Plants: (4–)6–8(–10.5) cm. : Secondary stem leaves 2–3.2 × 1–1.7 mm. Branch: leaves oblong-ovate to ovate, 1–2.2 × 0.5–0.8 mm; margins serrate at apex; apex obtuse to broadly acute; basal laminal cells 5–8 × 1–2 µm; medial juxtacostal cells long-rhomboidal, longest axis parallel to costa, 3–5 × 1–3 µm; apical cells subquadrate to short-rhomboidal, 2–4 × 1–2 µm. Sexual: condition dioicous.
Rock, humus, base of trees, shaded banks, boulders, cliffs. moderate elevations. B.C., Alaska, Calif., Conn., Idaho, Mont., N.Y., N.C., Ohio, Oreg., Pa., Wash., Europe (Czech Republic, Germany, Italy), Asia.
Thamnobryum neckeroides is distinguished by the distinctly concave, almost boat-shaped branch leaves, and the rounded to broadly rounded apex. The apical laminal cells are mostly subquadrate to short-rhomboidal and the medial juxtacostal cells have their longest axis parallel to the costa.