Orthocerida
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Orthocerida
Orthocerida, from Ancient Greek ὀρθός (''orthós''), meaning "straight", and κέρας (''kéras''), meaning "horn", also known as the Michelinocerida, is an order of extinct Orthoceratoidea, orthoceratoid cephalopods that lived from the Early Ordovician () possibly to the Late Triassic (). A Zhuravlevia, fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous (), and the Eocene fossil ''Antarcticeras'' is sometimes considered a descendant of the orthocerids although this is disputed. They were most common however from the Ordovician to the Devonian. Shell form The shell is usually long, and may be straight ("Orthocone, orthoconic") or gently curved. In life, these animals may have been similar to the modern squid, except for their long shell. The internal structure of the shell consists of concavo-convex Camera (anatomy), chambers linked by a centrally-placed tube called a siphuncle. There is a tendency for the chambers to develop c ...
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Orthoceratoidea
Orthoceratoidea, from Ancient Greek ὀρθός (''orthós''), meaning "straight", and κέρας (''kéras''), meaning "horn", is a major subclass of nautiloid cephalopods. Members of this subclass usually have orthoconic (straight) to slightly cyrtoconic (curved) shells, and central to subcentral siphuncles which may bear internal deposits. Orthoceratoids are also characterized by dorsomyarian muscle scars (a small number of large scars concentrated at the top of the body chamber), extensive cameral deposits, and calciosiphonate connecting rings with a porous and calcitic inner layer. Currently, Orthoceratoidea comprises the orders Riocerida, Dissidocerida, Actinocerida, Pseudorthocerida, Lituitida and Orthocerida. Orthocerida is a noteworthy paraphyletic order which is ancestral to the major cephalopod groups such as the extinct ammonoids and living coleoids (cephalopods without external shells, including squids, octopus, cuttlefish, etc.). Taxonomy As a superorder, ...
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Geisonoceratidae
Geisonoceratidae is an extinct family of orthoceroid cephalopods endemic to what would be Asia, Europe, and North America from the Middle Ordovician to the Middle DevonianSweet, W. C. 1964. Nautiloidea- Orthocerida; Treatise on Invertebrate Paleontology Part K, Teichert & Moore eds; pp K224- K242 living from about 470—380 mya, existing for approximately 90 million years. With the possible addition of an Early Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ... orthocerid from the western Caucasus the range of this group increases dramatically to some 350 million years, thus making it one of the longest lived families of the Nautiloidea. Morphology Shells of geisonoceratids are orthoconic or cyrtoconic, that is long and either straight or curved, with a subcircular cr ...
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Orthoceratidae
Orthoceratidae, from Ancient Greek ὀρθός (''orthós''), meaning "straight", and κέρας (''kéras''), meaning "horn", 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 . Taxonomy Orthoceratidae was named by McCoy (1844) and assigned to the Orthocerida by Teichert and Miller (1939),(as Orthocerotidae);Sweet, Walter C., (1964), Nautiloidea --Orthocerida, in ''Treatise on Invertebrate Paleontology''. Part K. Mollusca 3. pp K224-K231. to the Michelinoceratida by Flower (1962),R. H. Flower. 1962. Memoir 10, Part 2; Notes on the Michelinoceratida. New Mexico Bureau of Mines and Mineral Resources, Socorro NM. and to the Orthocerataceae by Sweet (1964). It has been subsequently included in the Orthocerataceae in Evans (1994) and in the Orthocerida in Evans (2005) and in Kröger e ...
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Paraphragmitidae
Paraphragmitidae is an extinct family (biology), family of actively mobile aquatic animal, aquatic carnivorous cephalopods belonging to the Class (biology), subclass Orthoceratoidea endemic to what would be Asia and Europe during the Silurian living from 436 to 418.7 Annum, mya, existing for approximately . In life, these animals may have been similar to the modern squid, except for the long shell. The internal structure of the shell consists of concavo-convex chambers linked by a centrally-placed tube called a siphuncle. Taxonomy The Paraphragmitidae was named and defined by Flower (1950) as containing annulated orthocones and cyrtocones included in the Michelinocerida, Michelinoceratida. Walter Sweet, (in Teichert ''et al'' 1964), included them in the Orthocerataceae, one of two superfamilies then of the Orthocerida (=Michelinocerida) . With the recognition of the Pseudorthocerida as a separate order the two superfamilies became obsolete leaving the Paraphragmitidae simply an o ...
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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, existing for approximately . Taxonomy Baltoceratidae was named by Kobayashi (1935) and assigned to the Ellesmeroceratida by Flower and Kummel (1950) where it was retained by Unklesbay and Young (1956), again by Flower (1964),Flower 1964. The Nautiloid Order Ellesmeroceratida (Cephalopoda), Memoir 12, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM and by Furnish and Glenister in Teichert et al. (1964).Teichert et al 1964, Treatise on Invertebrate Paleontology Part K Mollusca 3, Nautiloidea-Ellesmerocerida by Furnish and Glenister, K129- K153 Flower (1964) included the Baltoceratidae in the ellesmeroceratid suborder Ellesmeroceratina. Further study of baltoceratid interiors, namely regarding the generally thin connecting rin ...
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Cephalopod
