Orthoceratoidea
Encyclopedia
The Orthoceratoidea is a superorder (Wade 1988), sometimes considered an infraclass or even a subclass, that comprizes nautiloid orders that have orthoconic to slightly cyrtoconic shells and central to subcentral siphuncles in which there may be internal deposits. Orders include the Orthocerida
, Pseudorthocerida
, and Ascocerida
.
(=Ellesmeroceratoidea of some) from which the others are derived, the Endoceratoidea, Actinoceratoidea
, Discosoratoidea
, and Nautilitoidea
.
Some classifications (e.g. Kröger 2008, Teichert 19880 separate orthoceratoids, endocerids and actinocerids as co-equal taxa to the Nautiloidea, which becomes much reduced in scope. Wade (1988) instead proposed separating the Nautiloidea in to phylogenetically related superorders while retaining the basic concept of the subclass; externally shelled cephalopods with simple concave septa and retrochoanitic siphuncles from which the convexly septate Ammonoidea with prochoanitic siphuncles are distinguished.
In Kröger 2008, Orthoceratoidea is used as a subclass, referring to McCoy (1844), revising his (Kröger 2004) perception of the Order Orthocerida Kuhn (1940) as part of the Nautiloidea, in the sense of Sweet 1964 in the Treatise
.
In the classification of Teichert (1988) the subclass Orthoceratoidea is expanded to include the orders found in the Plectronoceratoidea and Orthoceratoidea of Wade (1988)combining forms with thick-ringed ventral siphuncles with those with thin-ringed central siphuncles.
The Orthoceratoidea in Kröger (2008) includes the Orthocerida, Ascocerida, Pseudorthocerda as in Wade (1988) plus the Dissidocerida
and Lituitida
. The Lituitida, or Lituitiae, has been shown to have evolved from within the Tarphycerida
by a straightening of the adult shell, a common character of many tarphycerids. The Dissidocerida, separated from the Orthocerida by Zhuravleva (1964) includes the Troedssonellidae
and two small monogeneric orders, the Polymeridae and Rangeroceratidae, both established by Evans (2005).
Orthocerida
Orthocerida is an order of extinct nautiloid 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...
, Pseudorthocerida
Pseudorthocerida
Pseudorthocerida are generally straight longiconic nautiloids with a subcentral to marginal cyrtochoanitic siphuncle composed of variably expanded segments which may contain internal deposits that may develop into a continuous parietal lining.. Cameral deposits are common and concentrated ventrally...
, and Ascocerida
Ascocerida
The Ascocerida are comparatively small, bizarre nautiloids known only from Ordovician and Silurian sediments in Europe and North America, uniquely characterized by a deciduous conch consisting of a longiconic juvenile portion and an inflated breviconic adult portion that separate sometime in...
.
Taxonomy
The Orthoceratiodea is one of six superorders within the Nautiloidea, the others being the PlectronoceratoideaPlectronoceratoidea
Plectronoceratoidea is a superorder of primitive nautiloids from the Late Cambrian and Early Ordovician that include the ancestors of subsequent cephalopod orders...
(=Ellesmeroceratoidea of some) from which the others are derived, the Endoceratoidea, Actinoceratoidea
Actinocerida
The Actinocerida comprise an order of generally straight, medium to large cephalopods that lived during the early and middle Paleozoic, distinguished by a siphuncle composed of expanded segments that extend into the adjacent chambers, in which deposits formed within contain a system of radial...
, Discosoratoidea
Discosorida
Discosorida is a unique 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 chambers in cephalopods, which unlike...
, and Nautilitoidea
Nautilitoidea
The Nautilitoidea is a superoder within the subclass Nautiloidea, comprizing the phylogenetically related Nautilida, Oncocerida, and Tarphycerida....
.
