Natural Orthoceras fossilized squid from Morocco. Orthoceras are a famous and very large fossil deposit of animals that can be found in Morocco, North Africa. Ancestors to ammonites, Orthoceras are extinct sea creatures, and depending on what source you refer to, they date from the lower Ordovician to Triassic ages (500 to 190 million years ago). 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 preserved in black limestone. Today, this prehistoric sea floor is ironically, found in the dramatic Atlas Mountain Range in southern Morocco at the northern fringe of the Sahara Desert.