Arthonia ilicinella

Arthonia ilicinella is a species of crustose lichen belonging to the family Arthoniaceae. First described in 1867, it is characterised by its immersed thallus that appears white-grey to cream-white, and its small black reproductive structures. The species has a widespread global distribution, occurring across Europe (including the United Kingdom, Ireland, Germany, Portugal, Spain, and Switzerland), South America (Argentina and Chile), and parts of Asia (South Korea). In the British Isles, it serves as an ecological indicator species used in environmental assessments, and has been noted in Scotland as an old-growth forest indicator that has significantly declined over recent decades....read more on Wikipedia.