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The evolution of thecideide microstructures and textures: traced from Triassic to Holocene

Simonet Roda, Maria; Griesshaber, Erika; Angiolini, Lucia; Harper, David A.T.; Jansen, Ulrich; Bitner, Maria Aleksandra; Henkel, Daniela; Manzanero, Eloy; Müller, Tamás; Tomašových, Adam; Eisenhauer, Anton; Ziegler, Andreas; Schmahl, Wolfgang W.

The evolution of thecideide microstructures and textures: traced from Triassic to Holocene Thumbnail


Maria Simonet Roda

Erika Griesshaber

Lucia Angiolini

Ulrich Jansen

Maria Aleksandra Bitner

Daniela Henkel

Eloy Manzanero

Tamás Müller

Adam Tomašových

Anton Eisenhauer

Andreas Ziegler

Wolfgang W. Schmahl


Thecideide brachiopods are an anomalous group of invertebrates. In this study, we discuss the evolution of thecideide brachiopods from the Triassic to the Holocene and base our results and conclusions on microstructure and texture measurements gained from electron backscatter diffraction (EBSD). In fossil and Recent thecideide shells, we observe the following mineral units: (1) nanometric to small granules; (2) acicles; (3) fibres; (4) polygonal crystals; and (5) large roundish crystals. We trace for thecideide shells the change of mineral unit characteristics such as morphology, size, orientation, arrangement and distribution pattern. Triassic thecideide shells contain extensive sections formed of fibres interspersed with large, roundish crystals. Upper Cretaceous to Pleistocene thecideide hard tissues consist of a matrix of minute to small grains reinforced by acicles and small polygonal crystals. Recent thecideide species form their shell of mineral units that show a wide range of shapes, sizes and arrangements. We find from Late Triassic to Recent a gradual decrease in mineral unit size, regularity of mineral unit morphology and orientation and the degree of calcite co‐orientation. While crystallite co‐orientation is the highest for fibrous microstructures, it is strikingly low for taxa that form their shell out of nanogranular to acicular mineral units. Our results indicate that Upper Jurassic species represent transitional forms between ancient taxa with fibrous shells and Recent forms that construct their shells of acicles and granules. We attribute the observed changes in microstructure and texture to be an adaptation to a different habitat and lifestyle associated with cementation to hard substrates.


Simonet Roda, M., Griesshaber, E., Angiolini, L., Harper, D. A., Jansen, U., Bitner, M. A., …Schmahl, W. W. (2021). The evolution of thecideide microstructures and textures: traced from Triassic to Holocene. Lethaia: An International Journal of Palaeontology and Stratigraphy, 54(4), 558-577.

Journal Article Type Article
Acceptance Date Jan 22, 2021
Online Publication Date Apr 3, 2021
Publication Date 2021-10
Deposit Date Apr 3, 2021
Publicly Available Date Apr 7, 2021
Journal Lethaia
Print ISSN 0024-1164
Electronic ISSN 1502-3931
Publisher Scandinavian University Press
Peer Reviewed Peer Reviewed
Volume 54
Issue 4
Pages 558-577


Published Journal Article (Early View) (20.9 Mb)

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Copyright Statement
Early View © 2021 The Authors. Lethaia published by John Wiley & Sons Ltd on behalf of Lethaia Foundation

This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made

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