Fossil cephalopod orthoceras. Lower ordovician to triasic. 500-190mil. Location Morocco. 170-230 grams.
Orthoceras is an extinct genus of nautiloid cephalopod, primarily found in Middle Ordovician marine limestones of the Baltic States and Sweden. Sometimes referred to as Orthoceratites, it is often misspelled as Orthocera, Orthocerus, or Orthoceros. The name "Orthoceras" is derived from the Ancient Greek words orthós (meaning "straight") and κέρας (meaning "horn"), referring to the creature's straight, horn-shaped shell.
Previously, Orthoceras was believed to have had a worldwide distribution due to its classification as a "wastebasket taxon" for various species of conical-shelled nautiloids across the Paleozoic and Triassic periods. However, after a re-cataloging effort, Orthoceras now specifically refers to Orthoceras regulare, found in the Ordovician-aged limestones of the Baltic Sea and surrounding areas.
These remarkable creatures had slender, elongated shells, with a constriction in the middle of the body chamber and a subcentral orthochoanitic siphuncle. The shell's surface is decorated with fine lirae, creating a distinct pattern. Similar species are often classified under the genus Michelinoceras, but Orthoceras remains a fascinating part of ancient marine life for collectors and enthusiasts alike.