Kasimovian

The Kasimovian is a special time period in Earth's history, known as a geochronologic age or chronostratigraphic stage. It is part of the ICS geologic timescale and falls within the Pennsylvanian epoch of the late Carboniferous period. The Kasimovian lasted from about 307 to 303.7 million years ago (Ma).

This stage comes after the Moscovian and is followed by the Gzhelian. During the Kasimovian, a significant event happened called the Carboniferous Rainforest Collapse, which led to many changes in plant and animal life.

In North America, this time is called the Missourian, while in western Europe it is known as the Stephanian. Studying the Kasimovian helps scientists understand how Earth's climate and life have changed over millions of years.

Name and definition

The Kasimovian is named after the Russian city of Kasimov. This time period was defined in 1926 by a scientist named Boris Dan'shin, who originally called it the Teguliferina horizon. After Dan'shin’s death, the name was changed to Kasimov horizon, and later in 1949, it became known as the Kasimovian.

The start of the Kasimovian is marked by certain fossils, such as particular types of fusulinid biozone and the first appearance of an ammonite genus. The end of this stage is also identified by the appearance of new fossils, including specific fusulinids and the conodont Streptognathodus zethus.

Biozones

The Kasimovian time period can be divided into three special layers based on tiny, ancient teeth called conodonts. These layers are:

• Idiognathodus toretzianus Zone
• Idiognathodus sagittatus Zone
• Streptognathodus excelsus and Streptognathodus makhlinae Zone