A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symmetry, bilateral body symmetry, a prominent head, and a set of cephalopod arm, arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt Cephalopod ink, ink. The study of cephalopods is a branch of malacology known as teuthology. Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, Extant taxon, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by ''Nautilus (genus), Nautilus'' and ''Allonautilus''. In the Coleoidea, the molluscan shell has been internalized or is absent, where ...
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Lamellorthoceratidae
Lamellorthoceratidae is a family of fossil orthoceratoids in the Orthocerida, defined by Curt Teichert in 1961. The lamellorthoceratids are placed in the superfamily Orthocerataceae in the ''Treatise on Invertebrate Paleontology'' (Walter Sweet, 1964). Lamellorthoceratids are distinguished by cameral deposits consisting of simple or bifurcating episeptal, or rarely hyposeptal lamellae, set radially with respect to the siphuncle; often filling the entire posterior part of the shell. Lamellorthoceratid shells are straight or slightly endogastric with a slender, cylindrical subcentral orthochoanitic siphuncle, free or organic deposits. The ''Lamellorthoceratidae'' are known from the Lower and Middle Devonian and possibly from the Lower Carboniferous, and is represented by three genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclat ...
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Antarcticeras
''Antarcticeras'' is an extinct genus of enigmatic cephalopod from the Eocene of Antarctica. It contains a single species, ''A.'' ''nordenskjoeldi''. It is either considered the last of the " orthocone"-type cephalopods, the only member of its subclass Paracoleoidea & a descendant of the orthoceratids, and a remarkable example of convergent evolution with coleoid cephalopods, or an oegospid squid and a transitional form in the development of the modern squid gladius, of which it is the only preserved example. It is named after Swedish geologist and Antarctic explorer Otto Nordenskjöld. Discovery ''Antarcticeras'' is represented by two fossil shell fragments from the Early Eocene La Meseta Formation from Seymour Island, Antarctica. These are straight shells that closely resemble those of the orthocones, although they are thought to have been internal akin to those of certain coleoids such as the cuttlebone of cuttlefish and the "rams horn" shell of spirulids. The shells ...
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Siphuncle
The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusc. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ''Spirula''. In the case of the cuttlefish, the siphuncle is indistinct and connects all the small chambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes through small openings in the Septum (cephalopod), septa (walls) dividing the Camera (cephalopod), camerae (chambers). Some older studies have used the term siphon for the siphuncle, though this naming convention is uncommon in modern studies to prevent confusion with a Siphon (mollusc), mollusc organ of the same name. Function The siphuncle is used primarily in emptying water from new chambers as the shell grows. To perform this task, the cephalopod increases the saltiness of the blood in the siphuncle, ...
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Orthoceras
''Orthoceras'', from Ancient Greek ὀρθός (''orthós''), meaning "straight", and κέρας (''kéras''), meaning "horn", is a genus of extinct nautiloid cephalopod restricted to Middle Ordovician-aged marine limestones of the Baltic States and Sweden. This genus is sometimes called ''Orthoceratites''. Note it is sometimes misspelled as ''Orthocera'', ''Orthocerus'' or ''Orthoceros''. ''Orthoceras'' was formerly thought to have had a worldwide distribution due to the genus' use as a wastebasket taxon for numerous species of conical-shelled nautiloids throughout the Paleozoic and Triassic. Since this work was carried out and re-cataloging of the genus, ''Orthoceras'' '' sensu stricto'' refers to ''Orthoceras regulare'', of Ordovician-aged Baltic Sea limestones of Sweden and neighboring areas. These are slender, elongate shells with the middle of the body chamber transversely constricted, and a subcentral orthochoanitic siphuncle. The surface is ornamented by a network ...
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Proteoceratidae
Proteoceratidae is an extinct family of actively mobile aquatic carnivorous cephalopods belonging to the subclass Orthoceratoidea endemic to what would be Asia, Australia, Europe, South America and North America during the Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ... living from 490—445.6 Ma, existing for approximately . Taxonomy Proteoceratidae was named by Flower (1962). Its type is '' Proteoceras''. It was assigned to Michelinoceratida by Flower (1962); to Pseudorthocerataceae by Teichert et al. (1964), Sweet (1964) and Evans (1994); to Pseudorthocerida by Kröger and Isakar (2006); and to Orthocerida by Kröger et al. (2007). B. Kröger, M. S. Beresi, and E. Landing. 2007. Early orthoceratoid cephalopods from the Argentine Precordillera (Lower-Middle ...
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Engorthoceratidae
Engorthoceratidae is a small family of Devonian Orthocerida, orthocerids and a class of cephalopod found in eastern North America (Ohio and Indiana), containing only the genus ''Engorthoceras''.R. H. Flower. (1962). "Notes on the Michelinoceratida". State Bureau of Mines and Mineral Resources, New Mexico Institute of Mining and Technology, Memoir 10, Part II Engorthoceratidae
PaleoBiology Database


Taxonomy

Engorthoceratidae was named in 1962 by Rousseau Flower to contain the genus ''Engorthoceras'', also named by Flower (1962), and assigned to the Michelinocerida, Michelinceratida. The genotype is ''Orthoceras worthoni''.


Morphology

''Engorthoceras'' produced straight conical shells with a subcircular cross section and a small completely marginal siphuncle. ...
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