Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Thallus: foliose (to fruticose), umbilicate, deeply branched rosettes or cushions, lobules usually flat on the substrate, central lobules in very polyphyllous thalli ± erect, 0.5-1.5 mm wide, stretched, sparingly branched, often with broadened or furcate tips, upper surface: black, with coarse globose isidia (50-250 µm) that usually become scale-like (c. 0.5 mm), lower surface: furrowed Apothecia: rare, sessile to stipitate, marginal, rarely on laminal folds, lecanorine, 0.25-0.6 mm wide, with a persisting thalline margin; disc: dark red; exciple: lacking; hymenium: up to 140 µm high, hyaline, amyloid; paraphyses: distinctly septate, sparingly branched and anastomosing, apical cells indistinctly thickened; hypothecium: ± inverse cone-shaped, up to 70 µm high, hyaline asci: 8-spored ascospores: rarely well developed, simple, hyaline, broadly ellipsoid, sometimes curved, 9.5-14 x 4.5-9.5 µm; walls: thin Pycnidia: immersed, ± globose, c. 0.25 mm wide; pycnidial wall: convoluted with age conidia: cylindrical, hyaline, 2.5-4 x 1 µm Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: on (calcareous) volcanic rocks, limestone or siliceous rock; on steep, sheltered or shaded rock faces, in clefts and along seepage tracks; coastal to montane World distribution: SW North and Central America Sonoran distribution: obviously confined to strictly Sonoran Desert habitats in Arizona, Sonora, Sinaloa and Baja California Sur, not extending northwards onto the Colorado Plateau or high altitudes in southern Arizona. Notes: It is distinguished from D. divergens by the predominatly flat rosettes with fewer lobules, and the more sparingly branched and slightly broader lobes with less pronounced diverging tips that are often broadened or shortly furcate.