Ber. S. Gall. Naturw. Ges. 1876–1877: 330. 1878. -- Hypnum oedipodium Mitt., J. Linn. Soc. Bot. 8: 35. 5. 1864.
Brachythecium curtum (Lindb.) J. Lange & C. Jens., Medd. Grönland 3: 337. 1887. -- Hypnum curtum Lindb., Helsingfors Dagblad 1878 (342): 2. 1878.
Plants loosely matted, green to brownish-green or olivaceous, irregularly branched to regularly once pinnate, with stems prostrate and branches prostrate to ascending. Primary stems to 10 cm long with leaves somewhat broader and more divergent than the somewhat complanate branch leaves. Leaves to 2.5 mm, about 2.5: 1, symmetric and straight but with a twisted acumen, lightly or not at all concave, not at all plicate, ovate-lanceolate with acumen only gradually differentiated, loosely imbricated to rather distantly inserted. Margins entire at immediate base, but serrulate to serrate above the middle and on the acumen, somewhat recurved at base but plane above. Stem leaves with a rather broad decurrency which extends to the base of the next lower leaf; branch leaves decurrent by a 1–2 cell wide strip which extends only a few cells down stem. Median cells smooth, spinulose and thin-walled, to 10 µm wide, mostly 8–12: 1, not pitted. Basal juxtacostal cells short-rectangular, thin-walled with little pitting. Alar region poorly demarcated, with short rectangular, thin-walled, enlarged and pellucid cells to 25 µm wide, mostly 2–3.5: 1, gradually transitting to the more narrow and relatively longer cells of the mid-lamina. Marginal cells of alar region not significantly different from more interior alar cells. Costa ending near leaf middle, rather broad and flattened at base but tapering to its apex, mostly spinose at apex especially on branch leaves. Juvenile leaves strongly inflexed over bud, to 200 µm long, broadly ovate to almost orbicular, 1–1.2: 1, dentate across the bluntly rounded apex. Axillary hairs persistent, to 60 µm, 2-celled with a single pale brown basal cell, thin-walled throughout with some diameter increase in the distal cell. Rhizoids abundantly produced on prostrate stems, elongate and planar branched, brown to reddish-brown, smooth, to 18 µm in diameter, clustered on the abaxial leaf base. Stem cross-section with central strand, a stereome 1–3 cells thick, but without an hyaloderm.
Autoicous. Perigonia bud-like, produced near the perichaetia on prostrate stems and large branches. Perichaetial leaves to 1.5 mm long, with costa absent or nearly so, sheathing at base but reflexed to squarrose in the abruptly contracted acumen, entire to minutely serrulate on margin, without alar differentiation. Seta red-brown, papillose distally but sometimes almost smooth near the base, to 30 mm long, distally geniculate. Capsule dark brown to reddish brown, inclined to horizontal, lightly arcuate, not distorted or sulcate when dry. Urn to 2 mm, about 2: 1. Exothecial cells isodiametric to short rectangular, in regular rows, 25–30 µm wide, 1–2: 1, with thick lateral walls (lumen: wall ratio 3–4: 1) but with thin and oblique end walls. Stomata present on slightly raised pustules at base of capsule, short and vertical pored. Operculum conic, about 1/4 as long as urn. Annulus present, of two rows of thick-walled cells. Exostome teeth inserted at mouth of capsule, united near base, to 500 µm long, narrowly lanceolate and obscurely shouldered, about 6: 1, tapering to a very narrow tip, horizontally striate, yellow to yellow-brown. Endostome segments lightly papillose, very narrow, about as long as exostome, with basal membrane about as long as the segments. Cilia 1–3, lightly papillose and appendiculate. Spores smooth or occasionally finely papillose, 12–15 µm.
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