Plants robust, brownish to reddish in distal part, black and frequently defoliated proximally. Stems 5-10 cm, central strand absent. Leaves straight appressed when dry, erectopatent when moist, lanceolate, 2.7-3.5 × 0.5-0.75 mm, sharply keeled distally, margins narrowly reflexed on both sides, awns terete, firm and short, denticulate, costa 70-120 µm wide at base, channeled distally, circular, projecting on dorsal side; basal juxtacostal laminal cells elongate with extremely thick, slightly nodulose walls; basal marginal laminal cells in a few rows short-rectangular, thin-walled; medial laminal cells short- to long- rectangular with extremely thick and sinuose lateral walls; distal laminal cells 1-stratose, apex and margins 2-stratose. Gemmae absent. Sexual condition dioicous. Seta cygneous, 3-4 mm. Capsule sporadically present, exserted, yellowish brown, ovoid, smooth, exothecial cells thin-walled with incrassate corners, annulus present, operculum rostrate, peristome teeth orange, 40-60 µm wide at base, split and perforated, smooth proximally, papillose distally. Calyptra not seen.
Racomitrium alternuatum Müller Hal. & Kindberg in J. Macoun and N. C. Kindberg, Cat. Canad. Pl., Musci, 73. 1892