Era
Cretaceous
32
Mesozoic
20
Pleistocene
15
Ordovician
12
Paleozoic
12
Pennsylvanian
11
Tertiary
10
Cambrian
9
Devonian
9
Carboniferous
8
Permian
8
Quaternary
8
Cenozoic
7
Mississippian
7
Eocene
6
Jurassic
6
Miocene
6
Pliocene
6
Precambrian
6
Oligocene
5
Triassic
4
Neogene
3
Holocene
2
Phanerozoic
2
Silurian
1