The limestone specimen in the picture weighs 8 pounds and measures 9” long, and is 3” thick. It was quarried from a limestone deposit located in the in Sahara desert, Morocco.
The orthoceras were among the most advanced of the invertebrates having eyes, jaws, and a sophisticated nervous system. They swam freely using a jet propulsion system by squirting water from their bodies. They had tentacles and ink sacs much like the present-day squid. As they died, their shells accumulated in great numbers on the sea floor where they were aligned by currents, buried by sediments, and transformed over the ages into stone by various physical and chemical processes.