Thallus ashy, scant or lacking. Apothecia to 0.8 mm broad, occasionally to 1.5 mm, adnate, dense; margin thick, waxy, yellowish-rusty, shining; hypothecium hyaline; epihymenium yellowish brown, granulöse; hymenium 75-80 µm, hyaline; paraphyses coherent, septate, slender, 1.5-2 µ , tips not thickened; spores narrowly oblong, sometimes slightly curved, 11-17 X 4-6 µm, septum 2.5-3 µm.

This species is found on old driftwood. It is known from western Siberia, Novaya Zemlya, and Scandinavia, and was reported from the Reindeer Preserve, Northwest Territories, by Ahti et al. (1973) on Picea twigs.

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, without elongated lobes; prothallus: absent surface: gray, smooth, without asexual propagules Apothecia: adnate, 0.3-0.8 mm in diam., lecanorine disc: dark reddish orange, slightly convex, epruinose margin: persistent, slightly raised; thalline margin present or absent, concolorous with thallus; proper margin visible, concolorous with disc parathecium: irregular hyphae or elongate to oval cells; exciple below hypothecium amorphous epihymenium: golden, K+ red, C+ red or C+ violet hymenium: hyaline, (70-)75-90 µm tall paraphyses: 1-2 tip cells slightly swollen, with some branching or frequently branched; subhymenium hyaline asci: cylindrical, 8-spored ascospores: hyaline, 2 locules, ellipsoid, 11-17 x 5.5-8.5 µm, isthmus 3-5.5 µm, spore end wall thin Pycnidia: present, mostly immersed, ostiole orange Spot tests: apothecial margin K-; thallus K- Secondary metabolites: parietin and emodin. Substrate and ecology: on bryophytes or detritus World distribution: Europe and North America Sonoran distribution: southern California, Arizona, Baja California, western Chihuahua and Sonora. Notes: Caloplaca ammiospila has a thin dark gray thallus and red to red-brown apothecia. Most of the older apothecia have a thin gray thalline margin. The apothecia of this species are usually less convex than C. sinapisperma and that species never has thalline margins.