Thallus: rimose-areolate; areoles: 0.6-2.0 mm in diam., plane, thick upper surface: reddish brown to brown, smooth, shiny or dull, epruinose Ascomata: perithecioid, immersed, up to 0.8 mm in diam.; disc: blackish, plane; proper exciple: up to 65 µm thick; hymenium: 120-140 µm high asci: cylindrical to subclavate, 6-8-spored ascospores: brown, muriform, broadly ellipsoid, 16-26 x 8-18 µm; transverse septa 4-6, longitudinal septa 1-2 per transverse segment Pycnidia: not seen Spot tests: K-, C+ red, KC-, P-, UV- Secondary metabolites: gyrophoric and lecanoric acids (both major) and orsellinic acid (minor). Substrate and ecology: on siliceous rocks World distribution: endemic to southwestern North America Sonoran distribution: rare, in mountainous regions at an elevation of c. 1300-2700 m in Arizona, Baja California Sur, Chihuahua and Sonora. Notes: This species can be readily identified by the presence of gyrophoric acid, the brownish thallus, and the perithecioid ascomata. Diploschistes badius is similar to D. aeneus and the differences between the two species are discussed under the latter.