Era
Cretaceous
43
Tertiary
21
Precambrian
17
Paleozoic
15
Mesozoic
13
Permian
13
Jurassic
11
Miocene
11
Devonian
9
Cenozoic
7
Triassic
7
Quaternary
6
Mississippian
5
Silurian
5
Cambrian
4
Carboniferous
4
Pennsylvanian
4
Oligocene
3
1864-1945
2
Archaean
2
Eocene
2
Paleocene
2
Pliocene
2
1857-1920
1
1887-1956
1
1890-1980
1
1918-1964
1
19th century
1
Ordovician
1
Pleistocene
1
Proterozoic
1