Distribution: C - Laz (Ravera 2001). S - Pugl (Nimis & Tretiach 1999), Bas (Nimis & Tretiach 1999, Potenza 2006, Potenza & al. 2010), Cal (Puntillo & Vezda 1994, Puntillo 1995, 1996, Grube & Giralt 1995).
Description: Thallus crustose, endosubstratic or thinly episubstratic, continuous to rimose, white to creamy white, effuse or delimited by a brown-black prothalline line. Apothecia arthonioid, scattered, rounded to irregular in outline, 0.4-1.3 mm across, more rarely elongate and c. 1.4 x 0.4 mm, >130 µm tall, flat and level with thallus or convex and raised, dark brown-black to black, epruinose but sometimes appearing grey, especially when young, due to fragments of bark on the surface. Proper exciple poorly developed; epithecium reddish brown, of mainly anticlinally arranged, brown-walled hyphae, K+ olivaceous, often covered with a 10-20 µm high, hyaline, gelatinous layer; hymenium colourless to yellowish brown, K+ pale green, I+ blue turning wine-red; paraphysoids anastomosing, branched in upper part, c. 1 µm thick, the apical cells 1.5-2 µm wide; hypothecium colourless, 10-30 µm high. Asci 8-spored, broadly clavate, semi-fissitunicate, with a large apical dome, and a distinct ocular chamber, the apex with a K/I+ blue, elongated ring structure and paler bluish tholus flanks, Arthonia-type. Ascospores (3-)4-septate, hyaline but often turning brown and faintly verruculose when overmature, clavate-obovoid, with one of the terminal cells enlarged, straight to slightly curved, (13-)15-18 x (4.5-)5-7 µm. Photobiont trentepohlioid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: thallus without lichen substances.
Note: only locally abundant in humid riparian forests of central and southern Italy, mostly on the smooth, base-rich bark of broad-leaved deciduous trees (e.g. Fraxinus). The species is included in the Italian red list of epiphytic lichens as “Vulnerable” (Nascimbene & al. 2013c).
Growth form: Crustose
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)