Evolution What the Fossils Say and Why it Matters

Time-Rock Units
of the Geologic
Column

Time Units of the Geologic Time Scale

(Numbers are numerical dates in millions

of years before the present)

Quaternary

Neogene

Eon Era Period Epoch

Holocene

Pleistocene

Paleogene

Cretaceous

Phanerozoic Eon

Jurassic

Triassic

Permian

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

Late

Late

Middle

ProterozoicEonEarly

Paleozoic Era

Carboniferous

Mezozoic Era

Cenozoic Era

Tertiary

ArcheanEon

3800

3200

2800

2500

Sponges

First insects

Trilobites

Soft-bodied

animals

Annelida

Platyhelminthes

(flatworms)

Mollusca

(clams, snails,

octopus, squid)

Cnidaria

(sea anemone,

jellyfishes, corals)

Arthropoda

(insects, crabs,

shrimps, barnacles)

Single-celled

organisms

1600

1000

550

488

444

416

360

318

300

251

200

145

66

56

34

23

5

2

0.01

Middle

Early

??? Hadean No record Origin of earth about 4.6 billion years ago

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Precambrian

comprises

about

87%

of the

geologic

time scale