Description: Thallus crustose, thinly episubstratic, continuous, whitish, with rounded to irregular, dark brown to blackish, 0.1-0.25 mm wide, flat to slightly convex, rough, sometimes confluent soralia. Soredia farinose, 12-20 µm in diam., with clusters of algal cells surrounded by short-celled hyphae (cells 4-8 x 2.5-4 µm); surface of outer soredial hyphae dark brown to blackish, but pale brown to more or less hyaline in inner part, K-, N-. Apothecia lecideine, black, 0.2-0.4 mm across, with a flat to slightly convex disc and a thin (20-30 µm), persistent proper margin, which sometimes appears whitish due to a thin layer of hyaline hyphae. Proper exciple brown in outer part, with capitate dark hyphae, colourless within, inspersed with oil droplets; epithecium brown, K-, N-; hymenium colourless, inspersed with oil droplets, 35-40 µm high; paraphyses simple or sparingly branched, 1.5-2 µm thick at mid-level, the apical cells 3-5 µm wide; hypothecium brown-green to brownish, 10-15 µm high, inspersed with oil droplets. Asci 8-spored, clavate, with a K/I+ blue outer coat and a K/I+ uniformly blue apical dome, Catillaria-type. Ascospores 1-septate, hyaline, oblong-ellipsoid, 10-12 x 3-3.5 µm, without a perispore. Photobiont chloroccoid. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a recently-described, apparently mainly western species of base-rich bark, also reported from Switzerland and the Czech Republic. To be looked for, especially in Tyrrhenian Italy.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)