Era
Cretaceous
30
Eocene
17
Tertiary
10
Carboniferous
8
Permian
8
Paleocene
4
Precambrian
4
Paleozoic
3
-1995
2
Archaean
2
Miocene
2
Mississippian
2
Pleistocene
2
Proterozoic
2
Triassic
2
19th century
1
Cambrian
1
Cenozoic
1
Devonian
1
Jurassic
1
Mesozoic
1
Paleogene
1
Pennsylvanian
1
Pliocene
1
Quaternary
1