Era
Cretaceous
11
Permian
8
Eocene
7
Pennsylvanian
7
Triassic
7
Paleozoic
6
Cenozoic
5
Devonian
5
Jurassic
4
Miocene
4
Pleistocene
4
Precambrian
4
Holocene
3
Paleocene
3
Mississippian
2
Quaternary
2
Tertiary
2
1880-1930
1
1906-1984
1
Cambrian
1
Carboniferous
1
Huronian
1
Mesozoic
1
Oligocene
1
Proterozoic
1