Microhardness of the conodont mineralized tissues

The article considers the data on the microhardness of mineralized tissues of conodonts, represented by organo-mineral composites based on collagen and fluorohydroxyapatite. Information on the mechanical properties of tissues is important for biomechanical interpretations, and also provides an opportunity to evaluate the functional significance of tissue differentiation of conodont elements. The conodont elements of good preservation from the Upper Devonian - Carboniferous of the East European Platform, the east of the Pechora Plate, and the southern Cis-Timans were used for the study. The peculiarities of the composition and structure of the main tissues were studied and their Vickers’ microhardness was measured. According to the results of microprobe analysis, the average composition of the mineral component of various tissues differs slightly. At the same time, the tissues vary significantly in the content of the protein component and the structural and textural characteristics. Microhardness measurements showed differences between tissues and the presence of variations within a single tissue type. Paralamellar tissue has the highest average microhardness (3.1 GPa), this value is somewhat lower in albid tissue (2.9 GPa), and even lower in lamellar and interlamellar tissues (2.6 GPa and 2.1 GPa, respectively). Microhardness demonstrates the absence of a significant dependence on variations in the chemical composition of the mineral component (content of F, Sr, and Na), but it strongly depends on the content of organic matter and tissue porosity. In general, the differentiation of tissues by microhardness is due to textural and structural differences and variations in the content of the organic component.