Description: Encrusting, small attached as a disk up to 6mm diameter with free, often thickened, margins, surface smooth.

Habitat: Common. Epiphytic on Corallina officinalis or Furcellaria, overgrowing Melobesia. Common in rock pools of the lower littoral into the sublittoral to depths of 15m or more.

Distribution: Widespread around the British Isles from the Shetlands to the Channel Islands. Europe: Mediterranean, Azores, Portugal, Atlantic coasts of Spain and France, Baltic, Norway and the Faroes. Atlantic coast of North America: Canada, Maine, New Hampshire, Massachusetts, Rhode Island, Connecticut and Long Island. Further afield: Bahamas, Jamaica, the Canary Isles, Pacific U.S.A., India, Japan, Australia, New Zealand and West Africa.

Similar Species: Few encrusting corallines can easily be determined with confidence. Microscopic examination often required.

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

iNaturalist: Titanoderma pustulatum at iNaturalist World Species Observations database.

WoRMS: Titanoderma pustulatum at World Register of Marine Species.