Orthoceras, also known as Orthoceratites, is a genus of extinct nautiloid cephalopod. Its name is derived from the words “straight horn”, referring to it’s long, conical shell. These creatures roamed the seas during the Ordovician Period (485 million - 443 million years ago). They are the ancient ancestors of ammonites and squid that can be found in sizes ranging from a centimeter to over 14 feet long. Orthoceras are commonly found on a rock matrix,most of the time being limestone. A majority of specimens on the market have been coming out of Morocco, Scandinavia, Sweden, and the Baltic states.