Dimeriaceae E. Müll. & Arx ex Arx & E. Müll., Stud. Mycol. 9: 104 (1975).
MycoBank number: MB 80704; Index Fungorum: IF 80704; Facesoffungi number: FoF 06390, 73 species.
Parasitic on living leaves, colonies dark brown, mycelium superficial, dark brown, amphigenous. Sexual morph: Ascomata superficial, subglobose, with hyphal appendages, flexuous, cylindrical, septate, dark brown, roughened. Asci 8-spored, bitunicate, fissitunicate, saccate-oblong to ellipsoidal, apically thickened. Ascospores conglobate, ellipsoid-fusiform to subclavate, ends rounded, olivaceous-brown to brown, 1-septate, darkly pigmented at the septum, upper cell wider than lower cell, septum supramedian. Asexual morph: Hyphomycetous.
Type: Dimerium (Sacc. & P. Syd.) McAlpine.
Notes: Dimeriaceae accommodates taxa occurring on the surface of living leaves (Hawksworth and Eriksson 1986; von Arx and Müller 1975; Barr 1987b, 1997). Its members are characterized by solitary, superficial ascomata with hyphal appendages and 1-septate ellipsoidal, dark brown ascospores darkly pigmented at the septum (Boonmee et al. 2017). Dimerium olivaceum was assigned as the type species (Boonmee et al. 2017). However, the family lacks molecular data to confirm the taxonomic placement.