Distribution: N - Frl (Baruffo & al. 2006), TAA (Ravera & al. 2019b), Piem (Baruffo & al. 2006), VA (Baruffo & al. 2006), Emil (Baruffo & al. 2006, Fariselli & al. 2020). C - Tosc (Baruffo & al. 2006, Benesperi & al. 2007), Sar (Baruffo & al. 2006).
Description: Thallus crustose to subleprose, whitish to whitish grey, up to 0.7 mm thick, entirely consisting in a mass of granules, usually well-delimited, sometimes indistinctly sublobate at margin. The thallus starts developing as isolated, dispersed granules that form piles, or aggregations (best visible along the margins, where the dispersion of the young granules is most readily observed) which eventually overlap and become confluent, giving the false appearance of a continuous thallus in older areas. Granules rather firmly attached, coarse, 60-260(-320) μm in diam., with a compact, pseudocorticate surface, rarely with a few, short projecting hyphae. Medulla absent or very thin. Photobiont chlorococcoid. Spot tests K+ yellow, C-, KC-, P+ yellowish, UV-. Chemistry: atranorin, rangiformic acid (major), norrangiformic acid (traces).
Note: a circumboreal species growing on siliceous rocks and over epilithic mosses, mostly on horizontal or weakly inclined surfaces wetted by rain, with optimum in the oroboreal to Alpine belts of the Alps, but also occurring in the high Mediterranean mountains.
Growth form: Leprose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)