Distribution: N - Frl, Ven (Nascimbene & Marini 2010), Lomb. S - Camp, Bas.
Description: Thallus crustose, episubstratic, smooth, continuous, yellowish white to grey-white. Apothecia arthonioid, at fist semi-immersed, then slightly protruding, rounded, elliptical or weakly lobed, 0.5-1 mm across, with an initially flat, but soon convex to hemispherical, black but heavily bluish-pruinose disc, without a proper margin. Proper exciple poorly developed, of brown hyphae; epithecium brownish; hymenium colourless or yellowish, 50-80 µm high, I+ red; paraphysoids thin, branched and anastomosing, the apical cells only slightly swollen; hypothecium colourless or very pale yellowish brown. Asci (6-)8-spored, clavate to subglobose, semi-fissitunicate, with a large apical dome and a distinct ocular chamber, Arthonia-type. Ascospores (2-)3-4-septate, pointed at one end, with the opposite terminal cells distinctly enlarged, hyaline or pale brown when overmature, 11-18 x (4-)5-7 µm. Pycnidia numerous, black, more or less immersed. Conidia bacilliform, straight, 4.5-6 x 0.5-1 µm. Photobiont trentepohlioid. Spot tests: thallus K- or K+ faintly yellow, C-, KC-, P+ yellow-orange. Chemistry: thallus with psoromic acid.
Note: a mild-temperate species found on smooth bark of deciduous trees in dense humid forests. The old records from Campania and Basilicata (see Nimis 1993: 74) need re-confirmation. The species is included in the Italian red list of epiphytic lichens as “Critically Endangered” (Nascimbene & al. 2013c).