Life Habit: lichenized Thallus: foliose, but almost squamulose in one species upper surface: gray or various shades of brown upper cortex: paraplectenchymatous, of roundish-angular cells, with an epinecral layer which either consists of compressed or air filled hyphae medulla: of filamentous, 2-4 µm thick, hyaline hyphae, turning red or reddish brown in Melzer's iodine in some species algal layer: irregularly dispersed or in vertical columns; forming a rather discontinuous layer situated mainly in the lower part of the upper cortex lower cortex: of Dermatocarpontype with the outermost part light to dark brown lower surface: light to dark brown to almost black, smooth, rugose, verrucose, papillose, reticulate, finely granular or with rhizinomorphs Ascomata: perithecial, laminal, immersed, broadly obpyriform to subglobose, without involucrellum exciple: hyaline, with the uppermost part light to dark brown, interascal filaments evanescent; hymenial gel amyloid (I+ blue, KI+ blue); ostiolar filaments (periphyses) present asci: bitunicate, thin-walled, clavate or cylindrical, always 8-spored, wall non-amyloid ascospores: colorless, smooth, without halo, occasionally 1-septate in few species Conidiomata: pycnidial, Dermatocarpontype (i.e plurilocular, paraplectenchymatous tissue, conidiophores of type VIII according to Vobis ), laminally immersed conidia: bacilliform Secondary metabolites: none detected Geography: world-wide, mainly temperate Substrate: rocks, more commonly basaltic rocks. Notes: The type-species of the genus, Dermatocarpon miniatum, is a common species in the Northern Hemisphere. It is a very plastic species and according to recent molecular study (Heiômarsson 2003) the D. miniatum-complex even includes D. leptophyllum and D. linkolae. D. miniatum has been recorded from the Sonoran area but when the specimens were further scrutinized it came clear that they differ substantially from D. miniatum. What has been considered as D. miniatum in the Sonoran area belongs to at least two different taxa, D. americanum which differs from D. miniatum by the positive reaction in medulla when exposed to Melzer's iodine, D. taminium on the other hand has longer spores than D. miniatum. Both of these taxa are on separate branches from D. miniatum in a phylogeny based on ITS1-5.8S-ITS2 sequences (Heiômarsson 2003). Lugol's iodine with chlorine added afterwards has the same effect as Melzer's.