Distribution: N - Ven, TAA (Nascimbene & al. 2007b). C - Sar (Zedda & Sipman 2001, Neuwirth 2018).
Description: Thallus crustose, mostly endosubstratic, rarely superficial, thin, white to yellowish white. Apothecia lecanorine only when young, but soon appearing biatorine, rounded, broadly adnate, 0.4-0.7 mm across, with a pale to dark reddish brown, finally also grey-black, epruinose to strongly pruinose, flat to strongly convex disc, and a soon excluded, thin, smooth thalline margin; proper margin inconspicuous, cream-coloured, excluded in older apothecia. Proper exciple 40-75 μm wide laterally, strongly gelatinised, with a variable amount of crystals visible under polarized light and dissolving in K; epithecium brownish, with yellowish brown granules, sometimes with a greenish, N+ red-violet pigment, especially near the margins; hymenium 40-55 μm high, strongly inspersed with yellowish brown granules and with brown to green-black pigment streaks in upper part; paraphyses branched and sometimes anastomosing, 0.5-1.5 μm thick, the apical cells to 2 μm wide; hypothecium colourless, 50-130 μm high. Asci 8-spored, similar to the Micarea-type. Ascospores 1-celled, hyaline, ellispoid to broadly ellipsoid, 7-12.5 x (3-)4-5(-6) μm. Pycnidia black, semi-immersed, globose or pyriform, with a brown to dark greenish, N+ reddish walls. Conidia bacilliform, often slightly curved, 5-9 x 1-2 μm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: isousnic acid.
thallus with isousnic acid (major); apothecia with the Cinereorufa-green pigment.
Note: on decorticated trunks, more rarely on the bark of conifers in upland areas; probably more widespread in the Alps. The sample from Sardinia deviates in having paler apothecia and a yellowish epihymenium.