Description: Thallus crustose, endosubstratic, pale to (rarely) dark brown, poorly evident, facultatively lichenized. Perithecia black, 0.15-0.3 mm across, circular or elliptical in outline, often with a depressed ostiole. Involucrellum dimidiate, brown, K-, of thick-walled hyphae extending into the surrounding bark tissues; exciple colourless throughout; interascal tissue absent or pseudoparaphyses soon gelatinized, but the ostiolar region lined with short, 7-15 x 1-1.5 μm, unbranched periphysoids oriented downwards; hymenial gel sometimes I+ pale blue. Asci 8-spored, obpyriform to saccate, thick-walled and fissitunicate with rostrate dehiscence, 33-45 x 14-20 μm. Ascospores 1-septate, constricted at septum, each cell often biguttulate, the lower cell sometimes with a median constriction, hyaline, biseriately arranged in the asci, (12-)14-17(-21) x 4-5.5 μm, with a very narrow or indistinct gelatinous sheath. Pycnidia rare, black. Conidia 1-celled, narrowly ellipsoid or bacilliform, 3-4 x c. 1 μm. Photobiont absent or trentepohlioid. Spot tests: all negative. Chemistry: without lichen substances.
Note: a temperate coloniser of the smooth bark of deciduous trees and shrubs, especially Carpinus and Corylus, most frequent in upland areas. Thalli vary from having no detectable to abundant Trentepohlia. The species was probably mistaken for A. punctiformis and related species in the past. It is included in the Italian red list of epiphytic lichens as “Near-threatened” (Nascimbene & al. 2013c). See also note on A. coppinsii and A. tuscanensis.
Growth form: Crustose
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)