Mass extinction at the end of the Permian Period (252 million years ago)
Scientists estimate about 90% of the plant and animal species on Earth during the Permian Period were extinct by the end of the period. Marine animals living in reefs and shallow waters were especially hard hit, and the loss of marine species reached about 96%.
Permian marine fossils of now extinct species found in eastern Kansas Permian and older Pennsylvanian rocks include corals, brachiopods, bryozoans, ammonoids, and fusulinids. Trilobites likely died out just before the mass extinction, and only a few Pennsylvanian and Permian specimens have been found in Kansas.
On land, more than two-thirds of amphibian and reptile species and nearly one-third of insect species were wiped out. The demise of so many insects is noteworthy because insects tend to be survivors and this is the only mass extinction that greatly affected them.
In central Kansas, a fossil site near the town of Elmo in Dickinson County is one of the world’s best-known sources of Permian insect fossils, especially winged species. Meganeuropsis, a giant dragonfly with a wingspan of nearly 2½ feet, is among the thousands of specimens that have been found there. Fossils of crickets, cockroaches, and other insects from the Permian and earlier Pennsylvanian subperiod have been found in a quarry near the town of Hamilton in Greenwood County.
As with the end-Cretaceous mass extinction, the cause of the end-Permian extinction is difficult to determine. The possibilities include an asteroid strike, natural pollution that deprived the oceans of oxygen needed to sustain life, and dust clouds emitted by massive volcanic eruptions that blocked the sun and cooled Earth. Evidence for each of these theories, and others, has been found, but it is hard to determine whether any single event was powerful enough to create such widespread chaos. In the end, several causes may have acted together to create the perfect storm.