Era
Miocene
36
Tertiary
25
Devonian
23
Cambrian
22
Mississippian
17
Mesozoic
15
Paleozoic
15
Ordovician
14
Cenozoic
13
Oligocene
12
Triassic
12
Quaternary
9
20th century
7
Silurian
6
Pleistocene
5
Precambrian
5
Cretaceous
4
19th century
3
Carboniferous
3
Eocene
3
Holocene
3
Jurassic
3
Pennsylvanian
3
1875-1963
2
1946-
2
Neogene
2
Permian
2
-1905?
1
1735-1826
1
1828-1891
1
1846-1850
1
1848-1917
1
1850-1950
1
1854-
1
1855-approximately 1912
1
1859-1950
1
1870-1950
1
1876-1959
1
1908-1987
1
1909-1988
1
1922-2016
1
1941-
1
2001-2009
1
Pliocene
1