Ecology and distribution. Semi-dry lowlands to páramo and puna; exposed sites, typically found on soil and rocks. Occasional, at elevations from 15-4300 m (Venezuela: 15-3750 m, Colombia: 740-4300 m, Ecuador: 1800-4175 m (Galapagos Islands: 275-300 m), Peru: 500-4175 m, Bolivia: 260-3690 m). Rather widespread; common in the Andes and southeast Brazil. This species is assigned to subgenus Trichostomum by Zander (1993).
Trichostomum brachydontium is characterized by the ligulate leaves to ca. 2.5 mm, acute to ± rounded apex with a stout, recurved mucro, basal cells differentiated across insertion, setae to 10 mm, cylindrical to ellipsoidal capsules to 1.5 mm, mostly reduced peristome; the recurved mucro is a good aid in differentiating other Trichostomum species. Trichostomum duidense E.B. Bartram and T. novogranatense Broth. & Irmsch. in Irmsch. are synonyms.