Didymodon pruinosus (Mitt.) R.H.Zander, a little known South American species, is described and illustrated in detail. Examination of type specimens of Barbula glaucescens Hampe, Barbula glaucescens var. latifolia Herzog, Barbula punae Herzog, Bryoerythrophyllum columbianum var. atacamense R.H.Zander & M.A.Lewis, and Bryoerythrophyllum fuscinervium (Mitt.) R.H.Zander revealed that are new synonyms of Didymodon pruinosus. A lectotype for Barbula punae is proposed. The range of Didymodon pruinosus is extended to Brazil, Colombia, and Venezuela.