An important event in the history of life that began around 540 million years ago and concluded around 510 million years ago. During this interval nearly all the major types of organisms now known on Earth, as well as several novel extinct types, appeared in the fossil record.

the term used to describe the very sudden appearance of a huge variety of fossil organisms with hard skeletons in the sedimentary rocks of the middle Cambrian.

Fossils that seem to show that all modern living kinds suddenly appeared from nothing.

Great diversification of multicellular life forms in the Earth's oceans that started during the Cambrian about 570 million years ago.

The Cambrian explosion is the geologically sudden appearance in the fossil record of the ancestors of familiar animals, starting about 542 million years ago (Mya). In addition, a similar pattern of diversification is seen in other organisms such as phytoplankton and the various colonial calcareous microfossils grouped together as calcimicrobes. The base of the Cambrian is also marked by strong geochemical perturbations, including excursions in carbon and sulfur isotopes.