Syst. Lich. Germ.: 276, 1855. Basionym: Lichen abietinus Ach. - K. Vetensk.-Akad. Nya Handl., 16: 139, 1795.
Synonyms: Lecanactis illecebrosa var. megaspora G. Merr.; Lecanactis megaspora (G. Merr.) Brodo; Lecidea abietina (Ach.) Ach.; Pyrenotea leucocephala (Ach.) Fr.; Schismatomma abietinum (Ach.) A. Massal. non (Humb.) Almq.
Distribution: N - Frl (Tretiach 1993, Egea & Torrente 1994), TAA (Nascimbene & al. 2007b), Piem. C - Tosc (Benesperi & al. 2007), Abr (Stofer 2006).
Description: Thallus crustose, thinly episubstratic, continuous to rimose, white, grey-white or rarely cream-coloured, often with a violet hue. Apothecia not always present, round to irregular in outline but never lirelliform, constricted at base, 0.5-2 mm across, with a flat to slightly convex, brown-black but yellowish grey-pruinose disc, and a thin, initially raised, finally often excluded proper margin. Proper exciple brown-black, extending below the hymenium, the outer hyphae completely encrusted with granules which dissolve in K, giving rise to needle-like crystals; epithecium ochraceous brown, thin, granulose; hymenium colourless, (65-)90-110 µm high, not inspersed with oil droplets, I+ reddish or I+ blue in the upper and lower parts, K/I+ blue; paraphysoids branched and anastomosing, 1.5-2 µm thick, the apical cells 3-4 µm wide; subhymenium brownish, 25-50 µm high; hypothecium brown-black, K+ greenish. Asci 8-spored, cylindrical-clavate, fissitunicate, the apex with a K/I+ pale blue apical dome penetrated by a small ocular chamber, and a poorly evident I+ blue ring-structure. Ascospores 3(-4)-septate, hyaline, acicular-fusiform, curved, (25-)28-40(-46) x 3-6 µm, with a very thin, usually not evident gelatinous perispore. Pycnidia usually abundant, especially in sterile specimens, prominent, hemispherical to short-cylindrical, covered with a whitish pruina at least at the top, the wall K+ green. Microconidia 9-15 x 0.8-1.2 µm; macroconidia (11-)12-17(-20) x 2-3.5(-4) µm, both straight or slightly curved. Photobiont trentepohlioid. Spot tests: thallus K-, C-, KC-, P-; pruina of the pycnidia C+ red; medulla UV+ yellow- or glaucous-grey. Chemistry: lecanoric and schizopeltic acids, plus an unknown UV+ substance in the medulla.
Note: a cool-temperate lichen, mostly found in mixed montane forests with Abies, on dry undersides of trunks and old branches, in crevices of the bark, much more rarely on old Quercus. It is included in the Italian red list of epiphytic lichens as “Endangered” (Nascimbene & al. 2013c).