Two widespread and morphologically similar species, P. subulatum (Hedw.) Rabenh. and P. acuminatum Lindb., have caused much confusion since their inception. Correlations of key characters (sexual conditions and lamina thickness) with chromosome numbers suggest that the two species are distinct. The two species are maintained and lectotypified.

Key words: biodiversity, cleistocarpous mosses, Ditrichaceae, nomenclature, taxonomy