Pseudocolonies of Silurian Rugoses Microplasma schmidti Dybowski from Estonia: Morphology and Origin

Microplasma schmidti Dybowski, 1874 (Rugosa: Stauriida: Cystiphyllidae) is briefly described. The species is characterized by a primitive septum zone, dissepiments that occupy the central corallite zone and the frequent occurrence of pseudocolonies. Based on the material from the collection of the Tallinn University of Technology from the Wenlock of Estonia (Sepise Section, Jaagarahu Stage), the mechanism of the pseudocolony formation by regenerative budding of the maternal corallite is described and the main reasons of its appearance are discussed.