Psathyloma, a new genus in Hymenogastraceae described from New Zealand.

A new genus Psathyloma is described based on collections of agarics from New Zealand. We describe two new species in the genus, Ps. leucocarpum and Ps. catervatim, both of which have been known and tentatively named for a long time awaiting a formal description. Morphological traits and phylogenetic analyses reveal that Psathyloma forms a strongly supported sister clade to Hebeloma, Naucoria and Hymenogaster Morphologically Psathyloma resembles Hebeloma from which it differs mainly by producing smooth basidiospores with a germ pore. The geographical range of the genus has been demonstrated to include several regions in the southern hemisphere. A survey of published environmental sequences reveals that Psathyloma spp. were isolated from ectomycorrhizal root tips from Tasmania and Argentina, indicating an ectomycorrhizal association with southern beech.