Thallus to 30 cm long, pendant, often rather narrow, composed of usually 4-6 main branches arising from close to the point of attachment. Branches rather thin, 0.2-0.6 mm diam., mostly even in thickness, usually with many short to 1 cm long fibrils arising at right-angles from the main branches, regularly but unevenly distributed along their entire length in a fish-bone-like arrangement. Branching variously sympodial or dichotomous. Thallus surface typically grey-green, often darker in the older parts and blackened towards the base, which may be transversely cracked but not annellated. Main branches typically densely papillate and with tubercles, which usually produce abundant isidia or isidiomorphs and can also occur on side branches where they are usually less frequent, but are absent towards the apices which narrow to a point and are often laterally fractured into ± cylindrical segments. Soralia punctiform. Cortex thick, medulla dense to compact, axis relatively thick.
Anamorph: not known.
Teleomorph: ascomata (apothecia) rarely formed.
Chemistry: thallus C–, K+ yellow→red, KC–, Pd+ orange (salazinic and usnic acids).
A markedly pendulous species, very variable regarding the number of main branches (2-30); also varies in the abundance and shape of the tubercles and papillae, the formation of isidia, soredia and isidiomorphs, the frequency of associated fibrils, the degree of subsidiary branching, the presence of cylindrical segments and colour which may range from pale yellow-grey to dark green-black.
Richly branched, K– specimens with white tubercules probably belong to U. ceratina. Attempts to define new entities from this polymorphic species have proved unsuccessful; in the British Isles the various morphs appear to represent a continuum. The isidia arise from papillae which may occasionally become abraded and appear sorediate; such rare specimens may resemble U. ceratina.
In GB&I, reported from SW England, Ireland, Wales and Scotland.
On acid-barked trees, usually Pinus, Larix or Betula and more rarely Salix, especially in exposed mountain woods; locally abundant.