The two Mycosphaerella and Sphaerella species described from filmy ferns (Hymenophyllaceae) turned out to be lichenized and to belong to different ascomycete orders, the Trichotheliales and Pyrenulales. As one epithet antedates the names currently in use for the taxon, the following new combination is proposed: Trichothelium assurgens (syn. Sphaerella assurgens Cooke, Trichothelium marianense Harada, T. nanum Malcolm & Vězda). These unexpected redispositions serve as an example of the current state of knowledge about the taxonomy of foliicolous ascomycetes, both non-lichenized and lichenized. They also show that type studies are essential to evaluate the identity of Mycosphaerella and Sphaerella species, and that the resulting number of accepted species in the huge genus Mycosphaerella, and consequently in the ascomycetes as a whole, might be lower than currently thought. Strigula phyllogena and Porina albicera are reported as new for Samoa.