The Ordovician Period (from the name of an ancient British tribe, the Ordovices) extended from 510 mya until 439 mya. At the end of the Cambrian, sea levels fell, causing extinctions.
The continents were moving together during this period, and mountain-building was taking place in the northeastern North American continent. The rest of the continent was relatively quiet.
Classic Fossil-Bearing Sites
Whiterock Formation, Utah, Nevada
Cincinattian Series, Ohio, Indiana, Kentucky
A 24 km craterform structure dated about 472 mya is found in Australia. While not yet found, a mass extinction at the end of the period implies the possibility that another major impact site exists.
Significant Events
First Vertebrates
It was in the Ordovician that the first animals with backbones arose. The Agnatha, the jawless fishes, were the first animals with true bony skeletons.
Mass Extinction
The Ordovician Period ended with a mass extinction. About 25% of all families did not make it into the Silurian.
Ordovician Graphics
| |
|
|
| Trilobite |
Cephalopod |
Echinoderm |
| |
|
|
| Ordovician Sea |
Endoceras |
Maclurites |
| |
|
|
| Mollusk |
Homotelus |
Snails |
Return to Life Through Geologic Time
Return to Earth History Resources