Distribution: N - Emil (Nimis & al. 1996, Fariselli & al. 2020).
Description: Thallus areolate-subsquamulose, densely chalk-white-pruinose, forming patches to 5 cm diam. Areoles (2-)3-5(-6) mm wide, 0.2-2 mm thick, rounded, mostly convex, slightly lobed; lower surface attached by a few rhizines. Cortex densely filled with crystals visible under polarized light; algal layer continuous; medulla filled with crystals. Apothecia lecanorine, 1-2(-3) mm across, round, at first immersed, later sessile, with a flat to slightly convex, dark brown to almost black, epruinose disc, and a thick thalline margin. Epithecium yellowish brown, K+ yellow turning red (acicular crystals); hymenium colourless, 50-180 μm high, I+ blue; paraphyses coherent, simple to sparingly banched in upper part, 1.5-2.5 μm thick at base, the apical cell slightly swollen; hypothecium colourless, 40-85 μm tall, K+ yellow turning red (acicular crystals). Asci c. 100-spored. clavate, with a distinct apical dome, I . Ascospores 1-celled, hyaline globose or subglobose, 3-6 x 3-7 μm in diam. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC-, P-. Chemistry: apothecia with norstictic acid.
Note: a xeric subtropical species of weathered gypsum in open habitats, usually below the montane belt. To be looked for in other gypsum outcrops (e.g. in Sicilia).
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Subcontinental: restricted to areas with a dry-subcontinental climate (e.g. dry Alpine valleys, parts of Mediterranean Italy)