Description: This crustose lichen has a dark grey, areolate (cracked into islands), K- thallus and sessile, black-coloured discs with frosted edges (exciples). It grows most frequently on horizontal calcareous surfaces, for example, bridges, limestone staircases, wall copings and tomb tops. C. chalybeia is much paler and thicker with immersed discs and grows on harder limestones. In Ireland, the species has a restricted distribution, for example, the Burren and Arran Islands.

Key Identification Features:

• Thallus K-, very dark grey with black, sessile discs frosted at the edges
• On horizontal calcareous stone.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Pyrenodesmia variabilis at iNaturalist World Species Observations database.