Life habit: lichenized Thallus: immersed, crustose, without elongated lobes, without asexual propagules; prothallus: absent cortex: absent Apothecia: adnate, 0.3-0.5(0.8) mm in diam., lecanorine disc: orange, flat to slightly convex, epruinose margin: persistent, flush; thalline margin absent; proper margin visible, little lighter than disc parathecium: elongate to oval cells; exciple below hypothecium amorphous epihymenium: golden, K+ red, C- hymenium: hyaline, (60-)70-85(-90) µm tall paraphyses: 2-3 tip cells slightly swollen, not branched or with few branches; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, (14)15.5-18(-19.5) x 5.5-7(-8.5) µm, isthmus 1-3 µm, spore end wall thin Pycnidia: not observed Secondary metabolites: unidentified anthraquinones. Substrate and ecology: in or on calcareous rocks World distribution: Europe, North America, New Zealand Sonoran distribution: southern California, Arizona, and Baja California Sur. Notes: Caloplaca crenulatella has small apothecia and is usually found on calcareous rocks. The spores are slightly larger that in C. nashii. Caloplaca crenulatella has a wider distribution all across North America while C. nashii is only known from the Sonoran Region.