Opegrapha physciaria

About

Opegrapha physciaria is a species of lichenicolous (lichen-dwelling) fungus in the family Opegraphaceae. This tiny black fungus lives harmlessly within the tissues of the common sunburst lichen, producing small dark disc-shaped fruiting bodies that emerge from the host's surface. It is found in Europe and North America, typically growing on tree bark in woodlands where its host lichen forms bright orange patches.

Summary from Wikipedia