Leaves: usually contorted when dry, lanceolate to broadly subulate from an ovate or oblong sheathing base, 1.5–4 mm, apex acute to narrowly obtuse, margins entire or with a few teeth apically; costa subpercurrect to excurrent as a subula; distal laminal cells subquadrate or short-rectangular. Perichaetial: leaves distinctly larger than the cauline, convolute-sheathing. Seta: elongate, 0.5–1.5 cm. Capsule: long-exserted, cylindric with neck strongly differentiated, conic to long-cylindric; peristome absent or present, of 16 simple, forked or perforate teeth, vertically barred on external surface; operculum differentiated, obliquely long-rostrate. Calyptra: cucullate. Spores: medium-sized, 20–30 µm, papillose. Worldwide, mainly temperate areas.
Species ca. 25 (6 in the flora). Trematodon is clearly in need of revision, with more than 80 correct binomials extant but only about 25 species commonly accepted as well characterized. It clearly intergrades with Bruchia. Within the genus, only T. ambiguus and T. longicollis have strumose capsules.