Rhizocarpon macrosporum

Rhizocarpon macrosporum (lemon map lichen) is a smooth, bright yellow crustose aereolate lichen found in the Sonoran Desert of California and Arizona, and in Africa and Asia. It grows on non-calciferous rock in clearings in coniferous forests, from .
It is very similar to "R. geographicum" except for the size of the spores. "Macrosporum" means "large spore". Areoles are in diameter and round to angular.
The prothallus is black and often not distinct. The medulla is white. 