Description: Thallus crustose, mostly endosubstratic and inconspicuous, pale brown or olive-grey, sometimes with a pink hue when fresh. Apothecia arthonioid, immarginate, more or less immersed, rounded, shortly ellipsoid or weakly and irregularly lobed, 0.1-0.5 mm wide, 45-70 μm tall, with a dark brown to brown-black, epruinose, mostly flat disc. Epithecium yellowish brown to reddish-brown, c. 5 μm high, K+ purple-violet, the pigments dissolving; hymenium colourless to spottily pale orange-brown, the pigmented parts K+ purple-violet, 33-50 μm high; paraphysoids 0.5-1.5 μm thick, brown-walled, the apical cells to 2.5 μm wide; hypothecium red-brown, 5-30 μm high, the pigment K+ grey or olive. Asci 8-spored, subglobose, semi-fissitunicate, with a large apical dome and a distinct ocular chamber, Arthonia-type. Ascospores 1-septate and slightly constricted at septum, with subequal to unequal cells, at first hyaline and smooth, later brownish and warted, ovoid, (12-)14-18 x 4-8 μm, thick-walled, but without a gelatinous sheath. Pycnidia rare, immersed, the wall red-brown, K+ olive-grey. Conidia bacilliform, 3.5-4 x c. 0.7 μm. Photobiont trentepohlioid. Spot tests: K-, C-, KC-, P-. Chemistry: thallus without lichen substances; anthraquinones in pigmented parts of the apothecia.
Note: a cool-temperate species found on smooth, acid bark in humid areas, most frequent in the beech belt of Tyrrhenian Italy.
Growth form: Crustose
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)