Comparative histology of conodonts and early vertebrates

Журавлев, А. В.

doi:10.19110/2221-1381-2017-4-37-42

Cited by 3 publications

(3 citation statements)

References 24 publications

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“…Hyaline tissue is built of densely packed prismatic or pinacoidal crystals arranged in distinct lamellar pattern with porosity developed in interlamellar spaces or as intercrystalline nanopores (Wright 1989; Trotter et al . 2007; Zhuravlev 2017). Albid tissue consists of extraordinarily large (~100’s μm) apatite monocrystals arranged in the same optical orientation and possesses a weak longitudinal lamellar structure visible on broken surfaces (Wright 1989; Trotter et al .…”

Section: Discussionmentioning

confidence: 99%

“…Albid tissue consists of extraordinarily large (~100’s μm) apatite monocrystals arranged in the same optical orientation and possesses a weak longitudinal lamellar structure visible on broken surfaces (Wright 1989; Trotter et al . 2007; Zhuravlev & Gerasimova 2015; Zhuravlev 2017). Numerous micro‐ and nanopores of the albid tissue are responsible for its optical opacity (Trotter et al .…”

Section: Discussionmentioning

confidence: 99%

“…Numerous micro‐ and nanopores of the albid tissue are responsible for its optical opacity (Trotter et al . 2007; Zhuravlev & Gerasimova 2015; Zhuravlev 2017). The increasing ordering and complexity of the albid structure of conodont elements during the Palaeozoic is shown; this tissue may, however, be lacking in some Late Palaeozoic forms (Zhuravlev & Gerasimova 2015; Zhuravlev 2017).…”

Section: Discussionmentioning

confidence: 99%

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Structural, chemical and isotope evidence for secondary phosphate mineralization of grasping spines of Early Palaeozoic chaetognaths

Wierzbowski

Szaniawski

Błażejowski

2021

LET

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Microscope, cathodoluminescence, chemical and oxygen isotope studies have been conducted to determine the original mineralogy and diagenetic alteration of phosphatic grasping spines of Cambrian chaetognaths. The obtained data, along with a comparison to the composition of conodont apatite, show the presence of a few generations of diagenetic phosphate phases. A thin, outer layer of the spines is composed of very early diagenetic phosphate, which incrusted the original cuticle layer contributing to the preservation of an original shape and structural details of the fossils. This process can be linked to the ‘Orsten’‐type phosphatization mainly known from Lower Palaeozoic strata. Successive phosphate generations are observed within the middle and inner layers as well as internal cavities of the spines. Plastic deformations and diagenetic features of the spines show that they were originally composed of slightly flexible chitinous organic matter similar to that of modern chaetognaths. This conclusion is substantiated by rare findings of purely organic remnants of Cambrian chaetognath grasping spines.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Structural, chemical and isotope evidence for secondary phosphate mineralization of grasping spines of Early Palaeozoic chaetognaths

Wierzbowski

Szaniawski

Błażejowski

2021

LET

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Paleo‐evo‐devo implications of a revised conceptualization of enameloids and enamels

Houée,

Goudemand,

Germain

et al. 2024

Biological Reviews

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Understanding the origin and evolution of the mineralized skeleton is crucial for unravelling vertebrate history. However, several limitations hamper our progress. The first obstacle is the lack of uniformity and clarity in the literature for the definition of the tissues of concern, especially of enameloid(s) and enamel(s), resulting in ambiguous terminology and inconsistencies among studies. Moreover, the identification criteria currently employed to characterize hypermineralized tissues in extinct taxa, such as the presence or absence of tubules for enameloids, may lead to unsupported conclusions. We suggest that comparative developmental studies may be key to unambiguous terminology, truly diagnostic identification criteria and developmentally informed evolutionary hypotheses. We exemplify this approach by: (i) introducing a new conceptual framework for enameloid(s) and enamel(s), with clear terminologies, definitions and interactions between concepts; (ii) suggesting more rigorous ways to identify tissues, based on the observation of defining or additional properties, as well as on the comparison of developmental scenarios when possible; (iii) constructing a clear phylogenetic framework to discuss their homologies and highlighting possible transitions between these tissues; and by (iv) proposing developmental models that explain both enamel and enameloid formation, and suggest possible transitions between them.

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Composition, structure and model of the formation of conodont lamellar tissue

Журавлев¹

2020

Lithosphere

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Research subject. This research was focused on the most common mineralized tissue that composes conodont elements. The aim was to investigate the characteristics of the composition and structure of this tissue and to reconstruct its formation process. Materials and methods. The work was based on a collection of well-preserved conodont elements from the Upper Devonian of the East European Platform and the Upper Devonian – Lower Carboniferous of the east of the Pechora Plate. Oriented and polished thin sections made from some of the elements were studied using light and electron microscopy, as well as a microhardness tester. Energy dispersive spectroscopy was used to determine the chemical (elemental) composition of the lamellar tissue. In addition, the carbon isotope ratio was determined for organic matter. Results. The study showed that the lamellar tissue in conodont elements consists of fluorohydroxylapatite crystallites of various morphology, surrounded by organic matter, which makes up 2–3% of the tissue. Variations in the composition of major elements incorporated in fluorohydroxylapatite of the lamellar tissue are insignificant. Organic matter is represented by a collagen-like protein, likely to be of a non-fibrillar type, with a light carbon isotopic composition (–26.2 ‰ PDB). The lamellar tissue has an average microhardness of 2.6 GPa, the variations of which are due to textural and structural features and the distribution of organic matter. In conodont elements, the lamellar tissue is in contact with other types of tissue. Transitions between tissues are relatively sharp at the borders of the lamellae and gradual within the same lamella. Conclusions. A model was developed, according to which the growth cycle of a conodont element covered the sequential formation of two lamellae preceded by the resorption of one external lamella. In the structures formed by the lamellar tissue, both lamellae consisted of this tissue. The lamellar tissue is of interest as a natural model of an organic-mineral composite based on protein and calcium phosphate.

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Comparative histology of conodonts and early vertebrates

Cited by 3 publications

References 24 publications

Structural, chemical and isotope evidence for secondary phosphate mineralization of grasping spines of Early Palaeozoic chaetognaths

Structural, chemical and isotope evidence for secondary phosphate mineralization of grasping spines of Early Palaeozoic chaetognaths

Paleo‐evo‐devo implications of a revised conceptualization of enameloids and enamels

Composition, structure and model of the formation of conodont lamellar tissue

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