The extinction of Metapolygnathus parvus marks the end of the Carnian, for example, while the start of the Rhaetian is defined by the first appearance of the genus Misikella.

Metapolygnathus parvus 灭绝标 Carnian 结， 例， Rhaetian 开始是由 Misikella 属首次出现定义。