Pyrgillus mammosus (Pyrenulaceae, lichenized Ascomycota), a new species from Taiwan

Pyrgillus mammosus, a new species from Xitou, Taiwan is described and illustrated. It is similar to P. tibellii and P. rufus but differs in its potassium hydroxide reaction of the thallus (K+ red) as a main distinguishing feature, additional chemical compounds detected by thin layer chromatography, and larger conical to hemispherical ascomata. Morphological and chemical differences among the closely similar taxa are discussed.