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

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