Description: Thallus foliose, heteromerous, dorsiventral, rather loosely attached, forming 4-12 cm wide, regular or irregular rosettes, the lobes swollen, hollow inside, 2-6 mm wide, sometimes with lateral, much smaller lobules. Upper surface grey to grey green, sometimes with a brownish hue especially in peripheral parts, strongly folded in central parts, with diffuse to pustulate soredia originating from the folds; lower surface jet black, except in the brown marginal parts, rugose, erhizinate. Upper cortex of tightly packed, more or less anticlinally oriented hyphae, the cell walls with Cetraria-type lichenan; medulla soon becoming hollow, lining the cavity inside the lobes; lower cortex dark, paraplectenchymatous. Apothecia lecanorine, 5-17 mm across, stipitate, the stipes 3-9 mm high, with a brown, imperforate, concave to convex, often cracked disc and a smooth, persistent thalline margin. Epithecium brown; hymenium colourless, 25-35 μm high; paraphyses coherent, simple or sparingly branched in upper part, 2-3 μm thick; hypothecium colourless. Asci 8-spored, clavate, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 4.5-7 x 2.5-5.5 μm. Pycnidia black, immersed. Conidia cylindrical, 4-7 x 1-1.5 μm. Photobiont chlorococcoid. Spot tests: upper cortex K+ yellow, C-, KC+, P- or P+ faintly yellow; medulla K-, C-, KC+ pink, P-. Chemistry: upper cortex with atranorin and chloroatranorin; medulla with physodic acid and 2 unknown compounds.
Note: a species of the Mediterranean mountains, also known from Morocco, Macaronesia, Serbia and Turkey, found on acid bark in humid montane forests.
Growth form: Foliose, narrow lobed
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)