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Geological Periods - Home

Cambrian Period
Ordovician Period
Silurian Period
Devonian Period
Carboniferous Period
Permian Period
Triassic Period
Jurassic Period
Cretaceous Period
Tertiary Period
Quaternary Period
The Cambrian Period
543 to 490 Million Years Ago

Start:

Trace fossil, lowest occurrence of Treptichnus (Phycodes) pedum. Near base of negative carbon-isotope excursion.

Index Fossils:

Trilobites, Brachiopods, Graptolites

Evolution:

Invertebrate sea life

Geography:

Shallow Seas, four major continents

Rocks:

conglomerate, sandstone, shale, limestone and dolostone

Anomalous Fossils:

Fish Fossil

Chengjiang: It was believed that the first vertebrate animals evolved during the Ordovician Period (443-490 mya) or possible late in the Cambrian Period (490 mya). Two fossils were recently discovered in Chengjiang China by Chinese paleontologists of fish species similar to the modern day hagfish and lampreys. The rock these fish were found are dated at 530 million years old, very early in the Cambrian Period and about 50 million years before it was believed fish had evolved. This discovery has caused scientists to rethink the evolution of vertebrates. These fish actually predate the assumed ancestors of the fish.