In the seas, a novel major group of ammonoid cephalopods called clymeniids appeared, underwent tremendous diversification and spread worldwide, then just as suddenly went extinct.
[9] The International Commission on Stratigraphy divides the Famennian into four informal substages based primarily on conodont zonation.
The Famennian corresponds to four historical subdivisions in German stratigraphy: the Nehdenian, Hembergian, Dasbergian, and Wocklumian (from oldest to youngest).
[8] North American subdivisions of the Famennian include the Chautauquan, Canadaway, Conneaut, Conneautan, Conewango and Conewangan.
The lower GSSP, ratified in 1993, is located within the Coumiac Formation near Cessenon in southern France.