Panaeolus xiaolanii M. Q. He & R. L. Zhao, sp. nov.

Panaeolus xiaolanii M. Q. He & R. L. Zhao sp. nov. Fig. 17 Etymology. xiaolanii is in honor of the Chinese mycologist Xiao-Lan Mao, who made a great contribution to the macrofungal research in China. Diagnosis. Panaeolus xiaolanii has small basidiomes with gray, hygrophanous pileus, limoniform basidiospores, and cylindrical, flexuose cheilocystidia. Holotype. CHINA. Xizang Autonomous Region: Shigatse Municipality, Yadong County, Xiayadong Village, Boluoka grassland, 27.22.8°N, 88.58.25°E, alt. 2872 m, 22 July 2022, Mao-Qiang He, HMAS 287493 (ZRL 20220031). Description. Pileus 11–38 mm in diam., conical to broadly conical, surface dry, smooth, hygrophanous, color variable, from gray (pantone 427 c), grayish yellow (pantone 7536 c) to grayish black (pantone 412 c), usually paler at edge, some with crenulate margin, margin usually covered by white veil remnants. Lamellae adnate, close, broad, mottled grayish first then becoming blackish when mature, entire, with a white edge. Stipe equal, hollow, 34–130 mm long, 1–3 mm thick, always the same color as pileus, gray to black, dark purple, paler above, smooth, pruinose especially on the side close to the cap, base getting darker when touched or bruised and occasionally with whitish mycelium. Basidiospores 13.8–16.3 × 10.7–12.0 μm, [x = 15.3 ± 0.7 × 11.4 ± 0.3, Q = 1.2–1.5, Q m = 1.3 ± 0.1, n = 20], limoniform, blackish brown when mature, smooth, thick wall, protruding germ pore. Basidia 19.1–26.9 × 12.9–15.8 μm, 4 - spored, smooth, hyaline. Cheilocystidia 23.3–32.4 × 3.9–7.4 μm, cylindrical or narrowly clavate, flexuose, hyaline, smooth. Pleurocystidia absent. Cuticle composed of large vesicles, pileocystidia not observed. Caulocystidia 31.4–55.7 × 5.5–9.6 μm, cylindrical or narrowly clavate, flexuose, hyaline and light brown, smooth. Habitat. Grows in pastures, on dung of horses and cows. Psilocybin-producing. Nonproducing (ZRL 20220031, see Suppl. material 1: fig. S 5). Notes. Compared with other phylogenetically closely related species, P. xiaolanii can be distinguished from P. papilionaceus in the field by its more conical and darker pileus. Additionally, the two species differ in basidiospores, with P. papilionaceus having ellipsoid basidiospores, whereas P. xiaolanii has limoniform basidiospores. It is difficult to separate P. xiaolanii from P. parvisporus in the field. A relatively distinguishable difference is the larger basidiospores of P. xiaolanii. Other specimen examined. China. Jilin Province: Yanbian Korean Autonomous Prefecture, Longjin City, Xianfeng National Forestry Park, 23 July 2016, ZRL 20160575; Xizang Autonomous Region: Shigatse Municipality, Yadong County, Xiayadong village, Boluoka grassland, 27.22.8°N, 88.58.25°E, alt. 2872 m, 22 July 2022, collected by Mao-Qiang He, ZRL 20220039, ZRL 20220044, ZRL 20220154, ZRL 20220155; Renqinggang, 27.25.20°N, 88.55.6°E, alt. 3254, 23 July 2022, Mao-Qiang He, ZRL 20220360, ZRL 20220381; Dinggyê County, Chentang Town, 27.52.17°N, 87.25.18°E, alt. 2600 m, 30 July 2022, Mao-Qiang He, ZRL 20220451, ZRL 20220452; Gyirong County, Jilonggou, 28.24.35°N, 85.18.54°E, alt. 2935 m, 1 st August 2022, Rui-Lin Zhao, ZRL 20220560; Chongse, 28.22.39°N, 85.19.40°E, alt. 2780 m, 2 nd August 2022, Bin Cao, ZRL 20220697.