Life habit: lichenized Thallus: crustose, continuous, without elongated lobes; prothallus: absent surface: gray, smooth, without asexual propagules Apothecia: adnate, 0.3-0.8 mm in diam., lecanorine disc: dark reddish orange, slightly convex, epruinose margin: persistent, slightly raised; thalline margin present or absent, concolorous with thallus; proper margin visible, concolorous with disc parathecium: irregular hyphae or elongate to oval cells; exciple below hypothecium amorphous epihymenium: golden, K+ red, C+ red or C+ violet hymenium: hyaline, (70-)75-90 µm tall paraphyses: 1-2 tip cells slightly swollen, with some branching or frequently branched; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, 11-17 x 5.5-8.5 µm, isthmus 3-5.5 µm, spore end wall thin Pycnidia: present, mostly immersed, ostiole orange Spot tests: apothecial margin K-; thallus K- Secondary metabolites: parietin and emodin. Substrate and ecology: on bryophytes or detritus World distribution: Europe and North America Sonoran distribution: southern California, Arizona, Baja California, western Chihuahua and Sonora. Notes: Caloplaca ammiospila has a thin dark gray thallus and red to red-brown apothecia. Most of the older apothecia have a thin gray thalline margin. The apothecia of this species are usually less convex than C. sinapisperma and that species never has thalline margins.