Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2004. Lichen Flora of the Greater Sonoran Desert Region. Vol 2.

Thallus: crustose, inconspicuous, thin to scurfy, sometimes scant surface: pale green or gray, glaucous Apothecia: scattered to aggregated, usually immersed, later becoming sessile, 0.3-0.7 mm in diam. disc: pale yellow-brown to pale orange or dark brown, not rarely secondarily almost black, deeply concave, waxy, up to 0.25 mm in diam. margin: smooth, sometimes overrun by thallus exciple: thick, smooth, usually even, radiate, creamy to brownish or yellowish pink hymenium: hyaline, 90-115 µm tall; paraphyses: capitate, up to 3-4 µm wide at tips, septate; hypothecium: hyaline to pale yellow asci: cylindrical to elongate-clavate, 8-spored ascospores: hyaline, fusiform, without conical elongations on the ends, weakly muriform with 6 or more cells visible in optical view, 4-9 septate transversely, 1-2 septate longitudinally, (14-)1728(-31) x 5-9 µm; sometimes with cross septa only Spot tests: thallus K-, C-, KC-, P- Secondary metabolites: none detected. Substrate and ecology: usually on nutrient-rich bark of mature trees, mostly Acer, Ulmus and Fraxinus, but also Quercus or Salix; sometimes on wood, in areas with a humid climate World distribution: probably circumboreal-temperate in the Northern Hemisphere, in Europe, Greenland and North America Sonoran distribution: coastal, central California. Notes: Although Gyalecta truncigena is not yet recorded for the Sonoran region, it is included here since it is reported to occur in coastal central California and may have been overlooked (or confused with other species) in southern California. Considering the world distribution of the species, it is quite possible that G. truncigena does occur in the Sonoran region.