Synarthonia stigmatidialis

Synarthonia stigmatidialis is a species of corticolous (bark-dwelling) crustose lichen of uncertain familial classification in the order Arthoniales. Originally described from a single collection in the Mexican state of San Luis Potosí in 1895, this lichen remains known only from its type locality, making it one of the rarest members of its genus. The species is distinguished by its whitish crusty growth on bark and its clustered fruiting structures that are dusted with a delicate white powder, as well as its distinctive ascospores that develop enlarged cells at their tip and turn pale brown at maturity....read more on Wikipedia.