Stems with branches spirally attached; paraphyllia abundant on stems and branches; axillary hairs with a brown, short basal cell and 2--4 hyaline, oblong distal cells. Stem leaves with costa single, ending at base of or before acumen, adaxial surface with paraphyllia attached along base, smooth or irregularly serrate distally; proximal cells irregular, oblong or subquadrate with incrassate walls, sporadically porose walls; cells at midleaf irregular and incrassate, rhombic, oblong or subquadrate. Branch leaves with margins plane or recurved proximally, plane and serrate or serrulate distally; costa single, about 1/2--2/3 the leaf length. Specialized asexual reproduction absent. Perichaetia lateral; perichaetial leaves differentiated from stem leaves, outermost with an oblong base rather abruptly narrowed to a finely acuminate, flexuose tip, plicate; costa ending in acumen, margins entire proximally and serrate at base of acumen; distal cells linear or oblong-linear, smooth, walls thin or incrassate and sporadically porose. Seta 2--3 cm, twisted when dry, smooth. Capsule inclined, curved and asymmetric or straight, cylindric; annulus revoluble; operculum convex-conic, rostellate or rostrate; peristome hypnoid; exostome teeth 16, lanceolate, yellowish, connate and cross-striolate proximally, papillose distally; endostome hyaline, basal membrane high, distal segments alternating with 3--4 long, appendiculate cilia. Calyptra not observed. Spores globose or subglobose, 10--16 µm, minutely papillose.

Usually on humus over soil or rock, also bark of conifers and hardwoods, rotting logs, moist coniferous forest or mesic tundra; B.C.; Alaska.

Echinophyllum sachalinensis is best distinguished from similar species by the combination of stem leaves with slender, recurved tips; coarsely serrate-dentate leaf margins often with cilia attached proximally; one massive papilla per leaf cell; branch leaves with a smooth, lanceolate terminal cell; paraphyllia with smooth, lanceolate terminal cells; and lanceolate, papillose pseudoparaphyllia. This species is known from five localities in North America along the northern Pacific Rim, all discovered since 1992. Specimens from four of the localities are reported by T. J. O’Brien and D. Horton (2000); a fifth locality is near Mother Goose Lake in Alaska (W. B. Schofield, personal communication).