Description: This is a lichenicolous lichen of Pertusaria species so the substratum will be determined by the host which, most likely, will be siliceous rock. Popular hosts include Pertusaria pseudocorallina and P. flavicans. Discs (0.4–0.7mm diam.) may occur scattered or as tight clusters; there is no recognisable thallus. Spores are blue-black, one-septate and about 20µm long.

Key Identification Features:

• Thallus not present; discs often clustered containing blackish or brown one-septate spores
• Growing on rock-inhabiting Pertusaria species.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Rhizocarpon advenulum at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Rhizocarpon advenulum at iNaturalist World Species Observations database.