Distribution: N - Frl, Ven (Nimis 1994), TAA (Nascimbene 2008b, Nascimbene & al. 2022), Lomb (Dalle Vedove & al. 2004), Piem (Isocrono & al. 2004), Emil (Fariselli & al. 2020). C - Tosc, Abr (Nimis & Tretiach 1999), Sar.
Description: Thallus squamulose, very thick, forming up to more than 10 cm wide patches. Squamules 1-5 mm wide, pale brown but densely white-pruinose, becoming darker when wet, more or less convex, contiguous to overlapping, the peripheral ones more flattened, longer and slightly lobulate; lower surface pale brown. Upper cortex paraplectenchymatous, well delimited against the thick, white medulla. Apothecia rather rare, rounded, lecanorine, sessile, strongly constricted at base, 2-10 mm across, with a concave to flat, pale brown, initially pruinose disc, and a thick, irregularly crenulated thalline margin. Epithecium brownish, granular; hymenium colourless, I+ blue; paraphyses slightly thickened above; hypothecium colourless. Asci 8-spored, clavate to cylindrical-clavate, the apical dome K/I+ dark blue, the wall I-, but the thin outer gel I+ blue, Bacidia-type. Ascospores 1-celled, hyaline, ellipsoid, 11-18 x 4-6 µm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P ; medulla P+ yellow. Chemistry: cortex with usnic acid, medulla with psoromic acid.
Note: on steeply inclined surfaces of calcareous rocks with short periods of water seepage after rain, mostly near and above treeline; rarer in the Apennines than in the Alps, to be looked for in the mountains of southern Italy.