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.[1] It grows on non-calciferous rock in clearings in coniferous forests, from 1475mto3030mm (4,839feetto9,940feetm).[1]
It is very similar to R. geographicum except for the size of the spores.[1] "Macrosporum" means "large spore". Areoles are 1.4mm2mm in diameter and round to angular.[1]
The prothallus is black and often not distinct.[1] The medulla is white.[1]