Thallus foliose, adnate, to 5–8 (–12) cm wide. Lobes imbricate, flat, linear-elongate to subirregular, irregularly branched, 1.5–4 (–8) mm wide; apices elongated or crenate and subrotund. Upper surface yellow-green to deep olive-green, sometimes blackening, shiny becoming dull, emaculate, smooth, without soredia; lobe margins often black; isidia usually dense, cylindrical, usually becoming densely branched and coralloid, often forming a dense isidiose mat; isidia apices syncorticate, intact, commonly black. Medulla white. Lower surface black, fading to black-brown or brown at apices of marginal lobes; rhizines sparse, simple, concolorous. Apothecia sessile, 2–4 (–7) mm wide; disc concave, brown to dark brown; thalline exciple isidiate. Ascospores 7–9 × 4.5–7 µm. Pycnidia rare. Conidia bifusiform, 5–6 ×0.5 µm. CHEMISTRY: cortex K-, UV-; medulla K+ yellow then dark red, C-, KC-, P+ intense yellow; containing usnic acid, norstictic acid (major), ±salazinic acid (trace) and ±connorstictic acid.