Abstract
Grammatus labyrinthinus gen. et sp. nov. is proposed based on DNA sequences data and morphological characteristics. It is known so far from southern, tropical China. The new species is characterised by an annual, resupinate basidiocarp with a shallow, subporoid hymenophore, a hymenium restricted to the bottom of the tubes, a dimitic hyphal system, presence of encrusted skeletocystidia and dendrohyphidia, longitudinally septate basidia and smooth, oblong-ellipsoid to cylindrical, acyanophilous basidiospores. Phylogenetic analyses based on ITS + nLSU DNA sequences data indicate that G. labyrinthinus belongs to Auriculariaceae in which it has an isolated position. Phylogenetic inferences show G. labyrinthinus to be related to Heteroradulum. However, the ITS sequences similarity between G. labyrinthinus and H. kmetii, the type species of Heteroradulum, were 89.84% and support the establishment of the new genus. Inversely, Heteroradulum semis clustered with G. labyrinthinus with strong support and it is transferred to Grammatus.