Orthoceras is a group of extinct nautiloid cephalopods, the ancestors of the modern squid, that lived in the oceans about 400 million years ago, during the Devonian period of the Paleozoic era.
The specimens of this group had tentacles and long, pointed conical shells divided into several internal chambers. To float in the ocean, they filled the internal compartments of the shells with air and expelled water to propel themselves. Their food consisted of small marine animals and bacteria. The average size of an orthoceras was about 15 cm, but it could grow up to 4.2 meters in length.
Orthoceras are found fossilized in limestone sediments, usually in the mountains of the Sahara Desert, especially in Morocco. The rocks in which the shells are found are carved and polished, and then used as ornaments or jewelry that highlight the impressive geometry of the sectioned shell.
