Pleopsidium flavum

Pleopsidium flavum (gold cobblestone lichen) is a distinctively colored, bright lemon-yellow to chartreuse crustose lichen that grows in high elevations (montane to alpine) on vertical or overhanging hard felsic rock (e.g. granite) in western North America. Its thallus grows in a circular outwardly radiating pattern (crustose placoidioid), with 1mm wide lobed edges. It was formerly classified as Acaraspora chlorophana. It is in the Pleopsidium genus of the Acarosporaceae family.

It is similar to Acarospora schleicheri, which grows on soil (terricolous lichen) and rarely on rock, and to Pleopsidium chlorophanum, which favors dry arctic or alpine sandstone cliffs and boulders.