Distribution: N - TAA (Knudsen & al. 2015), VA (Piervittori & Isocrono 1999, Knudsen & al. 2015).
Description: Thallus crustose, episubstratic, areolate-subsquamulose, densely white-pruinose. Areoles 0.5-1(-2) mm wide, 0.3-0.6 mm thick, at first flat, then convex and fissured, dispersed or usually contiguous and separated by deep fissures, redddish brown, but almost always appearing white due to a thick layer of pruina, the margin most often dark. Epicortex to 30 µm thick, with small crystals dissolving in K; cortex 20-70 µm thick, brown in upper part, colourless in lower part, the cells mostly 3-4 µm wide; algal layer continuous; medulla white, to 0.4 µm thick, I-. Apothecia lecanorine, immersed, 0.3-1 mm across, with a black to brown-black sometimes slightly pruinose disc and a thick, often radially fissured thalline margin. Proper exciple prosoplectenchymatous, I-; epithecium brown; hymenium (80-)120-150 µm high, I+ blue rapidly turning red-brown, K/I+ blue; paraphyses 1-3 µm thick, the apical cells hardly swollen; hypothecium thin, colourless. Asci 100-200-spored, clavate, the apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid, 6-9(-12) x 2.5-3.5(-4) µm. Pycnidia immersed. Conidia simple, ellipsoid, c. 2 x 1.5 µm. Photobiont chlorococcoid. Spot tests: thallus and medulla K-, C-, KC-, P-. Chemistry: without lichen substances.
Note: on weathered base-rich siliceous rocks, restricted to dry-warm Alpine valleys with a continental climate. Superficially similar to A. versicolor, but a different species (Knudsen & al. 2015).
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Subcontinental: restricted to areas with a dry-subcontinental climate (e.g. dry Alpine valleys, parts of Mediterranean Italy)