Era
Cretaceous
46
Tertiary
32
Jurassic
30
Quaternary
28
Mesozoic
22
Paleozoic
19
Mississippian
15
20th century
13
Cenozoic
13
Carboniferous
11
Triassic
10
Miocene
9
Permian
9
Devonian
8
Pennsylvanian
8
Silurian
8
Pliocene
7
21st century
6
Oligocene
6
Pleistocene
6
Precambrian
6
To 1867
5
1867-1959
4
Cambrian
4
Ordovician
3
1745-1819
2
1761-1806
2
1779-1843
2
1900-1959
2
1945-
2
1959-
2
19th century
2
Eocene
2
Neogene
2
-1932
1
1709-1746
1
1720-1806
1
1797-1879
1
1821-1871
1
1838-1914
1
1846-1896
1
1853-1947
1
1855-1934
1
1863-1920
1
1868-1940
1
1883-1975
1
1887-1970
1
1892-1918
1
18th century
1
1906-1954
1
more ...