Orthoceras fossil plaque

Orthoceras, meaning "straight horn," were marine animals with a long, straight, conical shell divided into chambers. The soft body of the creature resided in the last, largest chamber. These fossils are typically found in black limestone, which was originally ancient seafloor mud, and date back to the Ordovician period, around 400-500 million years ago. Many polished Orthoceras fossils originate from Morocco. Orthoceras are thought to have been intelligent invertebrates with a sophisticated nervous system, eyes, and jaws, and are believed to have used jet propulsion for movement. Relation to other species: Orthoceras are related to ammonites and are considered ancestors of modern-day squid.