(provisionally placed here, ICN Art. 36.1b). Basionym: Caloplaca aetnensis B. de Lesd. - Bull. Soc. Bot. France, 82: 317, 1935.
Synonyms: Caloplaca aetnensis B. de Lesd.; Pyrenodesmia aetnensis (B. de Lesd.) S. Y. Kondr.
Distribution: C - Tosc (TSB 18723). S - Si (Loppi & al. 1997, Ottonello & Puntillo 2009).
Description: Thallus crustose, episubstratic, white, thick, areolate. Areoles flat to convex, contiguous to scattered, more or less smooth, white-pruinose, usually forming a large crust. Apothecia common, lecanorine/zeorine, rounded, sessile, slightly constricted at base, up to 1.5 mm across, with a bright rusty red, flat to convex disc, a thick, somehow paler proper margin, and a white thalline margin which is well-evident only in young apothecia. Proper exciple orange in outer part, colourless within, the pigmented parts K+ red, C+ purple in section; epithecium orange-brown, K+ red, C+ purple; hymenium colourless, 70-90 μm high; paraphyses simple or sparingly branched, thickly septate towards the tips, the apical cells to 4 μm wide. Asci 8-spored, cylindrical-clavate, Teloschistes-type. Ascospores 1-septate, polarilocular, hyaline, ellipsoid 12-18 x 7-10 μm, the septum 1/4-1/5 of spore length. Pycnidia red, immersed. Conidia ellipsoid, 1-celled. Photobiont chlorococcoid. Sopt tests: thallus K-, C-, KC-, P-; apothecia K+ red, C+ purple (both disc and proper margin). Chemistry: thallus without lichen substances; apothecia with chlorinated anthraquinones in both margin and disc: 7-chloroemodin (major), fragilin and emodin (minor), sometimes traces of parietin.
Note: a Mediterranean lichen found on soil deriving from volcanic base-rich rocks, more rarely directly on soft rocks, common only in parts of Sicily, especially in the small volcanic islands, clearly related to Kuettlingeria erythrocarpa.