Remarks: Gloeosoma was defined as a taxon growing on dead branches of Nothofagaceae in Patagonia and remained monotypic over the years. A lack of information on G. vitellinum in phylogenetic studies precluded any conclusion regarding its taxonomic sta-tus. It was a matter of personal decision whether to accept the genus or consider it a synonym of Aleurodis-cus, as the microscopic features were quite typical of the latter in a broad sense.
Our study includes sequences of G. vitellinum for the first time and shows that together with G. zealandicum, G. mirabile, and Gloeosoma decor-ticans, sp. nov. (described below), they form a well- defined group of species with strong phylogenetic sup-port. This group clustered in the Stereaceae clade but was distant from A. amorphus (Pers.) J. Schröt., the type species of Aleurodiscus. The latter differs from Gloeosma morphologically by the simple-septate generative hyphae.

Remarks: Stereodiscus is characterized by smooth, thin-walled, cylindric, broadly ellipsoid to citriform basidiospores up to 25 μm long and absence of any of the typical cystidia in Aleurodiscus s. lat., i.e., acantho-cystidia, acanthophyses, gloeocystidia, and dendrohy-phidia, but with skeletocystidia present in three species (S. antarcticus, S. parmuliformis, and S. trivialis). The hyphal system is monomitic with simple-septate hyphae, except in the recently described S. patagonicus (as Aleu-rodiscus), which features scattered clamps on the hyphae and at the bases of basidia (Phookamsak et al. 2019). The latter is consistent with its phylogenetic position, as it is excluded from the main cluster of species (FIG. 1). Otherwise, the five species grouped with strong support.
Stereodiscus is most closely related to Gloeosoma (FIG. 1). Gorjón et al. (2013) suggested the cluster of Aleurodiscus antarcticus, A. parmuliformis, and A. trivialis warranted segregation at the genus level characterized by possession of simple-septate hyphae and presence of skeletocystidia and geographic distribu-tion occurring only in the Southern Hemisphere. Our analyses show that two other taxa are included in this group, widening its morphological definition, and it indeed deserves generic rank.