Plants 1-5 mm. Leaves lanceolate, lingulate to lingulate-ovate, 0.5-1.3 mm, margins recurved to revolute from near apex to near base, apex obtuse, rounded or emarginate, piliferous; costa excurrent, with an abaxial epidermis, filaments 2-12 cells, cells cylindric, thin-walled, with 2-4 hollow papillae on apical cell, terminal cell cylindric or conic; cells of leaf base 7-58 µm, medial and distal cells 7-22 µm, smooth. Sexual condition dioicous or cladautoicous. Seta 6-13 mm. Capsule urn ovoid-cylindric, 0.9-2.2 mm; operculum 0.6-1 mm; peristome strongly twisted, 400-900 µm. Spores spheric, nearly smooth to conspicuously papillose, 9-15 µm.

Capsule mature Dec-Jul. Soil and rocks, on banks and dry washes, under shrubs in desert areas; moderate to high elevations (500-1700 m); Ariz., N.Mex., Tex., Utah; Mexico; Europe; Asia (China, India); n Africa; Atlantic Islands (Canary Islands).

Crossidium crassinervium is characterized by the smooth-walled leaf cells and long, thin-walled filaments with cylindric to conic terminal cells. Papillae are present on the apex of the terminal cell and, occasionally, on the distal leaf cells.