A comparative study of eggshells of Gekkota with morphological, chemical compositional and crystallographic approaches and its evolutionary implications

Choi, Seung Hyun; Han, Sungjun; Lee, Yuong‐Nam

doi:10.1371/journal.pone.0199496

Cited by 28 publications

(72 citation statements)

References 61 publications

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“…Except for this ornamentation, the external surface is smooth (see PLM observation above) and uniform in thickness. Considering the fact that non-ornamented plain parts of the eggshell have consistent thickness (e.g., Choi et al, 2018Choi et al, , 2020, it also supports the non-taphonomic origin of ornamentation structure described herein.…”

Section: Scanning Electron Microscopysupporting

confidence: 82%

“…In addition, lapped and polished materials used for EPMA and EBSD analyses were observed in the backscattered electron (BSE) mode. See Choi et al (2018) for further detail.…”

Section: Scanning Electron Microscopy (Sem)mentioning

confidence: 99%

“…These specimens were used for chemical compositional analysis using field emission electron probe microanalyzer [FE-EPMA; JEOL JXA-8530F housed at the National Center for Inter-University Research Facilities (NCIRF), SNU] and crystallographic analysis using electron backscatter diffraction (EBSD; Oxford Instrument Symmetry detector attached to JEOL JSM-7100F in SEES, SNU). We acquired and curated EPMA (Choi et al, 2018;Kim et al, 2019) and EBSD data (Moreno-Azanza et al, 2013; following the established methods.…”

Section: Electron Probe Microanalyzer (Epma) and Electron Backscattermentioning

confidence: 99%

“…In some cases, exposed section of a calcite layer shows numerous vesicle-like structures with varying sizes (Figure 6C). In a few cases, horizontal or slightly inclined gully-like structures are seen ( Figure 6D), which might be the trace of dissolved organic fiber (e.g., see Choi et al, 2018, Supplementary Figures S2I-L). The width of this structure is consistent with that of large vesicles.…”

Section: Scanning Electron Microscopymentioning

confidence: 99%

“…Modern avian eggshells are mostly composed of calcite (96%) with a rare amount of organic matrix (2%) and trace elements such as Mg, P, and S (Hincke et al, 2012;Dauphin et al, 2018). Likewise, modern crocodylian and (rigid) gecko eggshells are mostly composed of calcium carbonate in the form of calcite (Ferguson, 1982;Schleich and Kästle, 1988;Marzola et al, 2015;Choi et al, 2018) unlike turtle eggshells, which are mainly composed of aragonite (Lawver and Jackson, 2014). In all rigid eggshells of modern amniotes, organic materials are certainly a minor and easily degradable component so that they are rarely preserved in the fossil record (Hirsch, 1996, Table 2; Smith and Hayward, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Raman Spectroscopy Detects Amorphous Carbon in an Enigmatic Egg From the Upper Cretaceous Wido Volcanics of South Korea

et al. 2020

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Raman spectroscopy has been widely used in micropaleontology and organic geochemistry to identify carbonaceous materials and evaluate their thermal maturity in fossils or metasedimentary rocks. Meanwhile, fossil egg researches have mostly focused on biomineralized calcite, but preserved carbonaceous (or possibly organic) materials inside the eggshells have been usually neglected until recently. Here we report an enigmatic egg from the Wido Volcanics (Upper Cretaceous) of South Korea that was analyzed using diverse methods including polarized light microscope, scanning electron microscope, electron probe microanalyzer, electron backscatter diffraction, and Raman spectroscopy. The eggshell not only shows the crystallography of archosaurian eggshells but also contains peculiar dark bands, which were previously known as the trait of fossil and modern Crocodyliformes eggshells. Raman spectroscopic analysis showed that the dark bands are mainly due to amorphous carbon, as evidenced by the clear graphite (G) and disordered (D) bands. The deconvolution of amorphous carbon peaks and resultant parameters made it possible to infer the paleotemperature inscribed in the eggshell. The result suggests that preserved amorphous carbon in the fossil eggshells can be identified using Raman spectroscopy and Raman parameters may make it possible to compare the thermal maturity of spatiotemporally diverse fossil eggshells. The biogenicity of the dark band is not clear because Raman spectroscopic analysis is not sufficient to confirm biogenicity. However, overall distribution of the dark band may imply the biogenic origin. It is apparent that the material of this study is not a dinosaur egg but might belong to a crocodyliform or choristoderan egg, and even other non-dinosaur archosaur can be a candidate as well.

