Orthoceras Pillar Orthoceras – Ancient Marine Predator The Orthoceras is an extinct marine cephalopod that lived around 400 million years ago during the Paleozoic era. It is known for its elongated, straight shell and is considered an ancestor of modern squids and nautiluses. Its fossils are primarily found in limestone and are often used for decorative items and jewelry. The Orthoceras played a crucial role in ancient marine ecosystems as a fast and agile predator, hunting smaller creatures in the ocean.