Rhytidium is an anomalous genus without clear affinities. Suggestions for a new familial classification of pleurocarpous mosses. N. C. Kindberg, Bih. 1882 Greek rhytis , wrinkle, in reference to the strongly rugose leaves Hypnum sect. Rhytidium W. S. Sullivant in A. Gray, Manual ed.
Branch leaves smaller, less falcate-secund, otherwise similar to stem leaves.
N. C. Kindberg, Bih. Mostly on rock or on thin layer of soil or humus overlying rock, especially of calcareous or mafic composition. Photographs of Rhytidium rugosum Even though it is widespread, Rhytidium rugosum is infrequent, presumably because of its preference for exposed calcareous or mafic bedrock in a cool habitat. The species is rarely found with sporophytes. Perhaps almost total reliance on asexual reproduction explains the strong morphological uniformity seen among specimens of R .