Cambrian
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The Cambrian is the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran period 538.8 Ma to the beginning of the Ordovician Period 485.4 Ma.
Archeocyathids from the Poleta formation in the Death Valley area
Stromatolites of the Pika Formation (Middle Cambrian) near Helen Lake, Banff National Park, Canada
Trilobites, like these Elrathia kingii were very common arthropods during this time
Pikaia was a stem-chordate from the Middle Cambrian
Ediacaran biota
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The Ediacaran biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period. These were enigmatic tubular and frond-shaped, mostly sessile, organisms. Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The term "Ediacara biota" has received criticism from some scientists due to its alleged inconsistency, arbitrary exclusion of certain fossils, and inability to be precisely defined.
Life in the Ediacaran Period, as imagined by researchers in 1980.
Palaeontologist Guy Narbonne examining Ediacaran fossils in Newfoundland
Modern cyanobacterial-algal mat, salty lake on the White Sea seaside
A reconstruction of the Ediacaran biota at the Field Museum in Chicago