Orthoceras are the fossilized remains of an extinct marine animal of Cephalopod family. They are ancestors to the modern-day squid and octopus and are dated to the Devonian Period about 500 million years ago. They range in length from a few inches to over six feet. They could swim as well as crawl on the ocean floor. By filling the chambers of their shells with air they could float through the seas propelling themselves by squirting jets of water. They had tentacles and ink sacs much like the squid of today. After they died, their shells accumulated on the sea floor where they were buried by sediments, and over the ages turned to stone. These Orthoceras fossils have been dug out of the Atlas Mountains in southern Morocco, at the northern fringe of the Sahara Desert, which was once under the sea.