Authors: Roxanne I. Hastings & Dr. Henk C. Greven

Plants in dense cushions to hoary tufts, dark green to brown. Stems 0.3--0.5(--1) cm, Stem leaves oblong-ovate, 1--1.7 × 0.4--0.8 mm, keeled, awn 0.3--1 mm; distal laminal cells 1-stratose, marginal cells 1-stratose; medial laminal cells quadrate to short-rectangular, slightly sinuose, slightly thick-walled; basal juxtacostal laminal cells quadrate to short-rectangular, straight, thin-walled; basal marginal laminal cells quadrate to short-rectangular, straight, thin-walled. Sexual condition gonioautoicous. Seta sigmoid, 0.2--0.3 mm. Capsule usually present, exothecial cells thin-walled, annulus of 1--2 rows, quadrate, thin-walled, operculum mammillate, peristome present, fully developed, perforated and split in distal half.

Exposed calcareous sandstone, limestone, and occasionally concrete; 50--2400 m; Greenland; Alta., B.C., N.W.T., Nunavut, Ont., Sask.; Alaska, Cal., Col., Idaho, Ill., Iowa, Minn., Mont., Neb., Nev., N.Mex., N.Dak., S. Dak., Utah, Wis., Wyo.; South America; Eurasia; Pacific Islands (New Zealand); Antarctic.

Grimmia plagiopodia has a widespread and continuous distribution on calcareous rockacross the northern Great Plains of North America reaching as far east as Illinois. It is rare in eastern North America with a disjunct site in southern Ontario. In the west it reaches into the mountains on limestone and basic sandstone deposits, but its continuous range does not extend west of a line from Utah to south-central B.C. There is a disjunct location near Carson City, Nevada and Lake Tahoe, California. In the Arctic it is known from a few scattered localities extending from northwestern Greenland and nearby Ellesmere Island to the North Slope of Alaska. Compared to Grimmia anodon, G. plagiopodia tends to occupy more prairie-like sites and is typically at lower elevations. Commonly fertile, Grimmia plagiopodia is recognized by its immersed, peristomate capsule on a sigmoid seta with fully developed teeth that are perforated and split distally. Grimmia americana is similar but has a short, straight to arcuate seta. In this subgenus, only G. plagiopodia has both 1-stratose laminae and margins; the other species have 2-stratose margins. The stem leaves in Grimmia plagiopodia also are relatively more keeled. The other widespread species in the group, Grimmia anodon, lacks a peristome.