Arthonia invadens

Arthonia invadens is a species of lichen-dwelling fungus in the family Arthoniaceae. The fungus produces small, dark brown fruiting bodies that erupt through the bark surface, forming narrow star-shaped or branching patterns typically 0.2–1 mm across. It produces ascospores that are initially colourless and smooth but later become covered with brown granular warts, with the upper cell larger than the lower cells. The species is rare in Britain and Ireland, known from only a few localities including the New Forest, West Cork, and North Devon, where it grows on various hardwood trees including oak, holly, alder, and beech....read more on Wikipedia.