarily for defence, whether against predators or conspecifics, then this 'bony armour' might be predicted to have different structural and/or mechanical properties compared to other hard tissues (generally intended for support and locomotion). The cellular and biomineralisation mechanisms by which osteoderms are formed could also be different from those of other hard tissues, as reflected in their material composition and nanostructure. Material properties, especially the combination of malleability and resistance to impact, are of interest to the biomimetics and bioinspired material communities in the development of protective clothing and body armour. Currently, the literature on osteoderms is patchy and is distributed across a wide range of journals. Herein we present a synthesis of current knowledge on lizard osteoderm evolution and distribution, micro- and macrostructure, development, and function, with a view to stimulating further work.
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Affiliation(s)
- Catherine Williams
- Department of Biomedical Sciences, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada.,Department of Biology, Aarhus University, Ny Munkegade 114-116, Aarhus C, DK-8000, Denmark
| | - Alexander Kirby
- Department of Medical Physics and Biomedical Engineering, University College London, London, WC1E 6BT, U.K.,Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, U.K
| | - Arsalan Marghoub
- Department of Mechanical Engineering, University College London, London, WC1E 7JE, U.K
| | - Loïc Kéver
- Département Adaptations du Vivant, UMR 7179 MECADEV C.N.R.S/M.N.H.N., Bâtiment d'Anatomie Comparée, 55 rue Buffon, Paris, 75005, France
| | - Sonya Ostashevskaya-Gohstand
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, Silwood Park Campus, Berkshire, SL5 7PY, U.K
| | - Sergio Bertazzo
- Department of Medical Physics and Biomedical Engineering, University College London, London, WC1E 6BT, U.K
| | - Mehran Moazen
- Department of Mechanical Engineering, University College London, London, WC1E 7JE, U.K
| | - Arkhat Abzhanov
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, Silwood Park Campus, Berkshire, SL5 7PY, U.K
| | - Anthony Herrel
- Département Adaptations du Vivant, UMR 7179 MECADEV C.N.R.S/M.N.H.N., Bâtiment d'Anatomie Comparée, 55 rue Buffon, Paris, 75005, France
| | - Susan E Evans
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, U.K
| | - Matt Vickaryous
- Department of Biomedical Sciences, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada
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17
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Pritchard AC, Sues HD, Scott D, Reisz RR. Osteology, relationships and functional morphology of Weigeltisaurus jaekeli (Diapsida, Weigeltisauridae) based on a complete skeleton from the Upper Permian Kupferschiefer of Germany. PeerJ 2021; 9:e11413. [PMID: 34055483 PMCID: PMC8141288 DOI: 10.7717/peerj.11413] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 04/15/2021] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Weigeltisauridae is a clade of small-bodied diapsids characterized by a horned cranial frill, slender trunk and limbs, and a patagium supported by elongated bony rods. Partial skeletons and fragments are definitively known only from upper Permian (Lopingian) rocks in England, Germany, Madagascar and Russia. Despite these discoveries, there have been few detailed descriptions of weigeltisaurid skeletons, and the homologies of many skeletal elements-especially the rods supporting the patagium-remain the subject of controversy. MATERIALS & METHODS Here, we provide a detailed description of a nearly complete skeleton of Weigeltisaurus jaekeli from the upper Permian (Lopingian: Wuchiapingian) Kupferschiefer of Lower Saxony, Germany. Briefly addressed by past authors, the skeleton preserves a nearly complete skull, postcranial axial skeleton, appendicular skeleton, and patagial supports. Through comparisons with extant and fossil diapsids, we examine the hypotheses for the homologies of the patagial rods. To examine the phylogenetic position of Weigeltisauridae and characterize the morphology of the clade, we integrate the material and other weigeltisaurids into a parsimony-based phylogenetic analysis focused on Permo-Triassic non-saurian Diapsida and early Sauria (61 taxa, 339 characters). RESULTS We recognize a number of intriguing anatomical features in the weigeltisaurid skeleton described here, including hollow horns on the post-temporal arch, lanceolate teeth in the posterior portion of the maxilla, the absence of a bony arch connecting the postorbital and squamosal bones, elongate and slender phalanges that resemble those of extant arboreal squamates, and patagial rods that are positioned superficial to the lateral one third of the gastral basket. Our phylogenetic study recovers a monophyletic Weigeltisauridae including Coelurosauravus elivensis, Weigeltisaurus jaekeli, and Rautiania spp. The clade is recovered as the sister taxon to Drepanosauromorpha outside of Sauria (=Lepidosauria + Archosauria). CONCLUSIONS Our anatomical observations and phylogenetic analysis show variety of plesiomorphic diapsid characters and apomorphies of Weigeltisauridae in the specimen described here. We corroborate the hypothesis that the patagial ossifications are dermal bones unrelated to the axial skeleton. The gliding apparatus of weigeltisaurids was constructed from dermal elements unknown in other known gliding diapsids. SMNK-PAL 2882 and other weigeltisaurid specimens highlight the high morphological disparity of Paleozoic diapsids already prior to their radiation in the early Mesozoic.
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Affiliation(s)
- Adam C. Pritchard
- Department of Paleontology, Virginia Museum of Natural History, Martinsville, Virginia, United States
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, United States
| | - Hans-Dieter Sues
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, District of Columbia, United States
| | - Diane Scott
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | - Robert R. Reisz
- Department of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada
- Dinosaur Evolution Research Centre and International Centre of Future Science, Jilin University, Changchun, China
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18
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Kandyel RM, Elwan MM, Abumandour MMA, El Nahass EE. Comparative ultrastructural-functional characterizations of the skin in three reptile species; Chalcides ocellatus, Uromastyx aegyptia aegyptia, and Psammophis schokari aegyptia (FORSKAL, 1775): Adaptive strategies to their habitat. Microsc Res Tech 2021; 84:2104-2118. [PMID: 33852761 DOI: 10.1002/jemt.23766] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 03/17/2021] [Accepted: 03/25/2021] [Indexed: 12/13/2022]
Abstract
The current investigation was planned utilizing SEM, histological, and furthermore cytokeratin immunohistochemical to give a full depiction of skin of three reptiles species; Chalcides ocellatus (Scincidae), Uromastyx aegyptia aegyptia (Agamidae), and Psammophis schokari aegyptia (Colubridae) captured from Egypt with various ecological environment. Our SEM results showed different scales covered epidermis of three reptile's species with diverse surface microstructure. Overlapped rhomboid scales with numerous lenticular sense organs with numerous pores and oberhäutchen layer with microridges in C. ocellatus. In U. aegyptia, scales were overlapped elliptical-shaped possess lens-like sense structure with several scattered pits and oberhäutchen layer with polygonal outlined cells. While in P. schokari aegyptia, smooth scales flattened with two large dome-shaped scale receptors/sensilla and lens-like sense structure, moreover polygonal-shaped micro-ornamentation in scale hinge joints were observed. Histologically, skin of three species had outer epidermis with stratum germinativum, stratum corneum (α-keratin, β-keratin layer) capped by surface Oberhäutchen and inner dermis. Osteoderms were observed with dermis of C. ocellatus. There are marked variation within pigment cells types among examined species. Melanophores observed in dermal layer of C. ocellatus, while in U. aegyptia, three pigment cells in tegument dermis; melanophores, xanthophores, and iridophores whereas, P. schokari aegyptia had two forms of chromatophore cells (melanophores and iridophores) in dermis and few melanophores scattered between stratum germinativum cells. The highest cytokeratin immunostaining observed in epidermal cell layer of U. aegyptia aegyptia than two other species. Conclusion, dry scaly skin of reptiles reflects a great range of functional aspects and success to adapt with terrestrial life.
