Nova Hedwigia, 38: 86, 1983. Basionym: Biatora castanea Hepp - Flecht. Eur.: nr. 270, 1857.
Synonyms: Lecanora castanea (Hepp) Th. Fr.; Lecanora castanea var. septata Arnold
Distribution: N - Frl (Tretiach & Hafellner 2000), Ven, TAA (Lang 2009), Lomb, Piem (Isocrono & al. 2004), VA (Piervittori & Isocrono 1999), Emil (Fariselli & al. 2020).
Description: Thallus crustose, whitish, grey or brownish, thin, continuous to rarely granulose, often indistinct. Apothecia lecanorine, sessile, constricted at base, 0.5-2(-3) mm across, with a dark reddish brown, initially concave, then flat, sometimes faintly pruinose disc, and a thick, crenulate-undulate thalline margin. Thalline exciple cupular, reddish brown in outer part, colourless within, not inspersed with granules; epithecium reddish brown; hymenium colourless, 50-70 µm high, K/I+ blue; paraphyses simple, conglutinated, 1.5-2.5 µm thick, the apical cells 3-5 µm wide; hypothecium pale brown to almost colourless, 50-60 µm high. Asci 8-spored, Lecanora-type. Ascospores 1-celled (rarely 1-2-septate), hyaline, ellipsoid-cylindrical, thick-walled, 13-20(-28) x 5-7(-10) µm. Photobiont chlorococcoid. Spot tests: thallus K+ yellow then red (crystals, visible in a section under the microscope), C-, KC-, P- or P+ pale yellow; medulla UV-. Chemistry: norstictic acid.
Note: a mainly arctic-alpine, circumpolar lichen found on soil, mosses, plant remains and on other lichens in Alpine grasslands, mostly in sites with a long snow-lie, on siliceous substrata.
Growth form: Crustose
Substrata: soil, terricolous mosses, and plant debris