Plants: medium-sized to large, shelf-forming, light to dark green or sometimes yellowish, usually shiny. Stems: creeping, irregularly branched; paraphyllia present or absent. : Secondary stem and branch leaves (central) erect, erect-spreading, or spreading, sometimes secund, ovate, obovate, oblong, oblong-ligulate, or oblong-lanceolate, asymmetric, flat to strongly undulate; margins entire to serrate, teeth recurved; apex obtuse to acuminate; costa double and short, sometimes single or ecostate; basal laminal cells linear to rectangular, walls pitted or not. Sexual: condition autoicous or dioicous; perichaetial inner leaves oblong, oblong-lanceolate, or ovate-subulate. Seta: (0.1–)0.2–1.2 cm. Capsule: cylindric, oblong, or globose; exostome teeth lanceolate, smooth to densely papillose, somewhat cross striate basally; endostome basal membrane low to high, segments smooth to densely papillose. Spores: 12–39 µm. North America, Mexico, West Indies, Central America, South America, Europe, Asia, Pacific Islands, Australia.

Species 73 (5 in the flora). Neckera is distinguished by its asymmetric and dimorphic leaves, that is, central versus lateral leaves. The central leaves are inserted dorsally or ventrally and the costa is almost aligned with the central stem axis; in lateral leaves the insertion line surrounds the stem, and thus costa alignment is displaced toward one side. Lateral leaves can be distinguished as dorsal or ventral; if the leaf is inserted dorsally (with costa on the dorsal side), then there will be a small fold on the ventral side. The secondary stems are perpendicular to pendent, and unbranched, irregularly branched, or pinnate. The primary stem leaves are erect to erect-spreading, triangular, lanceolate, broadly ovate, or obovate, with margins recurved to plane basally and entire to slightly serrate; the apex is acute, narrowly acute, or sometimes long-acuminate; and the costa is absent, single, or double and short. The alar cells are undifferentiated to differentiated and short-quadrate; the basal laminal cells are usually rectangular; and the distal medial cells are fusiform to linear. The inner perichaetial leaves have margins that are entire to slightly serrate at the abruptly to gradually acute apices, costae to mid leaf or absent, and fusiform to linear distal medial laminal cells. The capsules are erect; the exostome teeth are sometimes perforate.