Two strains isolated from the lichen Cryptothecia rubrocincta collected in Mexico are described as new members of the sterigmatoconidia-producing genus Fellomyces. Based on the identical sequences of the D1/D2 regions of 26S rDNA, as well as the results of the cluster analysis of the AFLP fingerprints, the strains have been shown to be conspecific. The 26S rDNA-based phylogeny has indicated that Fellomyces mexicanus clusters within a clade including species such as four other Fellomyces isolates from lichens: F. chinensis, F. lichenicola, F. sichuanensis and F. thailandicus. F. mexicanus is characterised by the presence of xylose in the cell walls and CoQ10 in the mitochondrial membrane. The type culture is strain HB25=CBS8279.