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Affiliation(s)
- Ramadan M Kandyel
- Department of Zoology, Faculty of Science, Tanta University, Tanta, Egypt
| | - Mona M Elwan
- Department of Zoology, Faculty of Science, Tanta University, Tanta, Egypt
| | - Mohamed M A Abumandour
- Department of Anatomy and Embryology, Faculty of Veterinary Medicine, Alexandria University, Alexandria, Egypt
| | - Eman E El Nahass
- Department of Zoology, Faculty of Science, Tanta University, Tanta, Egypt
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19
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Ősi A, Magyar J, Rosta K, Vickaryous M. Cranial ornamentation in the Late Cretaceous nodosaurid ankylosaur Hungarosaurus. PeerJ 2021; 9:e11010. [PMID: 33717709 PMCID: PMC7936564 DOI: 10.7717/peerj.11010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 02/04/2021] [Indexed: 11/20/2022] Open
Abstract
Bony cranial ornamentation is developed by many groups of vertebrates, including ankylosaur dinosaurs. To date, the morphology and ontogenetic origin of ankylosaurian cranial ornamentation has primarily focused on a limited number of species from only one of the two major lineages, Ankylosauridae. For members of the sister group Nodosauridae, less is known. Here, we provide new details of the cranial anatomy of the nodosaurid Hungarosaurus from the Santonian of Europe. Based on a number of previously described and newly identified fragmentary skulls and skull elements, we recognize three different size classes of Hungarosaurus. We interpret these size classes as representing different stages of ontogeny. Cranial ornamentation is already well-developed in the earliest ontogenetic stage represented herein, suggesting that the presence of outgrowths may have played a role in intra- and interspecific recognition. We find no evidence that cranial ornamentation in Hungarosaurus involves the contribution of coossified osteoderms. Instead, available evidence indicates that cranial ornamentation forms as a result of the elaboration of individual elements. Although individual differences and sexual dimorphism cannot be excluded, the observed variation in Hungarosaurus cranial ornamentation appears to be associated with ontogeny.
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Affiliation(s)
- Attila Ősi
- Department of Paleontology, Eötvös Loránd University, Budapest, Hungary.,Hungarian Natural History Museum, Budapest, Hungary
| | - János Magyar
- Department of Paleontology, Eötvös Loránd University, Budapest, Hungary
| | - Károly Rosta
- Department of Paleontology, Eötvös Loránd University, Budapest, Hungary
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20
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Galea GL, Zein MR, Allen S, Francis-West P. Making and shaping endochondral and intramembranous bones. Dev Dyn 2020; 250:414-449. [PMID: 33314394 PMCID: PMC7986209 DOI: 10.1002/dvdy.278] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 11/13/2020] [Accepted: 11/20/2020] [Indexed: 12/13/2022] Open
Abstract
Skeletal elements have a diverse range of shapes and sizes specialized to their various roles including protecting internal organs, locomotion, feeding, hearing, and vocalization. The precise positioning, size, and shape of skeletal elements is therefore critical for their function. During embryonic development, bone forms by endochondral or intramembranous ossification and can arise from the paraxial and lateral plate mesoderm or neural crest. This review describes inductive mechanisms to position and pattern bones within the developing embryo, compares and contrasts the intrinsic vs extrinsic mechanisms of endochondral and intramembranous skeletal development, and details known cellular processes that precisely determine skeletal shape and size. Key cellular mechanisms are employed at distinct stages of ossification, many of which occur in response to mechanical cues (eg, joint formation) or preempting future load‐bearing requirements. Rapid shape changes occur during cellular condensation and template establishment. Specialized cellular behaviors, such as chondrocyte hypertrophy in endochondral bone and secondary cartilage on intramembranous bones, also dramatically change template shape. Once ossification is complete, bone shape undergoes functional adaptation through (re)modeling. We also highlight how alterations in these cellular processes contribute to evolutionary change and how differences in the embryonic origin of bones can influence postnatal bone repair. Compares and contrasts Endochondral and intramembranous bone development Reviews embryonic origins of different bones Describes the cellular and molecular mechanisms of positioning skeletal elements. Describes mechanisms of skeletal growth with a focus on the generation of skeletal shape
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Affiliation(s)
- Gabriel L Galea
- Developmental Biology and Cancer, UCL GOS Institute of Child Health, London, UK.,Comparative Bioveterinary Sciences, Royal Veterinary College, London, UK
| | - Mohamed R Zein
- Centre for Craniofacial and Regenerative Biology, Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, London, UK
| | - Steven Allen
- Comparative Bioveterinary Sciences, Royal Veterinary College, London, UK
| | - Philippa Francis-West
- Centre for Craniofacial and Regenerative Biology, Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, London, UK
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21
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Griffin CT, Stocker MR, Colleary C, Stefanic CM, Lessner EJ, Riegler M, Formoso K, Koeller K, Nesbitt SJ. Assessing ontogenetic maturity in extinct saurian reptiles. Biol Rev Camb Philos Soc 2020; 96:470-525. [PMID: 33289322 DOI: 10.1111/brv.12666] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 10/09/2020] [Accepted: 10/28/2020] [Indexed: 01/06/2023]
Abstract
Morphology forms the most fundamental level of data in vertebrate palaeontology because it is through interpretations of morphology that taxa are identified, creating the basis for broad evolutionary and palaeobiological hypotheses. Assessing maturity is one of the most basic aspects of morphological interpretation and provides the means to study the evolution of ontogenetic changes, population structure and palaeoecology, life-history strategies, and heterochrony along evolutionary lineages that would otherwise be lost to time. Saurian reptiles (the least-inclusive clade containing Lepidosauria and Archosauria) have remained an incredibly diverse, numerous, and disparate clade through their ~260-million-year history. Because of the great disparity in this group, assessing maturity of saurian reptiles is difficult, fraught with methodological and terminological ambiguity. We compiled a novel database of literature, assembling >900 individual instances of saurian maturity assessment, to examine critically how saurian maturity has been diagnosed. We review the often inexact and inconsistent terminology used in saurian maturity assessment (e.g. 'juvenile', 'mature') and provide routes for better clarity and cross-study coherence. We describe the various methods that have been used to assess maturity in every major saurian group, integrating data from both extant and extinct taxa to give a full account of the current state of the field and providing method-specific pitfalls, best practices, and fruitful directions for future research. We recommend that a new standard subsection, 'Ontogenetic Assessment', be added to the Systematic Palaeontology portions of descriptive studies to provide explicit ontogenetic diagnoses with clear criteria. Because the utility of different ontogenetic criteria is highly subclade dependent among saurians, even for widely used methods (e.g. neurocentral suture fusion), we recommend that phylogenetic context, preferably in the form of a phylogenetic bracket, be used to justify the use of a maturity assessment method. Different methods should be used in conjunction as independent lines of evidence when assessing maturity, instead of an ontogenetic diagnosis resting entirely on a single criterion, which is common in the literature. Critically, there is a need for data from extant taxa with well-represented growth series to be integrated with the fossil record to ground maturity assessments of extinct taxa in well-constrained, empirically tested methods.
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Affiliation(s)
- Christopher T Griffin
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
| | - Michelle R Stocker
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
| | - Caitlin Colleary
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Vertebrate Paleontology, Cleveland Museum of Natural History, 1 Wade Oval Drive, Cleveland, OH, 44106, U.S.A
| | - Candice M Stefanic
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Anatomical Sciences, Stony Brook University, 100 Nicolls Road, Stony Brook, NY, 11794, U.S.A
| | - Emily J Lessner
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Pathology and Anatomical Sciences, University of Missouri, 1 Hospital Drive, Columbia, MO, 65212, U.S.A
| | - Mitchell Riegler
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, FL, 32611, U.S.A
| | - Kiersten Formoso
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Earth Sciences, University of Southern California, 3651 Trousdale Pkwy, Los Angeles, CA, 90089, U.S.A
- Dinosaur Institute, Natural History Museum of Los Angeles County, 900 W Exposition Boulevard, Los Angeles, CA, 90007, U.S.A
| | - Krista Koeller
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
- Department of Biology, University of Florida, 220 Bartram Hall, Gainesville, FL, 32611, U.S.A
| | - Sterling J Nesbitt
- Department of Geosciences, Virginia Tech, 926 West Campus Drive, Blacksburg, VA, 24061, U.S.A
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22
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Johnson MM, Young MT, Brusatte SL. The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution. PeerJ 2020; 8:e9808. [PMID: 33083104 PMCID: PMC7548081 DOI: 10.7717/peerj.9808] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 08/03/2020] [Indexed: 12/11/2022] Open
Abstract
Teleosauroidea was a clade of ancient crocodylomorphs that were a key element of coastal marine environments during the Jurassic. Despite a 300-year research history and a recent renaissance in the study of their morphology and taxonomy, macroevolutionary studies of teleosauroids are currently limited by our poor understanding of their phylogenetic interrelationships. One major problem is the genus Steneosaurus, a wastebasket taxon recovered as paraphyletic or polyphyletic in phylogenetic analyses. We constructed a newly updated phylogenetic data matrix containing 153 taxa (27 teleosauroids, eight of which were newly added) and 502 characters, which we analysed under maximum parsimony using TNT 1.5 (weighted and unweighted analyses) and Bayesian inference using MrBayes v3.2.6 (standard, gamma and variation). The resulting topologies were then analysed to generate comprehensive higher-level phylogenetic hypotheses of teleosauroids and shed light on species-level interrelationships within the clade. The results from our parsimony and Bayesian analyses are largely consistent. Two large subclades within Teleosauroidea are recovered, and they are morphologically, ecologically and biogeographically distinct from one another. Based on comparative anatomical and phylogenetic results, we propose the following major taxonomic revisions to Teleosauroidea: (1) redefining Teleosauridae; (2) introducing one new family and three new subfamilies; (3) the resurrection of three historical genera; and (4) erecting seven new generic names and one new species name. The phylogeny infers that the Laurasian subclade was more phenotypically plastic overall than the Sub-Boreal-Gondwanan subclade. The proposed phylogeny shows that teleosauroids were more diverse than previously thought, in terms of morphology, ecology, dispersal and abundance, and that they represented some of the most successful crocodylomorphs during the Jurassic.
