Scleroderma microcarpum Gonkhom, Sysouph. & Thongkl. 2025, sp. nov.

Scleroderma microcarpum Gonkhom, Sysouph. & Thongkl. sp. nov. Fig. 3 Diagnosis. Different from the similar species S. dictyosporum in having smaller basidiomata and larger basidiospores. Holotype. Thailand • Chiang Mai Province, Mae On District, 9 October 2019, collected by Didsanutda Gonkhom, DG 002 (MFLU 19-1347). Etymology. The species name “ microcarpum ” refers to the small size of the basidiomata. Description. Basidiomata epigeous, 20–21 mm in diam. 10–20 mm in height, circular when young, depressed at maturity; surface smooth and with small scales when young stage, light yellow (5 A 4-5), covered with brown (7 E 6-8) squamules when mature. Stipe sessile or short pseudostipitate (less than 4 mm long). Rhizomorphs at the base, white, branched, narrowing towards the base. Context up to 2 mm thick, light yellow (5 A 4-5). Peridium layer formed by simple hyphae septate, hyaline to yellow brown. Exoperdium 6.9–9.3 µm in diam., with clamp connections. Endoperidium 4.2–8.2 µm in diam., with or without clamp connections. Gleba white – yellowish white (3 A 1-2), compact, and powdery when mature. Basidiospores (n = 50) globose to subglobose, echinulate, grayish brown in KOH, (3.97 –) 6.07–6.51 (– 8.15) × (8.24 –) 10.77–11.61 (– 13.33) µm in diam. Basidia not observed. Habitat and distribution. Caespitose or fasciculated on soil, epigeous, in northern Thailand. Known distribution. Northern Thailand. Note. Scleroderma microcarpum is characterized by small basidiomata with a smooth and small scale on the surface and larger basidiospores and globose echinulate. Scleroderma microcarpum is phylogenetically related to S. dictyosporum Pat. with low BS (Fig. 1). Both species have echinulate basidiospores. However, S. dictyosporum has a larger basidiomata (24–28 mm in diam.) (Sanon et al. 2009) and has smaller basidiospores (7–9 µm wide) (Patouillard 1896; Sanon et al. 2009).