Thallus 4-7 (-12) cm, decumbent; branches ca 1 mm diam., frequent, terete or slightly compressed towards the base, frequently with depressions; branching isotomic-dichotomous, the basal branches dying away, dark brown to black, the apices paler, olivaceous to pale brown, exceptionally concolorous with main stems; lateral spinules 2-7 mm, with slightly constricted bases, numerous, arising at right angles to main stems, frequently bow-like; soralia present, arising from pseudocyphellae, grooved, concave to flat; soredia often sparse, mixed with short spinules arising in tufts from the soralia.
Anamorph: not known.
Teleomorph: not known.
Chemistry: medulla and soralia C–, K–, KC–, Pd– (lichen products not detected by TLC).
Assessed by Woods & Coppins as Critically Endangered (B). It is a former BAP Priority Species.
A well-defined species, characterized by its soralia mixed with short spinules, and its Pd– reaction; it most resembles Bryoria bicolor, which lacks soralia, has a medulla which is Pd+ red, and is rarely on trees.
Now known only from two sites on Dartmoor (VC3 S Devon and VC4 N Devon).
On bark of Quercus petraea in ancient upland oak woods.