Life habit: lichenized Thallus: little or none, crustose, continuous or areolate, margin thinning at edge, without elongated lobes; prothallus: absent surface: yellowish orange, greenish yellow, or gray, smooth, without asexual propagules cortex: cellular, 14-35 µm thick, granules absent Apothecia: adnate, 0.4-0.8 mm, lecanorine disc: orange, flat or convex, epruinose margin: persistent or disappearing, flush; thalline margin absent; proper margin visible, concolorous with disc parathecium: consisting of radiating hyphae; exciple below hypothecium irregular hyphae epihymenium: golden, K+ red, C- hymenium: hyaline, 70-85 µm tall paraphyses: 2-3 tip cells slightly swollen, with few branches; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, (11-)12.5-17(-19.5) x 5.5-7 µm, isthmus 1-3 µm, spore end wall thin Pycnidia: present, totally immersed, ostiole orange; Thallus K- or K+ red Secondary metabolites: parietin, fallacinal, emodin, teloschistin, and parietinic acid. Substrate and ecology: on non-calcareous or calcareous rocks World distribution: coastal, western North America Sonoran distribution: southern California and Baja California. Notes: Caloplaca ludificans is close to C. luteominia and is often difficult to separate. The thallus in C. ludificans usually has a waxy translucent appearance and is smooth. The apothecial margins are thin and flush with the discs. In C. luteominia the thallus is dull and the apothecial margins are thicker and raised.