Synonyms: Squamaria valesiaca (Müll. Arg.) H. Olivier
Distribution: N - TAA, Piem (Clerc & al. 1999), VA (Piervittori & Isocrono 1999), Emil (Fariselli & al. 2020), Lig (Petrak 1960).
Description: Thallus crustose-placodioid, episubstratic, rimose-areolate, pale greenish yellow but densely pruinose throughout and appearing whitish to yellowish white, 0.1-0.5(-1) mm thick, forming regular rosettes 1-2(-4) cm in diam. Central areoles contiguous, 0.5-0.7 mm across, flat; marginal lobes flat to slightly convex, 1-2(-5 mm) long, 0.3-0.7(-1) mm wide, clearly radiating, moderately crenate-incised, with undulating margins. Cortex 20-30 µm thick, inspersed with greyish crystals insoluble in K, not overlain with an epinecral layer; medulla white, thickly inspersed with granules. Apothecia common, lecanorine, at first semi-immersed, then sessile, 0.5-1.5(-2) mm across, with a yellowish brown to brown, flat to convex, sometimes pruinose disc, and an entire to crenate, persistent, incurved margin level with disc, sometimes with an indistinct parathecial ring paler than disc. Amphithecium corticate, with an algal layer extending below the hypothecium, with coarse crystals insoluble in K in the medulla; parathecium pale grey in outer part, colourless or pale yellow in inner part; epithecium inspersed with fine yellow-brown granules soluble in K; hymenium colourless, 55-75 µm high; paraphyses mostly simple, scarcely thickened at tips; hypothecium colourless to yellowish. Asci 8-spored, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid to broadly ellipsoid, 9-12 x 4-7 µm. Pycnidia immersed, often inconspicuous. Conidia filiform, mostly curved, 15-20 µm long. Photobiont chlorococcoid. Spot tests: thallus K-, C-, KC- or KC+ pale yellow, P-. Chemistry: cortex with usnic acid; medulla with roccellic acid.
Note: on base-rich rocks (gneiss, porphyr, schists, etc.) containing some calcium, in warm-dry situations. For the non-accepted records from southern Italy see Nimis (1993: 373).
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)