Plants to 1 cm, . Stem leaves stiff, erect-appressed when dry, oblong-lanceolate to lanceolate, 2-3.5 mm; margins plane or weakly recurved, entire; apex blunt to obtuse; basal laminal cells quadrate to rectangular, walls thin, not nodose; distal cells 10-15 µm, 1-stratose, papillae 1 or 2 per cell, conic, small. Specialized asexual reproduction absent. Sexual condition gonioautoicous. Seta 0.5-0.8 mm. Capsule immersed, oblong, 1.2-1.9 mm, distinctly 8-ribbed, constricted below mouth when dry; stomata immersed; peristome single or rarely with fugacious endostome; prostome absent; exostome teeth 16, incurved-erect to spreading-recurved when dry, reticulate-papillose; endostome segments absent or 8, not well developed, of 1 row of cells, , smooth. Calyptra oblong-conic, smooth, hairy, hairs papillose. Spores 12-19 µm.

Calcareous rock; low elevations (90-150 m); Ark., Ill., Ind., Iowa, Kans., Ky., Minn., Mo., Wis.

Orthotrichum parvulum is most frequent in the central highlands of Missouri and Arkansas. The species differs from O. strangulatum (with 2-7-stratose leaf margins) and O. lescurii (with revolute, 1-stratose leaf margins) in having plane leaf margins and completely 1-stratose distal laminal cells. The stomata are found in the distal capsule, almost covered by subsidiary cells, and the endostome segments are hyaline.