Synarthonia bicolor

Synarthonia bicolor is a species of corticolous (bark-dwelling) crustose lichen of uncertain familial classification in the order Arthoniales. This tropical lichen forms thin, whitish-grey crusts on tree bark and is distinguished by its fruiting bodies that start as single structures but later cluster together into compound formations surrounded by white margins. It is chemically unique within its genus due to the presence of lichexanthone, a lichen product that causes the thallus to glow bright yellow under ultraviolet light. The species has a disjunct distribution, being known from Costa Rica where it was originally described and from mangrove forests in the Sundarbans region of India....read more on Wikipedia.