A new species of Skeletocutis (Polyporales, Basidiomycota) from Vietnam

The genus Skeletocutis Kotl. & Pouzar was established in 1958 and its type species is Skeletocutis amorpha Fr. Kotlába & Pouzar.1 The genus is widely distributed around the world, but the majority of the species known so far are found in the Northern Hemisphere.2‒5 Species in Skeletocutis cause white rot. They mostly have resupinate basidioma although the genus type has pileate or effused-reflexed basidioma. The generative hyphae, at least, partly covered by fine crystals and the tiny basidiospores are the most important characteristics of the genus.3,5 Skeletocutis is phylogenetically close to Tyromyces P. Karst., Ceriporiopsis Domański and Piloporia Niemelä, and they cluster within the Tyromyces clade.6,7 Currently only two species have been described from Southeast Asia, Skeletocutis falsipileata (Corner) T Hatt8 in Malaysia and Skeletocutis bicolor (Lloyd) Ryvarden9 in Singapore. Seven species (Skeletocutis fimbriata Juan Li & YC Dai, S. luteolus BK Cui & YC Dai, S. substellae YC Dai, S. bambusicola LW Zhou & WM, S. inflata BK Cui & YC Dai, S. yunnanensis LS Bian, S. pseudo-odora LF Fan & Jing Si) were described in five provinces in southern China.10‒16 During a survey of lignicolous fungi in Vietnam in October 2017, two specimens were collected growing on angiosperm trunks, and have resupinate basidioma with a distinct cottony sterile margin, relatively small pores, plenty of hyphal pegs, a dimitic hyphal structure, generative hyphae bearing clamp connections and fine, sharp-pointed encrustations especially at the dissepiment edges, bottle-shaped cystidioles and pyriform to ovoid basidiospores. These characters fitted the genus of Skeletocutis, but we could not assign them to a name and so we describe the collections as a new species.