Cabalodontia albofulva Westphalen & Gugliotta sp. nov.

Figs 7 A, 7 B, 11 A, 11 J

Etymology.

Refers to the white basidiomes that become yellowish when dried.

Diagnosis.

Differs from C. queletii by thinner and more fragile aculei and smaller basidiospores.

Typification.

Brazil. Rio Grande do Sul: São Francisco de Paula, Parador Hampel, 19 Jun. 2017, M. C. Westphalen 563 / 17 (SP 467080).

Description.

Basidiomes adnante, annual, resupinate, not detaching, forming small patches on the substrate, very soft and brittle; sterile margins white, membranaceous, up to 1 mm wide. Hymenophore odontioid, white to cream when fresh, becoming yellowish to beige upon drying. Aculei thin, up to 0.8 mm long, somewhat clustered and very brittle upon drying, 6–8 per mm. Subiculum, white to cream, homogeneous, cottony, thin and fragile, up to 0.5 mm thick.

Hyphal system monomitic, hyphae loosely arranged; generative hyphae clamped, thin- to slightly thick-walled, hyaline, often branching near the septa, 3–5 μm wide, CB –. Skeletocystidia abundant, arising from sclerified generative hyphae in the subiculum and projecting into the trama and above the hymenium, clavate, usually tapering towards the apex, encrusted portion 25–60 (– 70) × 6–11 μm; thin-walled leptocystidia present on tips of the aculei, clavate to capitate, 4–7 μm wide. Basidia clavate, tetrasterigmate, 12–15 × 3.5–5 μm. Basidiospores ellipsoid, hyaline, thin-walled, IKI –, CB –, (4 –) 4.3–5.1 (– 5.3) × 2.4–3.0 (– 3.1) μm.

Habitat and distribution.

Known only from the type locality in Araucaria forests in Rio Grande do Sul State. Growing on dead logs of unidentified angiosperms.

Notes.

Cabalodontia albofulva is characterized by fragile basidiomes with thin aculei measuring 0.5–0.8 mm long and ellipsoid basidiospores measuring (4 –) 4.3–5.1 (– 5.3) × 2.4–3.0 (– 3.1) µm. Cabalodontia queletii (Bourdot & Galzin) Piątek is morphologically similar but differs by having thicker aculei and larger basidiospores, measuring 5–6 × 3–3.5 µm (Bernicchia and Gorjón 2010). Phylogenetically, C. albofulva is closely related to C. lincangense, from which it differs by approximately eight bp in the ITS sequences, four in the tef 1 - α coding region, and five in the rpb 1 coding region. Morphologically, however, C. lincangense is distinct, displaying more widely spaced and longer aculei (2–4 per mm, 1–1.5 mm long) and shorter basidiospores measuring (3.5 –) 3.8–4.2 (– 4.5) × (2.3 –) 2.5–2.8 µm (Dong et al. 2024). Cabalodontia albofulva is currently known only from its type locality in southern Brazil. Despite extensive sampling in the surrounding region, including adjacent Araucaria forests, no additional specimens have been collected, suggesting that it could represent a rare taxon.