Chlorophyllum tenue sp. nov. (Agaricaceae, Basidiomycota) from the Brazilian Caatinga semiarid region

Chlorophyllum tenue sp. nov. is described based on morphological and molecular (nrDNA-ITS, nrDNA-LSU) data. The new species belongs to Chlorophyllum sect. Ellipsoidospororum due to its small sized agaricoid basidiomata with furfuraceous pileal squamules, a loose hymenioderm covering, and basidiospores lacking germ pores. As specific characteristics, the new species has light grayish brown to dark cream pileus with a distinct reddish brown umbo breaking up into appressed light brown to rosy beige irregularly shaped squamules, thin context, cylindrical and subradicant stipe, and stipe surface changing color. Microscopically, the new species has ellipsoid basidiospores smaller than 10 µm long, 4-spored basidia, slender clavate-subcapitate cheilocystidia, and pileus covering formed by elements varying from broadly clavate, clavate to slender clavate sinuous. Additionally, Chlorophyllum tenue sp. nov. represents an independent lineage among Chlorophyllum sect. Ellipsoidospororum and is closely related to C. africanum, C. demangei, and C. hortense.