The Marine Realm and The End-Permian Extinction
The Permian marine fauna was similar to that of the Carboniferous. Corals, stromatolites, sponges, bryozoans, brachiopods, and foraminiferans formed reef ecosystems in the warm shallow waters. Ammonoids, nautiloids, echinoderms, and gastropods were still common predators. The great diversity of fishes included agnathans (jawless fishes), chondrichthyans (such as sharks), and many types of bony fishes. This collection of marine species represents the last of the Paleozoic Fauna, which first rose to dominance in the Ordovician, some 200 million years previously.

The end of the Permian was marked by the greatest mass extinction of the last 600 million years of Earth history, during which perhaps 90% of marine animal species disappeared. Major groups such as trilobites, fusulinid foraminiferans, rugose and tabulate corals, acanthodian and placoderm fishes, and blastoid echinoderms vanished entirely, Although they did survive, brachiopods, bryozoans, ammonoids, sharks, bony fishes, crinoids, eurypterids, ostracods, and many echinoderms lost the majority of their species. Finally, insects suffered their greatest mass extinction in Earth history.

Several factors have been implicated in this massive extinction. The formation of Pangea reduced the continental shelves, decreasing the area available for shallow-water organisms. Rapid warming and glaciation both occurred during the Permian as well. These events do not seem to have happened at the same time as the extinction event, however. Indeed, a first extinction pulse actually occurred during the Middle Permian and may have been caused by a dramatic drop in sea level. A more likely cause for the end-Permian extinction was a series of volcanic eruptions in Siberia, which produced massive outpourings of lava called flood basalts. This volcanism covered an area about two-thirds the size of the United States and erupted very rapidly just at the time of the extinction. It may have caused significant atmospheric disturbances, global warming, and anoxic (low-oxygen) ocean waters. The other possible cause is the impact of a large extraterrestrial object, as occurred with the extinction at the end of the Cretaceous. Direct evidence for such an impact is sparse, but the available data are consistent with such a cause.