Distribution: N - Ven, TAA, Lomb. C - Tosc. S - Camp.
Description: Thallus foliose-umbilicate, monophyllous or of a few connected lobes, rather thin (0.2-0.5 mm thick when dry), attached by one or rarely a few central holdfasts. Lobes usually concave (5-)7-18(-25) mm wide. Upper surface grey to almost black in parts; lower surface smooth to partly verrucose. Upper cortex (40-)50- 90(-110) μm thick, brown in the uppermost part, with an epinecral layer of air-filled hyphae; medulla consisting of c. 3 μm thick hyphae; lower cortex (30-)40-60(-70) μm thick, the outermost part brown, consisting of 5-8 cell layers; crystals visible in polarized light and soluble in K present in the lower cortex. Perithecia dark brown to black, immersed, with a slightly protruding ostiole, more or less spherical, without involucrellum, the wall colourless except in the brown uppermost part. Hamathecium or periphyses and periphysoids, interascal filaments absent; hymenial jelly hemiamyloid. Asci 8-spored, cylindrical, the wall thickened above, not amyloid, with more or less uniseriate ascospores. Ascospores 1-celled, hyaline, broadly ellipsoid to subglobose, (7-)8-10(-11.5) x (4.5-)6-7 μm. Pycnidia very rare, black. Conidia 5-6 x c. 1 μm. Photobiont chlorococcoid. Spot tests: cortex and and medulla K-, C-, KC-, P-, UV-. Chemistry: no lichen substances.
Note: a species of the D. miniatum group with umbilicate thalli usually provided with blackish grey concave lobes, and subglobose uniseriate ascospores in cylindrical asci, found on horizontal or depressed rock faces of calcareous rocks in seasonally wet places. Most of the Italian records are old and require re-confirmation (see Nimis 1993: 274).
Growth form: Foliose, umbilicate
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
On otherwise dry surfaces with short periods of water seepage after rain