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Affiliation(s)
| | - Mark T Young
- School of GeoSciences, University of Edinburgh, Edinburgh, UK
| | - Stephen L Brusatte
- School of GeoSciences, University of Edinburgh, Edinburgh, UK.,National Museum of Scotland, Edinburgh, UK
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23
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Kirby A, Vickaryous M, Boyde A, Olivo A, Moazen M, Bertazzo S, Evans S. A comparative histological study of the osteoderms in the lizards Heloderma suspectum (Squamata: Helodermatidae) and Varanus komodoensis (Squamata: Varanidae). J Anat 2020; 236:1035-1043. [PMID: 31986227 PMCID: PMC7219622 DOI: 10.1111/joa.13156] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 12/03/2019] [Accepted: 01/06/2020] [Indexed: 12/23/2022] Open
Abstract
We describe the histological appearance of the osteoderms (ODs) of Heloderma suspectum and Varanus komodoensis using multiple staining and microscopy techniques to yield information about their morphology and development. Histological analysis showed that the ODs of H. suspectum are composed of three main tissue types, a superficial layer, herein identified as osteodermine, capping a base composed of Sharpey-fibre bone and lamellar bone rich in secondary osteons (Haversian bone tissue). In contrast, ODs in V. komodoensis are composed of a core of woven bone surrounded by parallel-fibred bone without a capping tissue. Thus, in these two species, ODs differ both in terms of their structural composition and in details of their skeletogenesis. The histology of the mineralised tissues observed in these two reptile taxa provides insights into the mechanism of formation of lizard ODs and presents a direct comparison of the histological properties between the ODs of the two species. These data allow greater understanding of the comparative histological appearance of the dermal bones of lizards and highlight their structural diversity.
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Affiliation(s)
- Alexander Kirby
- Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUK
| | | | - Alan Boyde
- Dental Physical Sciences, Barts and The London School of Medicine and DentistryQueen Mary University of LondonLondonUK
| | - Alessandro Olivo
- Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUK
| | - Mehran Moazen
- Department of Mechanical EngineeringUniversity College LondonLondonUK
| | - Sergio Bertazzo
- Department of Medical Physics and Biomedical EngineeringUniversity College LondonLondonUK
| | - Susan Evans
- Department of Cell and Developmental BiologyUniversity College LondonLondonUK
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24
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Schucht PJ, Rühr PT, Geier B, Glaw F, Lambertz M. Armored with skin and bone: A combined histological and
μCT
‐study of the exceptional integument of the
Antsingy
leaf chameleon
Brookesia perarmata
(Angel, 1933). J Morphol 2020; 281:754-764. [DOI: 10.1002/jmor.21135] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 04/12/2020] [Accepted: 04/17/2020] [Indexed: 12/20/2022]
Affiliation(s)
- Pia J. Schucht
- Institut für ZoologieRheinische Friedrich‐Wilhelms‐Universität Bonn, Poppelsdorfer Schloss Bonn Germany
| | - Peter T. Rühr
- AG Morphologische DynamikenInstitut für Zoologie, Biozentrum, Universität zu Köln Köln Germany
- Zentrum für Molekulare BiodiversitätsforschungZoologisches Forschungsmuseum Alexander Koenig Bonn Germany
| | - Benedikt Geier
- Max Planck Institute for Marine Microbiology Bremen Germany
| | - Frank Glaw
- Sektion HerpetologieZoologische Staatssammlung München (ZSM‐SNSB) Munich Germany
| | - Markus Lambertz
- Institut für ZoologieRheinische Friedrich‐Wilhelms‐Universität Bonn, Poppelsdorfer Schloss Bonn Germany
- Sektion HerpetologieZoologisches Forschungsmuseum Alexander Koenig Bonn Germany
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25
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First fossil frog from Antarctica: implications for Eocene high latitude climate conditions and Gondwanan cosmopolitanism of Australobatrachia. Sci Rep 2020; 10:5051. [PMID: 32327670 PMCID: PMC7181706 DOI: 10.1038/s41598-020-61973-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 03/04/2020] [Indexed: 11/08/2022] Open
Abstract
Cenozoic ectothermic continental tetrapods (amphibians and reptiles) have not been documented previously from Antarctica, in contrast to all other continents. Here we report a fossil ilium and an ornamented skull bone that can be attributed to the Recent, South American, anuran family Calyptocephalellidae or helmeted frogs, representing the first modern amphibian found in Antarctica. The two bone fragments were recovered in Eocene, approximately 40 million years old, sediments on Seymour Island, Antarctic Peninsula. The record of hyperossified calyptocephalellid frogs outside South America supports Gondwanan cosmopolitanism of the anuran clade Australobatrachia. Our results demonstrate that Eocene freshwater ecosystems in Antarctica provided habitats favourable for ectothermic vertebrates (with mean annual precipitation ≥900 mm, coldest month mean temperature ≥3.75 °C, and warmest month mean temperature ≥13.79 °C), at a time when there were at least ephemeral ice sheets existing on the highlands within the interior of the continent.
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26
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Iacoviello F, Kirby AC, Javanmardi Y, Moeendarbary E, Shabanli M, Tsolaki E, Sharp AC, Hayes MJ, Keevend K, Li JH, Brett DJL, Shearing PR, Olivo A, Herrmann IK, Evans SE, Moazen M, Bertazzo S. The multiscale hierarchical structure of Heloderma suspectum osteoderms and their mechanical properties. Acta Biomater 2020; 107:194-203. [PMID: 32109598 DOI: 10.1016/j.actbio.2020.02.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 02/13/2020] [Accepted: 02/18/2020] [Indexed: 12/27/2022]
Abstract
Osteoderms are hard tissues embedded in the dermis of vertebrates and have been suggested to be formed from several different mineralized regions. However, their nano architecture and micro mechanical properties had not been fully characterized. Here, using electron microscopy, µ-CT, atomic force microscopy and finite element simulation, an in-depth characterization of osteoderms from the lizard Heloderma suspectum, is presented. Results show that osteoderms are made of three different mineralized regions: a dense apex, a fibre-enforced region comprising the majority of the osteoderm, and a bone-like region surrounding the vasculature. The dense apex is stiff, the fibre-enforced region is flexible and the mechanical properties of the bone-like region fall somewhere between the other two regions. Our finite element analyses suggest that when combined into the osteoderm structure, the distinct tissue regions are able to shield the body of the animal by bearing the external forces. These findings reveal the structure-function relationship of the Heloderma suspectum osteoderm in unprecedented detail. STATEMENT OF SIGNIFICANCE: The structures of bone and teeth have been thoroughly investigated. They provide a basis not only for understanding the mechanical properties and functions of these hard tissues, but also for the de novo design of composite materials. Osteoderms, however, are hard tissues that must possess mechanical properties distinct from teeth and bone to function as a protective armour. Here we provide a detailed analysis of the nanostructure of vertebrate osteoderms from Heloderma suspectum, and show that their mechanical properties are determined by their multiscale hierarchical tissue. We believe this study contributes to advance the current knowledge of the structure-function relationship of the hierarchical structures in the Heloderma suspectum osteoderm. This knowledge might in turn provide a source of inspiration for the design of bioinspired and biomimetic materials.
