Ecology and distribution. At elevations from 910-4150 m (Venezuela: 2900-3300 m, Colombia: 2000 m, Peru: 2000-4150 m, Bolivia: 1530-3500 m, NW Argentina: 910-2090 m). United States, Central America, and Andes; also Europe. Previously recognized as a variety of T. australasiae, see comments under that species.
Didymodon umbrosusis characterized by the presence of a stem hyalodermis, long lanceolate to oblong-lanceolate leaves to 3 mm, acute to obtuse apices, entire, plane margins, unistratose lamina or bistratose in distal 1/3 of leaf, subpercurrent to percurrent costa, dorsal stereid band present, ventral stereid band absent, rectangular upper adaxial costal (epidermal) cells, and differentiated marginal base cells in 2-6 rows (narrowly long rectangular and firm-walled). Previously recognized as a variety of T. australasiae, see comments under that species. Two species described from northwest Argentina including Asteriscium flavisetum Herzog based on a collection made by Hosseus from Orán (Province of Salta), and Barbula curvipes Müll. Hal. based on a collection by Lorentz from Siambon (Province of Tucumán), are synonyms.