Distribution: N - Piem (Isocrono & al. 2004), VA (Piervittori & Isocrono 1999), Lig (UPS-L-670367). C - Sar. S - Si (Calatayud & Rambold 1998, Campisi & al. 2020).
Description: Thallus crustose, episubstratic, areolate, 0.2-0.3 mm thick, brown, somewhat shiny, often delimited by a pale prothallus, forming large patches to several cm in diam. Areoles contiguous, slightly concave to flat, angular, very irregular in outline, 0.3-0.8 mm wide, with a slightly raised, whitish-grey margin. Upper surface with an up to 20 µm thick epinecral layer, cortex 10-25 µm thick, brown in upper part; medulla white, I+ blue. Apothecia cryptolecanorine, immersed, 1 per areole, 0.2-0.3(-0.4) mm across, round to very irregular in outline, with a brownish black, epruinose, flat disc, and a whitish-grey thalline margin, the proper margin corresponding to the phenocortex and algal layer of the areoles. Proper exciple very thin, poorly developed; epithecium brown to greenish brown, c. 10 µm high; hymenium colourless, 100-110 µm high, I+ blue; paraphyses branched and anastomosing, 1.5-2 µm thick at base, the apical cells 3-5 µm wide; hypothecium colourless, c. 50 µm high, underlain by an algal layer. Asci 8-spored, narrowly cylindrical-clavate, with a I+ blue tholus and an internal, darker I+ tubular structure, the external gel I+ faintly blue, Porpidia-type. Ascospores 1-celled, hyaline, ellipsoid, 8-18 x 5-9 µm, halonate, non-amyloid. Pycnidia dark, immersed in the areoles, sometimes with a prominent ostiole. Conidia bacilliform. Photobiont chlorococcoid. Spot tests: K-, C+ faintly red, KC+ faintly red, P-. Chemistry: gyrophoric acid.
Note: an arctic-alpine lichen of siliceous rocks starting the life-cycle on Buellia-species; most frequent in the Alps above treeline, extremely rare in southern Italy. Records from lowland areas published after Nimis (1993) are certainly due to misidentifications, and are not cited here.