Life habit: lichenized Thallus: crustose, continuous to areolate, margin thinning at edge, without elongated lobes; prothallus: present, yellow orange surface: orange, smooth, without asexual propagules cortex: cellular, 15-20 µm thick, granules absent, medulla dense, without granules Apothecia: adnate, 0.3-0.5 mm in diam., lecanorine disc: orange, flat or convex, epruinose margin: persistent, flush; thalline margin absent; proper margin visible, concolorous with disc parathecium: elongate to oval cells; exciple below hypothecium amorphous epihymenium: golden, K+ red, H-, 10%N-, cN-, C- hymenium: hyaline, 70-84 µm tall paraphyses: 3-4 tip cells swollen, not branched; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, 11-14 x 5.5-7 µm, isthmus 3-5.5 µm, spore end wall thin Pycnidia: present, totally immersed, ostiole orange Spot tests: apothecial margin K+ red; thallus K+ red, H-, 10%N-, cN-, C- Secondary metabolites: parietin, fallacinal, emodin, and teloschistin. Substrate and ecology: on non-calcareous rocks or occasionally on calcareous rocks World distribution: coastal western North America Sonoran distribution: southern California and Baja California. Notes: Caloplaca rosei is characterized by its apricot-orange thallus with only scattered slightly convex areoles with no elongated areoles at the margins and with a paler orange prothallus:. On the North American west coast it might be confused with C. marina subsp. americana which has a discontinuous thallus of strongly convex areoles and more concave apothecia.