Parmelia sulcata

Parmelia sulcata, commonly known as the hammered shield lichen or cracked shield lichen, is a foliose lichen in the family Parmeliaceae, first described by Thomas Taylor in 1836. It is one of the most prevalent lichen species in the world, valued for its resilience to pollution and its cosmopolitan distribution across temperate and cold regions of both hemispheres. Its thallus forms a circular shape up to 10 centimeters across, with a glaucous white to grey upper surface, a black lower surface, broadly lobed structures, and a distinctive reticulate pattern of pseudocyphellae. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/