Murrayoceras

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Murrayoceras
Temporal range: M Ordovician
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
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 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.

Orthocerida order of molluscs

Orthocerida is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerda that lived from the Early Ordovician possibly to the Late Triassic. A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous. They were most common however from the Ordovician to the Devonian.

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, existing for approximately 20 million years.

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.

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 about 474 -472 mya.

Cartersoceras is a genus of nautiloid cephalopods placed in the Orthocerid family Baltoceratidae, established by Rousseau Flower (1964), for species formally included in part in Murrayoceras, and in part in "Sacotoceras". This group is typical of Murrayoceras in all features except that the siphuncle segments are convex in outline. It is known from the Middle Ordovician of the eastern United States.

The Sactorthoceratidae comprise Orthocerataceaen genera with a subcentral suborthochoanitic siphuncle composed of slightly expanded segments and free of organic deposits. The camerae (chambers) of the phragmocone likewise have organic deposits that are typically retarded or sparse.

Related Research Articles

Plectronocerida order of molluscs

Plectronocerida is a primitive order from which subsequent cephalopod orders are ultimately derived.

The Ellesmerocerida is an order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.

The Ellesmeroceratidae constitute a family within the cephalopod order Ellesmerocerida. They lived from the Upper Cambrian to the Lower Ordovician. They are characterized by straight and endogastric shells, often laterally compressed, so the dorso-ventral dimension is slightly greater than the lateral, with close spaced sutures having shallow lateral lobes and a generally large tubular ventro-marginal siphuncle with concave segments and irregularly spaced diaphragms. Connecting rings are thick and layered, externally straight but thickening inwardly with the maximum near the middle of the segment so as to leave concave depressions on internal siphuncle molds. Septal necks are typically orthochoanitic but vary in length from almost absent (achoanitic) to reaching halfway to the previous septum (hemichoanitic) and may even slope inwardly (loxochoanitic).

Bickmorites is an extinct nautiloid cephalopod genus known from the upper Ordovician to the middle Silurian of North America and northern Europe (Norway).

Bactroceras is a genus of the family Baltoceratidae, orthoceroid cephalopods that lived during the early Middle Ordovician, from about 472—464 mya, existing for approximately 8 million years.

Cyrtobaltoceras is an extinct cephalopod genus known from the upper Lower Ordovician Fort Cassin Formation at Valcour, N.Y. that is included in the Nautiloid family Baltoceratidae

Rioceras is an extinct genus of orthocerid cephalopods of the family Baltoceratidae that lived in what would be North America during the Early Ordovician from 480—472 mya, existing for approximately 8 million years.

Microbaltoceras is an extinct genus of the cephalopod family Baltoceratidae that lived in what would be North America during the Early Ordovician. It was named by Rousseau Flower (1964) and assigned by him to the Baltoceratidae. The type species is Microbaltoceras minore which was found in the Threadgill Member of the Tanyard Formation in Gillespie County, Texas, USA.

The Tripteroceratidae is a family of depressed, straight to slightly curved nautiloid cephalopods from the middle and upper Ordovician with generally flattened venters and empty siphuncles with straight to inflated sedments included in the Oncocerida.

Phragmoceratidae family of molluscs

The Phragmoceratidae is a family of extinct nautiloid cephalopods from the Order Discosorida that lived during the latter part of the Silurian.

The Actinoceriatidae are a family of actinocerids named by Saemann in 1853 for those that grew to have large shells with blunt apecies and large siphuncles with widely expanded segments and a generally arcuate endosiphucular canal system. Their range is from the upper Middle Ordovician to the Lower Silurian. Actinocerids are generally straight-shelled nautiloid cephalopods with a siphuncle composed of expanded segments, typically with thin connecting rings, in which the internal deposits are penetrated by a system of canals

<i>Armenoceratidae</i> family of molluscs

The Armenoceratidae are a family of early Paleozoic nautiloid cephalopods belonging to the order Actinocerida.

Protcycloceratidae is an extinct family of slender, commonly annulate, members of the cephalopod order Ellesmerocerida that lived during the Early Ordovician.

Centroonoceras is a middle Ordovician cyrtoconic nautiloid cephalopod, otherwise similar to the orthoconic Sactorthoceras and also included in the Sactorthoceratidae. It was named by Kobayashi, 1934, and has been found in Korea and in New York state in the eastern U.S.

Simardoceras is a genus in the discosorid family Westonoceratidae from the Middle Ordovician of Quebec.

Cyrtogomphoceras is a genus of nautiloid cephalopods, recognized by its large breviconic shell with a notable endogastric curvature. The shell is fusiform in profile, reaching maximum width at or near the base of body chamber, which narrows toward the aperture. The siphuncle is large and slightly removed from the ventral side, that with the concave longitudinal profile. Siphuncle segments are short, as are chambers; septal necks recurved, connecting rings thick, bullettes at the apical end of the rings swollen. Cameral deposits are lacking.

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. 1 2 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
  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
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