Advances in the knowledge of the group (, ), through molecular and morphological studies.

constitutes a complex of species characterized by nodulose-angulose spores, absence of cortina and a more or less bulbous marginate stipe that is not darkening when desiccated. In order to elucidate species limits within the complex, an ITS-RPB2 phylogeny was performed and interpreted using morphological and ecological characters. Six supported clades were obtained in our analyses that correspond to , , and four new species to science: , , and . Species within this complex can be morphologically recognized through a unique combination of morphological characters, such as the spore shape, cystidial length and shape, presence and development of the velipellis and pileus colour and viscidity. Nevertheless, those characters overlap, especially among , and , and intermediate collections are therefore more reliably identified through ITS-sequencing. Two species, and are present in both North America and Europe, while the rest are so far only known in Europe, or Europe and Asia (). All species, except , seem to be able to establish ectomycorrhizal association both with conifers and angiosperms. Descriptions, colour illustrations and a key to all known species in the group are provided.