Jahnula Kirschst., Ann. mycol. 34(3): 196 (1936).

MycoBank number: MB 2526; Index Fungorum number: IF 2526; Facesoffungi number: FoF 07686; 17 morphological species (Huang et al. 2018, Species Fungorum 2020), 6 species with molecular data.

Type species: Jahnula aquatica (Plötner & Kirschst.) Kirschst., Ann. Mycol. 34: 196 (1936).

Amphisphaeria aquatica Plöttn. & Kirschst., in Kirschstner, Verh. bot. Ver. Prov. Brandenb. 48: 52 (1906)[1907].

Notes: The largest genus within Jahnulales, Jahnula, is characterised by perithecial, solitary, superficial to subimmersed ascomata, bitunicate, fissitunicate, cylindrical, pedicellate asci and light brown to dark brown ascospores. All 17 Jahnula species have been reported from wood or decorticated wood in freshwater habitats (Huang et al. 2018). The genus is currently polyphyletic, and Jahnula sensu stricto accommodates J. aquatica, J. granulosa, J. potamophila and J. rostrata (Suetrong et al. 2011; Huang et al. 2018).