Peltula obscurans

Peltula obscurans (common rock-olive) is a dark olive to dark gray squamulose lichen that grows on rock and soil in arid habitats around the world. It may grow as a rosette of squamulous lobes, or with widely scattered lobes. A single black apothecium may be centered on the lobe. The apothecia disc turns reddish-brown when wet, which contrasts with the lobes that turn olive-green when wet. It can be found in southern Europe, South America, southwestern North America, Africa, Asia, Australia, and Papua New Guinea....read more on Wikipedia.