The Kasimovian is the third stage in the Pennsylvanian (late Carboniferous), lasting from 306.5 ± 1.0 to 303.9 ± 0.9 Ma. The Kasimovian stage follows the Moscovian and is followed by the Gzhelian.
Coal Forests covered tropical Euramerica (Europe, eastern North America, northwesternmost Africa) and Cathaysia (mainly China). Climate change devastated these tropical rainforests in the late Moscovian early Kasimovian ages. This climate change caused by a cooler, drier climate severely affected the lycopsids which dominated the wetland areas (they were subsequently replaced by opportunistic ferns). By the late Kasimovian rainforests were fragmented, forming shrinking patches further and further apart. There was also a great loss of amphibian diversity while simultaneously, the drier climate spurred the diversification of reptiles. Terrestrial invertebrates were diverse and included annelids, molluscs, and arthropods, including the giant arthropleurids. Most were detritivorous, eating 'litter' off of the forest floor however, some had evolved herbivorous and predatory forms. By the end of the age, the Arthropleurids went extinct. Yogi111211