Description: Thallus crustose, episubstratic, areolate-verrucose, whitish to pale grey. Apothecia lecideine, sessile, 0.2-0.5(-0.7) mm across, with a flat to slightly convex, dark brown disc, and a thick, persistent proper margin. Proper exciple 30-45 μm wide laterally, aethalea-type, the dark outer part with hyphae with swollen cells. the paler inner part with hyphae similar in structure and orientation to the paraphyses; epithecium brown; hymenium colourless, 50-70 μm high, densely inspersed with oil droplets; paraphyses capitate, the apical cells 3-4(-5) µm wide, with a brown cap; hypothecium dark brown. Asci 8-spored, clavate, Bacidia-type. Ascospores 1-septate, brown with paler spore-ends, fusiform, (10-)11-15(-18) x (4.5-)5-6(-6.5) μm, Dirinaria-type, smooth, without a torus (ontogeny of type B). Conidia bacilliform, (5-)6-7 x c. 1 μm. Spot tests: thallus K+ yellow, C-, KC-, P+ faintly yellow. Chemistry: diploicin (major), atranorin (minor), isofulgidin (minor), fulgidin (trace) and an unknown substance.
Note: on acid bark, more rarely on lignum, in rather shaded and humid situations, with a western distribution in southern Europe. The species is included in the Italian red list of epiphytic lichens as “Endangered” (Nascimbene & al. 2013c). For further details see Giralt (2000).
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)