Pleopsidium flavum (gold cobblestone lichen)The Laws Field Guide to the Sierra Nevada, John Muir Laws, 2007 is a distinctively colored, bright lemon-yellow to chartreuseCrustose Rock Lichens, Wayne P. Armstrong, Wayne's World online textbook of natural history, crustose lichen that grows in high elevations (montane to alpine) on vertical or overhanging hard felsic rock (e.g. granite) in western North America.Mosses Lichens & Ferns of Northwest North America, Dale H. Vitt, Janet E. marsh, Robin B. Bovey, Lone Pine Publishing Company, Its thallus grows in a circular outwardly radiating pattern (placodioid), with 1mm wide lobed edges. This is the identity of the vivid, lime-green lichens often photographed on granite boulders in the Wichita Mountains Wildlife Refuge of Oklahoma. According to Prof. Wayne Armstrong of Mount Palomar College, This lichen only grows "a few millimeters" per century., making it the slowest growing of all known plants (sensu lato).
It was formerly classified as Acarospora 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.
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