Thallus 2-8(-20) cm tall, at first erect, ± tufted, sometimes ± becoming pendulous. Main branches to 1.5 mm diam., cylindrical, not inflated, branching irregular, isotomic-dichotomous with numerous laterals of unequal length. Surface pale to dark grey-green, usually conspicuously blackened at the base, with minute transverse cracking without interconnecting longitudinal cracks. Main branches often densely papillose especially towards the base, occasionally with white, rounded or oval abraded areas, terminal parts and fibrils smooth with scattered papillae and pseudocyphellae giving rise to ± tuberculate, irregularly rounded soralia with coarsely granular soredia. Soredia usually intermixed with secondarily ± corticate isidiomorphs which tend to persist on mature soralia. Medulla dense.
Anamorph: not known.
Teleomorph: ascomata (apothecia) occasional.
Chemistry: two chemotypes occur: (a) C–, K+ yellow, KC–, Pd+ yellow-orange (instantly), UV– (thamnolic and ± alectorialic acid, especially associated with apothecia); (b) C–, K–, KC–, Pd–, UV+ whitish blue (squamatic and usnic acids). Occasionally specimens with no or very low concentrations may be encountered.