Astrothelium sordithecium

Astrothelium sordithecium is a species of lichen-forming fungus in the family Trypetheliaceae. The lichen forms an olive-green to gray-green crusty patch on tree bark with a smooth to uneven surface. Its reproductive structures are grouped together in well-defined rounded clusters covered by a whitish layer, and these clusters fluoresce yellow under ultraviolet light while the surrounding lichen body does not. The species is known only from Atlantic Forest in southeastern Brazil, where it grows on bark in disturbed remnants of gallery forest along streams....read more on Wikipedia.