Rhizocarpon disporum (Naeg. ex Hepp) Müll. Arg.
Rhizocarpon montagnei Körb.
Single-spored Map Lichen, Map Lichen
This is one of several ”map lichens,” so-called because at (very) close range, each tiny lichen is bordered by black spores that resemble borders on a map.
Identification: This is a crustose lichen, meaning that it forms a very thin layer, in this case over rock. It is pale gray or brownish gray, looking a bit like paint that dried too fast and cracked. If fruiting bodies (apothecia) are present (for example, in photo 6), they appear as small black dots less than a millimeter in diameter.
Rhizocarpon disporum on Stephen Sharnoff Photography
Rhizocarpon disporum on Wayne's Word
Rhizocarpon disporum on the Global Biodiversity Information Facility
Rhizocarpon disporum on CalPhotos
Rhizocarpon disporum at the Consortium of North American Lichen Herbaria
Rhizocarpon disporum description by Thomas H. Kent, last updated 5 Oct 2016.