Racodium Fr., Syst. Mycol. (Lundae) 3(1): 229 (1829).
MycoBank number: MB 9681; Index Fungorum number: IF 9681; Facesoffungi number: FoF 06305; 5 morphological species (Wijayawardene 2020), 1 species with molecular data.
Type species – Racodium rupestre Pers., Neues Mag. Bot. 1: 123 (1794).
Notes – The black felt-like patches can be seen on extensive parts of rocks. Therefore, the phytosociological name has been given as Racodietum rupestris (Hawksworth et al. 2011). Vainio (1921) listed Coenogonium germanicum as a synonym of R. rupestre. Lepraria and Leproloma species mostly often grow mixed with Racodium rupestre, as well as Cystocoleus ebeneus (Hawksworth et al. 2011). Hawksworth et al. (2011) noted an interesting observation made by W. Watson in 1872-1960 that nitric acid used on a mixed collection of Coenogonium germanicum and Racodium rupestre caused the filament hyphae to twist in Coenogonium germanicum, while the dark hyphae were parallel in Racodium rupestre. Phylogenetic analyses indicated that Racodium rupestre is not close to Cystocoleus ebeneus, but forms a distinct clade within Capnodiales (Muggia et al. 2008, Hawksworth et al. 2011).