Cortinarius subsaniosus

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Cortinarius subsaniosus is a small webcap mushroom found in north and central Europe. It grows on sandy soil in association with willows and other trees, producing yellowish brown fruit bodies that are only a few centimeters across.

It was described in 2020 by Kare Liimatainen and Tuula Niskanen. The name reflects its close relationship to Cortinarius saniosus. In the same year, it was highlighted by Kew Gardens as one of six newly described British Cortinarius species.

Description
- Cap: 0.7–1.5 cm wide, starting cone-shaped and becoming convex to flat with a pointed center (umbo). It is yellowish brown, often darker in the center, and hygrophanous (changes color as it dries).
- Gills: brown and moderately spaced.
- Stem: 2–4 cm long and 0.15–0.3 cm thick, yellowish brown and cylindrical.
- Flesh and veil: the flesh is yellowish brown, darker at the base. A yellow universal veil forms girdle-like bands on the stem.
- Odor: none.

Microscopic features (used for identification)
- Spores: ellipsoid to almond-shaped, 9.5–11 by 6–7 μm, very warty; dextrinoid (stain reddish-brown with Melzer’s reagent).
- Basidia: 25–35 by 9–11 μm, with four sterigmata.
- Hyphae: gill tissue is golden; the cap surface (pileipellis) is rusty brown with parallel hyphae 5–8 μm wide and zebra-striped encrustations.

Taxonomy and related species
- Cortinarius subsaniosus sits in subgenus Telamonia, section Saniosi, near C. saniosus and other related species such as C. aureovelatus, C. chrysomallus, and C. aureomarginatus. It is described as part of the Cortinarius sansiosus species complex.

Distribution and ecology
- Known from the United Kingdom, Denmark, Estonia, Norway, Sweden, and Finland. It appears to be rare inland and is associated with willows and possibly other trees.

Origin of the name and discovery
- The type collection was made in 1999 at Sandscale Haws, Cumbria, England. The species was formally described in 2020.