Marasmius coronatospinosus T. Bau & W. N. Hou 2026, sp. nov.

Marasmius coronatospinosus T. Bau & W. N. Hou sp. nov. Figs 5 A – C, 11 Diagnosis. It is similar to Ma. siccus, but the latter has a golden-yellow pileus, a subcylindrical stipe, and pileipellis cells with subcylindrical main bodies bearing long, acute apical spines. However, Ma. coronatospinosus has a tomato-red pileus, a filiform stipe, and pileipellis cells with short clavate main bodies bearing short, blunt apical spinules arranged in a crown-like pattern. Etymology. “ coronatospinosus ” refers to the short spines arranged in a crown-like pattern at the apex of the pileipellis cells. Description. Basidiomata small. Pileus 0.4–0.6 cm diam., initially convex to campanulate, becoming plano-convex at maturity, with a mammillate disc; surface smooth, glossy when wet, with shallow longitudinal grooves and a concentric bulge at the center; disc tomato-red (RAL 3013), fading toward the margin to clay brown (RAL 8001) to orange-brown (RAL 8023); margin grayish-white (RAL 1013), reflexed. Context off-white (RAL 7047), very thin; odor indistinct. Lamellae free, with a collar-like structure, sparse, equal, 1–2 mm broad, L = 8, white (RAL 9003), translucent and tinged brown (RAL 7047) when wet. Stipe 1.6–3.2 cm long, 0.5 mm thick, filiform, equal or slightly thicker at apex; apex grayish-white (RAL 1013), translucent, darkening downwards; middle clay brown (RAL 8001) to olive-brown (RAL 8008), base dark brown (RAL 8011) to blackish-brown (RAL 8022); surface smooth, glossy; base directly attached to habitat. Basidiospores (10) 11–14 (14) × (2.5) 2.9–4.6 (4.9) µm, Q = (2.61) 2.83–4.2 (4.8) [3.47 ± 0.49], fusiform, smooth, thin-walled, hyaline, inamyloid. Basidia 21–26 × 5.8–8.9 µm, subcylindrical, equal in width, thin-walled, hyaline, 4 - (rarely 2 -) sterigmate; sterigmata 2.8–3.7 µm long. Basidioles 17–29 × 3.9–8.4 µm, clavate to fusiform, thin-walled, hyaline. Cheilocystidia 12–22 × 4.8–7.3 µm, with a subclavate main body, bearing 6–16 apical spines, 2.4–5.1 µm high. Pleurocystidia 24–36 × 7.3–10 µm, with subfusiform main body; apex apices with one or more constrictions, usually globose, moniliform with 1–3 similar elements in a chain, sometimes digitate; apical portion 2.9–14 µm long; smooth, thin-walled, hyaline, refractive or faintly refractive. Lamellar trama irregular; hyphae 3.2–3.8 µm wide, thin-walled, hyaline, weakly dextrinoid. Pileipellis hymeniform, composed of Siccus - type cells, main body 7.9–16 × 6–12 µm, short-clavate; apices unbranched or with 1–3 branches, bearing 9–17 short, blunt spinules, often adhering to one another and arranged in a crown-like pattern, thus difficult to count accurately; spines 2.4–4.9 µm long, pale brown. Pileus trama composed of interwoven, smooth, thin-walled, hyaline, weakly dextrinoid hyphae 3.3–4.8 µm wide. Stipitipellis composed of smooth, thick-walled, pale yellowish-brown hyphae 3.2–4.2 µm wide. Clamp connections present in all tissues. Typus. CHINA • Heilongjiang Province, Greater Khingan Mountains Region, Jiagedaqi District, roadside near National Highway G 111, on dead grass, 28 July 2024, 50°17'17"N, 124°14'44"E, alt. 422 m, W. N. Hou, FJAU 69397 (H 2472818), holotype!. Additional materials examined. CHINA • Inner Mongolia Autonomous Region, Tongliao City, Naiman Banner, Mengjiaduan National Wetland Park, 43°22'23"N, 120°58'52"E, alt. 278 m, on dead grass, 1 August 2025, W. N. Hou, FJAU 69399 (H 25080102). • Inner Mongolia Autonomous Region, Tongliao City, Naiman Banner, Mengjiaduan National Wetland Park, 43°22'24"N, 120°58'52"E, alt. 278 m, on dead grass, 1 August 2025, W. N. Hou, FJAU 69400 (H 25080103). Notes. It belongs to Marasmius subg. Globulares sect. Sicci. It is assigned to ser. Haematocephali due to the moniliform apex of its pleurocystidia. It resembles Ma. haematocephalus s. s. and Ma. asiaticus, two species recorded in China, in possessing a reddish pileus. However, Ma. haematocephalus s. s. exhibits an incurved to straight pileus margin and pileipellis cells with apices that are partially capitate, papillate, or rarely short-mucronate. Ma. asiaticus features red lamellar edges and pleurocystidia morphologically similar to those of Ma. haematocephalus s. s. In contrast, the present species has a reflexed pileus margin and subfusiform pleurocystidia. Their apices usually bear one or more constrictions and are arranged in a moniliform manner, sometimes digitate (Mešić and Tkalčec 2010; Tan et al. 2009). In the phylogenetic tree, Ma. coronatospinosus shows the closest relationship to Ma. coasiaticus J. S. Oliveira. Ma. coasiaticus, however, has a pileus with a flat to shallowly depressed center and pleurocystidia that are broadly clavate, rod-like to subovoid. It is noteworthy that the present species possesses a mammillate pileus center and subfusiform pileipellis cells. Ma. coronatospinosus is also phylogenetically related to Ma. roseus J. S. Oliveira, whereas Ma. roseus differs by having a grayish-pink to pale violet pileus with a flat or slightly rugulose center and pleurocystidia with apices devoid of projections or bearing only a single globose to short-mucronate projection (Oliveira et al. 2022). Ma. curreyi Berk. & Broome and Ma. coronatospinosus both preferentially grow on dead grass leaves. However, Ma. curreyi can be distinguished by its orange-tinged pileus with a brown central umbo, free lamellae, and the presence of a collarium (Berkeley and Broome 1879; Antonín 2007).