Plants: to 10 cm, yellowish green to golden brown. Stems: 2–3 mm wide across leafy stem, turgid from crowded leaves, often hooked at apices, branches to 10 mm. Stem: leaves 2.8–4.5 × 0.8–1.5 mm; alar cells many, 8–20 × 8–12 µm, region broad, triangular, along margin; medial laminal cells 25–55 × 4–6 µm. Branch: leaves 1.2–2.3 × 0.4–0.8 mm. Seta: 2–2.5 cm. Capsule: 2–2.5 mm. Phenology: Capsules mature summer.

Rock, thin layer of soil or humus overlying rock, calcareous or mafic, exposed rock ledges, rocky slopes, bluffs, semi-open dry forests, in tundra, much less common on moist sites. low to high elevations (100-3900 m). Greenland, Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., Que., Sask., Yukon, Alaska, Ariz., Colo., Conn., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., Mont., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Oreg., Pa., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis., Wyo., Mexico, Central America (Guatemala), South America (Bolivia), Eurasia, Africa (Kenya, Morocco, Uganda).

Though widespread, Rhytidium rugosum is infrequent, presumably because of a preference for exposed calcareous or mafic bedrock in a cool habitat. The plants are rarely found with sporophytes; perhaps almost total reliance on asexual reproduction explains the strong morphological uniformity seen among specimens of R. rugosum collected from across its broad range.