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Affiliation(s)
- Francesco Iacoviello
- Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London WC1E 7JE, UK
| | - Alexander C Kirby
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK
| | - Yousef Javanmardi
- Department of Mechanical Engineering, University College London, London WC1E 7JE, UK
| | - Emad Moeendarbary
- Department of Mechanical Engineering, University College London, London WC1E 7JE, UK; Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Murad Shabanli
- Department of Mechanical Engineering, University College London, London WC1E 7JE, UK
| | - Elena Tsolaki
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK
| | - Alana C Sharp
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Matthew J Hayes
- Department of Ophthalmology, University College London, London WC1E 6BT, UK
| | - Kerda Keevend
- Department of Materials, Meet Life, Swiss Federal Laboratories for Materials Science and Technology, (Empa), Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland
| | - Jian-Hao Li
- Department of Materials, Meet Life, Swiss Federal Laboratories for Materials Science and Technology, (Empa), Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland
| | - Daniel J L Brett
- Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London WC1E 7JE, UK
| | - Paul R Shearing
- Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London WC1E 7JE, UK
| | - Alessandro Olivo
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK
| | - Inge K Herrmann
- Department of Materials, Meet Life, Swiss Federal Laboratories for Materials Science and Technology, (Empa), Lerchenfeldstrasse 5, CH-9014 St. Gallen, Switzerland
| | - Susan E Evans
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Mehran Moazen
- Department of Mechanical Engineering, University College London, London WC1E 7JE, UK
| | - Sergio Bertazzo
- Department of Medical Physics and Biomedical Engineering, University College London, London WC1E 6BT, UK.
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27
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Clarac F, Scheyer TM, Desojo JB, Cerda IA, Sanchez S. The evolution of dermal shield vascularization in Testudinata and Pseudosuchia: phylogenetic constraints versus ecophysiological adaptations. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190132. [PMID: 31928197 PMCID: PMC7017437 DOI: 10.1098/rstb.2019.0132] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/01/2019] [Indexed: 01/18/2023] Open
Abstract
Studies on living turtles have demonstrated that shells are involved in the resistance to hypoxia during apnea via bone acidosis buffering; a process which is complemented with cutaneous respiration, transpharyngeal and cloacal gas exchanges in the soft-shell turtles. Bone acidosis buffering during apnea has also been identified in crocodylian osteoderms, which are also known to employ heat transfer when basking. Although diverse, many of these functions rely on one common trait: the vascularization of the dermal shield. Here, we test whether the above ecophysiological functions played an adaptive role in the evolutionary transitions between land and aquatic environments in both Pseudosuchia and Testudinata. To do so, we measured the bone porosity as a proxy for vascular density in a set of dermal plates before performing phylogenetic comparative analyses. For both lineages, the dermal plate porosity obviously varies depending on the animal lifestyle, but these variations prove to be highly driven by phylogenetic relationships. We argue that the complexity of multi-functional roles of the post-cranial dermal skeleton in both Pseudosuchia and Testudinata probably is the reason for a lack of obvious physiological signal, and we discuss the role of the dermal shield vascularization in the evolution of these groups. This article is part of the theme issue 'Vertebrate palaeophysiology'.
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Affiliation(s)
- François Clarac
- Department of Organismal Biology, Subdepartment of Evolution and Development, Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden
| | - Torsten M. Scheyer
- Paleontological Institute and Museum, University of Zurich, Karl Schmid-Strasse 4, 8006 Zurich, Switzerland
| | - Julia B. Desojo
- CONICET, División Paleontología Vertebrados, Museo de La Plata, Paseo del Bosque s/n°, B1900FWA La Plata, Argentina
| | - Ignacio A. Cerda
- CONICET, Argentina y Instituto de Investigacion en Paleobiología y Geología, Universidad Nacional de Río Negro, Museo Carlos Ameghino, Belgrano 1700, Paraje Pichi Ruca (predio Marabunta), 8300 Cipolletti, Río Negro, Argentina
| | - Sophie Sanchez
- Department of Organismal Biology, Subdepartment of Evolution and Development, Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden
- European Synchrotron Radiation Facility, 71 Avenue des Martyrs, CS-40220, 38043 Grenoble Cedex, France
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28
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Norman DB. Scelidosaurus harrisonii from the Early Jurassic of Dorset, England: the dermal skeleton. Zool J Linn Soc 2020. [DOI: 10.1093/zoolinnean/zlz085] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Abstract
Cranial exostoses (areas of periosteal ornamentation) are present on the external surfaces of the skull and mandible of Scelidosaurus harrisonii. True osteoderms have also been identified on the skull, forming a ‘brow-ridge’ of three supraorbital bones, dished plates that are attached to the lateral surface of the postorbitals and a pair of larger, horn-shaped structures that project from the posterodorsal surface of the occiput. Postcranial osteoderms form an extensive series of oval-based, ridged osteoderms that extend backward across the dorsal and lateral surfaces of the neck and torso. Smaller, narrow-based ridged osteoderms are also found on the lateral surfaces of the limbs. The tail is surrounded by four longitudinal rows of large, narrow-based, ridged or keeled osteoderms.
The neck, unlike the rest of the body, is encased dorsolaterally by a variety of osteoderms. These can be differentiated into two fundamental types: base-plate osteoderms that develop deep within the compact layers of the dermis and, superficial to each base-plate, tall, ridged or cap-like osteoderms. These latter, project outward from the skin surface and were covered by an epidermal scale or a rigid keratinous sheath. The base-plates are true osteodermal components, but to differentiate them from the more familiar superficial osteoderms, they will be called here simply ‘base-plates’. Lying on the dorsal midline between and beneath the occipital horns is a single, ridged, nuchal osteoderm comprising a base-plate and osteoderm cap. The nuchal plate is flanked by a pair of prominent ‘tricorn’ osteoderm arrays mounted on shallowly arched blocks of fused base-plate osteoderms. Behind the tricorn arrays is a succession of four partial collar-like arrays of osteoderms formed (at least in ontogenetically mature specimens) by coalesced base-plates that anchor tall and either carinate or more plate-like osteoderms. The largest of these are always positioned on the ventrolateral margin of each collar. The osteoderms become progressively smaller toward the midline. It is at present unclear whether the base-plate supported collar arrays on either side fuse together along the midline to form cervical half-rings, as is often reported in more derived ankylosaurian thyreophorans. Individual collar arrays do not imbricate with each other, but are likely to have been interconnected by sheets of tough connective tissue.
On the ventrolateral flanks of the pectoral region are found the largest, bladed osteoderms. In two partly articulated skeletons an osteoderm is preserved on the posterodistal surface of the scapular blade. Although this position is reminiscent of the parascapular spines found in some stegosaurs, these bones are not regarded as homologues; their placement is a coincidence of positioning an osteoderm row adjacent to the scapular blade.
The torso preserves three principal rows of large, ridged osteoderms that show no evidence of accompanying base-plates. The ventrolateral row has the largest osteoderms and these are succeeded in size by the lateral row and dorsolateral row, respectively. There is no evidence to support the existence of a midline dorsal row of osteoderms. The principal rows extend backward across the dorsal and lateral flanks of the body as far as the pelvic area. Smaller cap-shaped osteoderms are scattered between the principal rows, but whether they were organized into subsidiary rows or were more randomly distributed cannot be ascertained. Smaller, narrow-based, ridged osteoderms are found in oblique rows across the anterior chest; they also flank the proximal half of the forelimb (as far as the elbow) and extend to the ankle region in the hind limb.
The tail is surrounded by large, narrow-based, high-ridged osteoderms. Unlike the neck and torso, there is a row of dorsal midline osteoderms that are flanked by large, lateral osteoderms, and beneath these there is a midline ventral row. The latter are close-set and particularly deeply keeled in the area nearest to the pelvis.
Osteoderms vary considerably both in structure and texture. Base-plates have a rough, porous external texture as a consequence of the abundant vascular canals that penetrate these bones. Internally, their surface is arched and has a woven-textured fabric comprising bundles of mineralized fibres interspersed with large vascular foramina. Accompanying osteoderms are generally a little denser than their base-plates and have a smoother cortex, although abundant small foramina and shallow vascular channels pit and groove this external surface. The pair of occipital osteoderms closely resemble bovid (ungulate mammal) horn-cores and are likely to have been sheathed by keratin (as preserved exceptionally in the ankylosaurians Zuul and Borealopelta). Farther posteriorly, the principal osteoderms in the major rows along the torso and tail are generally thin-walled, cap-shaped and ridged. They have a rough and porous external surface, which suggests that the bone surface was covered by keratinous scales. The generally porous fabric of these osteoderms has been remarked upon and it is probable that these were flushed with blood. Interspersed between the visually dominant parasagittal rows of osteoderms is a scattering of smaller cap-shaped osteoderms and polygonal or rounded, flat ossicles. Scattered populations of these ossicles were probably lost because they were, in effect, ‘invisible’ during excavation and skeletal preparation, being of millimetric dimensions. These smaller osteodermal ossicles formed a mosaic-like pattern on the skin surface and toughened the flexible portions of the skin of the animal. Skin impressions and epidermal peels, probably deriving from the ventral surface of the body, reveal a closely packed mosaic of smaller flat osteoderms that underlie similarly shaped keratinous scales.
