Belemnitella was one of the latest surviving Belemnites. This sea was home to belemnites and oysters. The chalk often contains larger fossils including ammonites, belemnites and brachiopods. Other sea life included invertebrates such as mollusks, ammonites, squid-like belemnites, and plankton. "Plesiosaurus" fed on belemnites, fish and other prey. He also erected the genus "Belemnites" with 11 species. "Spirula" is likely the closest living relative of the extinct belemnites and aulacocerids. The Late Cretaceous Peedee beds are known for their belemnites and other mollusks. In addition to fish, belemnites and to an extent ammonites swarmed in shoals. The chalk deposits contain numerous fossils of sea urchins, clams and belemnites. Its streamlined body allowed it to chase fast prey such as belemnites. The mesohibolitid belemnites, using the same methods, had a lifespan of about a year. Like all elasmosaurid plesiosaurs, it probably ate small bony fish, belemnites, and ammonites. Shell debris (ammonites, belemnites, nautiloids, bivalves, etc.) and bioturbation are also present. Fossils within the Fossil Bluff Formation include ammonites, belemnites, bivalves, and serpulids.