Thallus filamentous, forming wefts or mats, often in small circular patches, the margin not delimited, of elongated but contorted, nodulose hyphae, closely surrounding and adhering to single filaments of the photobiont. Hyphal filaments numerous, spiky or wiry, 12-17 μm diam., very dark brown to sooty black, contorted, with randomly arranged branches, the mycobiont cells ca 4 µm diam., short and elongate-epidermoid with strongly thickened walls, I+ blue-black. Photobiont Trentepohlia.
Ascomata and conidiomata not known.
Chemistry: no lichen products detected by TLC.
Assessed by Woods & Coppins as of Least Concern.
Distinguished from the macroscopically indistinguishable Racodium rupestre by the epidermoid rather than cylindrical mycobiont cells making up the filaments.
SW & N England (Dartmoor, Peak District, Pennines), Wales, W Scotland. BLS map here.
On siliceous rock faces (rarely on tree trunks), in situations where the air is persistently humid but not directly wetted by water; mainly upland.