Arthothelium feuereri

Arthothelium feuereri is a rare species of saxicolous (rock-dwelling) crustose lichen in the family Arthoniaceae. It forms a thin, pale-brown, varnish-like film on sun-blasted rock and bears scattered black fruit-bodies whose spores are densely divided into many chambers (muriform) and have conspicuously enlarged end-cells. The thallus contains gyrophoric acid—a secondary metabolite common in some lichens but previously unknown in saxicolous members of Arthothelium. The species is known only from its type locality on the summit of Les Trois Frères on Mahé, Seychelles....read more on Wikipedia.