Belonopsis excelsior (P. Karst.) Rehm, the type species of Belonopsis, is characterized by extremely long ascospores (42–50 μm length) with multi-septa (Rehm 1896) and has been accommodated in several genera, such as Belonium (Boudier 1907) and Niptera Fr. (Dennis 1972). Dennis (1972) transferred some species of Belonopsis that occur on submerged grasses to Niptera including Belonopsis excelsior but withheld any taxonomic treatment for other terrestrial species of Belonopsis. Currently, Species Fungorum adopts “Belonium” excelsior (P. Karst.) Boud. However, the genus Belonium is also taxonomically problematic, and Baral (1994) pointed out that the generic name “Belonium” is used contrary to the nomenclatural rules and proposed to abandon the ambiguously used “Belonium” by transferring only the type species, Belonium graminis (Desm.) Sacc., to Cejpia Velen. (Incertae sedis, but closely related to Pyrenopezizaceae and Mollisiaceae), and the remaining species to Pyrenopeziza Fuckel. Therefore, applying “Belonium” to Belonopsis excelsior seems inappropriate even if the species is different from other Belonopsis species.

Trichobelonium has been treated as a synonym of Belonopsis (Aebi 1972; Nauta and Spooner 1999), but multi-gene analysis revealed that Trichobelonium species newly described in this study are phylogenetically distinct from other genera in Mollisiaceae (Fig. 1). The morphology of T. albobarbatum and T. miscanthi is consistent with the original description of Belonium subgen. Trichobelonium Sacc. (Saccardo 1889). Detailed morphological observations elucidated the following new features of Trichobelonium: the presence of anchoring hyphae between the base of apothecium and the subiculum, the presence of oil globules in young asci disappearing as the ascospore maturity, and the production of abundant crystals and soluble pigments in the colonies. From these results, we propose to retain the genus, Trichobelonium. The type species, T. kneiffii, lacks DNA sequences, but its morphological features such as abundant crystals in excipulum, long ascospores with multi-septum, and well-developed subiculum indicate that its congeneric with the two new species. The presence of the anchoring hyphae of T. kneiffii was also described as “filzigen oder spinnwebartigen Unterlage sitzend” (cobweb manner hyphal structure, translated by ourselves) by Schröter (1908)