Abstract
Agaricus is a monophyletic genus with a worldwide distribution and more than 400 described species. The genus grows on soil and can be easily recognized by the presence of an annulus on the stipe and free lamellae which become dark brown with spore maturation. Although Agaricus is easily recognized in the field because of its macroscopic characters, identification at the species level is difficult. Based on specimens collected in the states of Paraná and Santa Catarina, in the south of Brazil, we propose a new species Agaricus globocystidiatus. The new taxon is distinguished mainly by the presence of pleurocystidia, a rare morphological character in Agaricus. Molecular analyses based on nuc rITS1-5.8-ITS2 (ITS) barcode sequences show that A. globocystidiatus belongs to Agaricus subg. Minoriopsis.