Specimens of Rehmann 22 in South African herbaria, are T. mayottensis, while the specimen at BM is T. longicollis (Dixon in Sim corresp. in PRE as T. africanus). Trematodon mayottensis is separated from other species of Trematodon in Southern Africa, by its broad leaves and obtuse apices.
Plants small, gregarious or in loose tufts, light green; terricolous. Stems (l-)2-3 mm high, simple; in section central strand large, cortical cells large, becoming incrassate toward margin. Leaves contorted dry, erect-spreading wet; lanceolate to ovate-ligulate, 1.0-1.6 mm long; apex obtuse to rounded; margins weakly reflexed, entire to crenulate above, bistratose; in section marginal cells rounded, smaller than rectangular laminal cells. Costa ending below apex to subpercurrent; in section flattened, cells not strongly differentiated, guide cells somewhat larger, ventral cells in single layer, thin-walled, dorsal substereid band 1-2 cells thick, cells variable in size and thickening occasionally only incrassate, dorsal surface cells similar to ventral cells. Laminal cells smooth, short-rectangular to quadrate, thin-walled; basal cells larger, rectangular, lax. Perichaetial leaves not differentiated. Seta erect, 3 mm long, yellow-brown; capsule erect, yellow-brown, urn short-cylindrical, 1.8-2.0 mm long, neck 1 mm long, strumose at base; peristome reddish yellow, teeth triangular, to 240 µm high, irregularly perforated, with vertical bars below, apical segments free, papillose, hyaline; operculum long-beaked, 0.6 mm high; calyptra cucullate; spores subreniform, 22-27 µm, papillose.
Plants small, gregarious or in loose tufts. Stems 1-3 mm long. Leaves contorted when dry, erect-spreading when wet, narrowly ovate to ovate-ligulate, 1.0-1.6 mm long; apex obtuse to rounded; margins entire to crenulate above, bistratose; costa subpercurrent. Laminal cells short-rectangular to quadrate; basal cells larger, lax. Capsule erect, urn short-cylindrical, neck strumose at base; peristome reddish yellow, teeth triangular, apical segments free. Spores subreniform, papillose.