Synonyms: Arthonia dalmatica Zahlbr.; Arthonia neglecta Bagl. in Rabenh.
Distribution: N - Emil (Thiyagaraja & al. 2020, Fariselli & al. 2020), Lig (Sundin 1999, Watson 2014). C - Tosc, Laz, Sar. S - Camp.
Description: Thallus crustose, endosubstratic or thinly episubstratic, greyish white-pruinose, sometimes delimited by a poorly developed, dark prothallus. Apothecia arthonioid, rounded to ellipsoid, c. 0.2-0.5 mm wide, black, adnate, slightly erumpent from thallus. Proper exciple poorly developed; epithecium olivaceous brown, 20-25 μm high, K/I+ blue; hymenium colourless, (20-)30-50 μm high, I and K/I+ blue; paraphysoids branched and anastomosing, 1-1.5 μm thick, pale yellowish, densely arranged, the apical cells swollen and brown, 1.5-2 μm wide; hypothecium colourless to pale yellowish, poorly developed, 5-15 μm high. Asci 8-spored, broadly clavate to ovoid, semi-fissitunicate, with a large apical dome, a distinct ocular chamber, the apex with a K/I+ blue ring-structure. Ascospores (0-)3-septate, not constricted at septa, with almost equal loculi, hyaline, spindle-shaped to ovoid, 11-17 x 4-6 μm. Pycnidia black, semi immersed. Conidia straight, 3-5 x 1-2 µm. Photobiont probably absent. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: not known, but probably thallus without lichen substances.
Note: a mainly Mediterranean early coloniser of subacid to subneutral bark, e.g. of Fraxinus ornus and Ficus, but also reported from conifers, not lichenised.