Plants 5–11 cm. Stems with branches absent or few, attenuate; paraphyllia few to absent. Stem leaves (central) oblong-ovate, undulate, 2–3(–5) × 1.2–1.5 mm; margins serrulate to entire proximally, serrulate at apex; apex acute to broadly acute; ecostate or costa double, short; alar cells irregularly short-quadrate; basal laminal cells rectangular, 50–60 × 7–10 µm; distal medial cells oblong-linear, (23–)42–54 × 2–4 µm; apical cells oblong-rhombic, (15–)30–36 × (2–)3–5 µm. Sexual condition autoicous. Seta 0.1 cm. Capsule immersed.
Habitat: Base and trunks of trees, boulders, rock cliffs of conifer and deciduous forests to montane subalpine ecotones
Elevation: moderate to high elevations (300-2600 m)
Greenland, B.C., N.B., Nfld. and Labr., N.W.T., N.S., Ont., Que., Yukon, Alaska, Ariz., Colo., Conn., Ill., Ind., Iowa, Ky., Maine, Mass., Mich., Minn., Mont., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Europe, Asia, Pacific Islands (New Zealand), Australia.
Neckera pennata is recognized by its immersed sporophytes, undulate, acute to broadly acute leaves, and paraphyllia absent or scarce. The leaves have very few alar cells.