Peccania

Peccania is a genus of lichen-forming fungi in the family Phylliscaceae. These lichens are small and form thin, crusty patches or tiny scale-like structures that are tightly attached to rock surfaces. They partner with blue-green bacteria instead of the green algae found in most other lichens, which helps them survive in harsh, drought-prone environments and quickly resume photosynthesis after wetting. Peccania species grow exclusively on rocks, favouring well-lit locations on both limestone and acidic substrates in arid and semi-arid regions, though they can also occupy locally dry spots in otherwise humid landscapes. The genus includes about 22 species distributed worldwide, with their small fruiting bodies appearing as tiny disc-like structures that are often slightly sunken into the thallus surface....read more on Wikipedia.