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Section: Scanning Electron Microscopysupporting

confidence: 82%

“…In addition, lapped and polished materials used for EPMA and EBSD analyses were observed in the backscattered electron (BSE) mode. See Choi et al (2018) for further detail.…”

Section: Scanning Electron Microscopy (Sem)mentioning

confidence: 99%

Section: Electron Probe Microanalyzer (Epma) and Electron Backscattermentioning

confidence: 99%

Section: Scanning Electron Microscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Raman Spectroscopy Detects Amorphous Carbon in an Enigmatic Egg From the Upper Cretaceous Wido Volcanics of South Korea

et al. 2020

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Multiscale Mineralization in the Leopard Gecko Eggshell

Deering,

Nelea,

McKee

2024

Adv Funct Materials

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Reptilian (non‐avian) eggshell biomineralization is markedly different from avian eggshells. Despite discontinuous/variable mineralization, the reptilian eggshell (like in birds) is responsible for protective and developmental functions of the egg as part of a highly successful reproduction strategy. Using multiscale imaging and characterization methods including X‐ray and electron microscopy/tomography, a 3D overview of eggshell ultrastructure in the gekkotan Eublepharis macularius – the common leopard gecko is provided. Eggshell mineral is shown to be sensitive to aqueous preparations, where cryogenic methods are essential for accurate mineral and organic preservation. Interwoven with the mineral are underlying organic fibers involved in the formation of complex hierarchical order in the eggshell, including nucleation and growth of mineral. The calcitic mineral phase of the eggshell takes on three microstructural motifs at the shell surface: nodular scutes (≈40 µm), intermittent blunt or star‐shaped mineral rosettes (≈1 mm), and smaller mineral corollas (≈10 µm). Individual scutes have two hierarchical mineral structures – mineral nanospheres (≈500 nm) and mineral nanodomains (≈40 nm). Diverse and variable biomineralization features of reptilian eggshells likely reflect the importance of differences in ecology and physiology on egg formation, survival, and eggshell mechanics, and are likely related to hydration sensitivity, structural organic‐inorganic interactions, and mineral polymorphism.

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Do all geckos hatch in the same way? Histological and 3D studies of egg tooth morphogenesis in the geckos Eublepharis macularius Blyth 1854 and Lepidodactylus lugubris Duméril & Bibron 1836

Hermyt

Metscher

Rupik

2020

Journal of Morphology

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The egg tooth of squamates evolved to facilitate hatching from mineralized eggshells. Squamate reptiles can assist their hatching with a single unpaired egg tooth (unidentates) or double egg teeth (geckos and dibamids). Egg tooth ontogeny in two gekkotan species, the leopard gecko Eublepharis macularius and the mourning gecko Lepidodactylus lugubris, was compared using microtomography, scanning electron microscopy, and light microscopy. Investigated species are characterized by different hardnesses of their eggshells. Leopard geckos eggs have a relatively soft and flexible parchment (leathery) shell, while eggshells of mourning geckos are hard and rigid. Embryos of both species, like other Gekkota, have double egg teeth, but the morphology of these structures differs between the investigated species. These differences in shape, localization, and spatial orientation were present from the earliest stages of embryonic development. In mourning gecko, anlagen of differentiating egg teeth change their position on the palate during embryonic development. Initially they are separated by condensed mesenchyme, but later in development, their enamel organs are connected. In leopard geckos, the localization of egg tooth germs does not change, but their spatial orientation does. Egg teeth of this species shift from inward to outward orientation. This is likely related to differences in structure and mechanical properties of eggshells in the studied species. In investigated species, two hatching mechanisms are possible during emergence of young individuals. We speculate that mourning geckos break the eggshell through puncturing action with egg teeth, similar to the pipping phase of chick and turtles embryos. Egg teeth of leopard geckos cut egg membranes similarly to most squamates. Our results also revealed differences in egg tooth implantation between Gekkota and Unidentata: gekkotan egg teeth are subthecodont (in shallow sockets), while those in unidentates are acrodont (attached to the top of the alveolar ridge).

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A comparative study of eggshells of Gekkota with morphological, chemical compositional and crystallographic approaches and its evolutionary implications

Cited by 28 publications

References 61 publications

Raman Spectroscopy Detects Amorphous Carbon in an Enigmatic Egg From the Upper Cretaceous Wido Volcanics of South Korea

Raman Spectroscopy Detects Amorphous Carbon in an Enigmatic Egg From the Upper Cretaceous Wido Volcanics of South Korea

Multiscale Mineralization in the Leopard Gecko Eggshell

Do all geckos hatch in the same way? Histological and 3D studies of egg tooth morphogenesis in the geckos Eublepharis macularius Blyth 1854 and Lepidodactylus lugubris Duméril & Bibron 1836

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