This lichen is easily overlooked as another black disk on twigs, but internally has very distinctive spores, which are thin-walled other than at the septum where they are much thickened. Once thought to be rare on coastal twigs, but now recorded widely through southern England.
Thallus thin, pale grey, continuous or rarely rimose and flat; prothallus inconspicuous. Apothecia 0.25–0.3 mm diam., sessile, rarely contiguous; thalline margin absent or poorly developed; true exciple brown or colourless, rarely continuous below the hypothecium, ca 50 µm thick, concolorous with the disc, or more rarely with the thallus, entire and persistent; disc black, persistently flat; epithecium dark brown; hymenium 60–80 µm tall; hypothecium 30–60 (–80) µm high, dark brown, I+ blue. Asci 40–45 × 17–19 µm. Ascospores 11.5–19 × 6.5–9.5 µm, thin-walled, thickened only at the septum, Orcularia-type (Fig. 1F). Pycnidia black, ca 80 µm diam. Conidia filiform, 12–15 × 0.8 μm. Lichen products not detected by TLC.
Characterised by the pigmented true exciple, brown hypothecium and Orcularia-type ascospores. Easily overlooked in the field, but the thallus is more developed than Catillaria nigroclavata and with care the poorly developed thalline margin on some apothceia can be made out, which separates it from Amandinea punctata.
On bark and twigs.
Local. S. and S.W. England, W. and central Wales, W. Ireland, Channel Islands. Found much more frequently recently; either spreading or previously much overlooked.
Until recently thought to be a rare species of twigs in coastal locations in the south west. Subsequently records have greatly increased and it has now been found inland and eastwards towards central England. Possibly spreading in response to warmer weather and or a decline acidifying pollution. The 2012 assessment of Data Deficient (i.e. so little known it could either be Threatened or Least Concern) no longer stands, as it is clearly not Threatened.
Britain: Data Deficient & Notable (both require reassessment)
Cannon, P., Prieto, M., Coppins, B., Sanderson, N., Scheidegger, C. & Simkin, J. (2021). Caliciales: Caliciaceae, including the genera Acolium, Amandinea, Buellia, Calicium, Diploicia, Diplotomma, Endohyalina, Monerolechia, Orcularia, Pseudothelomma, Rinodina and Tetramelas. Revisions of British and Irish Lichens 15: 1-35.
Text by Neil A Sanderson based on Cannon et al (2021)