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 Carnian 结， 例如， Rhaetian 始是由 Misikella 属首次出现定义。