Description: Thallus foliose, heteromerous, dorsiventral, appressed to tightly adnate, forming up to 10 cm wide rosettes. Lobes contiguous, flat, 3-8 mm wide, with rounded apices. Upper surface yellowish green, turning brownish in the herbarium, smooth to weakly wrinkled, frequently maculate, often with very small, punctiform pseudocyphellae. Soredia white, farinose to granular, arranged into crescent- to lip-shaped soralia along the reflexed, wavy lobe margins, rarely laminal. Lower surface smooth to finely wrinkled, dark brown at margin, black in central parts, with simple or rarely forked, short, dark rhizines which usually lack in the marginal zone. Upper cortex paraplectenchymatous, with a non-pored epicortex, the cell walls with an intermediate type of lichenan; medulla white; algal layer continuous; lower cortex paraplectenchymatous. Apothecia rare, lecanorine, with a brown disc and an often sorediate thalline margin. Epithecium brownish; hymenium and hypothecium colourless. Asci 8-spored, clavate, Lecanora- type. Ascospores 1-celled, hyaline, ellipsoid, 9-12 x 5-7 µm. Pycnidia black, rare. Conidia straight, bifusiform, 7-11 µm long. Photobiont chlorococcoid. Spot tests: upper cortex K+ yellowish, KC-, C-, P-; medulla K-, C+ red, KC+ red, P-. Chemistry: upper cortex with usnic acid; medulla with lecanoric acid (major) and +5-chlorolecanoric acid (minor or trace).
Note: a mainly epiphytic species, restricted to Alpine valleys with a continental climate, certainly very rare in Italy. It is included in the Italian red list of epiphytic lichens as “Endangered” (Nascimbene & al. 2013c).
Growth form: Foliose, broad lobed
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly asexual, by soredia, or soredia-like structures (e.g. blastidia)
Subcontinental: restricted to areas with a dry-subcontinental climate (e.g. dry Alpine valleys, parts of Mediterranean Italy)