Eurotiomycetes

Eurotiomycetes is a large class of ascomycete fungi within the division Ascomycota, subphylum Pezizomycotina, currently comprising about 3,810 species organized into five subclasses, ten orders, 34 families, and 289 valid genera as of 2022. Its members are distinguished by enclosed, cleistothecial spore-producing structures called ascocarps and by spore sacs, or asci, that are mostly bitunicate, meaning they have a distinctive two-layered wall. The class is the third largest class of lichen-forming fungi, containing more than 1,200 lichenized species, and it encompasses most of the fungi once grouped under the now-obsolete morphological category Plectomycetes. Eurotiomycetes forms a clade with Lecanoromycetes, the largest lichen-forming fungal class, reflecting a close evolutionary relationship between the two groups.