Cystolepiota pyramidalis Sysoup. and Thongkl.
Pileus 15–45 mm diam., first parabolic or campanulate, expanding to convex or umbonate, with straight margin, when young completely covered with crowded pyramidal or irregular pyramidal squamules, brownish (6D7–8), soon breaking up into brownish (6D7–8) to light brown (6D4–5) pyramidal to granular pyramidal squamules or warts toward margin, sparse or fragile when mature, on orange-white to pale orange (5A2–3) background; margin covered with concolorous pyramidal to granular pyramidal velar remnants. Lamellae free, 3–5 mm wide, pale yellow (3A3), becoming brownish orange (6C4–6) when touched or mature, broadly ventricose, with 3–4 lamellulae, with concolorous smooth to slightly eroded edge. Stipe 25–40 × 4–5.5 mm, cylindrical, covered with concolorous squamules to those on pileus, sparse at apex, fragile when mature, on orange-white to pale orange (5A2–3) background. Annulus an annular zone with velar remnants and concolorous to pileus margin, sometimes fragile with age. Context white in pileus, up to 1 mm thick at center; hollow in stipe and concolorous with surface. Odor and taste not observed. Spore pint white.
Basidiospores (50,2,2) 3.8–4.5 × 2.5–3.2 µm, avl × avw = 4.1 × 3.0 µm, Q = 1.25–1.6, avQ = 1.37, ellipsoid-ovoid in frontal view, ellipsoid in side-view, slightly thick-walled, smooth, hyaline, non-dextrinoid, non-amyloid, cyanophilous. Basidia 15–18 × 4.5–7 µm, clavate, thin-walled, hyaline, four-spored, sometimes two-spored. Cheilocystidia 20–40 × 7–15 µm, variable in shape, irregular cylindrical, fusiform, narrowly utriform to utriform, lageniform, clavate with a narrowed apex, slightly thick-walled, hyaline. Pleurocystidia absent. Pileus covering an irregular epithelium composed of globose to subglobose elements, 35–65 µm in diam., slightly thick-walled, smooth, with pale brown to brown parietal and intracellular pigments. Stipe covering an irregular epithelium same as on pileus. Clamp connections present.
Habitat and habit: growing in small groups, saprotrophic on humus-rich soil of mixed deciduous forest with Castanopsis spp. and Lithocarpus spp. dominant; the species is rare and so far known from Oudomxay province, northern Laos, and Chiang Rai province, northern Thailand.
Additional material examined: Thailand, Chiang Rai Province, Muang District, Phoo Kham Fah Village, 15 August 2012, P. Sysouphanthong, PS2012-11 (MFLU12-1774, paratype).
Notes: Cystolepiota pyramidalis is rare in Laos and Thailand; it was found in two locations, not far apart from each other at similar elevations, viz., Oudomxay Province of northern Laos and Chiang Rai Province of northern Thailand. The specimens from these two locations are identical both in morphological and in molecular characters. It is distinguished by light brown to brown pyramidal squamules on basidiomata and pale yellow lamellae. This new species is distinguished from other species by yellow lamellae and the distinct pyramidal shape of the squamules on the pileus. Cystolepiota pyramidalis belongs to a clade of similar species. C. fumosifolia, known from North America and Europe (as C. cystidiosa (A.H. Smith) Bon, C. luteicystidiata (D.A. Reid) Bon, and L. lycoperdoides Kreisel), also has pyramidal granular warts on the pileus, but the cheilocystidia and abundant pleurocystidia have yellow contents, and the cheilocystidia are covered with yellow exudate. C. pseudofumosifolia from China has white lamellae and lacks the pyramidal warts on the cap. It lacks pleurocystidia, just like C. pyramidalis. There are some other species with yellow lamellae in the genus. First, Cystolepiota bucknallii (Berk. and Broome) Singer & Clémençon, known from temperate regions in Europe and North America, has pale yellow to pastel yellow lamellae, but the pileus and stipe are covered with lilac granulose squamules, and the much longer (7–9 µm) spores are dextrinoid. Second, Cystolepiota seminuda (Lasch) M. Bon also has white to yellowish creamy lamellae with a pale lemon-yellow tinge, but its basidiomata are much smaller and have a white to cream densely floccose-verrucose covering on the pileus, and it lacks cheilocystidia. Additionally, Cystolepiota oliveirae P. Roux, M. Paraíso, J.-P. Maurice, A.-C. Normand & F. Fouchier, described from Portugal, has distinctly white to reddish-brown squamules or warts on the pileus and stipe, but the species has white to cream lamellae and rough basidiospores, while C. pyramidalis has yellow lamellae and smooth basidiospores.