Late Carboniferous The top of the
Kasimovian stage is close to the first appearance of
Streptognathodus zethus. The
golden spike for the Kasimovian stage has not yet been assigned (in 2008). The Kasimovian is subdivided into three conodont
biozones: •
Idiognathodus toretzianus Zone •
Idiognathodus sagittatus Zone •
Streptognathodus excelsus and
Streptognathodus makhlinae Zone The base of the
Gzhelian is at the first appearance of
Streptognathodus zethus. The top of the stage (also the top base of the
Silesian and the base of the Permian system) is at the first appearance of
Streptognathodus isolatus within the
Streptognathus "wabaunsensis" chronocline. The Gzhelian stage is subdivided into five
biozones, based on the conodont genus
Streptognathodus: •
Streptognathodus wabaunsensis and
Streptognathodus bellus Zone •
Streptognathodus simplex Zone •
Streptognathodus virgilicus Zone •
Streptognathodus vitali Zone •
Streptognathodus simulator Zone
Early Permian The base of the
Asselian stage is at the same time the base of the
Cisuralian series and the Permian system. It is defined as the place in the stratigraphic record where
fossils of the species
Streptognathodus isolatus first appear. The global reference profile for the base (the
GSSP or golden spike) is located in the valley of the Aidaralash River, near
Aqtöbe in the Ural Mountains of Kazakhstan. The top of the Asselian stage (the base of the
Sakmarian stage) is at the first appearance of the species
Streptognathodus postfusus. The Asselian contains five conodont
biozones: • zone of
Streptognathodus barskovi • zone of
Streptognathodus postfusus • zone of
Streptognathodus fusus • zone of
Streptognathodus constrictus • zone of
Streptognathodus isolatus The base of the
Sakmarian stage is laid with the first appearance of
Streptognathodus postfusus in the fossil record. A global reference profile for the base had in 2009 not yet been appointed. The top of the Sakmarian (the base of the Artinskian) is defined as the place in the stratigraphic record where fossils of conodont species
Sweetognathus whitei and
Mesogondolella bisselli first appear. ==References==