Era
Miocene
37
Tertiary
28
Devonian
25
Mesozoic
24
Paleozoic
23
Cambrian
22
Cenozoic
20
Mississippian
18
Ordovician
16
Oligocene
13
Quaternary
13
Triassic
12
19th century
7
20th century
7
Silurian
7
Pleistocene
6
Jurassic
5
Precambrian
5
Cretaceous
4
Pennsylvanian
4
Carboniferous
3
Eocene
3
Holocene
3
Permian
3
1875-1963
2
1946-
2
Neogene
2
Pre-Quaternary
2
-1905?
1
1735-1826
1
1828-1891
1
1842-1901
1
1846-1847
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
1903-1987
1
1904-1979
1
1906-1947
1
1908-1987
1
1909-1988
1
1922-2016
1
1930-2015
1
1941-
1
2001-2009
1
more ...