The discovery of smaller, partly articulated skeletons has revealed aspects of the growth and development of the cervical osteoderm arrays. Individual base-plates begin to form deep in the dermis through mineralization of the woven connective tissue fibres in the stratum compactum and, as these thicken, they also involve the looser and more irregular fibres of the stratum superficiale. Individual base-plates expand peripherally, deepen and form shallowly convex pads externally upon which primordial osteoderms developed. The latter form initially as narrow, elongate, pup-tent-shaped structures with a posteriorly off-set apex and arched, slightly hollow bases. Differential patterns of mineral deposition progressively modify these ‘templates’ into the range of osteoderm morphologies seen in ontogenetically mature skeletons: from subconical curved horns, through tall, carinate blades, to extremely tall, plate-shaped structures, as well as to the simpler oval-based, ridged, pup-tent-shaped osteoderms. As the skeleton approaches full size, in the neck region the base-plates and their osteodermal caps fuse together, and adjacent base-plates interlock before finally fusing together to form partial collars that anchor and support transverse arrays of prominent osteoderms. Osteoderms had the potential to contribute to a number of biological roles in the life of these animals, including protection (defence-retaliation), thermoregulation and more subtle aspects of their behaviour.
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Affiliation(s)
- David B Norman
- Department of Earth Sciences, University of Cambridge, Cambridge, UK
- Christ’s College, Cambridge, UK
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29
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Bailleul AM, Li Z, O'Connor J, Zhou Z. Origin of the avian predentary and evidence of a unique form of cranial kinesis in Cretaceous ornithuromorphs. Proc Natl Acad Sci U S A 2019; 116:24696-24706. [PMID: 31740590 PMCID: PMC6900542 DOI: 10.1073/pnas.1911820116] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The avian predentary is a small skeletal structure located rostral to the paired dentaries found only in Mesozoic ornithuromorphs. The evolution and function of this enigmatic element is unknown. Skeletal tissues forming the predentary and the lower jaws in the basal ornithuromorph Yanornis martini are identified using computed-tomography, scanning electron microscopy, and histology. On the basis of these data, we propose hypotheses for the development, structure, and function of this element. The predentary is composed of trabecular bone. The convex caudal surface articulates with rostromedial concavities on the dentaries. These articular surfaces are covered by cartilage, which on the dentaries is divided into 3 discrete patches: 1 rostral articular cartilage and 2 symphyseal cartilages. The mechanobiology of avian cartilage suggests both compression and kinesis were present at the predentary-dentary joint, therefore suggesting a yet unknown form of avian cranial kinesis. Ontogenetic processes of skeletal formation occurring within extant taxa do not suggest the predentary originates within the dentaries, nor Meckel's cartilage. We hypothesize that the predentary is a biomechanically induced sesamoid that arose within the soft connective tissues located rostral to the dentaries. The mandibular canal hosting the alveolar nerve suggests that the dentary teeth and predentary of Yanornis were proprioceptive. This whole system may have increased foraging efficiency. The Mesozoic avian predentary apparently coevolved with an edentulous portion of the premaxilla, representing a unique kinetic morphotype that combined teeth with a small functional beak and persisted successfully for ∼60 million years.
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Affiliation(s)
- Alida M Bailleul
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China;
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
| | - Zhiheng Li
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
| | - Jingmai O'Connor
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
| | - Zhonghe Zhou
- Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, 100044 Beijing, China;
- Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 100044 Beijing, China
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Bailleul AM, O’Connor J, Schweitzer MH. Dinosaur paleohistology: review, trends and new avenues of investigation. PeerJ 2019; 7:e7764. [PMID: 31579624 PMCID: PMC6768056 DOI: 10.7717/peerj.7764] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 08/26/2019] [Indexed: 12/12/2022] Open
Abstract
In the mid-19th century, the discovery that bone microstructure in fossils could be preserved with fidelity provided a new avenue for understanding the evolution, function, and physiology of long extinct organisms. This resulted in the establishment of paleohistology as a subdiscipline of vertebrate paleontology, which has contributed greatly to our current understanding of dinosaurs as living organisms. Dinosaurs are part of a larger group of reptiles, the Archosauria, of which there are only two surviving lineages, crocodilians and birds. The goal of this review is to document progress in the field of archosaur paleohistology, focusing in particular on the Dinosauria. We briefly review the "growth age" of dinosaur histology, which has encompassed new and varied directions since its emergence in the 1950s, resulting in a shift in the scientific perception of non-avian dinosaurs from "sluggish" reptiles to fast-growing animals with relatively high metabolic rates. However, fundamental changes in growth occurred within the sister clade Aves, and we discuss this major evolutionary transition as elucidated by histology. We then review recent innovations in the field, demonstrating how paleohistology has changed and expanded to address a diversity of non-growth related questions. For example, dinosaur skull histology has elucidated the formation of curious cranial tissues (e.g., "metaplastic" tissues), and helped to clarify the evolution and function of oral adaptations, such as the dental batteries of duck-billed dinosaurs. Lastly, we discuss the development of novel techniques with which to investigate not only the skeletal tissues of dinosaurs, but also less-studied soft-tissues, through molecular paleontology and paleohistochemistry-recently developed branches of paleohistology-and the future potential of these methods to further explore fossilized tissues. We suggest that the combination of histological and molecular methods holds great potential for examining the preserved tissues of dinosaurs, basal birds, and their extant relatives. This review demonstrates the importance of traditional bone paleohistology, but also highlights the need for innovation and new analytical directions to improve and broaden the utility of paleohistology, in the pursuit of more diverse, highly specific, and sensitive methods with which to further investigate important paleontological questions.
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Affiliation(s)
- Alida M. Bailleul
- Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China
- CAS Center for Excellence in Life and Paleoenvironment, Beijing, China
| | - Jingmai O’Connor
- Key Laboratory of Vertebrate Evolution and Human Origins of the Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China
- CAS Center for Excellence in Life and Paleoenvironment, Beijing, China
| | - Mary H. Schweitzer
- Department of Biology, North Carolina State University, Raleigh, NC, USA
- North Carolina Museum of Natural Science, Raleigh, NC, USA
- Department of Geology, Lund University, Lund, Sweden
- Museum of the Rockies, Montana State University, Bozeman, MT, USA
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31
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Lemierre A, Germain D. A new mineralized tissue in the early vertebrate Astraspis. J Anat 2019; 235:1105-1113. [PMID: 31355451 DOI: 10.1111/joa.13070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2019] [Indexed: 11/27/2022] Open
Abstract
The dermoskeleton of the earliest vertebrates is well known but their endoskeleton is thought to have been largely cartilaginous until the Late Silurian. We confirm that the dermal plates of Astraspis are three-layered, with a superficial layer of enameloid and orthodentine, a middle layer of aspidin and a basal layer of lamellar acellular bone. This dermoskeleton is found in association with globular calcified cartilage, indicating the presence of a partially mineralized endoskeleton. In addition to the classical three-layered organization, some dermal plates exhibit alignments of chondrocyte-like lacunae, very similar to a pattern typical of chondroid metaplastic bone, previously unknown in early vertebrates. This discovery implies the presence of a proliferative cartilage, hitherto only known in Osteichthyans. This discovery indicates that a pattern similar to the first step of endochondral ossification was already present in the earliest vertebrates.
