Description: Thallus squamulose, heteromerous, brown, grey-brown or green-brown, dark green when wet, forming dense pillows of imbricate squamules. Squamules 0.5-2.5 mm wide, concave to flat, crenulate-lobulate; lower surface pale brown to black, erhizinate. Upper cortex pseudoparenchymatous; lower cortex absent; medulla white, of loosely interwoven hyphae. Perithecia black, globose to broadly pyriform, without involucrellum, immersed in the squamules, 0.15-0.3 mm across. Hymenium colourless, I+ brown-red; paraphyses absent, substituted by 20-45 μm long periphyses; hymenial algae rounded, 2-3 μm wide. Asci 2-spored, clavate to cylindrical-clavate, bi- and fissitunicate, thin-walled, the wall non-amyloid. Ascospores muriform, at first colourless, then pale brown, ellipsoid, 27-51 x 12-24 μm. Photobiont chlorococcoid (Stichococcus, present in both thallus and hymenium). Spot tests: thallus and medulla K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: on mineral-rich basic siliceous rocks with some water seepage, usually in upland areas, often associated to colonies of cyanobacteria; probably more widespread in the Alps.
Growth form: Crustose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
On otherwise dry surfaces with short periods of water seepage after rain