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