Cisuralian

Cisuralian is a formal division of the geologic timescale that corresponds to the earliest part of the Permian Period. The name derives from the Cis-Ural region, where rocks of this age were first studied, and in older literature it is often equated with the Early Permian. The Cisuralian spans roughly from 298.9 million to 272.3 million years ago, ending with the onset of the Guadalupian.

Within the International Commission on Stratigraphy framework, the Cisuralian is subdivided into four stages: Asselian, Sakmarian, Artinskian, and Kungurian. These stages reflect regional stratigraphy in the Urals, Central Asia, and nearby areas, and their exact regional boundaries are calibrated to global chronostratigraphic markers.

Geologically, the Cisuralian occurred during the final phases of the assembly of the supercontinent Pangaea, a time associated with climatic fluctuations and shifts in sea level. Depositional environments varied from coal-bearing basins to arid, continental interiors. The period records important evolutionary developments in terrestrial life, including diversification among amniotes such as therapsids and early reptiles, alongside ongoing changes in amphibians and plant communities.

In global stratigraphy, the Cisuralian provides a key framework for correlating Permian rocks across continents. While many regions now prefer more precise, regionally defined stage names, the Cisuralian remains a foundational reference for the early Permian, illustrating the transition from the late Paleozoic to the middle Permian in both climate and biotic evolution.