Ptychomitriaceae Schimp., Synopsis Muscorum Europaeorum. 1860.
Plants small to moderately large, sometimes robust, green to yellowish green above, brown or black below, in loose or dense tufts. Stems erect or ascending, simple or branched; central strand well developed. Leaves mostly imbricate, crowded in rows, often crisped or incurved, sometimes contorted when dry, spreading to wide-spreading when moist, linear-lanceolate to narrowly lanceolate or broadly lanceolate, sometimes keeled, concave above, blunt or acuminate at the apex; margins erect or recurved, entire to strongly serrate above; costa single, strong, percurrent or ending below the apex; upper and median leaf cells small, rounded-quadrate or subquadrate to rectangular, often bistratose, obscure, thick-walled, sometimes with sinuose walls; basal cells rectangular to linear, thin-walled, or with sinuose walls. Autoicous. Perigonia present just below perichaetia. Perichaetial leaves not differentiated or convolute-sheathing. Setae terminal, short or elongate, straight; capsules exserted, erect, symmetric, ovoid to oblong-ellipsoid, smooth; annuli mostly well developed, consisting of thick-walled cells, sometimes absent; peristome teeth haplolepidous, 16, lanceolate to linear-lanceolate, deeply and irregularly splitting into 2–3 filiform segments, densely papillose; opercula with a short to long beak. Calyptrae naked, mitrate, longitudinally plicate, lobed at the base, covering half to almost the entire capsule. Spores spherical, mostly coarsely to finely papillose, occasionally smooth.
There have been different opinions concerning the systematic and phylogenetic position of the Ptychomitriaceae. The family appears to be closely related to the Grimmiaceae within the suborder Grimmiineae. In this treatment, we follow Vitt (1984) in recognizing four genera (Campylostelium Schimp. in B.S.G., Glyphomitrium Brid., Ptychomitrium Fürnr., and Ptychomitriopsis Dix.). Of these four genera, three are present in China. The genus Ptychomitriopsis is not known from the country. We recently found Campylostelium from Changbai Mountain, Jilin province. Glyphomitrium will be treated under the family Orthotrichaceae, following the Chinese edition of the Bryoflora of China.