Pseudostereodon procerrimus (Molendo) M. Fleischer

Plants large, rusty brown to golden brown or occasionally dark green, . Stems 2-8 cm, yellowish to brownish, suberect to procumbent, densely branched, regularly pinnate, branches 0.1-1.5 cm; hyalodermis absent, central strand present; pseudoparaphyllia foliose. Stem leaves falcate-secund, ovate-oblong, gradually narrowing to apex, 1-1.5 × 0.5-0.8 mm; base often auriculate; margins plane, entire to sinuate; acumen tapering; costa double and slender or ecostate; alar cells (many, subquadrate to hexagonal), region well defined in auriculate portion, , 7-8 cells high along margin, 6-8 cells wide; basal laminal cells slender, yellowish or brownish, walls porose; medial cells 60 × 8µm. Sexual condition dioicous. Sporophytes unknown.

Terrestrial, calcareous open terrain, rock, cliff ledges and bases, tundra, open spruce forests, edges of sandy beaches; low to moderate elevations (0-1500 m); Alta., B.C., Nfld. and Labr. (Nfld.), N.W.T., Nunavut, Yukon; Alaska, Mont.; Europe.

Hypnum procerrimum has an interrupted distribution in Arctic and alpine areas of the Northern Hemisphere, usually in well-drained sites. Plants of H. procerrimum have blunt, weakly toothed pseudoparaphyllia and triangular alar regions; the medial laminal cells are linear-flexuose with somewhat pitted walls. The species is very distinctive; some small forms might be confused with Ctenidium molluscum, but the toothed leaves and the laminal cells often with projecting distal ends distinguish the latter.