Plants: medium-sized to large, in moderately dense mats, green, yellowish, brownish, or brownish yellow. Stems: to 8 cm, creeping, terete-foliate, irregularly or often regularly pinnate, branches to 8 mm, straight to slightly curved, terete- to subcomplanate-foliate. Stem: leaves erect to erect-spreading, loosely imbricate to somewhat spaced, ovate-lanceolate, lanceolate, or narrowly ovate-triangular, broadest at 1/10–1/7 leaf length, slightly concave, plicate, 1.7–2.6 × 0.6–1 mm; base shortly rounded, narrowly short-decurrent; margins plane or recurved at places, serrulate to serrate; apex gradually tapered or long-acuminate; costa to 60–75% leaf length, strong, terminal spine present; alar cells subquadrate to short-rectangular, same size as or smaller than basal cells, 12–20 × 10–13 µm, walls moderately thick, region clearly delimited, of 3–6 × 3–5 cells; laminal cells linear, 40–100 × 6–9 µm; basal cells to 10–12 µm wide, region in 1 or 2 rows, not markedly different from more distal cells. Branch: leaves with basal laminal cells enlarged across base. Sexual: condition autoicous. Seta: orange-brown to dark brown, 1–2 cm, smooth. Capsule: horizontal, brown to dark brown, elongate, curved, 2 mm; annulus separating by fragments; operculum long-conic. Spores: 13–17 µm.

Soil, rock, tree bases, rotten logs, exposed to shady habitats. low to moderate elevations (0-1500 m). N.B., Nfld. and Labr. (Nfld.), Ont., Que., Yukon, Calif., Colo., N.Mex., Utah, Eurasia, n Africa, Australia.

Brachythecium salebrosum was considered widespread in North America, but a revision of herbarium collections from eastern North America demonstrated mostly B. acutum, B. campestre, B. rotaeanum, and marginal phenotypes of B. laetum among these. However, plants of B. salebrosum that are identical with European plants occur in western North America and in eastern Canada. Brachythecium salebrosum is characterized by slightly falcate, plicate, and lanceolate leaves, rather distinctly serrulate leaf margins, narrow laminal cells almost reaching the leaf base near the costa, and a small quadrate alar region composed of subquadrate cells. Brachythecium salebrosum is autoicous, and this distinguishes it from B. laetum. Brachythecium rotaeanum has erect-appressed and usually not falcate leaves and a basal areolation that is more homogeneous, without a clear angular group and with rather lax areolation in the basal juxtacostal area. Brachythecium acutum has a lax and even basal areolation and gradually tapering leaves that are rarely falcate-secund. Sterile plants of B. campestre are difficult to separate from B. salebrosum as the most important character for delimitation is the rough seta in the former species. Well-developed sterile plants of B. campestre can be distinguished by the broadening of the leaf distal to the alar group resulting in a more or less lax supra-alar region of cells, but underdeveloped, sterile B. campestre is probably almost impossible to distinguish from B. salebrosum.