Description: Thallus crustose, grey-white, thin, continuous, ecorticate, becoming waxy and pruinose in the herbarium. Apothecia zeorine/biatorine, frequent, 0.3-0.5(-0.8) mm across, often crowded, round to slightly crenulate, first immersed, then sessile, with an initially concave, then mostly flat to finally convex, bright orange disc, a concolorous or slightly paler, finally excluded proper margin, and sometimes a poorly developed, whitish thalline margin enveloping the sides of young apothecia. Epithecium orange, K+ red; hymenium and hypothecium colourless; paraphyses sometimes branched in upper part, lax, the apical cells often swollen, to c. 4.5 μm wide. Asci 12-16-spored, cylindrical-clavate, functionally unitunicate, apically thickened with a broad internal beak, the inner part of apex and external cap I+ blue, Teloschistes-type. Ascospores 2-celled, polarilocular, hyaline, biseriate, ellipsoid, (7.5-)9-12(-14) x 3-6.5 μm, the equatorial thickening (“septum”) c. 1 μm (c. 1/8 of spore length). Pycnidia orange-red, often slightly erumpent. Conidia 3-4 x c. 1 μm, cylindrical with rounded ends, straight. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-; apothecia K+ red. Chemistry: thallus without lichen substances; apothecia with parietin (major), fallacinal, emodin, teloschistin and parietinic acid (minor), corresponding with chemosyndrome A of Søchting (1997).
Note: a temperate species found on base- or nutrient-rich bark (e.g. very common on Sambucus or on Juglans in open habitats), with optimum in the submediterranean belt. See also note on A. cerinelloides.