Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.
Life habit: lichenized Thallus: thin, effuse, granulose to inconspicuous surface: whitish or grayish Ascomata: 0.5-1.2 x 0.15-0.35 mm, scattered, simple; disc: slit-like, widening with age, ± white-pruinose exciple: closed, K+ dark green hymenium: 50-75 µm, I+ reddish; subhymenium: pale brown, 15-30 µm tall; paraphysoids: to 1.5 µm wide asci: cylindric-clavate, 42-65 x 12-14 µm, with large ocular chamber and an incipient apical nasse (between Calcarea-type and Vulgata-type) ascospores: oblong-ellipsoid, (12-)14-20 x (3-)4-5.5 µm, 3-5-septate (Calcarea-type) Pycnidia: immersed conidia: 4-6 x 1-1.2 µm, straight Spot tests: thallus K-, C-, KC-, P- Secondary metabolites: no substances. Substrate and ecology: on Cupressus macrocarpa, and other trees and woody or fleshy shrubs World distribution: Morocco, Spain (Baleares: Formentera), British Isles and North America (California, Mexico) Sonoran distribution: southern California and Baja California Sur. Notes: Opegrapha xerica was previously known only from few localities in Morocco and Formentera (Torrente and Egea 1992) and in the British Isles (Purvis et al. 1993).