Diarthonis spadicea

Diarthonis is a fungal genus in the family Graphidaceae. Originally created in 1909 but long unused, the genus was revived in 2020 to accommodate D. spadicea when molecular studies showed this species fell outside the main Arthonia clade. The species grows as a thin, greyish to greenish crust beneath tree bark, producing small black disc-like reproductive structures (apothecia) that resemble drops of tar. It is considered an indicator of ecological continuity in old-growth broadleaved forests, particularly those...