Description: This small, crustose lichen is very common on the tops of siliceous rocks and boulders, including artificial substrata. The thallus is an agglomeration of scattered, grey (sometimes pinkish) squamules, with red-brown discs. It can be variable, but may be separated from other Trapelia species by the squamulose (not crustose) thallus and lack of soralia (powdery patches). A dab of C (Calcium hypochlorite) will turn the thallus red.

Key Identification Features:

• Trapelia species are best confirmed using the C test
• The tiny clusters of squamules, often surmounted by pink discs are diagnostic.

Original text submitted by Simon Davey

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

iNaturalist: Trapelia coarctata at iNaturalist World Species Observations database.