Murrayoceras

Murrayoceras Temporal range: M Ordovician
Scientific classification
Class:	Cephalopoda
Subclass:	Nautiloidea
Order:	Orthocerida
Family:	Baltoceratidae
Genus:	Murrayoceras Foeste, 1926

Murrayoceras is a nautilid cephalopod included in the orthocerid family Baltoceratidae, wide spread 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 verntral siphuncle, 0.15 to 0.3 the dorso-ventral shell diameter.^[1] 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.^[2] 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 ^[2], putting it thereby in the rod-bearing Baltoceratidae, and closely related to Rhabdiferoceras and Cartersoceras, among others. In some recent classifications however^[3] Murrayoceras has been reassigned to the Sactorthoceratidae although Frey (1995)^[4] did retain the genus in the Baltoceratidae.

References

1. ^ W. M. Furnish and Brian Glennister, 1964. Nautiloidea- Ellesmerocerida; Treatise on Invertebrate Paleontology, Part K. Geol. Soc. of America and Univ. Kansas Press
2. ^ ^{a b} Rousseau H Flower, 1964. The Nautiloid Order Ellesmeroceratida (Cephalopoda). New Mexico Bureau of Mines and Mineral Resources Memoir 12.
3. ^ B. Kröger, et al.2007. Early orthoceratoid cephalopods from the Argentine Precordillera (Lower-Middle Ordovician). Journal of Paleontology 81(6):1266-1283 [1]
4. ^ 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:1-126 [2]