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Cortinarius is a speciose genus of mycorrhizal fungi that contains many cryptic and difficult to delineate taxa. Correct identification can be confounded for species where no genetic information is available from their respective type specimens. Cortinarius section Subcastanelli is known to contain several species for which there is ambiguity around their true identity, i.e. C. epiphaeus, C. subcastanellus and C. taylorianus. For example, it has been long hypothesised that C. napivelatus is conspecific with C. epiphaeus. In this study, the nuclear ribosomal internal transcribed spacer (ITS) region was sequenced from the holotypes of the afore mentioned species. The ITS sequences and morphological characteristics indicated that C. epiphaeus and C. napivelatus were conspecific. Consequently, C. napivelatus was synonymised with C. epiphaeus. Based on morphological and molecular evidence it is shown that the protologue of C. subcastanellus is a mixture of two species. Consequently, the morphologically similar C. wallacei is synonymised with C. subcastanellus, the protologue of C. subcastanellus is emended and the new species C. cesarioanus is erected. Similarly, C. taylorianus was found to be polyphyletic. The holotype of C. taylorianus was nested in section Archeriani while a paratype fell in section Subcastanelli. As the protologue is consistent with the clade containing the type, no emendations are required. In addition to the species in Subcastanelli, a new species in Delibuti is described: C. viridipileatus. This species is distinctive in section Delibuti in having a green pileus with mauve lamellae. Finally, a key to New Zealand rozitoid species is presented. [ABSTRACT FROM AUTHOR]

is a species-rich ectomycorrhizal genus containing taxa that exhibit agaricoid or sequestrate basidiome morphologies. In New Zealand, one of the most recognizable and common Cortinarius species is the purple sequestrate fungus, C. porphyroideus. We used genome skimming of the almost 100-y-old type specimen from C. porphyroideus to obtain the nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS barcode) and partial nuc rDNA 28S (28S) sequences. The phylogenetic position of C. porphyroideus was established, and we found that it represents a rarely collected species. Purple sequestrate Cortinarius comprise multiple cryptic species in several lineages. We describe four new species of Cortinarius with strong morphological similarity to C. porphyroideus: Cortinarius diaphorus, C. minorisporus, C. purpureocapitatus, and C. violaceocystidiatus. Based on molecular evidence, Thaxterogaster viola is recognized as Cortinarius violaceovolvatus var. viola. These species are associated with Nothofagus (southern beech) and have very similar morphology to C. porphyroideus but are all phylogenetically distinct based on molecular data. [ABSTRACT FROM AUTHOR]