''Cartersoceras'' is a genus of

nautiloid Nautiloids are a group of marine cephalopods ( Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and '' Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded speci ...

cephalopod A cephalopod is any member of the molluscan class Cephalopoda ( Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, ...

s placed in the

Orthocerid Orthocerida is an order of extinct Orthoceratoid cephalopods also known as the Michelinocerida that lived from the Early Ordovician () possibly to the Late Triassic (). A fossil found in the Caucasus suggests they may even have survived until t ...

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, exis ...

, established by

Rousseau Flower Rousseau Hayner Flower (1913–1988) was an extremely prolific 20th century paleontologist, known for his eccentric personality. Career Although trained as an entomologist, and a specialist in dragonflies and orthopterans, Flower began st ...

(1964), for species formally included in part in ''

Murrayoceras ''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 vent ...

'', and in part in "''Sacotoceras''". This group is typical of ''Murrayoceras'' in all features except that the

siphuncle The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ...

segments are convex in outline.Rousseau H Flower, (1964). The nautiloid order

Ellesmeroceratida 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. Morphology The Ellesmerocerida are characterized by shells that ar ...

(Cephalopoda). New Mexico Bureau of Mines and Mineral Resources Memoir 12. It is known from the Middle

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

of the eastern United States. The type species ''Cartersoceras shideliri'' Flower from the Carters Limestone, Beach Grove,

Tennessee Tennessee ( , ), officially the State of Tennessee, is a landlocked state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to ...

, shows a ventral rod secreted

calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scra ...

in the siphuncle and thick, fibrous connecting rings which are not layered as in early

Ellesmerocerida 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. Morphology The Ellesmerocerida are characterized by shells that ...

. ''C.noveboracense'', originally referred to ''Murrayoceras'', from the Amsterdam Limestone of New York, known from a weathered portion of the

phragmocone The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a ...

, shows part of the siphuncle filled with calcite, determined to represent a secreted ventral rod. The ventral rod and unlayered connecting rings were used to place this genus in the rod-bearing

. Frey (1995) retained ''Cartersoceras'' in the Baltoceratidae while Kroger et al. (2007) B. Kröger, et al . 2007. Early orthoceratoid cephalopods from the Argentine Precordillera (Lower-Middle Ordovician). Journal of Paleontology 81(6):1266-1283

/ref> included it in the

Sactorthoceratidae 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 (chambered portion) likewise ...

, in spite of the ventral rod. ''Carteroceras'' is probably closely related to genera like ''

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 abou ...

'' and ''

'' and more distantly to such as ''

Tajaroceras ''Tajaroceras'' is an extinct slender cephalopod from the uppermost Lower Ordovician of western North America, belonging to the Orthocerid family Troedssonellidae. Background The shell of ''Tajaroceras'' is smooth and straight. The siphuncle whi ...

'' and ''

Veneficoceras ''Veneficoceras'' is a genus of the rod-bearing Baltoceratidae, an extinct cephalopod family with characteristics of the orthoceratoid Dissidocerida, found in Cassinianage, Lower Ordovician, limestone in western Utah Utah ( , ) is a stat ...

References

{{Taxonbar, from=Q5047258 Prehistoric nautiloid genera Taxa named by Rousseau H. Flower