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 patches to over 3 cm in diam. Upper surface grey, lower surface brown to dark brown, smooth. Upper cortex composed of cells in irregular vertical columns; 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, the wall colourless except in the brown uppermost part. Hamathecium or periphyses and periphysoids, interascal filaments absent; hymenial jelly hemiamyloid. Asci 8-spored, clavate, the wall thickened above, not amyloid.. Ascospores 1-celled (to rarely 1-septate when overmature), hyaline. ellipsoid to narrowly ellipsoid, 13-21 x 5-8 µm Pycnidia common, black, immersed. Conidia 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)