A lichen of dry bark on veteran Oaks with a sub-oceanic distribution in Europe. It has an extensive whitish thallus with scattered black urceolate pycnidia, the white pruinose walls giving the impression of a neat white cuff-like thalline rim to the pycnidia. All parts K−, C−, KC−, Pd−. Appears to be very rare in Britain with single sites known in England (Shropshire) and Wales (Cardiganshire), but potentially overlooked as sterile Lecanactis abietina, which occurs in the same habitat, but this has C+ red pycnidia, which are also much less fluffy. This lichen should be looked for elsewhere on veteran Oaks in the less oceanic parts of the country.
See ITALIC 6.0, Atlas of Czech Lichens and Frisch et al (2015) The Lichenologist. 47: 233 - 256.
Thallus extensive, bright whitish grey to pale fawn, continuous, rimose or evanescent, largely immersed, the surface ecorticate, matt, scurfy to weakly felted-arachnoid, sometimes patchily granulose; prothallus absent. Apothecia (not known in British material) adnate, rounded to slightly undulate in outline, weakly to strongly convex, densely white-pruinose, 0·4–1 mm diam. and 110–200 μm tall; epithecium 10–25 μm tall, greyish to brown, inspersed with pale granular crystals 1–3 μm diam.; hymenium colourless to pale yellowish brown, 45–65 μm tall, only moderately gelatinized; hypothecium dark brown, 50–120 μm tall; paraphysoids 1–1·5 μm diam., the apices slightly widened to ca 2 μm diam., with sparse dark brown pigment attached to the outer wall; asci clavate to broadly clavate, 37–46 × 15–19 μm; ascospores obovoid, (11–) 13·5–16·5 (–19) × (4–) 4·5–5·5 (–6) μm, (2–) 3–4 (–5)-septate, with a slightly enlarged apical cell. Pycnidia emergent, 0·15–0·4 mm diam., dark brown to black but covered by a thick whitish pruina; conidia bacilliform, (4–) 4·5–6 × 1–1·5 µm. Thallus, apothecia and pycnidial pruina K−, C−, KC−, Pd−, thallus hyphae I+ pale blue, KI+ pale blue.
Recognised by its thin whitish thallus with scattered black urceolate pycnidia, the pruinose walls giving the impression of a neat white cuff-like thalline rim to the conidiomata.
On dry bark of veteran Oaks
Single sites in England (Shropshire) and Wales (Cardiganshire), sterile at both.
Although first found in 2012, this lichen has only been found in two sites on single Oaks since, but was still extant on the Shropshire tree in 2025. Although probably over looked to an extent, it appears to be very rare and threatened.
Britain: Vulnerable
Cannon, P., Ertz, D., Frisch, A., Aptroot, A., Chambers, S., Coppins, B. J., Sanderson, N. A., Simkin, J. & Wolseley, P. (2020) Arthoniales: Arthoniaceae, including the genera Arthonia, Arthothelium, Briancoppinsia,Bryostigma, Coniocarpon, Diarthonis, Inoderma, Naevia, Pachnolepia, Reichlingia, Snippocia, Sporodophoron, Synarthonia and Tylophoron. Revisions of British and Irish Lichens 1: 1 - 48
Text by Neil A Sanderson, based on Cannon et al (2020)