444 million years ago the sea levels plummeted by hundreds of feet, drastically changing the oceans environment, ecosystems, and physical layout. This devestating change resulted in the extinction of most Brachiopods, Bryozoeans, Graptolite, Conodonts, and Trilobites.

383-359 million years ago several pulses caused oxygen in the ocean to drop which dealt serious blows to conodonts and ancient shelled relatives of squid and octopi called Goniatites. Many reef-building creatures also died out as well as the Stromatoporoids, a species of sea sponge. In addition, jawless fish, more species of brachiopods, ammonites, corals, and all except one species of the trilobite family went extinct.

252 million years ago 96% of marine life was wiped out due to ocean acidification. Marine ecosystems took 4-8 million years to recover from this mass extinction event. Permian Oceans may have also been poisoned by CO2 resulting in more extinctions. Some of the species that went extinct include trilobites, rugose, tabulate corals, blastoids, crinoids, acanthodians, placoderms, and shallow, warm-water invertebrates.

201 million years ago 80% of all species on Earth went extinct. More specifically, 95% of all marine species went extinct as the CO2 levels quadrupled and acidified the Triassic Oceans making it much more difficult for marine creatures to build their shells from calcium carbonate. This resulted in the extinction of Ceratitic ammonoids, conodonts, brachiopods, gastrropods, and bivalves.

66 million years ago an asteroid hit earth killiing off 76% of all species on the planet. The asteroid caused global cooling which turned the waters too cold for some marine species. Marine invertebrates, 87% of coccolithophore and foaminiferal, free-swimming mollusks, ammonoids, belemnoids, hermatypic corals (only a fifth remained), orbitoides, rudist bivalves, exogyra and gryphaea, the Plesiosaurus and Mosasaurus all went extinct.