Era
Cretaceous
13
1860-1890
5
Tertiary
5
Cenozoic
4
Eocene
4
1834-1902
3
1849-1938
3
Mesozoic
3
Mississippian
3
Paleozoic
3
1890-1945
2
Jurassic
2
Ordovician
2
Triassic
2
1770-1838
1
1774-1809
1
1829-1887
1
1831-1899
1
1840-1897
1
1848-1860
1
1897-1948
1
1902-1968
1
19th century
1
Carboniferous
1
Holocene
1
Miocene
1
Neogene
1
Paleogene
1
Pennsylvanian
1
Permian
1
Pleistocene
1
Pliocene
1
Precambrian
1
Quaternary
1