Hedwigia 39: 290. 1900.
Plants on rock or terrestrial, forming discrete long-spreading mats or seldom cushionlike mats. Stems radially symmetric, creeping or decumbent, not readily fragmenting, irregularly forked, without budlike arrested branches, tips straight; main-stem indeterminate, lateral branches conspicuously or inconspicuously determinate, often strongly ascending, 1–3-forked. Rhizophores borne on upperside of stems, throughout stem length, 0.2–0.37 mm diam. Leaves monomorphic, in alternate pseudowhorls of 5, tightly appressed, ascending, green, linear-lanceolate to narrowly lanceolate, 2–3.5 × 0.35–0.5 mm (smaller on lateral branches); abaxial ridges prominent; base cuneate and decurrent to rounded and adnate on young lateral branches or buds, glabrous or sometimes pubescent; margins long-ciliate, cilia transparent, spreading to ascending, 0.07–0.17 mm; apex keeled, truncate in profile, obtuse to attenuate; bristle white to whitish or transparent, puberulent, 0.45–0.8 mm. Strobili solitary, 0.5–2.5 cm; sporophylls deltate-ovate to ovatelanceolate, abaxial ridges well defined, base glabrous, margins ciliate, apex truncate in profile, bristled. 2n = 18.
Habitat: Dry, alpine, rocky slopes, rock crevices, granite rock, limestone boulders, sandstone, bare open grassy tundra
Elevation: 130–2400 m
N.W.T., Yukon, Alaska, Asia in Japan and the former Soviet republics
Selaginella sibirica is most closely allied to S. rupestris. In addition to differences noted in the descriptions, it can be distinguished from S. rupestris by the numerous marginal cilia on the leaves and by the transparent sporophyll margins; S. rupestris has a variable number (usually few) of marginal cilia and nontransparent sporophyll margins.