Didymodon crassicostatus (Bartr.) Zand., Bull. Buffalo Soc. Nat. Sci. 32: 162. 1993.

Barbula crassicostata Bartr., Bryologist 49: 114. 1946. Protologue: Guatemala. Dept. San Marcos: along road between San Sebastián at km. 21 and km. 8, 8–18 miles northwest of San Marcos, alt. 2700–3800 m, Steyermark 35695 (F).

Plants robust, dull, green above, brown below, in loose tufts, 30–40 mm high. Stems red erect, sparsely and irregularly branched, sclerodermis and central strand present; rhizoids sparse, at base of stems or scattered throughout. Axillary hairs 4–5 cells long, basal cell brown. Leaves 4–6 mm long, linear-lanceolate to triangular-ovate, spreading at base, circinate-contorted above when dry, spreading to falcate-secund above when wet, plane along the costa on ventral surface; apices subulate; lamina unistratose, fragile; margins entire, recurved below, plane above; costa stout, 100–140 μm wide at base, filling the apex and percurrent to excurrent, ventral surface cells of costa quadrate, guide cells and two stereid bands well-developed, ventral and dorsal surface cells enlarged; upper and basal cells weakly differentiated, upper cells in regular rows, rounded, 8–10 x 8 μm, firm-walled, smooth, basal cells quadrate, rounded or short-rectangular, firm-walled, smooth, 10–30 x 10 μm, alar cells not differentiated. Sporophytes not known.