''Murrayoceras'' is a nautilid cephalopod included in the

orthocerid 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 ...

family

Baltoceratidae Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, exist ...

, widespread in the Middle Ordovician of North America, characterized by a depressed orthoconic shell with a subtriangular cross section and flattened venter and a proportionally large ventral siphuncle, 0.15 to 0.3 the dorso-ventral shell diameter. Septa are close spaced with sutures forming broad lobes on the upper flanks and ventral surface. As originally perceived ''Murrayoceras'' included species differing in siphuncle profile.Rousseau H Flower, 1964. The Nautiloid Order Ellesmeroceratida (Cephalopoda). New Mexico Bureau of Mines and Mineral Resources Memoir 12. Those in which the siphuncle segments are externally convex were redefined as Cartersoceras., leaving Murrayoceras with those having essentially straight, tubular, or slightly concave segments. ''Murrayoceras'' has a ventral rod in the siphuncle, putting it thereby in the rod-bearing Baltoceratidae, and closely related to ''

Rhabdiferoceras ''Rhabdiferoceras'' is an extinct genus of orthocerids belonging to the Baltoceratidae that lived in what would be North America during the Cassinian Stage at the end of the Early Ordovician, existing for approximately two million years from abo ...

'' and '' Cartersoceras'', among others. In some recent classifications however ''Murrayoceras'' has been reassigned to the Sactorthoceratidae although Frey (1995)R. C. Frey. 1995. Middle and Upper Ordovician nautiloid cephalopods of the Cincinnati Arch region of Kentucky, Indiana, and Ohio. U.S. Geological Survey Professional Paper 1066P:1-12

/ref> did retain the genus in the Baltoceratidae.

References

{{Taxonbar, from=Q6939548 Nautiloids Paleozoic life of Ontario