| Murrayoceras Temporal range: M Ordovician | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| 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 ventral 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.