Orthoceras fossils are dated back to the Silurian Age 400 + million years ago and are the earliest recognizable animals. They are ancestors to the modern day squid. Even though they were among the earliest forms of life, this class of nautiloid is still considered one of the most intelligent forms of ocean life. The Orthoceras ranged in size from a few inches in length to over six feet! They could swim as well as crawl on the ocean floor. By filling the chambers in their shells with air they could float through the seas propelling themselves by squirting jets of water. As they died their shells accumulated upon the ocean floor, then covered by sediments they transformed into stone over the ages. Having a long straight shell their fossils have an iridescent gemlike quality when polished. These Orthoceras specimens are from the Atlas Mountains in Morocco.