Cambrian
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The Cambrian is the first geological period of the Paleozoic Era and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma to the beginni
Ediacaran–Cambrian boundary section at Fortune Head, Newfoundland, GSSP
Diorama of the Burgess Shale Biota
Archeocyathids from the Poleta formation in the Death Valley area
Stromatolites of the Pika Formation (Middle Cambrian) near Helen Lake, Banff National Park, Canada
Ordovician
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The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 43.75 million years from t
Cambrian
…Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 486.85 Ma. Most of the continents were located in the southern hemisphere surrounded by the vast Panthalassa Ocean. The assembly of Gondwana…
External mold of the Ordovician bivalve Anomalodonta gigantea showing that the original aragonite shell dissolved on the sea floor, leaving a cemented mold for biological encrustation (Waynesville Formation of Franklin County, Indiana).
A diorama depicting Ordovician flora and fauna
Fossiliferous limestone slab from the Liberty Formation (Upper Ordovician) of Caesar Creek State Park near Waynesville, Ohio.
The trilobite Isotelus from Wisconsin