Orthocerida

Orthocerida, from Ancient Greek ὀρθός (orthós), meaning "straight", and κέρας (kéras), meaning "horn", also known as the Michelinocerida, is an order of extinct orthoceratoid cephalopods that lived from the Early Ordovician (490 million years ago) possibly to the Late Triassic (240 million years ago). A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous (140 million years ago), and the Eocene fossil Antarcticeras is sometimes considered a descendant of the orthocerids although this is disputed. They were most common however from the Ordovician to the Devonian.