Steccherinum elegantissimum Westphalen & R. M. Silveira 2026, sp. nov.

Steccherinum elegantissimum Westphalen & R. M. Silveira sp. nov. Figs 8 B, 9 B, 11 D, 11 L Etymology. Refers to the delicate basidiomes with thin aculei and the elongated projecting cystidia. Diagnosis. Characterized by effused basidiome with small aculei (up to 0.5 mm long), a cottony subiculum, elongated and thin skeletocystidia protruding above the hymenium, and basidiospores with (3.4 –) 3.5–5.0 (– 5.1) × 2.2–2.9 (– 3.0) µm. Typification. Brazil. São Paulo: Ribeirão Grande. Parque Estadual Intervales, 28 Feb. 2018, M. C. Westphalen 633 / 18 (SP 512681). Description. Basidiomes adnate, effused, usually not detaching when dried, but easily separable if pulled from the substratum, formed by the coalescence of several small patches, membranaceous and pliable when fresh, turning papery and fragile after drying; sterile margins entire, byssoid, smooth to finely fimbriate, thin, up to 0.5 mm wide. Hymenophore hydnoid, cream to pale salmon when fresh, more or less unchanging or slightly duller upon drying, aculei 0.3–0.5 (0.55) × 0.1–0.2 mm, with acute apices, pilose from the protruding cystidia, solitary or rarely fused at the base, sub-distant, 5–8 per mm. Subiculum white, homogeneous, with a loose cottony and soft consistency, up to 0.3 mm thick. Hyphal system dimitic, subicular hyphae loosely arranged, tramal hyphae intertwined and somewhat more densely arranged; generative hyphae clamped, thin to slightly thick-walled, hyaline, occasionally branched, 2–3 µm wide; skeletal hyphae thick-walled to almost solid, abundant throughout the basidiome, hyaline, 2–4 µm wide. Skeletocystidia abundant, arising from the trama and protruding above the hymenium, somewhat thin and elongated, covered with small crystals, 20–70 (– 75) × 4–8, but rarely above 6 µm wide; leptocystidia present, often scattered and more abundant at the apical portion of the aculei, clavate to fusoid, smooth. Basidia clavate, tetrasterigmate, 13–15 × 4.5–5 µm. Basidiospores ellipsoid to narrowly ellipsoid, hyaline, thin-walled, IKI –, CB –, (3.4 –) 3.5–5.0 (– 5.1) × 2.2–2.9 (– 3.0) µm. Mating system. Tetrapolar. Monosporic cultures obtained from specimens 720 / 21 and 721 / 21. Habitat and distribution. Known from Araucaria forest and Atlantic Rainforest areas in southern and southeastern Brazil. Specimens examined. Brazil • Rio Grande do Sul: Canela, FLONA, 22 Oct. 2021, M. C. Westphalen 720 / 21 and 721 / 21 (ICN 213870 and 213871). Notes. This species can be recognized by its small, sub-distant aculei and basidiomes formed by several concrescent small patches, typically growing on thin branches. Microscopically, the basidiospores are larger compared to other Neotropical Steccherinum species, measuring (3.4 –) 3.5–5.0 (– 5.1) × 2.2–2.9 (– 3.0) µm. Additionally, S. elegantissimum has the longest and thinnest cystidia in the group, covered by a layer of thin crystals (Figs 9 B, 11 L). The basidiomes with a cottony subiculum resemble those of S. perparvulum and S. molle, but the latter two species have smaller basidiospores and typically form larger patches that cover wider branches or logs.