Plants moderate-sized, normally erect; yellowish to reddish brown, greenish in shaded forms; capitulum moderately distinct and rounded. Stems dark brown; superficial cortex of 1(--2) layers of thin-walled enlarged cells. Stem leaves triangular-lingulate to ovate-lingulate, 0.9--1.5 mm, apex rounded , straight; hyaline cells mostly non-septate, fibrillose in distal 1/3--2/3 of leaf, a few ringed pores at corners of cells and along commissures on convex surface, ringed pores along the commissures on the concave surface usually in greater numbers than on convex surface. Branches short, not turgid. Branch fascicles with 2--3 spreading and 1--2 pendent branches. Branch leaves broad-ovate to ovate-lanceolate, 0.9--2.6 mm, straight; hyaline cells with numerous ringed pores (10--20) along the commissures on the convex surface, these reduced to cells angles and ends only at the base of the leaf, a few pseudopores and ringed pores (less than 8 per cell) occur on the cell angles on the concave surface; Sexual condition dioicous. Capsules exserted, with few pseudostomata. Spores 36--39 µm; coarsely papillose on both surfaces; proximal laesura less than or equal to 0.5 spore radius.

Ecology unclear, but growing in carpets in depressions, blanket mires; B.C.; Alaska; e Asia.

Sporophytes are rare. This species is frequently collected with S. tenellum, S. pacificum, S. andersonianum, and S. rubellum in weakly minerotrophic blanket mires. It is similar in size to S. subsecundum, with which its range completely overlaps. The latter species has many of the branch leaves subsecund while those of S. subobesum are straight. The stem leaves of S. subobesum are also conspicuously larger than those of S. subsecundum.