Era
Cretaceous
31
Precambrian
21
Pennsylvanian
13
Tertiary
12
Eocene
10
Jurassic
9
Triassic
8
Permian
7
Cenozoic
6
Paleozoic
6
Quaternary
6
Oligocene
5
1823-1890
2
Devonian
2
Mesozoic
2
Miocene
2
Mississippian
2
Pleistocene
2
1809-1865
1
1831-1881
1
1866-1948
1
1914-1989
1
1946-
1
1953-
1
19th century
1
20th century
1
Holocene
1
Paleogene
1
Pliocene
1