Local Crystallographic Texture of a Nummulite (Foraminifera) Test from the Eocene Deposits of the Crimea Peninsula

Simple Summary The tests of the unicellular protozoan Nummulites distans (Cenozoic era, Paleogene period) were studied using X-ray diffraction. In addition, the images obtained using X-ray microtomography and scanning electron microscopy were analyzed. A high degree of the calcite crystal orientation ordering that the test consists of has been revealed. It is higher than that of calcite from the shells of the bivalve mollusk Placuna placenta, whose shell is formed by a special multicellular tissue. So, it is found that already unicellular organisms have strict control over the crystal arrangement.Abstract Unicellular protozoa form calcium carbonate tests. It is important to understand the features and mechanisms of its formation. This may shed light on the processes of shell formation in metazoans. One of the most important characteristics of the Protozoa carbonate test is the degree of crystal ordering that can be described by crystallographic texture. The crystallographic texture data of calcite in the foraminifera Nummulites distans (Deshayes) test from the Eocene deposits (Cenozoic, Paleogene) of the Crimea Peninsula are obtained using X-ray diffraction. A very strict orientation of the crystals is revealed. The calcite texture sharpness is several times greater than in the shells of the bivalve mollusk Placuna placenta (Linnaeus), measured by the same method. It also exceeds the crystallographic texture and sharpness of the same mineral in the shells of the bivalves of Mytilus galloprovincialis (Lamarck), studied by neutron diffraction. It is concluded that a high level of control during test formation is already characteristic of protozoa. Studying the processes involved in the formation of a very sharp crystallographic texture can become an important direction for creating nature-like materials with desired properties.