Creatures in the Permian Period

Geography and Climate

• The earth's surface during the Permian period was dominated by the supercontinent of Pangaea and the giant ocean Panthalassa. A smaller body of water, the Tethys Sea, lay nestled in Pangaea's concave eastern side. Due to Pangaea's vast size, much of its interior was far from the oceans, leaving many areas extremely arid and subject to wide temperature variations. The Permian period's dry climate caused the decline of wet areas and spurred the proliferation of seed-bearing plants, especially conifers, and animals that were suited for these conditions, especially reptiles.

Terrestrial Creatures

• Terrestrial vertebrates abounded during the Permian period. There were large amphibians such as the nearly 400-lb. eryops, sail-backed reptiles such as the edaphosauras and dimetrodon, and large, armored herbivores such as peraiasaurs. The Permian period also saw the rise of therapsids, ancestors of mammals. These reptiles, which became the dominant terrestrial creatures of this epoch, comprised several groups, including dinocephalians, gorgonopsians, cynodonts, dicynodonts and theriodonts. Also, the first species of insects that metamorphose, going through egg, larva, pupa and adult stages, evolved during this era.

Marine Creatures

• Many marine creatures flourished during the Permian period, among them sharks, brachiopods, ammonoids, nautiloids and a number of bony fishes. Although corals made a comeback during this time, certain kinds, such as rugose and tabulate corals, perished at the Permian's end. Trilobites declined and eventually succumbed to mass extinction as well, as did their fellow marine arthropods the eurypterids. In fact, marine species fared the worst during the post-Permian extinction.

Causes of the Mass Extinction

• The cause of the mass extinction occurring at the close of the Permian period is unknown. Several possibilities have been proposed. For example, massive volcanic eruptions that occurred in Siberia could have caused catastrophic disruptions in the global climate; another view holds that an asteroid or comet strike could be to blame. Still another possible explanation is that Pangae's immense size played a role. Alternatively, a combination of gradual climatic and other changes may have been responsible.