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Affiliation(s)
- Alfred Lemierre
- CR2P, MNHN-CNRS-Sorbonne Université, Muséum National d'Histoire Naturelle, Paris, France
| | - Damien Germain
- CR2P, MNHN-CNRS-Sorbonne Université, Muséum National d'Histoire Naturelle, Paris, France
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Schoch RR, Klein N, Scheyer TM, Sues HD. Microanatomy of the stem-turtle Pappochelys rosinae indicates a predominantly fossorial mode of life and clarifies early steps in the evolution of the shell. Sci Rep 2019; 9:10430. [PMID: 31320733 PMCID: PMC6639533 DOI: 10.1038/s41598-019-46762-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Accepted: 07/04/2019] [Indexed: 11/09/2022] Open
Abstract
Unlike any other tetrapod, turtles form their dorsal bony shell (carapace) not from osteoderms, but by contribution of the ribs and vertebrae that expand into the dermis to form plate-like shell components. Although this was known from embryological studies in extant turtles, important steps in this evolutionary sequence have recently been highlighted by the Triassic taxa Pappochelys, Eorhynchochelys and Odontochelys, and the Permian Eunotosaurus. The discovery of Pappochelys shed light on the origin of the ventral bony shell (plastron), which formed from enlarged gastralia. A major question is whether the turtle shell evolved in the context of a terrestrial or aquatic environment. Whereas Odontochelys was controversially interpreted as aquatic, a terrestrial origin of turtles was proposed based on evidence of fossorial adaptations in Eunotosaurus. We report palaeohistological data for Pappochelys, a taxon that exemplifies earlier evolutionary stages in the formation of the bony shell than Odontochelys. Bone histological evidence reveals (1) evolutionary changes in bone microstructure in ribs and gastralia approaching the turtle condition and (2) evidence for a predominantly amphibious or fossorial mode of life in Pappochelys, which support the hypothesis that crucial steps in the evolution of the shell occurred in a terrestrial rather than fully aquatic environment.
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Affiliation(s)
- Rainer R Schoch
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, D-70191, Stuttgart, Germany.
| | - Nicole Klein
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, D-70191, Stuttgart, Germany
- Institut für Geowissenschaften, Abteilung Paläontologie, Nussallee 8, 53115, Bonn, Germany
| | - Torsten M Scheyer
- Universität Zürich, Paläontologisches Institut und Museum, Karl-Schmid-Strasse 4, CH-8006, Zurich, Switzerland.
| | - Hans-Dieter Sues
- Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, MRC 121, Washington, DC, 20560, USA
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Vieira L, Santos A, Hirano L, Menezes-Reis L, Mendonça J, Sebben A. Ontogeny of the skull of the Black Caiman (Melanosuchus niger) (Crocodylia: Alligatoridae). CAN J ZOOL 2019. [DOI: 10.1139/cjz-2018-0076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We describe the formation of the chondrocranium and the ossification pattern of the skull of the Black Caiman (Melanosuchus niger (Spix, 1825)). The embryos were cleared and double-stained with Alizarin Red S and Alcian Blue 8GX. Additionally, they were visualized by histological hematoxylin and eosin staining and computed tomography imaging. The chondrocranium of M. niger comprised the nasal capsule, orbitotemporal, and optic–occipital regions. Its development began at stage 9, with the chondrification of the acrochordal cartilage, trabeculae, and mandibular cartilage. The optic capsule was formed in the caudolateral portion of the chondrocranium at stage 13. The basal plate appeared at stage 14, with foramina for the hypoglossal. The chondrocranium was completely formed at stage 16. The first osteogenic events were noted at stage 13, in the bones, maxilla, jugal, postorbital, and pterygoid. The quadratojugal, prefrontal, frontal, and squamosal began their ossification at stage 14. The parietal bone began to ossify only at stage 20. The basisphenoid began at stage 15 and the parasphenoid began at stage 16. The jaw bones ossified between stages 13 and 16. The dermal elements started their ossification prior to the endochondral bones.
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Affiliation(s)
- L.G. Vieira
- Instituto de Ciências Biológicas, Universidade Federal de Goiânia (UFG), Chácaras Califórnia, Goiânia, Goiás, 74045-155, Brasil
| | - A.L.Q. Santos
- Faculdade de Medicina Veterinária, Universidade Federal de Uberlândia (UFU), Avenida Pará, 1720 – Umuarama, Uberlândia, Minas Gerais, 38400-902, Brasil
| | - L.Q.L. Hirano
- Faculdade de Agronomia e Medicina Veterinária, Universidade de Brasília (UnB), ICC Sul Campos Universitário Darci Ribeiro – Sul, Brasília, Distrito Federal, 70297-400, Brasil
| | - L.T. Menezes-Reis
- Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia (UFU), Avenida Pará 1720 – Bloco 2B – Sala 2B22, Uberlândia, Minas Gerais, 38400-902, Caixa Postal 592, Brasil
| | - J.S. Mendonça
- Instituto de Biociência, Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Rua Cristóvão Colombo, 2265 – Jardim Nazareth, São José do Rio Preto, São Paulo, 15054-000, Brasil
| | - A. Sebben
- Instituto de Ciências Biológicas, Universidade de Brasília (UnB), UnB 1° andar – Asa Norte, Brasília, Distrito Federal, 70910-900, Brasil
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Reichert MN, de Oliveira PRC, Souza GMPR, Moranza HG, Restan WAZ, Abe AS, Klein W, Milsom WK. The respiratory mechanics of the yacare caiman ( Caiman yacare). ACTA ACUST UNITED AC 2019; 222:jeb.193037. [PMID: 30498079 DOI: 10.1242/jeb.193037] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 11/20/2018] [Indexed: 01/30/2023]
Abstract
The structure and function of crocodilian lungs are unique compared with those of other reptiles. We examined the extent to which this and the semi-aquatic lifestyle of crocodilians affect their respiratory mechanics. We measured changes in intratracheal pressure in adult and juvenile caiman (Caiman yacare) during static and dynamic lung volume changes. The respiratory mechanics of juvenile caiman were additionally measured while the animals were floating in water and submerged at 30, 60 and 90 deg to the water's surface. The static compliance of the juvenile pulmonary system (2.89±0.22 ml cmH2O-1 100 g-1) was greater than that of adults (1.2±0.41 ml cmH2O-1 100 g-1), suggesting that the system stiffens as the body wall becomes more muscular and keratinized in adults. For both age groups, the lungs were much more compliant than the body wall, offering little resistance to air flow (15.35 and 4.25 ml cmH2O-1 100 g-1 for lungs, versus 3.39 and 1.67 ml cmH2O-1 100 g-1 for body wall, in juveniles and adults, respectively). Whole-system dynamic mechanics decreased with increasing ventilation frequency (f R), but was unaffected by changes in tidal volume (V T). The vast majority of the work of breathing was required to overcome elastic forces; however, work to overcome resistive forces increased proportionally with f R Work of breathing was higher in juvenile caiman submerged in water at 90 deg because of an increase in work to overcome both elastic and flow resistive forces. The lowest power of breathing was found to occur at high f R and low V T for any given minute ventilation (V̇ E) in caiman of all ages.
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Affiliation(s)
| | - Paulo R C de Oliveira
- Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, 14049-900, Brazil.,Instituto Federal do Paraná- Câmpus Avançado Goioerê, Goioerê, PR, 87360-000, Brazil
| | - George M P R Souza
- School of Medicine of Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, 14049-900, Brazil
| | - Henriette G Moranza
- Clinica Médica Veterinária, Universidade Estadual Paulista, Jaboticabal, SP, 14884-900, Brazil
| | - Wilmer A Z Restan
- Clinica Médica Veterinária, Universidade Estadual Paulista, Jaboticabal, SP, 14884-900, Brazil
| | - Augusto S Abe
- Departamento de Zoologia, Universidade Estadual Paulista, Rio Claro, SP, 13506-692, Brazil
| | - Wilfried Klein
- Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, 14049-900, Brazil
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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Hoffman DK, Heckert AB, Zanno LE. Disparate Growth Strategies within Aetosauria: Novel Histologic Data from the Aetosaur
Coahomasuchus chathamensis. Anat Rec (Hoboken) 2018; 302:1504-1515. [DOI: 10.1002/ar.24019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 08/08/2018] [Accepted: 09/15/2018] [Indexed: 11/09/2022]
Affiliation(s)
| | - Andrew B. Heckert
- Department of Geological and Environmental SciencesAppalachian State University Boone North Carolina
| | - Lindsay E. Zanno
- Department of Biological SciencesNorth Carolina State University Raleigh North Carolina
- Division of PaleontologyNorth Carolina Museum of Natural Sciences Raleigh North Carolina
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36
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Dubansky BH, Close M. A review of alligator and snake skin morphology and histotechnical preparations. J Histotechnol 2018. [DOI: 10.1080/01478885.2018.1517856] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Brooke H. Dubansky
- Department of Medical Laboratory Sciences & Public Health, Tarleton State University, Fort Worth, TX, USA
| | - Matthew Close
- Department of Biological Sciences, Radford University, Radford, VA, USA
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Bailleul AM, Holliday CM. Joint histology in Alligator mississippiensis challenges the identification of synovial joints in fossil archosaurs and inferences of cranial kinesis. Proc Biol Sci 2018; 284:rspb.2017.0038. [PMID: 28330922 DOI: 10.1098/rspb.2017.0038] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 02/14/2017] [Indexed: 11/12/2022] Open
Abstract
Archosaurs, like all vertebrates, have different types of joints that allow or restrict cranial kinesis, such as synovial joints and fibrous joints. In general, synovial joints are more kinetic than fibrous joints, because the former possess a fluid-filled cavity and articular cartilage that facilitate movement. Even though there is a considerable lack of data on the microstructure and the structure-function relationships in the joints of extant archosaurs, many functional inferences of cranial kinesis in fossil archosaurs have hinged on the assumption that elongated condylar joints are (i) synovial and/or (ii) kinetic. Cranial joint microstructure was investigated in an ontogenetic series of American alligators, Alligator mississippiensis All the presumably synovial, condylar joints found within the head of the American alligator (the jaw joint, otic joint and laterosphenoid-postorbital (LS-PO) joint) were studied by means of paraffin histology and undecalcified histology paired with micro-computed tomography data to better visualize three-dimensional morphology. Results show that among the three condylar joints of A. mississippiensis, the jaw joint was synovial as expected, but the otherwise immobile otic and LS-PO joints lacked a synovial cavity. Therefore, condylar morphology does not always imply the presence of a synovial articulation nor mobility. These findings reveal an undocumented diversity in the joint structure of alligators and show that crocodylians and birds build novel, kinetic cranial joints differently. This complicates accurate identification of synovial joints and functional inferences of cranial kinesis in fossil archosaurs and tetrapods in general.
