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Holmiceras
''Holmiceras'' is one of two ancestral lituitids from the late Early Ordovician (Arenigian). The other being ''Ancistroceras''. ''Holmiceras'' begins with about 1.5 to 2 loosely coiled whorls followed by a rapidly expanding orthocone, much like ''Ancistroceras'' except for the apical whorls and that Holmiceras is known only from the late Early Ordovician whereas ''Ancestroceras'' extends through the middle of the period. ''Holmiceras'' may have given rise to ''Angelinoceras'' which begins with an expanding open spiral. See also *List of nautiloids ''References'' * Flower, R. H. 1950. A Classification of the Nautiloidia. Jour Paleontology, V.24, N.5, pp 604–616, Sept. * Furnish & Glenister, 1964. Nautiloidea -Tarphycerida. Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lituitidae
The Lituitidae are a family of evolved tarphycerids characterized by a long orthoconic section that follows a coiled juvenile portion at the apex, along with a generally tubular siphuncle, which like that of the barrandeocerids is composed of thin connecting rings. Taxonomic position Flower and Kummel (1950) included the Lituitidae in the Barranderocerida which are now included in the Tarphycerida as a number of derived families. Furnish and Glenister (1964)Furnish & Glenister, 1964, Nautiloidea -Tarphycerida. Treatise on Invertebrate Paleontology Part K removed the Lituitidae to the Tarphycerida on the basis of observed similarities in the structure of the siphuncle. Other taxonomies, e.g. Dzik (1981) include the Lituitidae in the Orthocerida partly on the basis of the subcentral siphuncle and thin connecting rings, on the misconception that '' Rhynchorthoceras'' is ancestral. Classification The Lituitidae comprise two basic groups, based on general form. One is represented b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ancistroceras
''Ancistroceras'' is one of the two ancestral lituitids from the late Early Ordovician (Arenigian). The other being '' Holmiceras''. The shell is weakly annulate, starts off with 1.5 to 2 contiguous or slightly separated whorls followed by a rapidly expanding orthocone with an apical angle of about 30 deg. Growth lines are sinuous, show a pronounced hyponomic sinus in the coiled juvenile portion at the apex but almost none at the mature aperture of the orthcone. ''Holmiceras'' is similar except that its whorls are more loosely coiled and it is known only from the Arenigian whereas ''Ancistroceras'' ranges through most of the Middle Ordovician. ''Ancistroceras'' may have given rise to '' Rhynchorthoceras'' by a loss of the juvenile coiled portion, replacing it with a short semi-tubular cyrtoconic section. ''Ancistroceras'' may also have given rise to ''Lituites'' by evolving a narrower, less rapidly expanding, orthocone along with greater ornament and a complex aperture. Referen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angelinoceras
''Angelinoceras'' is a genus of lituitids from the Middle Ordovician that starts off with an open spiral of about 1.5 strongly compressed whorls followed by a straight orthoconic section that continues to expand for a length about equal to the diameter of the coiled portion before retaining a more or less consistent diameter. The juvenile spiral portion has a deep indentation on the ventral side of the aperture for the water-jet funnel, known as a hyponomic sinus, that becomes broad and shallow in the straight-shelled adult portion. ''Angelinoceras'' is most likely derived from '' Holmiceras'' by a further opening of the initial spiral and a reduction in the expansion of the orthocone An orthocone is the long, cone-shaped Exoskeleton, shell belonging to several species of ancient nautiloid cephalopod—the prehistoric ancestors of today's marine cephalopod Mollusca, mollusks, including the cuttlefishes, nautiluses, octopuses an .... ''References'' *Flower, R. H. 1950. A Class ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Nautiloids
This list of nautiloids is a comprehensive listing of all Genus, genera that have ever been included in the subclass Nautiloidea, excluding purely vernacular terms. The list includes all commonly accepted genera, but also genera that are now considered invalid, doubtful (''nomen dubium, nomina dubia''), or were not formally published (''nomen nudum, nomina nuda''), as well as synonym (zoology), junior synonyms of more established names, and genera that are no longer considered nautiloids. Most of the listed genera are found in Part K of the ''Treatise on Invertebrate Paleontology''. Some, added since the year of publication (1964) are found simply in various scientific journals and special publications. The named genera are based on type specimens which are housed in various museums and other academic institutions worldwide, available to interested researchers. Note that ''Allonautilus'' and ''Nautilus (genus), Nautilus'' are the only extant genera. A *†''Acanthonautilus'' *â ... [...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, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period Megaannum, Ma (million years ago) to the start of the Silurian Period Ma. 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 per ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Treatise On Invertebrate Paleontology
The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authored work of currently 55 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and extant (still living) invertebrate animals. The prehistoric invertebrates are described as to their taxonomy, morphology, paleoecology, stratigraphic and paleogeographic range. However, taxa with no fossil record whatsoever have just a very brief listing. Publication of the decades-long ''Treatise on Invertebrate Paleontology'' is a work-in-progress; and therefore it is not yet complete: For example, there is no volume yet published regarding the post- Paleozoic era caenogastropods (a molluscan group including the whelk and periwinkle). Furthermore, when needed, previously published vol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
