Orthocerida, from Ancient Greek ὀρθός, meaning "straight", and κέρας, meaning "horn", also known as the Michelinocerida, is an order of extinct orthoceratoid cephalopods that lived from the Early Ordo

Orthoceratoidea, from Ancient Greek ὀρθός, meaning "straight", and κέρας, meaning "horn", is a major subclass of nautiloid cephalopods. Members of this subclass usually have orthoconic to slightly cyr