Acarospora obnubila

Acarospora obnubila ("cloudy cobblestone lichen") is a dull brown squamulose areolate crustose lichen that may grow up to 4 mm in diameter or with squamules scattered among other lichens.[1]^: 217[2] They are common in Arizona, southern California, and Baja California.[2] They grow by themselves on acidic rock in full sunlight.[2] Squamules measure up to 2 mm in diameter and are round to irregular, with have a stipe.[2][1]^: 217 They may also grow on members of the genus Aspicilia (lichenicolous).[2] Competition for space with other lichens stimulates longer stipes to develop,[2] whereby the squamules may overlay other lichens.

Acarospora obnubila
Closeup of fertile areoles at 30X magnification
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Lecanoromycetes
Order:	Acarosporales
Family:	Acarosporaceae
Genus:	Acarospora
Species:	A. obnubila
Binomial name
Acarospora obnubila H.Magn. (1929)

There are 0-16 apothecia per squamule, that may are pointlike (punctiform) with a reddish-brown round concave 0.1–0.3 mm disc that is deeply immersed in the thallus tissue.[2] In very high elevations, the apothecia may rise as warty (verrucae) structure with thallus-like tissue (pseudo-lecanorine ) collaring discs that may be up to 1 mm diameter, with only one per squamule.[2] Lichen spot tests are all negative, with no known secondary metabolites (as of 2014).[2] A. obnubila was first described scientifically by lichenologist Adolf Hugo Magnusson in 1929.[3]