Description: This predominantly coastal, crustose lichen of mildly nutrient-enriched granitic rocks has a smooth, pale-grey thallus finely cracked into a mosaic of little ‘islands’ surrounded by a conspicuous black ring of prothallus also visible between the ‘island’ gaps. Small brown discs (to 1mm diam.) with a thin margin (the colour of the thallus) are common. Chemical spot tests are important for identification. The thallus is C + red (fresh bleach), K + yellow and Pd + yellow. In coastal situations it is most likely to be confused with certain forms of Buellia subdisciformis which is C-, K + yellow-red, or with Rinodina confragosa which is also C-. Throughout Ireland.

Key Identification Features:

• A finely cracked pale-grey thallus with abundant, small brownish discs and with a black ring around the thallus; coarse, granitic rocks; tolerates some mild enrichment
• Thallus: C + red, K + yellow.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Rinodina atrocinerea at iNaturalist World Species Observations database.