Distribution: N - Emil (Nimis & al. 1996, Fariselli & al. 2020). C - Marc (Nimis & Tretiach 1999), Umb (Nimis & Tretiach 1999, Ravera & al. 2006, Panfili 2007), Mol (Nimis & Tretiach 1999, Caporale & al. 2008), Sar. S - Pugl (Nimis & Tretiach 1999), Si (TSB 21465).
Description: Thallus crustose, endosubstraic or rarely very thinly episubstratic, grey, usually inconspicuous. Apothecia cryptolecanorine, broadly attached, often crowded or in groups of 2-4, round to irregular in outline by mutual compression, 0.2-0.4(-0.6) mm across, with a concave to flat, smooth, brown, reddish brown to rarely brown-black, epruinose disc, and a concolorous, thin, persistent, usually slightly raised, smooth, entire or slightly crenate, epruinose or slightly grey-pruinose margin. Thalline exciple 80-90 μm thick, corticate, the algal cells sparse or concentrated in the lower part, usually absent in upper part, giving the apothecia a biatorine appearance; cortex of adglutinated hyphae or prosoplectenchymatous, the external hyphae enlarged and blue-green, with sparse granules throughout or in outer part only; proper exciple distinct, thin; epithecium brown or olive-brown, K-, sometimes with sparse granules partly soluble in K and soluble in N; hymenium colourless, 45-60 μm high; paraphyses coherent, slender, simple or sparingly branched, the apical cells slightly expanded; hypothecium colourless, 40-50 μm high, without granules. Asci (4-)8-spored, clavate, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type Ascospores 1-celled, hyaline, broadly ellipsoid to ellipsoid, 6-14 x 4-8 μm. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-. Chemistry: with variable amounts of variolaric acid.
Note: a mild-temperate to Mediterranean lichen which is easily overlooked, most frequent on branches of Fraxinus, Populus and Sambucus; probably more widespread throughout Italy.