Trichothyrium Speg., Boln Acad. nac. Cienc. Córdoba 11(4): 555 (1889).

MycoBank number: MB 5598; Index Fungorum number: IF 5598; Facesoffungi number: FoF 06894; 25 morphological species (Species Fungorum 2020), molecular data unavailable.

Type species: Trichothyrium sarciniferum Speg.

Notes: Trichothyrium is characterized by flattened ascomata with an upper and lower, single-cell thick layer occurring on the surface of parallel hyphal bands. Another genus forming a similar cellular hypostroma with lobed thalli is Brefeldiella, which is characterized by ascomata dispersed beneath the band-like thallus and opening by a fissure of the upper covering cells. Hawksworth et al. (1983) included Trichothyrium under Microthyriaceae, Wu et al. (2011b) transferred Trichothyrium back to Trichothyriaceae based on its fungicolous life mode and a well-developed basal peridium. This was followed in subsequent studies (Hyde et al. 2013; Wijayawardene et al. 2018).