Abstract
Based on molecular and morphological evidence the new subfamily Pseudobaeosporoideae of the Tricholomataceae is established within the Tricholomatineae for accommodating the unique features of Pseudobaeospora such as gymnocarpic mycenoid/collybioid habit, small-sized spores with thick and dextrinoid wall, and presence of crassobasidia. Twenty-six Pseudobaeospora collections corresponding to eleven species (five types) were newly sequenced. Collections morphologically attributable to P.oligophylla (type of the genus) or to P.pillodii are here sequenced for the first time: accordingly, P.oligophylla is considered as a posterior synonym of P.pillodii. Quélet's original plate is selected as a lectotype for Collybiapillodii and a French collection as its epitype collection. Pseudobaeosporadeceptiva is described as a new species from Italy very close to P.pillodii from which it differs mainly by bigger spores and SSU and LSU rDNA sequences. The presence of P.pyrifera in Italy is documented for the first time and P.mutabilis is reduced to its later synonym. A neotype is established for P.jamonii which is here proved to be an independent species. Finally, a critical review of the characters used for interspecific distinctions in Pseudobaeospora was provided.