Description: This light-shy maritime lichen inhabits the dry, shady crevices of the ‘grey lichen zone’ of siliceous rocks on coasts around Ireland. The tiny, scattered, creamy-grey, minutely warted thallus has mostly pinkish-brown discs (0.1-0.2mm diam.) with a thin, unevenly wavy margin. Reactions: K+ yellow, Pd + red. Throughout Ireland.

Key Identification Features:

• Small, cream-grey, minutely warted thallus with pinkish-brown discs
• Only on sheltered rock surfaces of sea cliffs within the ‘grey lichen’ zone; coasts with siliceous rocks only.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Cliostomum tenerum at iNaturalist World Species Observations database.