Plants small to large, forming mats, dark green or yellow-green to blackish green; aquatic and saxicolous, in splash zone or submerged. Stems naked and black below when old, suberect, 15-80 mm long, branching irregular above stipe, subfastigiate; in section round to oval, central strand absent, inner cortical cells large, thin-walled, hyaline, in 5 or 6 rows, outer cortical cells smaller, yellowish, thick-walled, in 5 or 6 rows, epidermis absent; axillary hairs not seen; paraphyllia absent; pseudoparaphyllia absent. Leaves evenly spaced, spreading to crect-appressed wet, appressed dry, ± concave; on stipe lanceolate to triangular, 1.5-2.0 mm long; acute; margins plane, entire, eroded; upper stem and branch leaves variable; narrowly or broadly elliptical or short and broadly oblong, 1.2-2.2 mm long; acute to narrowly acuminate or occasionally mucronate to apiculate; rounded at base; margins plane, entire, cells not differentiated. Costa variable, absent, present only at base, present and discontinuous only at apex and base, or single and strong throughout, smooth; ventral and dorsal surface cells elongate; in section flat below, round above, guide cells not differentiated, in best development consisting of 3-6 rows of undifferentiated, thickened cells; most leaves with bistratose region at extreme base and thickened awn at apex. Upper laminal cells linear-fusiform and somewhat sigmoid, homogeneous, 57-89 µm long, 7-10 µm wide, walls thickened or rarely thin, smooth; basal cells linear to long-rectangular, 50-125 µm long, 7-10 µm wide, brownish yellow, walls incrassate, smooth; alar cells strongly differentiated, forming distinct groups, enlarged and inflated, hyaline, walls thin. Dioicous or rarely autoicous. Perichaetia at apex; perichaetial leaves numerous, broadly ovate, apex acute, sheathing below. Seta 4-6 mm long, yellow-brown to blackish, twisted clockwise when dry, smooth, thick. Capsule exserted, erect, short-cylindrical or rarely ovoid, 1.0-2.2 mm long, smooth but somewhat ribbed when young and dry, yellow-brown to black; urn short-cylindrical; neck not differentiated; exothecial cells irregular, rounded to quadrate or hexagonal, walls incrassate, cells at mouth quadrate, darker; annulus not differentiated, neck cells hexagonal to rectangular, thickened; stomata absent. Peristome rudimentary, yellow to orange; exostome teeth irregular, short-rectangular, truncate, erect, 40-50(-95) µm high, smooth with irregular prostome development; endostome absent. Operculum curved-rostrate, attached to columella, persistent, 1.0-1.3 mm long. Calyptra not seen. Spores rounded, 25-31(-37) µm, granulate, brown.