Cochlioceras

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Cochlioceras
Temporal range: 478 – 464  Ma Upper Lower to Lower Middle Ordovician
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Orthocerida
Family: Baltoceratidae
Genus: Cochlioceras
Eichwald (1860)

Cochlioceras is an extinct baltoceratid genus from the lower and middle Ordovician (Arenig - Llanvrin) of what are now Europe, the U.S. (Vermont), and China, having existed for approximately 14 million years, from about 478 to 464 mya. [1]

Taxonomy

Cochlioceras was named by Eichwald (1860). Its type is Cochlioceras avus. It was assigned to the Baltoceratidae by Furtnish and Glensiter in Teichert et al. (1964) [1] and removed, with the Baltoceratidae, from the Ellesmerocerida to the Orthocerida by Kroger et al. (2007) [2]

Related Research Articles

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Orthoceratidae is an extinct family of actively mobile carnivorous cephalopods, subclass Nautiloidea, that lived in what would be North America, Europe, Asia, Africa, and Australia from the Ordovician through Triassic from 490—203.7 mya, existing for approximately 286.4 million years.

Discosorida are an order of cephalopods that lived from the beginning of the Middle Ordovician, through the Silurian, and into the Devonian. Discosorids are unique in the structure and formation of the siphuncle, the tube that runs through and connects the camerae (chambers) in cephalopods, which unlike those in other orders is zoned longitudinally along the segments rather than laterally. Siphuncle structure indicated that the Discosorida evolved directly from the Plectronoceratida rather than through the more developed Ellesmerocerida, as did the other orders. Finally and most diagnostic, discosorids developed a reinforcing, grommet-like structure in the septal opening of the siphuncle known as the bullette, formed by a thickening of the connecting ring as it draped around the folded back septal neck.

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<span class="mw-page-title-main">Ellesmeroceratidae</span> Extinct family of molluscs

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).

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<span class="mw-page-title-main">Proteoceratidae</span> Extinct family of molluscs

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Eosomichelinoceras is an extinct genus from the actively mobile carnivorous cephalopod family Baltoceratidae that lived in what would be Asia and South America during the Ordovician from 461—452 mya, existing for approximately 9 million years.

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Plectronoceratoidea is a superorder or subclass containing primitive nautiloids from the Late Cambrian and Early Ordovician. This group is best considered a paraphyletic grade of early cephalopods, as it contains the ancestors of subsequent post-Cambrian cephalopod orders.

Shangtungendoceras is a conical plectronoceratoid cephalopod from the Upper Cambrian of north-eastern China, described by Sun (1937) as a primitive endoceroid. Because of its apparently poor preservation its ordinal and familial position is uncertain. It could be included in either the Plectronocerida, family Plectronoceratidae, or the Ellesmerocerida, family Ellesmeroceratidae. On the other hand, Teichert (1964) included Shungtangendoceras in the Ellesmoerocatidae.

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.

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. Septa are close spaced with sutures forming broad lobes on the upper flanks and ventral surface.

Apocrinoceratidae constitutes a family of Middle Ordovician nautiloid cephalopods characterized by straight or slightly curved, transversely ribbed shells having siphuncles composed of expanded segments, short recurved septal necks, and thick connecting rings. Derivation is from the Protocycloceratidae, a family of ellesmerocerids, which differ in having straight or concave siphuncle segments, but are otherwise similar in form.

Yanhecerida is a small order of Late Cambrian nautiloid cephalopods. They were similar to the more diverse Plectronocerida and Ellesmerocerida, with short shells, closely spaced septa, and diaphragms (partitions) within the siphuncle. Their most distinctive trait is the conical shape of the diaphragms, similar to the endocones which characterize the later nautiloid order Endocerida. While some authors have argued that Yanhecerida should be lumped into Ellesmerocerida, a phylogenetic analysis has maintained that Yanhecerida is a valid clade of early cephalopods closely related to a paraphyletic Ellesmerocerida.

References

  1. 1 2 Teichert et al 1964, Treatise on Invertebrate Paleontology Part K; Nautiloidea - Ellesmerocerida by W.M. Furnish and Brian F. Glenister, pp K129 -K160.
  2. Kroger, B. (2007). "Early orthoceratoid cephalopods from the Argentine Precordillera". Journal of Paleontology. 81 (6): 1266–1283. doi:10.1666/06-013.1.