Thallus foliose, lobate, ± closely attached centrally, ± subascendent marginally, spreading, often in very large rosettes 5-20(-50) cm diam., corticolous, rarely saxicolous. Lobes broad, rounded, overlapping, sinuses shallow, evenly rounded, margins entire or weakly crenulate, sinuous, sometimes ascending or ± deflexed. Upper surface bright lettuce-green and brownish at margins when wet, dull olive-brownish to red-brown when dry, undulate to roughened-corrugate, not scrobiculate or faveolate, matt or shining, continuous, without isidia, soredia or pseudocyphellae, minutely scabrid-cracked centrally, in older specimens small secondary lobules may develop centrally. Medulla white, with internal cephalodia often visible as swellings on lower (occasionally also on upper) surface. Lower surface pale yellowish-buff, darker centrally, whitish in narrow marginal zone, very slightly thickened and dark brown at margins, glabrous, smooth or slightly wrinkled or roughened at margins, tomentose centrally, tomentum short, uniform, soft, pale buff, darker centrally, often with scattered, simple or squarrose, buff rhizines centrally. Apothecia laminal, often ± central, numerous, sessile to subpedicellate, disc red-brown, waxy, shining, shallowly to deeply concave, plane or ± undulate in mature fruits, to 8 mm diam., smooth, matt or shining, epruinose, thalline margin very massive, pale, corrugate-scabrid, inflexed when young obscuring the disc, entire to striate-areolate or weakly crenulate, thalline exciple coarsely warted-papillate, ± areolate, pale brown to yellowish-buff. Ascospores colourless, linear-acicular with pointed ends, 2-4-septate, 25-52 × 5-12 µm. Pycnidia rare to frequent, immersed, visible as small, brownish hemispherical swellings on upper surface, 0.1-0.5 mm diam., ostiole black, excavate, carbonaceous. Conidia straight, rod-shaped, 3 × 1 µm. Chemistry: Cortex K-; medulla K-, C+ red, KC+ red, Pd-. Gyrophoric acid.