Marine Wildlife Encyclopedia
Black Shields Tephromela atra
Crustose lichens such as black shields, which form a crust over the rock, attach themselves so firmly using fungal filaments that they cannot be easily removed from it. Over time, these anchoring filaments break down the rock as they alternately shrink when dry and swell when moist. Black shields is a thick, gray lichen with a rough, often cracked, surface from which project a number of characteristic black fruiting bodies.