Mean atmospheric O2
Geologic Time Scale
Two jawless fish of the genus Pteraspis feed near the ocean's surface 410 million years ago during the Early Devonian. Pteraspis grew to a length of about 8 inches and is believed to have dined on shoals of plankton. A hard shell and spikes may have helped to protect Pteraspis from larger predators.
Copyright © Walter B. Myers. All rights reserved.
[ Home | What's New | The Graphics | Information | Site Map | ]