During a lot of things happened both geologically and biologically. The Cambrian Period was the first period of the Paleozoic Era, it lasted from 570 million years ago to 500 million years ago, 70 million years. It¹s very important because it corresponds with the firs t appearance of abundant fossils especially Trilobites, which characterizes a succeeding point in time. During the Cambrian Period the lapetus Ocean appeared, the predecessor of the Atlantic Ocean, which separated the young North American and Eurasian continents. Also Gondwa ....