A new species, Byssoloma orientale K. Miyaz. & Y. Ohmura, is described from East Asia. It is characterized by a minutely farinose light green thallus, apothecia with a well-developed byssoid margin that spreads laterally over the thallus surface, a pure black apothecial disc caused by the presence of an aeruginous pigment in the epithecium, (7–)9–12(–17)-septate cylindrical colourless ascospores, and oblong conidia. This species grows on living leaves as well as on tree bark. The molecular phylogenetic position of B. orientale within this genus was inferred based on mtSSU sequences, and the species was shown to be closely related to B. vanderystii, which has up to 7-septate ascospores and an absence of aeruginous pigment in the epithecium.
