Timmia sanjiangyuanensis W. Z. Huang, X. Yin Ma & Y. Huan Wu sp. nov.Figs 2, 3, 4, 5Diagnosis.Similar to Timmia sphaerocarpa, but differing in having stomata restricted to the basal part of the capsule; vegetative and perichaetial leaves with a distinctly differentiated sheathing base; limb laminal cells with strong mamillose; antheridia naked in the leaf axils; sinuose exothecial cells and larger spores (36–46 μm in diameter).Type.China • Qinghai Province, Guoluo Zangzu Autonomous Prefecture, Sanjiangyuan Region, Gande County, Qingzhen Town, along G 227 road, on soil, 34°5'48.90"N, 100°7'0.73"E, 4149 m a. s. l, 27 August 2025, W.-Z. Huang 20250827-06 (holotype: HTC! [HTC 0022010]; isotypes: HSNU!, KUN!).Description.Plants robust, in loose tufts, brownish below, green to yellowish-green above. Stems simple, 1.5–2.4 cm, central strand present. Rhizoids red-brown. Leaves lanceolate, acuminate, 5.0–6.3 × 1.2–1.6 mm, with well-differentiated sheathing base. Leaf margins serrate in distal 1 / 3–1 / 2, entire below. Costa single, robust, subpercurrent, smooth on the dorsal surface, strongly mamillose on the ventral surface in the limb, smooth in the sheath; transverse-section of the costa with one row of guide cells, with two stereid bands in the limb, the ventral stereid band poorly developed or absent in the sheath. Cells of limb strongly mamillose on the ventral, smooth on the dorsal side, quadrate, irregularly polygonal or horizontal rectangular, 4.0–14.0 × 10.0–16.0 μm. Laminal cells of the sheath clearly differentiated, long-rectangular, hyaline, smooth, 23.5–84.0 × 2.5–8.5 μm, gradually longer and narrower towards the margin.Autoicous. Antheridia naked in the leaf axils, 1.3–1.5 mm long. Perichaetial leaves lanceolate, widest just above the base, with a well-differentiated sheathing base, conspicuously larger than the vegetative leaves. Seta smooth, reddish, ca. 1.8 cm long. Capsule pyriform when wet, globose when dry and empty, ca. 1.4 mm in diameter, yellow-green when immature, yellow or brown and distinctly furrowed when mature. Stomata restricted to the basal part of the capsule. Exostome teeth 16, yellow at the base and pale yellow above, gradually tapering upwards; outer surface papillose and horizontally striate below, vertically barred and papillose above. Endostome segments 16, triangularly lanceolate, joined at base, inner surface of segments smooth, outer surface slightly granular above, not appendiculate. Operculum conical. Exothecial cells irregular, 14–34 × 16–32 μm, with thick and extremely sinuose walls throughout. Spores spherical, yellowish-brown, finely papillose, 36–46 μm in diameter.Etymology.The epithet “ sanjiangyuanensis ” refers to the Sanjiangyuan Region, where the new species was found.Distribution and habitat.Timmia sanjiangyuanensis is known only from Gande County in Sanjiangyuan Region, Qinghai Province, China, at an altitude of 4,149 m a. s. l, associated with Distichium hagenii Ryan ex Philib, Encalypta ciliata Hedw. and Pohlia elongata Hedw.Notes.Timmia sanjiangyuanensis is well characterised by the following features: (1) pyriform to spherical capsules with stomata confined to the basal part (Figs 2 C, 3 A, 3 I, 4 A, 4 B); (2) exothecial cells irregular, extremely sinuose (Fig. 3 H); (3) vegetative and perichaetial leaves lanceolate, with a well-differentiated sheathing base (Figs 2 D, 3 E, 4 C, 4 D); (4) antheridia naked in the leaf axils; (5) costa of the limb portion strongly papillose on the ventral surface, smooth on the dorsal surface and smooth on both dorsal and ventral sides in the sheath portion (Figs 2 H, 2 I, 4 I); (6) laminal cells of the sheathing base differentiated, long-rectangular, hyaline, smooth (Figs 2 L, 4 K); and (7) spores large, finely papillose, 36–46 μm in diameter (Figs 3 F, 4 F, 5 E – L).