[Amphiloma tonduzianum Müll.Arg., moreCaloplaca mexicana (B. de Lesd.) Zahlbr., Caloplaca mexicana var. citrina B. de Lesd., Caloplaca mexicana var. mexicana (B. de Lesd.) Zahlbr., Caloplaca tonduziana (Müll.Arg.) Zahlbr., Placodium mexicanum B. de Lesd.]
Nash, T.H., Ryan, B.D., Gries, C., Bungartz, F., (eds.) 2002. Lichen Flora of the Greater Sonoran Desert Region. Vol 1.
Thallus: placodioid, clearly forming rosettes, 2-3 cm wide, loosely adnate, lobate peripherally lobes: convex often folded, up to 5 mm long, and 0.5-1.5 mm wide upper surface: bright yellow to golden yellow, smooth to somewhat rugulose upper cortex: 10-20 µm thick medulla: yellow throughout, inspersed with yellow granules lower cortex: 20-30 µm thick under lobes but absent centrally lower surface: yellow peripherally but becoming pale yellow centrally; hapters: sometimes present, stout, peripheral Apothecia: occasional, sessile, up to 1.4 mm wide; margin: smooth, becoming crenulate with age, occasionally lobulate; disc: darker yellow than the thallus; epithecium: c. 5 µm thick; hymenium: c. 50-65 µm tall; paraphyses: simple, cylindrical or with somewhat swollen, up to 3 µm wide tips; hypothecium: c. 70-90 µm thick asci: clavate, 8-spored ascospores: narrowly ellipsoid to weakly kidney-shaped, (9-) 11-16.5 x 3.5-5 µm Pycnidia: frequent, spherical to broadly ellipsoid, immersed or appearing as raised warts on the thallus surface conidia: narrowly ellipsoid, 2-3 x 1.5 µm Spot tests: upper surface K+ reddish C-, KC-, P-; medulla K+ reddish, C-, KC-, P- Secondary metabolite: calycin. Substrate and ecology: on calcium free rocks and boulders in open montane habitats World distribution: northern South America to southwestern USA Sonoran distribution: relatively rare but conspicuous, extending from 1000 m. to at least 2200 m. in the foothills and mountains of Arizona, Chihuahua, Sonora and Baja California Sur.