SEM study of test ultrastructure of Chitinoidella, as well as Crassicollaria and the phylogenetically more progressive calpionellids indicates different calcification and diagenetic recrystallization, related to different original test structure. The walls of Chitinoidella loricas were thicker, composed of micritic substance with dispersed calcite rhombs. On the other hand, the lorica wall of other studied calpionellids was thinner, the calcite content in it was originally higher. In early diagenesis, the superficial calcite rhombohedrons grew, forming a continuous rim composed of scalenohedral crystals. This rim prevented further test destruction during later phases of diagenesis when the original organic substance had already been destroyed.