Collemopsidium Nyl., Flora, Regensburg 64: 6 (1881).
MycoBank number: MB 1182; Index Fungorum number: IF 1182; Facesoffungi number: FoF 07655; 16 morphological species (Species Fungorum 2020), 3 species with molecular data (Pérez-Ortega et al. 2016).
Type species: Collemopsidium iocarpum (Nyl.) Nyl., Flora, Regensburg 64: 6 (1881).
≡ Pyrenopsis iocarpa Nyl., Not. Sällsk. Fauna et Fl. Fenn. Förh., Ny Ser. 5: 26 (1861).
Notes: Grube and Ryan (2002) studied the types of Collemopsidium and Pyrenocollema and stated that the former is the correct generic name for species previously included in Pyrenocollema. Pérez-Ortega et al. (2016) showed that the genus as currently understood is paraphyletic and species occurring in marine and terrestrial and freshwater habitats belong to different lineages. Collemopsidium iocarpum was described growing close to the seashore and it is likely the correct name for the marine clade. Species concepts and taxonomy have to be thoroughly studied. Pérez-Ortega et al. (2016) showed that each of the species commonly accepted in the literature likely encompass dozens of different taxa. Cyanobacteria associated with Collemopsidium are largely undetermined, marine species likely belong to Hyella (Swinscow 1965b). Xanthocapsa may be involved in freshwater symbioses (Grube and Hafellner 1990).