Life habit: lichenized Thallus: little or none, crustose, without elongated lobes; prothallus: absent surface: gray, smooth, without asexual propagules Apothecia: adnate, 0.2-0.7 mm in diam., lecanorine disc: orange, flat, epruinose margin: persistent, flush; thalline margin absent; proper margin visible parathecium: amorphous; exciple below hypothecium irregular hyphae epihymenium: golden, K+ red, C- hymenium: hyaline, 70-75 µm tall paraphyses: 1-2 tip cells slightly swollen, with some branching to frequently branched; subhymenium hyaline asci: cylindrical, 8--spored ascospores: hyaline, 2 locules, ellipsoid, (12.5-)14-17 x 7-8.5(-10 µm, isthmus 3.4-4 µm, spore end wall thin Pycnidia: not observed Spot tests: apothecial margin K+ red, C- Secondary metabolites: parietin, fallacinal, emodin, teloschistin, and parietinic acid. Substrate and ecology: on bryophytes World distribution: worldwide Sonoran distribution: Arizona. Notes: Caloplaca tiroliensis is an alpine muscicolous species with little thallus, flat dirty orange apothecia with a narrow flush proper margin. Only one collection from this region was seen. Caloplaca schoeferi is similar but has thicker and raised apothecial margins and a pure orange disc.