Ascocerida

	Ascocerida The Ascocerida are comparatively small, bizarre Orthoceratoids 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 maturity.W.M . Furnish and Brian F Glenister; Nautiloidea-Ascocerida, K261-K277; Treatise on Invertebrate Paleontology , part K, Nautiloidea; Geological Society of America and the University of Kansas Press, 1964 Morphology The juvenile portion of an ascocerid consists typically of a narrow, circular cyrtocone that underwent periodic truncation. Cumulative length, including broken off segments, may have reached about in the largest individuals. The siphuncle is located half way between the shell axis and the venter, is thin walled and tubular with short, orthochoanitic septal necks and segments that are only slightly inflated. The juvenile portion is known as the deciduous conch, as it i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Cephalopod Orders 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, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt 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 subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by ''Nautilus'' and ''Allonautilus''. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been identified. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Ascoceratidae Ascoceratidae is a family of Ascocerida, bizarre orthoceratoid cephalopods, with longiconic, deciduous early growth stages which undergo period truncation and an inflated breviconic mature ascoceroid stage. The Ascoceratidae are divided into two, unequal subfamilies. Ascoceratinae have an exogastric ascoceroid stage characterized by the development of a protruding neck ending at the aperture, both ocular and hyponomic sinuses which form when fully grown, and camerae that are mostly confined to the dorsal half of the shell. The siphuncle is close to the venter and found only in the adapical portion. Siphuncle segments nummuloidal (beaded in appearance), septal necks cyrtochoanitic (flared outwardly) generally with recumbent (bent back on themselves) brims. The deciduous stage, which is the juvenile or immature, is orthoconic to cytroconic, with long but variable camerae, siphuncle with orthochoanitic septal necks and tubular segments, and generally straight sutures. Ascoce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Michelinocerida 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 the Early Cretaceous (). They were most common however from the Ordovician to the Devonian. Shell form The shell is usually long, and may be straight (" orthoconic") or gently curved. 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. There is a tendency for the chambers to develop cameral deposits, which were used as ballast to balance the long gas-filled shell. Depending on the family, the siphuncle has orthochoanitic (short and straight) or cyrtochoanitic (outwardly curved) septal necks, which protrude from the septa. The shell surface may be (depending on the specie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Choanoceratidae The Choanoceratidae is a small, mono-generic, family of extinct orthoceratoid cephalopods in the order Orthocerida that lived in what would be Europe during the middle Silurian from 428.2 to 426.2 mya, existing for approximately .Choanoceratidae PaleoBiology Database Taxonomy Chaonoceratidae was named as the family for its sole member ''Choanoceras'' by Miller (1932) who, along with Flower (1941) regarded it as belonging to the Ascocerida The Ascocerida are comparatively small, bizarre Orthoceratoids known only from Ordovician and Silurian sediments in Europe and North America, uniquely characterized by a deciduous conch consisting of a longiconic juvenile p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Orthoceratoidea Orthoceratoidea 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, Orthoceratiodea was one of six superorders within the Nautiloidea, the others being the Plectronoceratoidea (= E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Oskar Kuhn Oskar Kuhn (7 March 1908, Munich – 1990) was a German palaeontologist. Life and career Kuhn was educated in Dinkelsbühl and Bamberg and then studied natural science, specialising in geology and paleontology, at the University of Munich, from which he received his D. Phil. in 1932. He worked in the University of Munich Geological Institute, among other things on the ''Fossilium Catalogus'' (Catalogue of Fossils), and then in 1938 on a stipend from the Deutsche Forschungsgemeinschaft, moved to the University of Halle, where he worked on the Geiseltal fossils. In 1939 he achieved his Habilitation with a thesis on the Halberstadt Keuper fauna, and in 1940 was named Privatdozent in geology and paleontology. Informed by his Catholic religion, Kuhn was an exponent of idealistic morphology: he viewed evolution as operating only within predetermined morphological classes. In 1943 he declared, "The theory of descent has collapsed." After a political conflict with his mentor, Johann ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Paleontological Society The Paleontological Society, formerly the Paleontological Society of America, is an international organisation devoted to the promotion of paleontology. The Society was founded in 1908 in Baltimore, Maryland, and was incorporated in April 1968 in the District of Columbia. The Society publishes the bi-monthly ''Journal of Paleontology'' and the quarterly ''Paleobiology'', holds an annual meeting in the autumn in conjunction with the Geological Society of America, sponsors conferences and lectures, and provides grants and scholarships. The Society has five geographic sections—Pacific Coast (founded March 1911), North-Central (founded May 1974), Northeastern (founded March 1977), Southeastern (founded November 1979), Rocky Mountain (founded October 1985), and South-Central (founded November 1988). Medals and awards The Society recognizes distinguished accomplishments through three awards, one recognized by a medal, the other two by inscribed plaques normally presented annually: T ... [...More Info...] [...Related Items...] OR:* [Wikipedia] [Google] [Baidu]
	Journal Of Paleontology The ''Journal of Paleontology'' is a peer-reviewed scientific journal covering the field of paleontology. It is published by the Paleontological Society. Indexing The ''Journal of Paleontology'' is indexed in: BIOSIS Previews Science Citation Index The Zoological Record GeoRef __NOTOC__ The GeoRef database is a bibliographic database that indexes scientific literature in the geosciences, including geology. Coverage ranges from 1666 to the present for North American literature, and 1933 to the present for the rest of t ... References Paleontology journals Publications established in 1927 Academic journals published by learned and professional societies Cambridge University Press academic journals Bimonthly journals Paleontological Society {{paleo-journal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]

Taxonomy