Ostracods are by far the most complex organisms studied within the field of micropalaeontology. They are Metazoa and belong to the Phylum Arthropoda (as trilobites), Class Crustacea (as lobsters and crabs). An important distinguishing feature Ostracods share with other arthropods is the bilateral symmetry of their body form. The paired body parts are enclosed in a dorsally hinged carapace composed of low magnesium calcite, which is what is commonly preserved in the fossil record. They are found today in almost all aquatic environments including hot springs, caves, within the water table, semi-terrestrial environments, in both fresh and marine waters, within the water column as well as on (and in) the substrate. In fact almost anywhere that's wet, even if only for a brief period!