What are Some Cambrian Organisms?
Cambrian organisms lived during the Cambrian era, from approximately 542 to 488 million years ago. The Cambrian era is famous for the Cambrian explosion, an abrupt period of adaptive radiation during which representatives of all modern animal phyla (except bryozoans) appeared. This occurred approximately 530 million years ago and lasted for about 10 million years. The start of the Cambrian period has traditionally been defined as the emergence of shield-shaped arthropods called trilobites and early sponges (and the first reef-builders) called archeocyathids (literally “ancient cup”). Since then, its start has been redefined as an extinction event that marks the Cambrian-Precambrian boundary. The time of this event has been very precisely defined using changes in carbon isotope ratios occurring during this period, which indicate a large drop in planetary biomass. Cambrian faunas were the first truly diverse faunas to evolve. The start of the Cambrian period is marked by the aforestated
