Description: Look for this species on sheltered inland cliffs of siliceous rock and below shaded overhangs where there is some mineralization or subtle change in the geology of the surroundings. R. limborina strikes me as a species that is a poor competitor and therefore grows in microhabitats otherwise free of much crustose lichen rivalry. The thallus is barely a grubby stain but the discs when present are often abundant, and of an extraordinary beauty in the way nature has engineered them to resemble an engraved button or steel-nut for a machine part. In Ireland, it is restricted to the far south-west and north-west.

Key Identification Features:

• Thallus hardly visible; discs black (to 0.8mm diam.) folded into the centre like origami (gyrose) surrounded by a cracked outer ring
• Sheltered cliffs of siliceous or basaltic rock.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Rimularia limborina at iNaturalist World Species Observations database.