The moss family Hylocomiaceae is studied for the generic level taxonomy within a molecular phylogenetic approach. We confirm segregating of the species formerly known as Rhytidiadelphus triquetrus to Hylocomiadelphus Ochyra & Stebel from the genus Rhytidiadelphus. Hylocomiadelphus forms a clade with Loeskeobryum and Meteoriella, sharing with both genera cordate to auriculate leaf bases and non-squarrose leaves, and with the former undulate leaves and reticulate exostome teeth ornamentation. However, Loeskeobryum differs from Hylocomiadelphus in having paraphyllia, while Meteoriella has a straight capsule and reduced peristome, likely caused by its epiphytic ecology. In the group of species closely related to R. squarrosus, in addition to R. subpinnatus, the third species with North Pacific distribution is described as R. pacificum. Macrothamnium is found deeply nested in Rhytidiadelphus, although no nomenclatural implications are suggested at the moment due to insufficient sampling. Hylocomium splendens var. splendens and var. obtusifolium were found intermingled in the phylogenetic tree, indicating no correlation between morphology and variation in ITS region, thus supporting a view that these taxa are merely environmentally induced morphs.
