Life habit: lichenized Thallus: crustose, areolate or sub-squamulose, without elongated lobes; prothallus: present or absent, black surface: gray or tan, smooth, without asexual propagules cortex: cellular, 21-35 µm thick, granules absent; medulla without granules Apothecia: adnate, 0.3-0.8 mm, lecanorine disc: red or orange, flat, epruinose margin: persistent, flush; thalline margin present or absent, concolorous with thallus; proper margin visible, concolorous with disc parathecium: elongate to oval cells epihymenium: golden, K+ red, H-, 10%N-, cN-, C+ red hymenium: hyaline, 70-85 µm tall paraphyses: 2-3 tip cells slightly swollen, with some branching or frequently branched; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, 12.5-15.5 x 5.5-8.5 µm, isthmus 4-5.5 µm, spore end wall thin Pycnidia: present, totally immersed, ostiole red Spot tests: thallus K-, H-, 10%N-, red brown, C- Secondary metabolites: unidentified anthraquinones. Substrate and ecology: on non-calcareous rocks World distribution: southwestern North America Sonoran distribution: Arizona, Baja California Sur, western Chihuahua, and Sonora. Notes: Caloplaca sonorae is characterized by the dark orange discs and margins with outer gray margin in the older apothecia and the tan to gray subsquamulose thallus. Caloplaca atroflava is similar but has a thin areolate thallus. Caloplaca sideritis has a dark excipular ring on the apothecia.