[[File:Permian sponge reef.jpg|thumbnail|500px|Permian sponge reef in Guadalupe Mountains, west Texas.The top of the cliff was bound during the Permian by sponges and other reef-building organisms; the flanks are the ancient slopes connecting the reef with the basinal depth. Source: Wikimedia Commons]] | [[File:Permian sponge reef.jpg|thumbnail|500px|Permian sponge reef in Guadalupe Mountains, west Texas.The top of the cliff was bound during the Permian by sponges and other reef-building organisms; the flanks are the ancient slopes connecting the reef with the basinal depth. Source: Wikimedia Commons]] |