Most books place it with sponges in Phylum Porifora, but the eminent paleontologist Ernst Mayr thinks that it's more closely related to corals, and puts it in Phylum Cnidaria. The Stromatocerium found in the Nashville Group formed large mound shaped colonies It is called Stromatocerium pustulosum because of the pimple-like bumps on its surface. It is found occasionally in Bigby Cannon, and abundantly in Catheys Formation. There is a beautiful complete colony in the parking lot of Shoney's on Old Hickory Blvd. They all have tentacles and stinging cells to paralyze their prey.
Corals can be either small solitary animals or large reef-building colonies.
They very nearly became extinct at the end of the Paleozoic Era. Both of the two orders of paleozoic corals - the tabulate and rugose corals disappeared by the era's end. Modern corals are all in the class Scleractinia which is not found at all in the paleozoic era. For more information on Cnidaria, see the Berkeley exhibit. Cnidaria Two genera of tabulate corals and one genus of rugose corals are found in Nashville.