In 2019, cyanobacterial samples were collected from thermal sites in Yellowstone National Park. In this paper, we discuss the considerable richness of representatives of simple filamentous cyanobacteria. Using a polyphasic approach, one new genus, Copelandiella, with two species (C. yellowstonensis and C. thermalis) and eight additional new species Albertania prattii, K. anagnostidisii, Kovacikia brockii, Leptolyngbya tildenae, L. vaporiphila, Nodosilinea calida, N. igneolacustris, and Oculatella castenholzii were described. At the same time, by analyzing our new molecular data, we concluded that other genera of trichal cyanobacteria can be merged with existing genera: species within the genus Plectolyngbya are herein transferred to Leptolyngbya, and if some nomenclatural issues are resolved, species within the genus Leptothermofonsia will be subsequently transferred to the genus Kovacikia, an earlier synonym.

The application of modern molecular methods and phylogenetic approaches saw an explosion in cyanobacterial taxonomy in the first two decades of the twenty-first century. The relative ease of description of new taxa and the pressure to publish a high number of scientific papers has created apparent confusion. The situation is particularly complicated for ecologically oriented limnological research and practical hydrobiologists especially have numerous criticisms of this trend. On closer observation, however, the situation is not as tragic as it first appears. More than a thousand new species have been discovered or renamed and only 18 percent are freshwater planktonic species, which garner the most interest in routine analyses. Most new taxa are described from terrestrial habitats. Despite the increase in studies from tropical areas, most of the new species are from the temperate zone, which probably does not account for the reality. Significant advances in modern taxonomy are visible mainly for the trichal types, but other groups such as the pleurocapsal species are considerably less studied. In this article I try to show that, despite all the difficulties and limitations, it is not necessary to consider these rapid changes as a complication in common cyanobacteriological research.