Wikipedia
Floian
The '''Floian ''' is the second stage of the Ordovician. It succeeds the Tremadocian with which it forms the Lower Ordovician epoch. It precedes the Dapingian stage of the Middle Ordovician. The Floian extended from to million years ago. The lower boundary is defined as the first appearance of the graptolite species Tetragraptus approximatus.