Plants: slender, in interwoven mats. Stems: to 1(–2) cm, branches to 2(–5) mm, erect; axillary hair distal cell obtuse, pale brown. Stem: leaves ± subsecund, 0.3–0.5 mm wide; laminal cells 18–30 × 8–10 µm, smooth. Seta: 0.2–0.5 cm. Capsule: 0.7–1 mm; annulus 3- or 4-seriate, cells small, brown; exostome teeth blunt, partially connate; endostome basal membrane inconspicuous, segments 16, short, slender, unequally 2-fid, partially fused to basal membrane. Spores: finely roughened.
Tree trunks and bases, flood plain forests, calcareous rock. low to moderate elevations (0-400 m). Ala., Ark., Fla., Ga., Ill., Ind., Ky., La., Md., Miss., Mo., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va., Europe.
The inconspicuous plants of Clasmatodon parvulus form small, slender, straggly mats on tree trunks in southeastern North America north of Mexico. The species is characterized by a short costa (Leskea species have a strong costa ending near the apex), ovate, mostly bluntly acute leaves (Lindbergia has long-acuminate leaves), and a lack of erect, flagelliform branchlets (as in Platygyrium repens). The elliptic, erect capsules with a reduced peristome on short setae also are diagnostic.