Taxonomy of the fossil calcareous algae: Revision of genera Physoporella Steinmann and Oligoporella Pia (Dasycladales)

The taxonomic classification and mutual distinction of the genera Physoporella Steinmann and Oligoporella Pia (Dasycladales, green algae) have proven problematic and that has impeded their use in stratigraphy and other studies. The presence of single whorls of piriform laterals in Physoporella and double whorls in Oligoporella is considered as the main characteristic that separates these genera. According to that, diagnoses of genera and all species and varieties are changed or supplemented, and detailed descriptions are given. For this purpose the type-material from Pia's collection was re-examined and its redocumentation and reinterpretation performed. Additional information was obtained from abundant material from Croatia (Ivanščica Mt, Medvednica Mt, Žumberak Mt, Lika, Dalmatia). Only a few taxa were examined based on literature data. For all species and varieties reconstructions are given. Taxa from the Permian of East Asia are only briefly described. Among the investigated taxa, some of them have a structure that significantly differs from that present in the type species of the genera Physoporella and Oligoporella. They are separated into two new genera Ardeiporella and Neophysoporella. The revised genera Physoporella and Oligoporella, together with the newly established ones, give a clearer picture of phylogenetic relations.