Thallus normally ± stiffly pendent, often long and straggling, to 30 cm long, juvenile specimens more erect and tufted, rigid, pale or blackened at the base, annular cracks abundant and conspicuous. Main branches coarse, to 1.5 mm diam., of uniform thickness, only tapering at apices, typically rather straight when well-developed or somewhat twisted, often ± angular; branching usually sparse, occasionally with numerous, irregularly arranged lateral branches, with scattered or sometimes abundant, single or clusters of thin fibrils to 1 cm in length arising at right-angles to branches. Surface dark grey-green, glossy and vitreous (glassy) in appearance, conspicuously and coarsely warted with numerous white, raised ± hemispherical tubercles, these often bursting to form coarsely granular, ulcerose soralia and occasionally isidiomorphs. Main branches also with smaller, low, translucent, paler papillae. Medulla very compact, pale to deep pink, rarely white.
Anamorph: not known.
Teleomorph: ascomata apothecia, rare, lateral on main branches, the disc with a few marginal fibrils.
Chemistry: thallus C+ yellow-orange, K–, CK+ yellow-orange, Pd– (diffractaic, barbatic and usnic acids and ± several accessory substances).
In the UK as a whole considered to be of Least Concern, but Listed under Section 2(4) of the Nature Conservation (Scotland) Act 2004 due to its restricted distribution in that territory.
Diagnostic features include the pendant habit and the pink (not white) axis and medulla; care needs to be taken as the pigmentation may be subtle. Also characterized by the rigid, ± inflexible, coarse, scabrid texture and conspicuous white tubercles, often bursting with coarse soredia. Young thalli can be identified by their flesh-coloured to pink medulla (almost white when the pigment is in low concentration) and the presence of barbatic and diffractaic acid (CK+ yellow-orange).
Richly branched morphs may resemble U. filipendula but that species is usually more regularly branched, with a fish-bone-like appearance, lacks conspicuous white, hemispherical tubercles which become eroded and sorediate, has a K+ red medulla and is usually abundantly spinulose-isidiate on the main branches, especially towards the holdfast. Small, erect, pollution-damaged specimens superficially resemble U. cornuta which, however, has a lax medulla, persistently colourless axis and a different chemistry.
In GB&I, recorded from S & SW England, Wales and Ireland, rarely found in S Scotland (Dumfries & Galloway).
On acid-barked old trees, particularly Quercus and Fagus, in relict woodlands and parklands where it is characteristic of well-lit sites on trunks of ancient trees particularly along waysides and in glades, also often on inclined or horizontal trunks and boughs in thin tree canopies; locally frequent in the south and west.