Meripilus malayanus Y. C. Dai, Chao G. Wang & Yuan Yuan 2025, sp. nov.

Meripilus malayanus Y. C. Dai, Chao G. Wang & Yuan Yuan sp. nov. Figs 18, 19 Etymology. Malayanus (Lat.): refers to the species being found in Malaysia. Diagnosis. Differs from other Meripilus species by resupinate nodulose basidiomata with a honey buff to grayish brown pore surface when dry, angular and sometimes elongated pores of 7–8 per mm, thick-walled and apically encrusted hyphoid cystidia, subglobose basidiospores measuring 5–5.5 × 4.5–5 µm. Type. MALAYSIA • Selangor, Taman Botani Negara Shah Alam, on fallen angiosperm trunk, 12 April 2018, Dai 18529 (BJFC 026818, holotype). Description. Basidiomata annual, resupinate, nodulose, soft corky, and without odor or taste when fresh, becoming hard corky upon drying, up to 15 cm long, 6 cm wide, and 0.8 mm thick at the center. Pore surface white to cream when fresh, unchanged after bruising, honey buff to grayish brown when dry; sterile margin thinning out, grayish brown when dry; pores angular, sometimes elongated, 7–8 per mm; dissepiments thin, slightly lacerate. Subiculum pinkish buff, corky, up to 0.3 mm thick. Tubes concolorous with pore surface, hard corky when dry, up to 0.5 mm long. Hyphal system monomitic; generative hyphae simple septate, smooth, IKI -, CB +; tissues becoming reddish brown in KOH. Subicular hyphae distinctly thick-walled with a wide lumen, rarely branched and simple septate, more or less flexuous, interwoven, 5–8 µm in diam. Tramal hyphae slightly thick-walled with a wide lumen, occasionally branched, moderately simple septate, straight, subparallel along the tubes, agglutinated, 3.5–4.8 µm in diam. Hyphoid cystidia present, arising from tramal hyphae and completely embedded in trama, not projecting from the hymenium or dissepiment edge, thick-walled with swollen tips, apically encrusted, 7–9 µm in diam. at the apex. Hymenial cystidia absent; cystidioles fusoid, thin-walled, smooth, 14–17 × 4–5 µm; basidia barrel-shaped to capitate, with four sterigmata and a simple basal septum, 14–17 × 7–8 µm; basidioles of similar shape to basidia, but smaller. Basidiospores subglobose, hyaline, thin-walled, smooth, with one medium or small guttule, IKI -, CB -, 5–5.5 (– 6) × (4.2 –) 4.5–5 (– 5.5) µm, L = 5.20 µm, W = 4.68 µm, Q = 1.11 (n = 30 / 1). Notes. Meripilus malayanus is similar to M. rigidus in morphology by having resupinate and hard corky to rigid basidiomata with a honey buff to grayish brown or deep olive pore surface when dry, distinctly thick-walled subicular hyphae, and thick-walled and apically encrusted hyphoid cystidia. However, the latter has round and smaller pores (10–12 per mm vs. 7–8 per mm, Wang et al. 2024), smaller basidiospores (4–4.6 × 3.2–4 µm vs. 5–5.5 × 4.5–5 µm, Wang et al. 2024), and so far, it is only known from the type locality in Central America. In the phylogenetic analyses, Meripilus malayanus is closely related to M. dollingerii, but M. dollingerii has thin-walled and apically encrusted hyphoid cystidia and thin-walled smooth hymenial cystidia (Wang et al. 2024). Rigidoporus adnatus Corner and Polyporus pellicula Jungh. occur in Southeast Asia and have resupinate basidiomata. However, Rigidoporus adnatus has smaller basidiospores (2.5–3.2 × 1.7–2 µm vs. 5–5.5 × 4.5–5 µm, Corner 1987), and Polyporus pellicula has larger pores (1-3 per mm vs. 7–8 per mm, Teixeira 1992).