Cosmospora sensu Rossman accommodated nectroid fungi with small, reddish, smooth, thin-walled perithecia but recently was found to be polyphyletic and has been segregated into multiple genera. Not all cosmospora-like fungi have been treated systematically. Some of these species include C. vilior and many specimens often labeled "Cosmospora sp." The objectives of this research were to establish the identity of C. vilior through epitypication using a recent collection that agrees with the type specimen in morphology, host and geography and to determine its phylogenetic position within Cosmospora sensu lato and the Nectriaceae. A multilocus phylogeny was constructed based on six loci (ITS, LSU, MCM7, rpb1, tef1, tub) to estimate a phylogeny. Results from the phylogenetic analyses indicated that C. vilior forms a monophyletic group with other cosmospora-like fungi that have an acremonium-like anamorph and that parasitize Eutypa and Eutypella (Ascomycota, Sordariomycetes, Xylariales, Diatrypaceae). The group is phylogenetically distinct from other previously segregated genera. A new genus, Pseudocosmospora, is described to accommodate the type species, P. eutypellae, and nine additional species in this clade.
Keywords: GCPSR; Mycoparasite; Nectria; fungal systematics; one-to-one genus concept.