Thallus 3-8 cm diam. (sometimes to 12 cm diam. or more in other regions), spreading, rarely fragmentary, loosely appressed. Lobes 2-5 (-10) mm wide, robust, often coriaceous, the margins entire, decumbent or ± reflexed, rarely developing small folioles and/or or forming larger lobules by regeneration. Upper surface grey-brown to deep red-brown, ± smooth or partly undulate, without reticulations, soredia and isidia lacking. Medulla pale to golden yellow (usually K+ purple). Lower surface matt, smooth to longitudinally striate-ridged to wavy, pale at margins, becoming brown-black towards the centre, without a tomentum. Photobiont cyanobacterial (Nostoc). Anamorph: conidiomata pycnidia, infrequent, in marginal verrucae. Conidia bacilliform, 4-5 x 1-2 µm in size. Teleomorph: ascomata apothecia, frequent; (2-) 4-7 (-10) mm diam., rounded to reniform, disc red-brown-black, the margin entire to rarely subcrenulate, with a + raised thalline cuff, the dorsal surface conspicuously scabrid-areolate and ridged. Ascospores 17-20 × 5-7 μm.
Chemistry: medulla K+ purple, rarely K– (anthraquinones, hopane triterpenoid T6).