Cuphophyllus aureus K. P. D. Latha & M. K. Varsha sp. nov. Figs. 1–3

MycoBank no.: MB 859393

Diagnosis:— Characterized by small, omphalinoid basidiocarps with a golden yellow, glabrous, centrally depressed pileus, a compressed, fibrillose and striate stipe with a pale yellow strigose base, ellipsoid-oblong to lacrymoid basidiospores, a lamellar trama with an almost regular central strand flanked on either side by somewhat subregular hyphae, and a hymenium devoid of pleuro- and cheilocystidia. Differs from C. dingjieensis in having smaller basidiocarps with a centrally depressed, glabrous pileus, transvenose, intervenose, and occasionally furcate lamellae, a tapered, light orange to pale-yellow stipe, absence of cheilocystidia, and distinct nrITS, nrLSU, and rpb2 sequences.

Type:— INDIA. Kerala State: Malappuram District, Calicut University Campus, 11°07’41.7”N 75°53’31.1”E, 55 m, 12 July 2018, on soil, K. G. Greeshma Ganga DKP518 (holotype CALI!).

Etymology:— aureus (Latin), golden; refers to the color of the pileus.

Description:— Basidiocarp s small, omphalinoid. Pileus 2–10 mm diam., initially convex or convex with a small central depression, becoming broadly convex or plano-convex with a deep central depression at maturity; surface initially yellowish orange or dark orange (4A7, 5A8/OAC852, OAC789), becoming golden yellow (5B7/OAC790) all over at maturity, glabrous to the naked eye, somewhat rugulose under a lens, hygrophanous and becoming paler; margin incurved when young, becoming decurved or somewhat straight with age, entire or slightly wavy at maturity. Lamellae decurrent or arcuate-decurrent, close, seldom furcate towards the margin, transvenose and intervenose, initially grayish orange (5B6/OAC810), becoming pale yellow (4A3/OAC814) at maturity, up to 5 mm wide, with lamellulae in 2-4 tiers; edge entire, concolorous with the sides. Stipe 4–17 × 1–3 mm, central, compressed, mostly tapering towards the apex or at times equal, cartilaginous, stuffed when young, becoming hollow with age; surface initially light orange (5A5/OAC791) all over, becoming pale or light yellow (4A3, 4A4/OAC813) at maturity; appressed-fibrillose as well as longitudinally-striate all over or at times longitudinally twisted-striate towards the apex; base slightly enlarged with a pale yellow, strigose basal mycelium. Context soft, up to 1 mm wide, orange white (5A2/OAC815). Odor and taste not distinctive. Spore print brownish gray (5C2/OAC828).

Basidiospores 6–7(9) × 3–4 µm (6.55 ± 0.53 × 3.94 ± 0.45 µm), Q = 1.34–2.3, Qm = 1.77, ellipsoid-oblong to lacrymoid, thin-walled, hyaline, non-metachromatic, inamyloid. Basidia 25–44 × 5–7 µm, elongate, clavate or narrowly clavate, thin-walled, hyaline with or without vacuolar contents, 4-spored; sterigmata up to 4 µm long. Basidioles 17–41 × 2–7 µm, copious, narrowly clavate, clavate, cylindrical or flexuous-cylindric, a few with a capitate apex, thin-walled, hyaline with or without vacuolar contents. Lamella-edge fertile. Pleuro- and cheilocystidia absent. Lamellar trama with an almost regular central strand flanked on either side by somewhat subregular hyphae; hyphae 5–53(66) × 1–5 µm wide, narrowly cylindrical or cylindrical, thin-walled, hyaline or with a pale-yellow wall pigment, inamyloid. Subhymenium pseudoparenchymatous. Pileus trama subregular; hyphae 3–7 µm wide, thin-walled, hyaline or with a pale-yellow plasmatic pigment, inamyloid. Pileipellis a repent cutis; hyphae 2–5 × 11–37 µm wide, thin-walled, hyaline, inamyloid. Pileocystidia absent. Stipitipellis a cutis; hyphae 2–5 µm wide, thin-walled, hyaline or with a pale-yellow wall pigment, inamyloid. Caulocystidia absent. Stipe trama subregular with both narrow and inflated hyphae; hyphae 2–15(17) µm wide, thin-walled, with a pale-yellow wall pigment, inamyloid. Clamp connections observed on all tissues.

Habitat:— On soil, scattered or in small groups.

Geographical distribution range:— Known only from the type locality in Kerala State, India.

Additional specimens examined:— INDIA. Kerala State: Malappuram District, Calicut University Campus, 11°07’41.7”N 75°53’31.1”E, 55 m, 17 July 2018, on soil, K. P. Deepna Latha DKP522; 11°08’41.1”N 75°53’14.9”E, 72 m, 24 July 2024, on soil, M. K. Varsha MK28; 11°08’41.1”N 75°53’14.9”E, 72 m, 02 November 2024, on soil, M. K. Varsha MK34; 11°08’41.1”N 75°53’14.9”E, 72 m, 13 December 2024, on soil, M. K. Varsha MK36.