This is a large sized Orthoceras "Blade" from Morocco.
Orthoceras is a genus of extinct nautiloid cephalopod. Orthoceras fossils are dated back more than 400 million years ago and are ancestors to the modern day Squid and Octopus. As they died their shells accumulated upon the ocean floor, covered slowly by sediments they transformed into stone over the ages.
Orthoceras fossils have been found to occur in any marine rock, especially limestone and have a wide global distribution. This particular specimen was sourced from Morocco.
Goniatids, informally Goniatites, are ammonoid cephalopods that form the Order Goniatiida, derived from the more primitive Anarcestida during the Middle Devonian some 390 million years ago. Goniatites (goniatitida) survived the Late Devonian extinction to flourish during the Carboniferous and Permian only to become extinct at the end of the Permian some 139 million years later.