Synonyms: Dermatocarpon diffractum (Th. Fr.) Blomb. & Forssell; Dermatocarpon lorenzianum Anders; Dermatocarpon miniatum var. diffractum Th. Fr.; Dermatocarpon phonolithicum Anders
Distribution: N - VA (Piervittori & al. 2004). S - Cal (Puntillo 1996).
Description: Thallus foliose, monophyllous, consisting of 1-4 mm wide, subumbilicate, usually densely aggregated lobes, forming over 3 cm wide patches. Upper surface grey, lower surface brown to dark brown, smooth. Upper and lower cortices pseudoparenchymatous, composed of cells arranged in irregular vertical columns, the upper cortex overlain by an epinecral layer (best visible along margins) of broken, air-filled cells; medulla white, I-. Perithecia black, immersed in the thallus, without involucrellum, 0.2-0.3 mm high and 0.16-1.26 mm wide. Exciple colourless except in the brown uppermost part; hamathecium of periphyses and periphysoids, interascal filaments absent; hymenial gel hemiamyloid. Asci 8-spored, clavate, I-, fissitunicate, the wall thickened above, with an ocular chamber, dehiscent by extrusion of an endotunica to form a delicate rostrum, Verrucaria-type. Ascospores 1-celled (to rarely 1-septate when overmature), hyaline. ellipsoid to narrowly ellipsoid, 13-21 x 5-8 µm. Pycnidia common, black, immersed, multi-chambered. Conidia short-bacilliform. Photobiont chlorococcoied. Spot tests: cortex and medulla K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a temperate to southern boreal-montane species found on periodicaly inundated surfaces of basic siliceous rocks. The species is not easily recognised as belonging to Dermatocarpon, the thallus consisting of tightly arranged squamiform lobes (but with the pseudoparenchymatic lower cortex which is typical for the genus). For further details see Orange (1998).
Growth form: Squamulose
Photobiont: green algae other than Trentepohlia
Reproductive strategy: mainly sexual
Most common in areas with a humid-warm climate (e.g. most of Tyrrenian Italy)