Kasimovian

The Kasimovian is a geochronologic age or chronostratigraphic stage in the ICS geologic timescale. It is the third stage in the Pennsylvanian (late Carboniferous), lasting from to Ma. The Kasimovian stage follows the Moscovian and is followed by the Gzhelian.
The Kasimovian saw an extinction event which occurred around 305 mya, referred to as the Carboniferous Rainforest Collapse. It roughly corresponds to the Missourian in North American geochronology and the Stephanian in western European geochronology.
Name and definition.
The Kasimovian is named after the Russian city of Kasimov. The stage was split from the Moscovian in 1926 by Boris Dan'shin (1891-1941), who gave it the name "Teguliferina horizon". The name was posthumously changed in "Kasimov horizon" by Dan'shin in 1947. The name Kasimovian was introduced by Georgy Teodorovich in 1949.
The base of the Kasimovian stage is at the base of the fusulinid biozone of "Obsoletes obsoletes" and "Protriticites pseudomontiparus" or with the first appearance of the ammonite genus "Parashumardites". The top of the stage is close to the first appearances of the fusulinid genera "Daixina", "Jigulites" and "Rugosofusulina" or the first appearance of the conodont "Streptognathodus zethus".
Biozones.
The Kasimovian is subdivided into three conodont biozones: