Acarospora fuscata ("brown cobblestone lichen") is a glossy pale or yellowish-brown areolate lichen with angular areolas that grows up to 100NaN0 wide on non-calcareous rock in low and high elevations.[1] [2] It grows in Europe and North America.[2] It grows in southern California and on the eastern part of the Sierra Nevada range.[1] It may grow with the areolas disconnected.[1] The areolas may lift at the edges, but the areolas do not overlap like true squamules (sub-squamulose).[1] More common in the Sierras is the similar species Acarospora thamnina, which is truly squamulose with overlapping scales.[1]
It usually has 0-1 apothecium per areole, which may be point-like (punctiform) or fill the entire areole with a disc that is rough surfaced and reddish brown. The asci are club shaped (clavate), with over 100 spores.[2] Lichen spot tests are K−, C+ vaguely pink, KC+ red, and P−.[1] [2] Secondary metabolites include gyrophoric acid.[2]