Steccherinum resinaceum Westphalen & Minosso sp. nov. Figs 8 E, 9 E, 11 G Etymology. Refers to the hard and waxy consistency of the basidiomes when dried. Diagnosis. Distinguished from other species in the genus mainly by the waxy and dense basidiomes upon drying, the laterally fused aculei that bifurcate at apices, and the skeletocystidia encrusted with large crystals, usually embedded in the trama. Typification. Brazil. São Paulo: São Luís do Paraitinga, Parque Estadual da Serra do Mar, Núcleo Santa Virgínia, Trilha Pirapitinga, 05 Jun. 2017, M. C. Westphalen 551 / 17 (SP 512670). Description. Basidiomes adnate, resupinate, easily separable from the substratum and usually detaching upon drying, membranaceous to papery and pliable when fresh, turning waxy and somewhat rigid upon drying; sterile margins entire, smooth, pelliculose, up to 1 mm wide. Hymenophore hydnoid, cream to pale yellowish when fresh, turning beige to ochraceous upon drying, aculei (0.3 –) 0.4–0.75 × 0.15–0.3 (– 0.5) mm, usually with straight to bifurcate apices with a pilose appearance from the protruding cystidia, solitary or more commonly laterally fused, somewhat crowded, 5–6 per mm. Subiculum cream to beige, homogeneous, dense, up to 0.3 mm thick. Hyphal system dimitic, subicular hyphae very compact, tramal hyphae intertwined, subparallel; generative hyphae clamped, thin to slightly thick-walled, hyaline, occasionally branched, 2–4 µm wide, more abundant in the base of the subiculum; skeletal hyphae thick-walled to almost solid, hyaline to slightly yellowish, 2–4.5 µm wide. Skeletocystidia abundant, immersed in the trama or protruding into the hymenium, coarsely encrusted with large crystals, 25–45 (– 50) × (7 –) 9–11 (– 12) µm, some thinner and longer cystidia also observed immersed in the subiculum, up to 60 µm long and 6–8 µm wide; leptocystidia present, abundant in the apices of the aculei, clavate, ventricose, or capitate, smooth or with a crown of crystals. Basidia clavate, tetrasterigmate, 10–12 × 3.5–5 µm. Basidiospores broadly ellipsoid, hyaline, thin-walled IKI –, CB –, 2.7–3.4 (– 3.5) × 1.7–2.4 µm. Habitat and distribution. Known only from Atlantic Rainforest areas in southeastern Brazil. Specimens examined. Brazil • São Paulo: São Paulo, Parque Estadual Cantareira, Núcleo Engordador, Trilha da Cachoeira, 24 Apr. 2017, M. C. Westphalen 540 / 17 (SP 512671); • São Luís do Paraitinga, Parque Estadual da Serra do Mar, Núcleo Santa Virgínia, Trilha Olho d’ água, 13 Feb. 2019 M. C. Westphalen 665 / 19 (SP 512687, ICN 213880); • São Paulo, Parque Estadual das Fontes do Ipiranga, 18 Feb. 2019, M. C. Westphalen 679 / 19 (SP 512669). Notes. Steccherinum resinaceum is characterized by its waxy and somewhat hard basidiomes when dried, a hymenophore composed of laterally fused, often bifurcating aculei, and coarsely encrusted cystidia with large crystals. Macroscopically, the basidiomes of S. bononiae are somewhat similar but differ in having solitary aculei with a pilose appearance due to prominently protruding skeletocystidia, whereas in S. resinaceum the skeletocystidia are visible only at the apices of the aculei (Fig. 8 E). Additionally, the cystidia in S. bononiae are longer and typically covered with small- to medium-sized crystals. Steccherinum molle shares similar cystidial morphology and basidiospore size with S. resinaceum. Nonetheless, it can be distinguished by its softer basidiomes with a cottony subiculum and slightly shorter and thinner aculei. Unfortunately, we could not obtain monosporic cultures of S. resinaceum to confirm its mating system.

Published as part of Westphalen, Mauro Carpes, Minosso, Nathalia Michele Martins, Regio, Nicolas do Carmo, Gugliotta, Adriana de Mello, Rajchenberg, Mario & Silveira, Rosa Mara Borges da, 2026, Unveiling the hidden diversity of neotropical Steccherinum and allied genera (Steccherinaceae, Basidiomycota), pp. e 182915 in IMA Fungus 17 on page e182915, DOI: 10.3897/imafungus.17.182915