Xanthoparmelia mexicana
Xanthoparmelia mexicana (salted rock-shield)[1] is a foliose lichen that grows in 4–10 cm diameter rosettes of gray-green to yellow-green lobes in arid climates all over the world.[2] It grows on acidic rock and soil, in open and arid habitats all over the world.[2] It may loosely cling to the substrate (adnate).[2] It grows in 4–10 cm diameter rosettes of lobes,[2] with lobe tips lighter in color than the center of the rosette. The lower surface is pale to medium brown.[2] Apothecia are uncommon, with cinnamon to dark brown discs, smooth margins, and no pruina.[2] Lichen spot tests are negative for the upper cortex (K-, C-, KC-, P-). For the medulla they are K+ yellow to dark red, C-, KC-, and P+ orange.[2] It produces secondary metabolites including usnic acid and salazinic acid.[2] In the Sonoran Desert, it may be the most commonly found member of its genus.[2]