Learn more about the time period that took place 488 to 443 million years ago. 3 min read During the Ordovician period, part of the Paleozoic era, a rich variety of marine life flourished in the ...

The oldest echinoids come from the Late Ordovician Period and are approximately 450 million years old. The closest sister group to the echinoids are the holothurians and the two groups must have ...