Salted Rock-shield

Xanthoparmelia mexicana grows in 4–10 centimetres (1.6–3.9 in) diameter rosettes consisting of small lobes. The lower surface is pale to medium brown. Apothecia are uncommon; when present, they are cinnamon to dark-brown colored discs with smooth margins, and no pruina. 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. It produces secondary metabolites including usnic acid and salazinic acid.

Xanthoparmelia mexicana grows in open and arid climates all over the world. It may loosely cling to the substrate (adnate). In the Sonoran Desert, it may be the most commonly found member of its genus. The lichen has been recorded from western North America, Mexico, the Dominican Republic, South America, Africa, Asia, Australia, and New Zealand. In Nepal, X. mexicana has been reported from 3,070 to 3,700 m elevation in a compilation of published records.