Although corals first appeared in the Cambrian period, some, fossils are extremely rare until the Ordovician period, 100 million years later, when rugose and tabulate corals became widespread.
12.
The documented phosphatized microfossils of algae, multicellular thallophytes ( seaweeds ), acritarchs, ciliates, and cyanophytes, besides adult sponges and adult cnidarians ( coelenterates; these may be early forms of tabulate corals ( tetracorallians ) ).
13.
Into the Devonian, there were a small number of ammonoids, conodonts, tabulate corals, tetracorals, abundant crinoids, a moderate number of nautloids ( with both straight and coiled shells ), abundant pelecypods, abundant stromatoporoids, and trilobites.
14.
During the Mississippian, Missouri was home to fairly abundant ammonoids, abundant " Archimedes " screws, very abundant blastoids, abundant lacy bryozoans, tabulate corals, tetracorals, endothyroid foraminferans, a moderate number of nautiloids, fairly abundant pelecypods, fairly abundant trilobites, abundant worms.
