543 to 505 million years ago
Cambrian period. Cambrian is the name given to a period of time in Earth 's history (i.e., Cambrian Period), which spanned 570 – 510 million years ago. The proper name Cambrian is also given to all the rocks that formed during that time (i.e., Cambrian System). The Cambrian period (570 million years ago) marks an extraordinary shift in the evolution of life. It ushers in the beginning of the Paleozoic Era (the age of ancient life). Cambrian period and surrounding time periods. The Cambrian period, part of the Paleozoic era, produced the most intense burst of evolution ever known. The Cambrian Explosion saw an incredible diversity of life emerge, including many major animal groups alive today.  Cambrian The earliest geological period of the Palaeozoic era. It is estimated to have begun about 570 million years ago and lasted for some 100 million years. During this period marine animals with mineralized shells made their first appearance and Cambrian rocks are the first to contain an abundance of fossils. The Cambrian period (570 million years ago) marks an extraordinary shift in the evolution of life. It ushers in the beginning of the Paleozoic Era (the age of ancient life). Cambrian period and surrounding time periods. By Laura Klappenbach. The Cambrian Period (543 to 505 million years ago) is the first time period of the Paleozoic Era. It is preceded by the Precambrian. The Cambrian Period opened in the aftermath of a mass extinction. During the last 100 million years of the Precambrian, a unique fauna had developed. Early in the Cambrian Period the first bivalves and arthropods appeared followed by the first mollusks, brachiopods, and trilobites. During the Cambrian Period, all but one of the major groups of animals evolved during a period of 40 million years. This sudden burst of evolutionary innovation, known as the Cambrian Explosion, lasted from about 570 to 530 million years ago Trilobites were the dominant species during the Cambrian Period, 540 to 490 million years ago. Credit: Bill Frische | Shutterstock. View full size image. The Cambrian Period is the first geological time period of the Paleozoic Era (the “time of ancient life”). This period lasted about 53 million years and marked a dramatic burst of evolutionary changes in life on Earth, known as the Cambrian Explosion.. The end of the Cambrian Period is marked by evidence in the fossil record of a mass extinction event about 490 million years ago. The Cambrian Period was followed by the Ordovician Period. The Cambrian (/ˈkaembriən/ ˈkæmbriən /or/) ˈkeɪmbriən is the first geological period of The Paleozoic, era lasting from.541 ± 0.1 0 to.485 ± 4.1 9 million years (ago) mya and is succeeded by The. Ordovician its, subdivisions and indeed its, base are somewhat in. flux The Cambrian (/ˈkaembriən/ ˈkæmbriən /or/) ˈkeɪmbriən is the first geological period of The Paleozoic, era lasting from.541 ± 0.1 0 to.485 ± 4.1 9 million years (ago) mya and is succeeded by The. ordovician Cambrian Period. The Cambrian Period is the first period of the Paleozoic Era spanning from approximately 540 to 500 million years ago. It was named in 1835 by the geologist Adam Sedqwick, after the region of Cambria in Southern Wales and England, where rocks of this age were first found. 
http://www.encyclopedia.com/topic/Cambrian_period.aspx http://science.nationalgeographic.com/science/prehistoric-world/cambrian/ http://www.encyclopedia.com/topic/Cambrian_period.aspx http://animals.about.com/od/c/g/cambrian.htm http://www.livescience.com/28098-cambrian-period.html https://en.wikipedia.org/wiki/Cambrian http://personal.denison.edu/~hauk/bio380-2001/Cambrian.html
when was the cambrian period