Thallus closely attached, rarely forming regular or irregular rosettes, commonly compacted to encircle small twigs, to 10 cm diam., usually smaller, corticolous, best developed on twigs. Lobes numerous, usually small to medium, 1-2.5(-3) mm wide, on flat surfaces ± radiating at margins, main lobes ± obscured by short, overlapping secondary lobes, on twigs lobes imbricate-congested, sometimes lacking radiating marginal lobes. Marginal lobes irregularly branched, contiguous or ± imbricate throughout their entire length, margins sinuous-contorted or notched, sometimes zig-zag interlocking, sometimes blackened. Lobes hollow, lower side of internal cavity grey-white, lobe ends concolorous, often suffused-brownish. Upper surface plane, becoming ± convex, especially in areas of mutual compression, matt or shining, often finely rugose in older parts, grey or dull green-grey, often ± suffused or minutely spotted red-brown or dark brown but remaining greyish in shaded parts of thallus, without isidia or soredia. Perforations scattered, often rather sparse, small, c. 1.0 mm diam., rim depressed. Apothecia abundant, ± crowded in twig specimens, sometimes obscuring thallus, sessile or subpedicellate, (1-)2-4(-9) mm diam., disc concave at first, becoming ± plane at maturity, slightly roughened, shining, epruinose, red-brown or brown, margins thick at first becoming thin at maturity, entire, even or sometimes ± angular, shining, rarely sparingly thinly lacerate, entirely grey or ± red-brown-maculate or entirely brown. Epithecium 35-50 µm tall, densely red-brown granular. Asci 2-spored, ellipsoid or truncate-ellipsoid, 85-95 × 40-45 µm. Ascospores (43-)45-50(-56) × 27-35 µm, walls noticeably thickened when immature, 5-7 µm, thin at maturity, 3.5-4.5 µm thick. Chemistry: Atranorin (cortex), stictic, hypostictic and hyposalazinic acids; medulla K+ yellow → red, C-, KC+ red, Pd+ orange.