Plants small to large, often in dense tufts. Stems erect, simple or dichotomously to irregularly branched, usually with central strand, often densely radiculose, tips occasionally deciduous. Leaves in several rows around the stem, erect or secund, often falcate-secund, sometimes crispate, short- to long-lanceolate, whole leaves or their tips sometimes deciduous; costa single, usually strong, percurrent to excurrent, sometimes ending in a short to long hyaline awn, smooth, ridged or lamellose on abaxial surface, rhizoids occasionally on adaxial or abaxial surface near leaf base; laminal cells smooth or sometimes distal cells mammillose or papillose on one or both sides, papillae rarely forked, or toothed by projecting cell ends, pitted or nonpitted; proximal cells elongate, often differentiated in alar region, sometimes undifferentiated. Specialized asexual reproduction absent or occasionally present as brood leaves, microphyllous branches, borne in axils of distal leaves or as rhizoidal tubers. Sexual condition autoicous, dioicous or pseudomonoicous. Seta solitary or several per perichaetium, elongate, usually straight, sometimes flexuose or cygneous. Capsule exserted, erect, inclined, or sometimes curved, cylindrical or ovoid, smooth, ridged, furrowed or irregularly wrinkled, sometimes strumose; stomata present or absent, superficial; annulus present or absent, often compound, deciduous or persistent; operculum conic or obliquely rostrate from a conic base; peristome single, usually of 16 lanceolate teeth, deeply divided into 2 or rarely 3 divisions, usually vertically striolate or pitted-striolate proximally, papillose distally. Calyptra cucullate, smooth, naked, sometimes fringed at base, usually covering most of capsule, fugacious. Spores mostly spheric, smooth to papillose.
Genera 50-52, species ca. 900 (17 genera, 90 species in the flora): worldwide.
Distinctive characters of this large acrocarpous family include the erect, often tomentose stems; mostly narrow, lanceolate, occasionally falcate or falcate-secund leaves, with a single, narrow to broad costa, with or without rhizoids at the base, sometimes ending in a hyaline, occasionally toothed apex, costa in cross section with or without stereid bands, leaf cells usually smooth, sometimes mammillose, or rarely with a single papilla on one or both sides, papillae rarely forked, asexual propagation by specialized deciduous branches, deciduous leaves or leaf apices, rarely rhizoidal tubers; sporophytes usually solitary or rarely clustered, setae mostly elongate, straight or rarely flexuose or cygneous, capsule cylindric to ovoid, erect to horizontal, smooth or ribbed, sometimes strumose, operculum usually obliquely rostrate, peristome single, with 16 teeth often divided 1/2 way to the base, usually striolate or pitted-striolate proximally, papillose distally.