Era
Cretaceous
39
Precambrian
17
Tertiary
16
Paleozoic
14
Permian
13
Miocene
11
Jurassic
10
Mesozoic
10
Devonian
8
Cenozoic
7
Triassic
7
Silurian
5
Mississippian
4
Pennsylvanian
4
Quaternary
4
Carboniferous
3
Oligocene
3
Archaean
2
Cambrian
2
Eocene
2
Paleocene
2
Pliocene
2
Ordovician
1
Pleistocene
1
Proterozoic
1