Hemithecium

Hemithecium is a genus of lichen-forming fungi in the family Graphidaceae. These lichens form pale grey-white to yellow-olive crusts on tree bark and are characterized by straight to weakly curved fruiting bodies with charcoal-black walls that create sharp contrasts against the surface, along with distinctive spine-tipped filaments lining their interior chambers. The genus has a pantropical distribution, growing on shaded tree trunks and large branches in primary or lightly disturbed evergreen forests, where their marked sensitivity to canopy opening makes them practical indicators of intact, moisture-rich woodland habitat. ...read more on Wikipedia.