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

Marasmius jilinensis T. Bau & W. N. Hou sp. nov. Figs 4 A – C, 6 Diagnosis. It is similar to Ma. brunneoaurantiacus Antonín & Buyck but differs in having a non-umbilicate pileus center, sinuate lamellae, and lacrymoid basidiospores [Q = (2.58) 2.74–4.02 (4.29)]. Etymology. “ jilinensis ” refers to Jilin Province, China, where the type specimen was collected. Description. Basidiomata small to medium-sized. Pileus 0.4–1.4 cm diam, initially convex to parabolic, becoming obtusely conical at maturity; surface pale orange-yellow (RAL 2000), smooth, slightly darker at the disc, orange (RAL 2010); margin entire, not grooved; texture pliant and easily shriveling. Context very thin, white with a warm yellow tint (RAL 1015); odor indistinct. Lamellae sinuate, distant, equal, narrow, 1–2 mm wide, L = 15, cream (RAL 9001). Stipe 2–5 cm long, 0.5–1 mm thick, filamentous, equal; apex creamy white (RAL 9001), middle pale reddish-brown (RAL 3012) to reddish-brown (RAL 8012), base olive-brown (RAL 8011) to black (RAL 9004); surface smooth; basal mycelium white (RAL 9003). Basidiospores (8.7) 8.9–11 (12) × (2.4) 2.9–3.2 (3.6) µm, Q = (2.58) 2.74–4.02 (4.29) [3.37 ± 0.39], lacrymoid, thin-walled, hyaline, inamyloid. Basidia 15–26 × 4.3–6.9 µm, clavate, thin-walled, hyaline, 4 - (rarely 2 -) sterigmate; sterigmata 1.8–4.8 µm long. Basidioles 15–25 × 3.8–6.9 µm, fusiform, apex with a blunt mucro, thin-walled, hyaline. Cheilocystidia Siccus - type, 8–15 × 4.2–8 µm; main body short-cylindrical when young, becoming long-cylindrical to long-clavate at maturity, thin-walled, hyaline; apex with 4–10 small spines, spines 1.7–4.7 µm long, hyaline to pale brown in 5 % KOH. Pleurocystidia not observed. Lamellar trama irregular, interwoven; hyphae 3.5–7.3 µm wide, thin-walled, hyaline, dextrinoid. Pileipellis hymeniform, composed of Siccus - type cells, 7.4–14 × 4.3–13 µm; main body clavate, hyaline in 5 % KOH; apex with 4–12 spines, spines 2.6–4.4 µm long, brown in 5 % KOH. Pileus trama composed of irregular, interwoven, hyaline hyphae 3.5–5.5 µm wide. Stipitipellis composed of parallel, smooth, thick-walled, pale brown, dextrinoid hyphae. Clamp connections present in all tissues. Typus. CHINA • Jilin Province, Changchun City, Nanguan District, the campus of Jilin Agricultural University, on dead leaves of broad-leaved trees, 12 July 2023, 43°48'15"N, 125°25'10"E, alt. 243 m, S. E. Wang, FJAU 69327 (E 230797), holotype!. Additional materials examined. CHINA • Jilin Province, Changchun City, Nanguan District, Jingyuetan, on dead leaves of broad-leaved trees, 7 July 2024, 43°48'18"N, 125°29'02"E, alt. 348 m, Z. Q. Chen, FJAU 69329 (Q 247718). • Changchun City, Nanguan District, Jingyuetan, on dead leaves of broad-leaved trees, 7 July 2024, 43°48'05"N, 125°28'48"E, alt. 312 m, Q. R. Liu, FJAU 69328 (R 24709); • Changchun City, Nanguan District, Jingyuetan, on dead leaves of broad-leaved trees, 7 August 2026, 43°48'14"N, 125°28'49"E, alt. 365 m, W. N. Hou, FJAU 69462 (H 26070807). Notes. Phylogenetically, Ma. jilinensis forms a clade with two unidentified Marasmius. sequences, and this clade is sister to a group comprising Ma. bambusiniformis, Ma. graminicola, and Ma. occultatus. However, Ma. bambusiniformis differs by its umbilicate pileus center and a pileus surface covered with a pruinose layer (Singer 1976). Ma. occultatus differs by its finely tomentose pileus surface and a distinctly lignicolous habit (Takahashi 2000). Ma. graminicola is characterized by a pileus center that is slightly to strongly umbonate and a striate pileus surface with striations becoming more pronounced upon drying (Oliveira et al. 2020 a). Ma. jilinensis resembles Ma. siccus (Schwein.) Fr. and Ma. brunneoaurantiacus in possessing marasmioid basidiomata and an orange-toned pileus. Ma. siccus is widely distributed across China, whereas Ma. brunneoaurantiacus has been reported only from Shandong Province in China. Ma. jilinensis differs from Ma. siccus, which has free lamellae with a distinct collarium and pleurocystidia that are capitate-lageniform, lageniform, or subfusiform. Ma. brunneoaurantiacus was originally described from Madagascar by Antonín and Buyck (2006), based on the type specimen Buyck 99.450 collected from dead leaves of Uapaca ferruginea Baill. Ma. brunneoaurantiacus differs from the present species by its umbilicate pileus center, free lamellae, and ellipsoid basidiospores measuring 9.5–11 × 4.5–6 µm, with Q = 1.9–2.1 (Antonín and Buyck 2006; Shay et al. 2017). Although Ma. crinipes Antonín, Ryoo & H. D. Shin belongs to a different subsection, it nonetheless resembles this species in pileus color. Ma. crinipes can be distinguished by its pileus bearing a bluntly rounded center with fine wrinkles, while the remaining pileus surface shows conspicuous deep radial sulcations. Basidiospores of Ma. crinipes are elongate-clavate to fusiform (20–27 × 3.5–5.0 µm), and its cheilocystidia possess a rostrate or papillate apex, occasionally with an irregular morphology, and contain strongly refractive contents (Antonín et al. 2012 b). By contrast, Ma. jilinensis has a smooth pileus center, with the pileus surface lacking striations or exhibiting only indistinct ones; its basidiospores are lacrymoid, measuring 9.8–11 × 2.9–3.2 µm, and its cheilocystidia are of the Siccus - type. Ma. clocca F. E. Guard, Dearnaley & T. Lebel is a recently described species that is morphologically close to Ma. jilinensis (Crous et al. 2026). Nevertheless, Ma. clocca has a shallowly sulcate pileus surface across its outer two-thirds, and its basidiospores (14.7–17 × 3.5–4 µm, Q = 3.64–4.64) are distinctly longer. In addition, its basidioles are narrowly fusoid to clavate and lack a blunt mucro at the apex, which distinguishes it from Ma. jilinensis.