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Affiliation(s)
- Alida M Bailleul
- Department of Pathology and Anatomical Sciences, University of Missouri-School of Medicine, Columbia, MO, USA
| | - Casey M Holliday
- Department of Pathology and Anatomical Sciences, University of Missouri-School of Medicine, Columbia, MO, USA
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Griffing AH, Daza JD, DeBoer JC, Bauer AM. Developmental Osteology of the Parafrontal Bones of the Sphaerodactylidae. Anat Rec (Hoboken) 2017; 301:581-606. [DOI: 10.1002/ar.23749] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Revised: 10/23/2017] [Accepted: 10/31/2017] [Indexed: 12/28/2022]
Affiliation(s)
- Aaron H. Griffing
- Department of Biology; Villanova University; 800 Lancaster Avenue, Villanova Pennsylvania
| | - Juan D. Daza
- Department of Biological Sciences; Sam Houston State University; 1900 Avenue I, Huntsville Texas
| | - Jonathan C. DeBoer
- Department of Biology; Villanova University; 800 Lancaster Avenue, Villanova Pennsylvania
| | - Aaron M. Bauer
- Department of Biology; Villanova University; 800 Lancaster Avenue, Villanova Pennsylvania
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An Overview of the Presence of Osteoderms in Sloths: Implications for Osteoderms as a Plesiomorphic Character of the Xenarthra. J MAMM EVOL 2017. [DOI: 10.1007/s10914-017-9415-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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40
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Scute Patterns as an Individual Identification Tool in an American Crocodile (Crocodylus acutus) Population on Coiba Island, Panama. J HERPETOL 2017. [DOI: 10.1670/17-023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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41
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Brown CM. An exceptionally preserved armored dinosaur reveals the morphology and allometry of osteoderms and their horny epidermal coverings. PeerJ 2017; 5:e4066. [PMID: 29201564 PMCID: PMC5712211 DOI: 10.7717/peerj.4066] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 10/29/2017] [Indexed: 12/04/2022] Open
Abstract
Although the evolution and function of "exaggerated" bony projections in ornithischian dinosaurs has been subject to significant debate recently, our understanding of the structure and morphology of their epidermal keratinized coverings is greatly limited. The holotype of Borealopelta, a new nodosaurid ankylosaur, preserves osteoderms and extensive epidermal structures (dark organic residues), in anatomic position across the entire precaudal length. Contrasting previous specimens, organic epiosteodermal scales, often in the form of horn-like (keratinous) sheaths, cap and exaggerate nearly all osteoderms, allowing for morphometric and allometric analyses of both the bony osteoderms and their horny sheaths. A total of 172 osteoderms were quantified, with osteoderm spine length and height being positively allometric with respect to basal length and width. Despite tight correlations between the different measures amongst all other osteoderms, the large parascapular spines represent consistent outliers. Thickness and relative contribution of the keratinized epiosteodermal scales/sheaths varies greatly by region, ranging from 2% to 6% for posterior thoracics, to ∼25% (1.3×) for the parascapular spines-similar to horn sheaths in some bovid analogues. Relative to the bony cores, the horny portions of the spines are strongly positively allometric (slope = 2.3, CI = 1.8-2.8). Strong allometric scaling, species-specific morphology, and significant keratinous extension of the cervicoscapular spines is consistent with elaboration under socio-sexual selection. This marks the first allometric analysis of ornithischian soft tissues.
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Affiliation(s)
- Caleb M. Brown
- Royal Tyrrell Museum of Palaeontology, Drumheller, AB, Canada
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42
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Vieira LG, Lima FC, Mendonôa SHST, Menezes LT, Hirano LQL, Santos ALQ. Ontogeny of the Postcranial Axial Skeleton of Melanosuchus niger (Crocodylia, Alligatoridae). Anat Rec (Hoboken) 2017; 301:607-623. [PMID: 29150983 DOI: 10.1002/ar.23722] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 07/11/2017] [Accepted: 07/24/2017] [Indexed: 11/07/2022]
Abstract
This study proposes the description of the development of the postcranial axial skeleton, including vertebrae, gastralium, ribs, sternum, and interclavicle, in Melanosuchus niger. Six nests were marked and two eggs removed from each nest at 24-hr intervals until hatching. For posthatching evaluation, 30 hatchlings were kept in captivity and one exemplar was euthanized at three-day intervals. Samples were diaphanized using potassium hydroxide (KOH), alizarin red S, and Alcian blue. A routinely generally used method was applied for histological evaluation. It was difficult to define in which vertebrae the development of cartilaginous centers began, but it was possible to observe that this condensation advanced in the craniocaudal direction. The condensation started in the vertebral arches and was visibly stronger in the cervical and dorsal regions, advancing to the lumbar, sacral and, last, to the caudal region. The atlas showed a highly different morphology compared with the other cervical vertebrae, with a short intercenter, two neural arches, and a proatlas. The ossification process began in the body of cervical vertebrae III to VIII and alizarin retention decreased in the last vertebrae, indicating a craniocaudal direction in bone development, similar to cartilage formation. In the histological sections of gastralium and interclavicles of M. niger at several development stages, it was possible to observe that these elements showed intramembranous development. Anat Rec, 301:607-623, 2018. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- LucéLia Gonçalves Vieira
- Institute of Biomedical Sciences, Federal University of Uberlândia, Av. Pará 1720, Bloco 2B, Uberlândia, Minas Gerais CEP 38400-902 - CP 592, Brazil
| | - Fabiano Campos Lima
- Federal University of Goiás, Rodovia BR 364, Km 192. Setor Industrial, Jataí, Goiás CEP 75801615, Brazil
| | | | - Lorena Tannús Menezes
- Institute of Biomedical Sciences, Federal University of Uberlândia, Av. Pará 1720, Bloco 2B, Uberlândia, Minas Gerais CEP 38400-902 - CP 592, Brazil
| | - Líria Queiroz Luz Hirano
- University Center of Triângulo, Av. Raulino Cotta Pacheco, 70, apto 201, Osvaldo Resende, Uberlândia, Minas Gerais CEP 38400-370, Brazil
| | - André Luiz Quagliatto Santos
- Laboratory for Teaching and Research on Wild Animals, Federal University of Uberlândia, Rua Piauí, s/n, 4S, Uberlândia, MG, 38400-902, Brazil
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Clarac F, De Buffrénil V, Cubo J, Quilhac A. Vascularization in Ornamented Osteoderms: Physiological Implications in Ectothermy and Amphibious Lifestyle in the Crocodylomorphs? Anat Rec (Hoboken) 2017; 301:175-183. [PMID: 29024422 DOI: 10.1002/ar.23695] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/20/2017] [Accepted: 08/07/2017] [Indexed: 11/10/2022]
Abstract
Vascularization in the core of crocodylian osteoderms, and in their superficial pits has been hypothesized to be a key feature involved in physiological thermoregulation and/or acidosis buffering during anoxia (apnea). However, up to now, there have been no quantitative data showing that the inner, or superficial, blood supply of the osteoderms is greater than that occurring in neighboring dermal tissues. We provide such data: our results clearly indicate that the vascular networks in both the osteoderms and the pits forming their superficial ornamentation are denser than in the overlying dermis. These results support previous physiological assumptions and indicate that vascularization in pseudosuchian (crocodylians and close relatives) ornamented osteoderms could be part of a broad eco-physiological adaptation towards ectothermy and aquatic ambush predation acquired by the crocodylomorphs during their post-Triassic evolution. Moreover, regressions demonstrate that the number of enclosed vessels is correlated with the sectional area of the cavities housing them (superficial pits and inner cavities). These regressions can be used to infer the degree of vascularization on dry and fossilized osteoderms and thus document the evolution of the putative function of the osteoderms in the Pseudosuchia. Anat Rec, 2017. © 2017 Wiley Periodicals, Inc. Anat Rec, 301:175-183, 2018. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- F Clarac
