Plants small to large, usually in stiff, loose mats, dark green to golden brown. Stems creeping or ascending, usually regularly 1-3-pinnate, not stipitate; hyalodermis absent, central strand small; paraphyllia present, filamentous to foliose, cells papillose; pseudoparaphyllia foliose; axillary hairs usually with basal cell 1, short, brown, distal cells elongate, hyaline (all cells brown in Abietinella). Stem and branch leaves strongly differentiated; margins serrulate to crenulate ± throughout; costa single; alar cells not or poorly differentiated; laminal cells quadrate to short-rectangular, 1- or multipapillose on both surfaces or only abaxially, walls firm. Stem leaves usually spreading when moist, usually broadly ovate, concave; margins plane or recurved; apex acuminate; costa strong, ending in acumen to ± excurrent. Branch leaves usually spreading, ovate to oblong-ovate, smaller than stem leaves; margins usually plane; apex usually gradually acuminate to obtuse; costa weaker than in stem leaves; apical laminal cell usually truncate, multipapillose, walls not porose. Specialized asexual reproduction absent. Sexual condition autoicous or dioicous; perichaetia conspicuous, leaves erect, sometimes plicate, margins plane, apex long-acuminate, costa single, usually strong, laminal cells rectangular, more elongate than in vegetative leaves, usually smooth. Seta reddish, elongate, smooth to roughened throughout or rarely only distally. Capsule usually inclined to horizontal, rarely suberect, usually asymmetric and arcuate; exothecial cell walls thin to thick, not collenchymatous; annulus differentiated; operculum usually rostrate; peristome hypnoid, double, attached at mouth; exostome teeth bordered, shouldered, external surface cross striolate basally, sometimes with overlying papillae, internal surface papillose, trabeculate; endostome basal membrane high, segments keeled, not to narrowly perforate, cilia in groups of 1-4, nodulose. Calyptra cucullate, smooth or roughened, naked. Spores spheric, usually papillose.
SELECTED REFERENCES Buck, W. R. and H. A. Crum. 1990. An evaluation of familial limits among the genera traditionally aligned with the Thuidiaceae and Leskeaceae. Contr. Univ. Mich. Herb. 17: 55-69. Touw, A. 2001. A review of the Thuidiaceae (Musci) and a realignment of taxa traditionally accommodated in Thuidium sensu amplo (Thuidium Schimp., Thuidiopsis (Broth.) M. Fleisch., and Pelekium Mitt.), including Aequatoriella gen. nov. and Indothuidium gen. nov. J. Hattori Bot. Lab. 90: 167-209.