Some classifications (e.g. Kröger 2008, Teichert 19880 separate orthoceratoids, endocerids and actinocerids as co-equal taxa to the Nautiloidea, which becomes much reduced in scope. Wade (1988) instead proposed separating the Nautiloidea in to phylogenetically related superorders while retaining the basic concept of the subclass; externally shelled cephalopods with simple concave septa and retrochoanitic siphuncles from which the convexly septate Ammonoidea with prochoanitic siphuncles are distinguished.
In Kröger 2008, Orthoceratoidea is used as a subclass, referring to McCoy (1844), revising his (Kröger 2004) perception of the Order Orthocerida Kuhn (1940) as part of the Nautiloidea, in the sense of Sweet 1964 in the Treatise
Treatise on Invertebrate Paleontology
The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...
.
In the classification of Teichert (1988) the subclass Orthoceratoidea is expanded to include the orders found in the Plectronoceratoidea and Orthoceratoidea of Wade (1988)combining forms with thick-ringed ventral siphuncles with those with thin-ringed central siphuncles.
The Orthoceratoidea in Kröger (2008) includes the Orthocerida, Ascocerida, Pseudorthocerda as in Wade (1988) plus the Dissidocerida
Dissidocerida
The Dissidocerida comprise an order of Early Ordovician to the Early Silurian orthoceratoid cephalopods in which the siphuncle has a continuous lining or a longitudinal rod-like structure within....
and Lituitida
Lituitida
The Lituitida are the Lituitidae of the Treatise , reranked as an order and combined with other orthoceratoids.. They are considered to be more closely related to the Orthocerida than to the Ascocerida or Pseudorthocerida which are also included.Lituitids are characterized by smooth to annulate...
. The Lituitida, or Lituitiae, has been shown to have evolved from within the Tarphycerida
Tarphycerida
The Tarphycerida were the first of the coiled cephalopods. They are found in marine sediments from the Lower Ordovician to the Middle Devonian. Some like Aphetoceras and Estonioceras are loosely coiled, gyroconic, others like Campbelloceras, Tarphyceras, and Trocholites are tightly coiled, but...
by a straightening of the adult shell, a common character of many tarphycerids. The Dissidocerida, separated from the Orthocerida by Zhuravleva (1964) includes the Troedssonellidae
Troedssonellidae
Troedssonellidae is a family of orthoceroid cephalopods from the Ordovician, derived from rod-bearing Baltoceratidae, that have a continuous lining within the siphuncle that resembles very thin and slender endocones. Shells are generally slender and orthoconic. The siphuncle is central or...
and two small monogeneric orders, the Polymeridae and Rangeroceratidae, both established by Evans (2005).
References
- Flower 1950 in Flower and Kummel 1950, A Classification of the Nautiloidea; Journal of Paleontology 24(5):604-616, Sept 1950
- Kroger 2008, Brief Report, A new genus of middle Tremadocian orthoceratoids and the Early Ordovician origin of orthoceratoid cephalopods; Acta Palaeontologica Polonica 53 (4): 745–749, 2008
- Kroger 2004, Revision of Middle Ordovician orthoceratacean nautiloids from Baltoscandia; Acta Palaeontologica Polonica 49 (1): 57–74.
- Stanley & Techert 1976; Lamellorthoceratida (Cephalopoda, Orthoceratoidea) from the LOwer Devonian of New York; the University of Kansas Paleontological Contributions, Nov.12, 1976, Paper 86.
- Sweet, W..C. 1964. Nautiloidea- Orthocerida; Treatise on Invertebrate Paleontology, Part K, Teichert and Moore (eds) Geological Society of America and University of Kansas Press.
- Teichert C, 1988, Main Features of Cephalopod Evolution, Ch 2 in The Mollusca Vol 12 Paleontology and Neontology of Cephalopods, Clarke & Trueman (eds) Academic Press.
- Wade, M 1988. Nautiloids and their descendants: cephalopod classification in 1986; New Mexico Bureau of Mines & Mineral Resources Memoir 44, Oct 1988 :15-25.