Thallus 2-10(-15) cm tall, ± erect to decumbent-straggling, fragile, easily shattered when dry, stalked, attached to substrate by a root-like holdfast, stalk flattened to ± terete in lower part, ± canaliculate above, 1-3 mm diam and 3-20 mm tall, expanded above into a dissected, frond-like lobe. Lobes narrow, ± laciniate 2-4 mm wide, to expanded, 10-15 mm wide, margins crenate- incised or ragged or irregular, ± thickened, ± densely isidiate. Isidia minute, dark brown or greyish-blue, shining, style-forming, ± terete, delicate at first, densely clustered, becoming coralloid-lobulate and eventually ± phyllidiate, dorsiventral with age, primarily marginal, also developing on lamina and thallus fissures and rents, eventually becoming confluent in a diffract crust. Upper surface dark greyish-blue to black or dark red-brown when wet, dull brownish- grey when dry, often white-maculate (×10 lens) in parts, smooth, undulate to ± shallowly faveolate in parts, often cracked, torn or ± fenestrate, stalk dark brown-black. Lower surface dark brown, occasionally pale buff near margins, tomentose, tomentum uniform, thick, brown. Cyphellae white, round to irregular, rather sparse, sunk in tomentum, 0.1-1.8 mm diam. Apothecia not seen.