- Sorbonne Universités, UPMC Université Paris 06, CNRS, Institut des Sciences de la Terre Paris (ISTeP), Paris, F-75005, France.,Département Histoire de la Terre, Museum National d'Histoire Naturelle, UMR 7207 (CR2P), Sorbonne Universités, MNHN/CNRS/UPMC, F-75231, France
| | - V De Buffrénil
- Département Histoire de la Terre, Museum National d'Histoire Naturelle, UMR 7207 (CR2P), Sorbonne Universités, MNHN/CNRS/UPMC, F-75231, France
| | - J Cubo
- Sorbonne Universités, UPMC Université Paris 06, CNRS, Institut des Sciences de la Terre Paris (ISTeP), Paris, F-75005, France
| | - A Quilhac
- Sorbonne Universités, UPMC Université Paris 06, CNRS, Institut des Sciences de la Terre Paris (ISTeP), Paris, F-75005, France
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English LT. Variation in crocodilian dorsal scute organization and geometry with a discussion of possible functional implications. J Morphol 2017; 279:154-162. [DOI: 10.1002/jmor.20760] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Revised: 09/22/2017] [Accepted: 09/26/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Lauren T. English
- Department of Geology, Jackson School of Geosciences; The University of Texas at Austin; Austin Texas U.S.A
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Clarac F, Goussard F, Teresi L, Buffrénil V, Sansalone V. Do the ornamented osteoderms influence the heat conduction through the skin? A finite element analysis in Crocodylomorpha. J Therm Biol 2017; 69:39-53. [DOI: 10.1016/j.jtherbio.2017.06.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 06/01/2017] [Accepted: 06/04/2017] [Indexed: 10/19/2022]
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Dubansky BH, Dubansky BD. Natural development of dermal ectopic bone in the american alligator (Alligator mississippiensis
) resembles heterotopic ossification disorders in humans. Anat Rec (Hoboken) 2017; 301:56-76. [DOI: 10.1002/ar.23682] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 07/25/2017] [Accepted: 08/17/2017] [Indexed: 12/20/2022]
Affiliation(s)
- Brooke H. Dubansky
- Department of Medical Laboratory Sciences and Public Health; Tarleton State University; 1501 Enderly Place, Fort Worth Texas
| | - Benjamin D. Dubansky
- Department of Biological Sciences; University of North Texas, 1511 W. Sycamore St; Denton Texas
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Moustakas-Verho JE, Cebra-Thomas J, Gilbert SF. Patterning of the turtle shell. Curr Opin Genet Dev 2017; 45:124-131. [DOI: 10.1016/j.gde.2017.03.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 03/06/2017] [Accepted: 03/21/2017] [Indexed: 12/30/2022]
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An Exceptionally Preserved Three-Dimensional Armored Dinosaur Reveals Insights into Coloration and Cretaceous Predator-Prey Dynamics. Curr Biol 2017; 27:2514-2521.e3. [DOI: 10.1016/j.cub.2017.06.071] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Revised: 05/16/2017] [Accepted: 06/27/2017] [Indexed: 02/08/2023]
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Bailleul AM, Witmer LM, Holliday CM. Cranial joint histology in the mallard duck (Anas platyrhynchos): new insights on avian cranial kinesis. J Anat 2017; 230:444-460. [PMID: 27921292 PMCID: PMC5314395 DOI: 10.1111/joa.12562] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/11/2016] [Indexed: 01/09/2023] Open
Abstract
The evolution of avian cranial kinesis is a phenomenon in part responsible for the remarkable diversity of avian feeding adaptations observable today. Although osteological, developmental and behavioral features of the feeding system are frequently studied, comparatively little is known about cranial joint skeletal tissue composition and morphology from a microscopic perspective. These data are key to understanding the developmental, biomechanical and evolutionary underpinnings of kinesis. Therefore, here we investigated joint microstructure in juvenile and adult mallard ducks (Anas platyrhynchos; Anseriformes). Ducks belong to a diverse clade of galloanseriform birds, have derived adaptations for herbivory and kinesis, and are model organisms in developmental biology. Thus, new insights into their cranial functional morphology will refine our understanding of avian cranial evolution. A total of five specimens (two ducklings and three adults) were histologically sampled, and two additional specimens (a duckling and an adult) were subjected to micro-computed tomographic scanning. Five intracranial joints were sampled: the jaw joint (quadrate-articular); otic joint (quadrate-squamosal); palatobasal joint (parasphenoid-pterygoid); the mandibular symphysis (dentary-dentary); and the craniofacial hinge (a complex flexion zone involving four different pairs of skeletal elements). In both the ducklings and adults, the jaw, otic and palatobasal joints are all synovial, with a synovial cavity and articular cartilage on each surface (i.e. bichondral joints) ensheathed in a fibrous capsule. The craniofacial hinge begins as an ensemble of patent sutures in the duckling, but in the adult it becomes more complex: laterally it is synovial; whereas medially, it is synostosed by a bridge of chondroid bone. We hypothesize that it is chondroid bone that provides some of the flexible properties of this joint. The heavily innervated mandibular symphysis is already fused in the ducklings and remains as such in the adult. The results of this study will serve as reference for documenting avian cranial kinesis from a microanatomical perspective. The formation of: (i) secondary articular cartilage on the membrane bones of extant birds; and (ii) their unique ability to form movable synovial joints within two or more membrane bones (i.e. within their dermatocranium) might have played a role in the origin and evolution of modern avian cranial kinesis during dinosaur evolution.
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Affiliation(s)
- Alida M. Bailleul
- Department of Pathology and Anatomical SciencesUniversity of Missouri‐School of MedicineColumbiaMOUSA
| | - Lawrence M. Witmer
- Department of Biomedical SciencesHeritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
| | - Casey M. Holliday
- Department of Pathology and Anatomical SciencesUniversity of Missouri‐School of MedicineColumbiaMOUSA
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Microanatomy and life history in Palaeopleurosaurus (Rhynchocephalia: Pleurosauridae) from the Early Jurassic of Germany. Naturwissenschaften 2016; 104:4. [PMID: 28005148 DOI: 10.1007/s00114-016-1427-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Revised: 12/05/2016] [Accepted: 12/08/2016] [Indexed: 10/20/2022]
Abstract
The tuatara (Sphenodon punctatus) from New Zealand is often-erroneously-identified as a 'living fossil', although it is the lone survivor of a large, successful radiation of Rhynchocephalia, sister taxon to squamates (lizards and snakes), that thrived through the Mesozoic and Cenozoic and experienced an intricate evolution of life histories and feeding habits. Within Rhynchocephalia, only Pleurosauridae are thought to be marine and piscivorous. Here, we present bone histological data of the Jurassic pleurosaurid Palaeopleurosaurus, showing osteosclerosis (i.e. bone mass increase) in its gastralia, and some osteosclerosis in its rib but no increase in bone mass in the femur, supporting a gradual skeletal specialization for an aquatic way of life. Similar to Sphenodon, the bone tissue deposited in Palaeopleurosaurus is lamellar zonal bone. The femoral growth pattern in Palaeopleurosaurus differs from that of terrestrial Sphenodon in a more irregular spacing of growth marks and deposition of non-annual (i.e. non-continuous) rest lines, indicating strong dependency on exogenous factors. The annual growth mark count in adult but not yet fully grown Palaeopleurosaurus is much lower when compared to adult individuals of Sphenodon, which could indicate a lower lifespan for Palaeopleurosaurus. Whereas the gastral ribs of Palaeopleurosaurus and Sphenodon are similar in composition, the ribs of Sphenodon differ profoundly in being separated into a proximal tubular rib part with a thick cortex, and an elliptical, flared ventral part characterised by extremely thin cortical bone. The latter argues against a previously inferred protective function of the ventral rib parts for the vulnerable viscera in Sphenodon.
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