Hymenostylium, a genus of 16 species (Crosby et al. 2000), is found on limestone boulders and cliff faces or limey deposits in wet or seepy places. In Central America the genus often has leaves with entire margins that are narrowly recurved on one or both sides, and stems that have a sclerodermis rather than a hyalodermis, and no central strand. The leaf cells of Hymenostylium are mostly firm-walled and porose at least at the base and have either simple papillae scattered over the lumen of the upper and median cells or smooth leaf cells. In cross-section its costa has two stereid bands, but the ventral band is often weakly differentiated, and there is no enlarged ventral epidermal layer. Hymenostylium is gymnostomous and has systylius capsules. This last feature is only occasional to the genus and not a constant feature of even H. recurvirostrum (Zander 1977).

Species of Hymenostylium are sometimes placed in the genus Gymnostomum (e.g., Crum & Anderson 1981, Ireland 1982, Allen 1990). Zander (1993), however, considers Hymenostylium close to Leptodontium and places Gymnostomum into a different tribe. Gymnostomum differs from Hymenostylium in having a stem central strand, plane leaf margins, non-porose leaf cells, and non-systylius capsules. Leptodontium usually has larger plants and grows in drier habitats than Hymenostylium. It further differs from it in having a broader, reniform costae, sheathing perichaetial leaves, long-cylindrical capsules, peristomate capsules, and well-developed annuli. Zander (1977) provided an in-depth treatment of H. recurvirostrum (as Gymnostomum recurvirostrum) in Middle America.