Description: This is a parasitic species forming small patches among other lichens such as Aspicilia caesiocinerea. Although it is a yellow-coloured species and therefore easily overlooked for Rhizocarpon geographicum, the muriform spores are few-celled (five to nine), the epithecium brown-black and granular and the medulla I-. In Ireland, records are few; Counties Kerry and Cork.

Key Identification Features:

• Thallus yellow, parasitic forming small patches
• Spores muriform, few-celled, epithecium brown and granular.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Rhizocarpon viridiatrum at iNaturalist World Species Observations database.