Description: Thallus subfoliose to subfruticose, grey to grey-brown, loosely attached. Lobes flattened, 0.3-0.5(-0.8) mm broad, several cm long, linear, with prominent marginal cilia. Lower surface whitish, channelled, ecorticate. Upper cortex prosoplectenchymatous. Apothecia rare, round, lecanorine, strongly constricted to substipitate, to 5 mm diam, with a black, often faintly pruinose disc and a grey to grey brown, usually spinulose thalline margin. Epithecium brown; hymenium and hypothecium colourless. Asci 8-spored, thick-walled, the apex I+ blue with a wide, divergent axial body, Lecanora-type. Ascospores 1-septate, brown, ellipsoid, constricted at septa, thin-walled (Physconia-type) and ornamented, 30-45 x 12-20 µm. Pycnidia dark, semi-immersed. Conidia short-bacilliform. Photobiont chlorococcoid. Spot tests: all negative. Chemistry: without lichen substances.
Note: confined to beech forests in rather open but humid situations. Perhaps just a morphotype of A. ciliaris (intermediate morphs are common): a molecular study could solve the problem. The species is included in the Italian red list of epiphytic lichens as “Vulnerable” (Nascimbene & al. 2013c).
Growth form: Fruticose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)