Trichostomum crispulum Bruch in F. Muell., Flora 12: 395. 1829.
Protologue: Sardinia. Unter Gebüschen auf Hügeln bei Cagliari. [Fleischer].
Trichostomum involvens Card., Rev. Bryol. 40: 34. 1913. Protologue: Mexico. État de Puebla: Rancho Posada (Frère Nicolas, 1911, n° 5973 in parte, 5998, 6024). État de Vera-Cruz: Jalapa (C.R. Orcutt 1912, n° 5362).
Trichostomum chlorophyllum C. Müll. var. brevifolium Thér., Smithsonian Misc. Collect. 85(4): 8. 1931. Protologue: Mexico. Puebla: ( [Bro. Arsène] 4994, 4995).
Plants small to medium, green above, yellowish below, in loose tufts, to 6 mm high. Stems red, erect, irregularly branched, hyalodermis and central strand present; rhizoids sparse. Leaves 1.7–4 mm long, linear-lanceolate, erect at base, incurved, somewhat contorted and twisted above when dry, spreading to spreading-recurved when wet; apices obtuse to broadly acute, often cucullate, sharply mucronate; lamina unistratose, sometimes fragile; margins entire, erect to incurved; costa stoutly excurrent, guide cells and two stereid bands well-developed, ventral surface layer enlarged; upper cells subquadrate to rounded-hexagonal, 6–9 μm wide, firm-walled, pluripapillose, papillae scattered, basal cells rectangular, firm-walled or thin-walled, 30–100 x 6–14 μm, outer basal cells running somewhat up the margins in a v-shaped pattern. Dioicous. Sporophytes not seen. Setae 10–13 mm long; capsules cylindrical, 1.5–2.2 mm long, opercula high-conic, 1–1.2 mm long; annuli of 2–3 vesiculose cells; peristome teeth straight, yellow to brown, papillose to spiculose, basal membrane none or very low. Spores 10–14 μm, weakly papillose (Zander 1994a).