Volvopluteus platensis Xue T. Zhu & L. J. Liu s p. nov. (FIGURE.4–5) Index Fungorum number:—IF903302 Etymology:— platensis refers to the type locality, Qinghai-Tibet Plateau. Diagnosis:—Distinguished by small basidiomata and larger basidiospores (16.0–18.0 × 9.5–11.5 μm). Holotype:— CHINA. Qinghai Province, Hainan Tibetan Autonomous Prefecture, Gonghe County, near Qinghai Lake (36° 34′ 18.7″ N, 100° 31′ 38.7″ E, Elev. 3156 m), 25 July 2020, Zhu 3813 (HKAS 135866); GenBank: ITS = PQ451545. Description:— Basidiomata epigeous, small in size. Pileus 30–45 mm in diam., convex to applanate, slightly irregular umbonate, grayish white (Cool Gray 1 C) to dirty white (Warm Gray 1 C), sometimes with a cream tinge, glabrous, with short striations at the margin. Context of pileus white, unchanged on bruising, 3–4 mm thick near stipe. Lamellae free with lamellulae in 1–2 tiers, moderately crowded, up to 7 mm deep, light dusty pink (691 C) when young, become brownish pink with age (5005 C), edge serrated. Stipe 50–80 × 4–10 mm, tapered upwards, white, glabrous, solid. Volva free from the stipe, 10–15 × 8–10 mm, relatively thick, fragile, irregularly lobed, dirty white (Warm Gray 1 C). Odor and taste indistinct. Basidiospores [20/2/2] (15.5–) 16–18(–20) × (9–) 9.5–11.5(–12) μm, Q = (1.56–) 1.61–1.74 (–1.79), Q m = 1.69 ± 0.1, amygdaliform in side view, ellipsoid in front view, smooth, thin-walled, hyaline in water and 5% KOH, inamyloid. Basidia 35–68 × 15–20 μm, clavate, 4-spores, sterigmata 5–6 μm long. Pleurocystidia scattered, 65–95 × 18–40 μm, clavate, hyaline, thin-walled. Cheilocystidia not observed. Pileipellis 80–120 μm thick, ixocutiform, composed of procumbent hyphae, 4–10 μm diam, thin-walled, hyaline; terminal elements blunt, 40–50 × 4–6 μm. Volva made up of filamentous hyphae, 5–10 μm diam, thin-walled, hyaline. Clamp connections not observed. Habitat and distribution:—Solitarily distributed in the alpine meadows of the Tibetan Plateau. Additional Specimens examined:— CHINA, Qinghai Province, Hainan Tibetan Autonomous Prefecture, Gonghe County, near Qinghai Lake (36° 34′ 18.7″ N, 100° 31′ 38.7″ E, Elev. 3156 m), 25 July 2020, Zhu3815 (HKAS 135867). Notes:— Volvopluteus platensis and V. earlei are characterized by relatively small basidiomata, with pileus diameters not exceeding 45 mm. However, V. earlei can be distinguished by its smaller basidiospores (11–16 × 8–11 μm), the absence of pleurocystidia, and the presence of cheilocystidia (Shaffer 1957, Contu 2007, Justo & Castro 2010, Giannoni et al. 2018).

Published as part of Zhu, Xue-Tai, Liu, Li-Juan, Wang, Xiao-Qin & Dang, Yong-Xiang, 2025, Two new species of Volvopluteus (Pluteaceae, Agaricales) from Northwest China, pp. 133-143 in Phytotaxa 718 (2) on pages 138-139, DOI: 10.11646/phytotaxa.718.2.5, http://zenodo.org/record/18413211