Gymnostomum aeruginosum Sm., Fl. Brit. 3: 1163. 1804.
Trichostomum aeruginosum (Sm.) Lindb., Öfvers. Förh. Kongl. Svenska Vetensk.-Akad. 21: 229. 1864. Mollia aeruginosa (Sm.) Lindb., Musci Scand. 106. 1879. Eucladium aeruginosum (Sm.) C. Jens., Danmarks Mosser 2: 313. 1923. Protologue: Wales. Gathered in North Wales by J. W. Griffith Esq.
Anoectangium arizonicum Bartr., Moss Fl. N. Amer. 1(3): 192. 1938. Protologue: U.S.A. Arizona: ledges back of Daly’s mine, White House Canyon, Santa Cruz Co. Alt. about 6,500 ft. [E. B. Bartram 919] (FH).
Plants small and slender to medium-sized, forming tufts or caespitose, yellowish green to pale-green, saxicolous or terricolous. Stems 2–20 mm long, smooth, branching irregularly, sclerodermis and central strand usually present; rhizoids dimorphic: slender, red, smooth, branched ones scattered on the stem and massive, red, roughened, sparsely branched ones originating in leaf axils. Leaves somewhat distant and evenly spaced, wide‑spreading when wet, appressed when dry, apex contorted, ligulate to linear-lanceolate, 0.6–1.0 mm long; apices acute to obtuse or sometimes rounded; margins plane, entire to crenulate; costa ending just below apex, narrow, dorsal and ventral surfaces papillose, guide cells present, ventral stereid band not present in Central American material but weakly developed in robust collections outside the region, dorsal stereid band present, ventral surface cells enlarged, dorsal surface cells smaller than laminal cells and strongly thickened; upper leaf cells somewhat heterogeneous, rounded to quadrate sometimes transversely rectangular, 8–10 μm long, 1:1–2 (length:width), walls weakly thickened, papillose on both surfaces by scattered, low papillae, basal cells homogeneous, short-rectangular, 2–3:1 (length:width), thin-walled, smooth, marginal cells not differentiated, alar cells not differentiated. Gemmae in leaf axils. Dioicous. Perigonia terminal, geminate. Perichaetia terminal. Setae 4–6 mm long, yellow, smooth. Capsules exserted, erect, short-cylindrical, 0.5–0.8 mm long, smooth, brown; stomata in neck; opercula rostrate, beak erect, 0.5 mm long; peristome absent. Spores 9–12 μm, round, granulate, brown. Calyptrae cucullate, 0.7–1.0 mm long, smooth.