Contr. Univ. Michigan Herb. 17: 66. 1990.
Stems weakly and irregularly 2-pinnate, stems and branches smooth; paraphyllia 2–3(–5) cells in length, cells 2:1, only apical cell papillose. Stem leaves erect-incurved when dry, broadly ovate, 0.3–0.5(–0.6) mm; apex ± abruptly short- and broadly acuminate; costa 4/5 leaf length. Branch leaves erect-incurved when dry, 0.2–0.3 mm; apex acute; costa 3/4 leaf length, straight, covered with quadrate cells apically, projecting as low crests. Perichaetial leaves with margins subentire basally, serrulate distally. Seta smooth. Capsule with endostome cilia 1–2(–3).
Phenology: Capsules mature early spring–fall [Feb–Aug(-Oct)].
Habitat: Moist woods, rotten logs, rock, limestone, base of trees
Elevation: low to moderate elevations
N.B., Ont., Ala., Ark., Conn., Fla., Ga., Ill., Ind., Iowa, La., Maine, Md., Mich., Minn., Mo., N.J., N.Y., N.C., Ohio, Pa., S.C., Tenn., Va., W.Va., Mexico, West Indies, Central America, n, c South America, Europe.
Cyrto-hypnum minutulum is often confused with others in the family because of its wide range in eastern North America. In the southernmost part of the flora area, C. involvens is distinguished by quadrate-celled paraphyllia and a rough seta. Cyrto-hypnum pygmaeum is more delicate with elaborate branching, leaves erect when dry rather than more or less incurved, and papillose branches and stems. Rauiella scita has laminal cells strongly bulging, is more robust, 1-pinnate with larger, quadrate-celled paraphyllia, and has longer acuminate stem leaves. All the true species of Thuidium have branched paraphyllia and cells papillose only abaxially. Haplocladium (Leskeaceae) has 1-papillose laminal cells. Similarly, plants of Elodium blandowii (Helodiaceae) have 1-papillose laminal cells and are branched and long-celled.