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Najaceras
''Najaceras'' is a genus of straight, slender endocerid known only from the Whiterockian age Oil Creek Limestone of Oklahoma, introduced and named by Rousseau Flower in 1971 and further described by him in 1976. ''Najaceras'' is characterized by a longitudinal mound of material that runs forward from the apical region along the inside of the top of the siphuncle known as a dorsal process. This process, which is somewhat broad in aspect, is concave ventrally. The opening between the dorsal process and the endocone forms a dorsally concave crescent shape. The process is bisected in the lower port by which is known as a blade which bifurcates upwardly from about the middle. The genus ''Najaceras'' is based on ''Najaceras triangulatum'' (Flower, 1971) which comes from the Oil Creek Limestone on West Spring Creek, 3 miles east of Pooleville, Oklahoma. The holotype and paratype are at the U.S. National Museum. Two other species from the same area have been identified and named: ''N. b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meniscoceras
''Meniscoceras'' is a straight and slender Chazyan endocerid described by Rousseau Flower in 1941 The genus was originally included in the Proterocameroceratidae (Flower, 1955) but later (Flower, 1976) placed with its predecessor, ''Najaceras'', in the Najaceratidae. The siphuncle in ''Mensicoceras'' is large with short septal necks and thin connecting rings. Endocones are vertically asymmetric. The central cavity is dorsally concave where a broad dorsal process is formed in which is said to contain a pair of dorso-lateral blades, and flat ventrally. ''Mensicoceras'' from the Chazy and the earlier ''Najaceras'' from the Whiterock age are similar in having a longitudual process formed along the inner dorsal side of the siphuncle around which the endocones form, but differ in details such as with the central opening. On that basis the two have been separated into their own family, the Najaceratidae (Flower 1971,1976). The ''Treatise on Invertebrate Paleontology The ''Treati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), 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. The Ordovician, named after the Celtic Britons, Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same Rock (geology), rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed Stratum, strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Union of Geological Sciences, Intern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endocerida
Endocerida is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. Endocerida was a diverse group of cephalopods that lived from the Early Ordovician possibly to the Late Silurian. Their shells were variable in form. Some were straight (orthoconic), others curved (cyrtoconic); some were long (longiconic), others short (breviconic). Some long-shelled forms like '' Endoceras'' attained shell lengths close to . The related ''Cameroceras'' is anecdotally reported to have reached lengths approaching , but these claims are problematic. The overwhelming majority of endocerids and nautiloids in general are much smaller, usually less than a meter long when fully grown. Morphology Endocerids had a relatively small body chamber as well as a proportionally large siphuncle, which in some genera reached nearly half the shell diameter. This suggests that much of the visceral mass may have been housed within the siphuncle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whiterockian
The Whiterockian, often referred to simply as the Whiterock, is an earliest or lowermost stage of the Middle Ordovician. Although the Whiterockian or Whiterock Stage refers mainly to the early Middle Ordovician in North America, it is often used in the older literature in a global sense. The Whitetrock Stage was introduced by Cooper and Cooper (in Cooper, 1956, p. 6–7) "as a post-Canadian – pre-Chazyan chrono-stratographic unit" based on strata "in the Monitor and Antelope Ranges, flanking Antelope Valley, and in the Toquima Range of central Nevada", referred to as the Antelope Valley Limestone. The strato-type section in Whiterock Canyon in the northern Monitor Range and reference section at Meiklejohn Peak, Bare Mountain Quad. Nev. both show the boundary between the middle Ordovician Whiterock and underlying (mostly Canadian) Ibex series lies between the conodont ''Oepikodus evae'', below, and ''Tripodus laevis'', above, at the start of the ''Isograptus victoria ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 studying paleontology in the middle of the 1930s. He became an expert in North American cephalopods of the Devonian period as well as the stratigraphy of the early Paleozoic era. His main field was the nautiloids, which he studied intensely, often focusing on life habits and theoretical aspects of paleobiology, but he also penned many papers on fossil corals and other invertebrates. Flower described several hundred new fossil species and over 100 new genera. Eccentricities In the paleontology community, Flower's colorful behavior earned him admirers and enemies—whom he would occasionally "thank" in the acknowledgement sections of his papers or, in one case, in the name of a fossil species. His antics included mocking the alleged low-s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 ''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 septa (walls) dividing the 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 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, and the water moves from the more dilute chamber into the blood through osmosis. At the sam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus comes above species and below family (taxonomy), family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus. :E.g. ''Panthera leo'' (lion) and ''Panthera onca'' (jaguar) are two species within the genus ''Panthera''. ''Panthera'' is a genus within the family Felidae. The composition of a genus is determined by taxonomy (biology), taxonomists. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful: # monophyly – all descendants ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pooleville, Oklahoma
Pooleville is a community located in Carter County, Oklahoma, United States. It is west of the Arbuckles. During the territorial days, the community was originally known as Elk.Shirk, George H. ''Oklahoma Place Names'', Norman, Oklahoma: University of Oklahoma Press, 1965, p.71. At the time of its founding, the community was located in Pickens County, Chickasaw Nation.Charles Goins. ''Historical Atlas of Oklahoma'' (Norman: University of Oklahoma Press, 2006), p. 105. The Elk post office opened January 15, 1890, and the name was changed to Pooleville on July 20, 1907. The current ZIP Code is 73401 assigned to Ardmore. The community was named for an Ardmore banker, E.S. Poole.Shirk, George H. ''Oklahoma Place Names'', Norman, Oklahoma: University of Oklahoma Press, 1965, p.170. In 1907, when Oklahoma became a state, it was decided that Elk should be renamed because the mail kept getting mixed up with Elk City, and so a town meeting was called. Three possible names were chose ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several examples, but explicitly designated as the holotype. Under the International Code of Zoological Nomenclature (ICZN), a holotype is one of several kinds of name-bearing types. In the International Code of Nomenclature for algae, fungi, and plants (ICN) and ICZN, the definitions of types are similar in intent but not identical in terminology or underlying concept. For example, the holotype for the butterfly '' Plebejus idas longinus'' is a preserved specimen of that subspecies, held by the Museum of Comparative Zoology at Harvard University. In botany, an isotype is a duplicate of the holotype, where holotype and isotypes are often pieces from the same individual plant or samples from the same gathering. A holotype is not necessarily "typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paratype
In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). Often there is more than one paratype. Paratypes are usually held in museum research collections. The exact meaning of the term ''paratype'' when it is used in zoology is not the same as the meaning when it is used in botany. In both cases however, this term is used in conjunction with ''holotype''. Zoology In zoological nomenclature, a paratype is officially defined as "Each specimen of a type series other than the holotype.", ''International Code of Zoological Nomenclature'' In turn, this definition relies on the definition of a "type series". A type series is the material (specimens of organisms) that was cited in the original publication of the new species or subspecies, and was not excluded from being type material by the author (th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
