Early Cambrian

The Early Cambrian (also known as the Caerfai, Waucoban, or Georgian) is the first of three geological epochs of the Cambrian period. It spans the time between 542 ± 0.3 Ma and 513 ± 2 Ma (million years ago). The Cambrian explosion of complex organisms occurred during the Early Cambrian. The Early Cambrian is divided into two unnamed ICS stages. The rocks of the Early Cambrian are said to belong to the Lower Cambrian part of the stratigraphic succession.The Early Cambrian was a time of extreme change in both life on earth (Such as the Cambrian explosion) and in the geological land scape (such as the breakup of the Ediacaran supercontient pannotia).Abundant simple worm traces appeared to be common during during the Earliest Cambrian and in the late Ediacaran period but however they were soon followed by a set of small primitive shelled fossils known as the Small Shelly Fauna who thrived in the latest Ediacaran and the earliest Cambrian (or also known as the Manykian stage) the Small Shelly Fauna were eventually replaced by a more complex group of fossils known as the Tommotian fauna the relationship between modern fauna and the Tommotian fauna is not well known but however the Tommotian fauna quickly went extinct and were replaced by more modern fauna in the Cambrian explosion which followed the disappearance of the Tommotian fauna. The Cambrian explosion resulted in the appearance of most modern phyla as well as many extinct ones. The Ediacarian supercontient pannotia broke up during the Early Cambrian around 540 million years ago which resulted in the formation of the smaller Cambrian continents such as Laurentia, Baltica and Siberia. The shallow oceans of the Early Cambrian formed a hospitable environment for life which allowed light to reach aquatic plants more easily which allowed aquatic plants to increase in size and expand into new locations and allowed coral reefs to evolve and expand into wide belts that extended for of hundreds, or even thousands of kilometers along the coasts in the Cambrian period. The Atdabanian Age of the Early Cambrian epoch witnessed the appearance of the first trilobites, an important class of arthropods that would flourish during the first four periods of the Paleozoic era.

The first members of the Hexactinellid class of sponges first appeared during the Early Cambrian.

References

* [http://www.stratigraphy.org/geowhen/stages/Early_Cambrian.html GeoWhen Database - Early Cambrian]
* [http://www.palaeos.com/Paleozoic/Cambrian/EarlyCam.html Palaeos]