Cambrian Period
538.8 – 485.4 million years ago · Paleozoic Era
The Cambrian opens the Phanerozoic, the eon of visible animal life. Within a few tens of millions of years, the oceans filled with trilobites, early arthropods, mollusks, sponges and the first chordates, our own distant relatives.
At a glance
- Began
- 538.8 Ma
- Ended
- 485.4 Ma
- Duration
- 53.4 million years
- Era
- Paleozoic
- Climate state
- Greenhouse (warm, little or no polar ice)
- Land above sea level (PaleoDEM)
- ~20.5%
- Dinosaurs on our map
- 0
The world in the Cambrian
Open the interactive map at 510 Ma → Elevation view
What Earth was like
Most land was gathered in the southern hemisphere. The giant continent Gondwana (future Africa, South America, Antarctica, Australia and India) stretched from the equator toward the South Pole, while Laurentia (North America), Baltica (northern Europe) and Siberia were separate, smaller continents near the equator. The land itself was barren rock: no plants, no soil, no forests.
Climate
The Cambrian was a warm greenhouse world with high carbon dioxide and little or no polar ice. Sea levels rose through the period and flooded the continental margins, creating vast shallow seas where much of the new animal life evolved.
Life
Life was almost entirely marine. Fossil sites such as the Burgess Shale in Canada and Chengjiang in China preserve soft-bodied animals in extraordinary detail, including Anomalocaris, an apex predator nearly a meter long. Reefs were built by sponge-like archaeocyaths rather than corals.
Dinosaurs of the Cambrian
There were no dinosaurs yet. The first dinosaurs appear in the Late Triassic, around 233 million years ago.
How it ended
The Cambrian closed with a series of extinction pulses that hit trilobites especially hard, linked to changes in ocean oxygen and temperature. Its end is defined at 485.4 million years ago, the start of the Ordovician.
Key facts
- Most modern animal phyla first appear in the Cambrian fossil record.
- The first eyes and hard shells spread rapidly, likely driven by predation.
- There was still no life on land beyond microbial crusts.
Data: land and sea
Across the Cambrian, an average of 20.5% of Earth’s surface stood above reconstructed sea level (range 18.8–21.3%). Today the same model gives 31.8%.
Where this data comes from
- Continent positions: GPlates Web Service, Merdith et al. (2021) full-plate model, used for 250–540 Ma.
- Elevation and shorelines: PALEOMAP PaleoDEMs, Scotese & Wright (2018), doi:10.5281/zenodo.5460860, CC BY 4.0.
- Period boundaries: ICS International Chronostratigraphic Chart (2023/09).
These are scientific reconstructions, not observations. Uncertainty grows the further back in time you go. About & data sources
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- About & data sourcesWhere the reconstructions and fossil data come from.