Era
Cretaceous
91
Eocene
43
Tertiary
31
Carboniferous
18
Permian
18
Precambrian
18
Paleocene
13
Paleozoic
13
Triassic
8
20th century
7
Jurassic
7
-1995
6
Pleistocene
6
1866-1895
5
1876-1933
5
19th century
5
Mississippian
5
Proterozoic
5
Quaternary
5
Archaean
4
Devonian
4
Mesozoic
4
Miocene
4
Pennsylvanian
4
Pliocene
4
Cenozoic
3
Paleogene
3
1804-1881
2
1860-1890
2
1882-
2
1976-1998
2
Cambrian
2
approximately 1775-1813
2
1814-1892
1
1829-1887
1
1834-1902
1
1836-1902
1
1844-1933
1
1846-1922
1
1848-1860
1
1859-1952
1
1860-1958
1
1861-1944
1
1868-1952
1
1870-1952
1
1880?-1903
1
1883-1969
1
1907-1991
1
1913-2003
1
1929
1
more ...