The development of cephalic armor in the tokay gecko (Squamata: Gekkonidae: <scp><i>Gekko gecko</i></scp>)

Laver, Rebecca J.; Morales, Cristian Hernández; Heinicke, Matthew P.; Gamble, Tony; Longoria, Kristin; Bauer, Aaron M.; Daza, Juan D.

doi:10.1002/jmor.21092

Cited by 16 publications

(18 citation statements)

References 76 publications

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“…ODs are virtually absent from iguanians with two published exceptions, a species of leaf chameleon ( Brookesia perarmata ) and some individual specimens of the marine iguana ( Amblyrhynchus cristatus ) (de Queiroz, 1987 ; Schucht et al ., 2020 ). ODs are rare in gekkotans, but have been reported from a small number of species across two different clades: Gekkonidae and Phyllodactylidae (Schmidt, 1912 a ; Levrat‐Calviac, 1986 ; Levrat‐Calviac & Zylberberg, 1986 ; Vickaryous et al ., 2015 ; Paluh et al ., 2017 ; Scherz et al ., 2017 ; Laver et al ., 2020 ). It is worth noting that small, superficially OD‐like elements have been described for two genera of sphaerodactylid geckos ( Aristelliger and Teratoscincus ) (Bauer & Russell, 1989 ; Griffing et al ., 2018 ).…”

Section: Evolutionary History and Distribution In Squamatesmentioning

confidence: 99%

“…CT scanning is non‐invasive, able to generate high‐resolution two‐dimensional and three‐dimensional data rapidly, and can be used to map the distribution of ODs across body regions or the entire lizard (e.g. Maisano et al ., 2002 ; Bever et al ., 2005 ; Paluh et al ., 2017 ; Maisano et al ., 2019 ; Laver et al ., 2020 ; Iacoviello et al ., 2020 ), as reviewed in Broeckhoven & du Plessis ( 2018 ). Further, there are several open‐source repositories of CT data archiving OD‐bearing lizards, including Digimorph ( digimorph.org ) and Morpho Source ( morphosource.org ).…”

Section: Osteoderm Macro‐ and Microstructurementioning

confidence: 99%

“…Heloderma (Mead et al ., 2012 ; Iacoviello et al ., 2020 ; Kirby et al ., 2020 ); Figs 3A and 4 ), interlocking tesserae [cranial ODs in Gekko gecko , Fig. 2E (Vickaryous et al ., 2015 ; Laver et al ., 2020 )], cycloid [ Geckolepis (Schmidt, 1912 a ; Paluh et al ., 2017 )] or palmate shapes ( Anniella spp. ; Bhullar & Bell, 2008 ), and compound elements consisting of multiple plates joined together [e.g.…”

Section: Osteoderm Macro‐ and Microstructurementioning

confidence: 99%

“…Although their formation is relatively delayed compared to the rest of the skeleton, ODs have been documented among comparatively small, skeletally immature lizards (Schmidt, 1912 a , 1912 b , 1914 a ; Vickaryous et al ., 2015 ; Stanley, 2016 ; Laver et al ., 2020 ). Early OD development takes place asynchronously across the body, and appears to be associated with maturation of the epidermis and dermis (Vickaryous & Sire, 2009 ).…”

Section: Developmentmentioning

confidence: 99%

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A review of the osteoderms of lizards (Reptilia: Squamata)

et al. 2021

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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 a...

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Section: Evolutionary History and Distribution In Squamatesmentioning

confidence: 99%

Section: Osteoderm Macro‐ and Microstructurementioning

confidence: 99%

Section: Osteoderm Macro‐ and Microstructurementioning

confidence: 99%

Section: Developmentmentioning

confidence: 99%

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A review of the osteoderms of lizards (Reptilia: Squamata)

et al. 2021

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“…Osteoderms are particularly common and diverse in lizards [5], where their shapes, range from compound plates, and scales [5,32] to needles [33]. They also vary in size from centimeters to millimeters [26,34], but size is not always correlated with body length and it is not uncommon for small lizards to present large osteoderms [35].…”

Section: Introductionmentioning

confidence: 99%

The multiscale hierarchical structure of Heloderma suspectum osteoderms and their mechanical properties

et al. 2020

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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 fibreenforced 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 dampening the external forces. These findings reveal the structure-function relationship of the Heloderma suspectum osteoderm in unprecedented detail .

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The role of cranial osteoderms on the mechanics of the skull in scincid lizards

Marghoub

Kéver

Williams

et al. 2023

The Anatomical Record

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Osteoderms (ODs) are calcified organs formed directly within the skin of most major extant tetrapod lineages. Lizards possibly show the greatest diversity in ODs morphology and distribution. ODs are commonly hypothesized to function as a defensive armor. Here we tested the hypothesis that cranial osteoderms also contribute to the mechanics of the skull during biting. A series of in vivo experiments were carried out on three specimens of Tiliqua gigas. Animals were induced to bite a force plate while a single cranial OD was strain gauged. A finite element (FE) model of a related species, Tiliqua scincoides, was developed and used to estimate the level of strain across the same OD as instrumented in the in vivo experiments. FE results were compared to the in vivo data and the FE model was modified to test two hypothetical scenarios in which all ODs were (i) removed from, and (ii) fused to, the skull. In vivo data demonstrated that the ODs were carrying load during biting. The hypothetical FE models showed that when cranial ODs were fused to the skull, the overall strain across the skull arising from biting was reduced. Removing the ODs showed an opposite effect. In summary, our findings suggest that cranial ODs contribute to the mechanics of the skull, even when they are loosely attached.

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The development of cephalic armor in the tokay gecko (Squamata: Gekkonidae: Gekko gecko)

Abstract: This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as

Cited by 16 publications

References 76 publications

A review of the osteoderms of lizards (Reptilia: Squamata)

A review of the osteoderms of lizards (Reptilia: Squamata)

The multiscale hierarchical structure of Heloderma suspectum osteoderms and their mechanical properties

The role of cranial osteoderms on the mechanics of the skull in scincid lizards

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