Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2007. Lichen Flora of the Greater Sonoran Desert Region. Vol 3.

Life habit: lichenized Thallus: crustose, continuous or areolate, without elongated lobes; prothallus: absent surface: gray, verruculose, without asexual propagules Apothecia: adnate, 0.3-1 mm in diam., lecideine disc: dark reddish orange, flat or convex, epruinose margin: persistent or disappearing, flush; thalline margin absent; proper margin not visible or visible, concolorous with disc parathecium: elongate to oval cells, exciple below hypothecium amorphous epihymenium: golden, K+ red, C+ violet hymenium: hyaline, 60-120 µm tall paraphyses: 1-2 tip cells slightly swollen, with few branches or with some branching; subhymenium hyaline asci: cylindrical, 4--spored ascospores: hyaline, 2 locules, ellipsoid, 21-28 x 12.5-17 µm, isthmus 3.5-5.5 µm, spore end wall thin Pycnidia: not observed Spot tests: thallus K- Secondary metabolites: parietin and emodin. Substrate and ecology: on bryophytes, soil, or detritus World distribution: Europe and North America Sonoran distribution: Arizona. Notes: Caloplaca tetraspora has a very thin gray thallus and the apothecia are red-brown and soon become convex. This is the only Sonoran species with only four spores per ascus.