Claudopus niger (Entolomataceae - Basidiomycota), a new species from the Argentinean Atlantic Forest

The genus Claudopus (Entolomataceae) is characterised by its crepidotoid or pleurotoid basidiomata, a highly reduced and lateral or almost absent stipe, flesh-brown, salmon or pinkish-brown spore-print, and basidiospores that are distinctly angular in all views. Currently, ca. 20 species of Claudopus have been described worldwide. Some samples collected in the Argentinean Atlantic Forest have shown a set of characters that does not match with any of the species of Claudopus described until date. The aim of this work is to describe and illustrate a species of Claudopus new to science. Claudopus niger is distinguished from other species of Claudopus by its dark, almost black pileus surface, pinkish brown to brownish gray, ventricose lamellae; heterodiametric basidiospores, 5-7 angled (in profile view) and 8.5-11.5 x 5.5-7.5 mu m in size, and a hymenium lacking cystidia. Claudopus byssisedus, the most phenetically related species and with a wide distribution in temperate and cold regions, has a paler colour and slightly larger basidiospores.