- For the orchid genus, see the Taxonomy of the orchid family. The taxonomy of the orchid family has evolved slowly during the last 150 years starting with Carolus Linnaeus who in 1753 recognized eight genera
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| Orthoceras regulare (Schlotheim, 1820) |
Orthoceras ("straight horn") is a genus of extinct nautiloid cephalopod. Ernst Friedrich Baron von Schlotheim ( April 2, 1764 - March 28, 1832) German Palaeontologist and politician was born Year 1820 ( MDCCCXX) was a Leap year starting on Saturday (link will display the full calendar of the Gregorian calendar (or a Leap year A genus (plural genera from Γένος Latin genus "descent family type gender" is a low-level Taxonomic Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by This genus is sometimes called Orthoceratites. Note it is sometimes misspelled as Orthocera, Orthocerus or Orthoceros (Sweet 1964:K222). Orthoceras ("straight horn" is a Genus of extinct Nautiloid Cephalopod.
Orthoceras fossils are common and have a global distribution, occurring in any marine rock, especially limestones. Limestone is a Sedimentary rock composed largely of the Mineral Calcite ( Calcium carbonate: CaCO3
These are slender, elongate shells with the middle of the body chamber transversely constricted, and a subcentral orthochoanitic siphuncle. The body chamber, also called the living chamber, is the outermost or last chamber in the shell of a Nautiloid or ammonoid Cephalopod The siphuncle is a strand of tissue passing longitudinally through the shell of a Cephalopod Mollusk. The surface is ornamented by a network of fine lirae (Sweet 1964:K224). Lirae (sing lira are fine lines or ridges (much finer than ribs that serve as ornament on Mollusc (e Orthoceras ("straight horn" is a Genus of extinct Nautiloid Cephalopod. Many other very similar species are included under the genus Michelinoceras. Michelinoceras is the oldest known genus of the Michelinocerida more commonly known as the Orthocerida, characterized by long slender nearly cylindrical orthocones Orthoceras's closest living relative is the Nautilus. Nautilus (from Greek ναυτίλος, 'sailor' is the common name of any marine creatures of the Cephalopod family Nautilidae, the sole
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Monospecific assemblages
These orthocone cephalopods are conspicuous in the fossil record for their occasional but persistent appearances in monospecific assemblages dense enough to be rock-forming. An orthocone is a usually long straight shell of a Nautiloid Cephalopod.
Based on studies of size distributions of the orthocone shells, some scientists have concluded that these assemblages likely represent post-mating mass deaths, as are common among modern cephalopods (though not modern nautiloids) and indeed among many semelparous species. Reproduction is the Biological process by which new individual Organisms are produced However, such studies have not been entirely convincing and do leave the door open for alternate interpretations. These assemblages, are known mostly from Ordovician rocks but do occur later as well, at least into the Devonian. The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 The Devonian is a geologic period and system of the Paleozoic era spanning from to million years ago. Well-known examples occur in Morocco, Scandinavia, the Alps, and Iowa (USA).
One often finds on eBay highly polished and beautiful-looking fossils from Morocco that are called Orthoceras, almost all of which have been touched up in some way. eBay Inc is an American Internet company that manages eBaycom an Online auction and shopping Website in which people and businesses buy and FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Morocco (المغرب "al-Maghrib" officially the Kingdom of Morocco (المملكة المغربية is a country located in North Africa While these specimens (or rather the original, untouched versions) are indeed members of the order Orthocerida, none can be said to belong to the genus Orthoceras. Orthocerida are an order of extinct Nautiloid Cephalopods that lived from the Early Ordovician (about 500 million years ago to the Late Permian
The Baltic island of Öland off the southern coast of Sweden has many quarries that yield orthocone nautiloids of great beauty. is the second largest Swedish island and the smallest of the traditional Provinces of Sweden. An orthocone is a usually long straight shell of a Nautiloid Cephalopod. For centuries Öland has supplied greater Europe with material for floors, stairs and grave stones. This hard limestone is durable and the fossil inclusions make it very desirable. Occasionally the chambers of the fossil shells are colored differently. The ground water minerals that percolated the strata during diagenesis determines the color. In Geology and Oceanography, diagenesis is any chemical physical or biological change undergone by a Sediment after its initial deposition and during Greens and browns are most common.
History of the name
Originally Orthoceras referred to all nautiloids with a straight-shell , called an ("orthocone") (Fenton & Fenton 1958:40). Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses An orthocone is a usually long straight shell of a Nautiloid Cephalopod. Orthoceras ("straight horn" is a Genus of extinct Nautiloid Cephalopod. But later research on their internal structures, such siphuncle, cameral deposits and others, showed that these actually belong to a number of groups, even different orders. The siphuncle is a strand of tissue passing longitudinally through the shell of a Cephalopod Mollusk. In Biology, Camera can refer to Camera (anatomy, spaces or chambers enclosed between two adjacent septa in the Phragmocone
In the authoritative Treatise on Invertebrate Paleontology, the name Orthoceras is now only used to refer to the type species O. The Treatise on Invertebrate Paleontology (or TIP) published by the Geological Society of America and the University of Kansas Press is a definitive multi-authored In Taxonomy, a type species is the species that originally defined a genus. regulare (Schlotheim 1820) from the Middle Ordovician of Estonia, Lithuania, Sweden and parts of the former Soviet Union such as Ukraine and Belarus. Orthoceras ("straight horn" is a Genus of extinct Nautiloid Cephalopod. The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 Estonia, officially the Republic of Estonia ( Eesti or Eesti Vabariik) is a Country in Northern Europe in the Baltic region Lithuania, officially the Republic of Lithuania (Lietuvos Respublika is a Country in Eastern often referred to as Northern Europe or in the "Sverige" redirects here For other uses see Sweden (disambiguation and Sverige (disambiguation. The Union of Soviet Socialist Republics (USSR was a constitutionally Socialist state that existed in Eurasia from 1922 to 1991 The genus might include a few related species.
Confusion with Baculites
Orthoceras and related orthocone nautiloid cephalopods are often confused with the superficially similar Baculites and related Cretaceous orthocone ammonite cephalopods. Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses Baculites ("walking stick rock" is a Genus of extinct marine animals in the Phylum Mollusca and Class The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Both are long and tubular in form, and both are common items for sale in rock shops (often under each others' names). Both lineages evidently evolved the tubular form independently of one another, and at different times in earth history. Orthoceras lived much longer ago (Middle Ordovician Period) than Baculites (Late Cretaceous Period). The Ordovician is a geologic period and system, the second of six of the Paleozoic era, and covers the time between 488 Baculites ("walking stick rock" is a Genus of extinct marine animals in the Phylum Mollusca and Class The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of The two types of fossils can be distinguished by many features, most obvious among which is the suture line: simple in Orthoceras, intricately foliated in Baculites and related forms. Baculites ("walking stick rock" is a Genus of extinct marine animals in the Phylum Mollusca and Class
References
- Fenton, C. L. & M. A. Fenton (1958), The Fossil Book, Doubleday & Co. , Garden City, New York
- Sweet, Walter C. (1964), Nautiloidea -- Orthocerida, in Treatise on Invertebrate Paleontology. Part K. Mollusca 3, Geological Society of America, and University of Kansas Press, New York, New York and Lawrence, Kansas
See also
- Baculites - another type of extinct, straight-shelled cephalopod. Baculites ("walking stick rock" is a Genus of extinct marine animals in the Phylum Mollusca and Class
- Hamites
- Lituites
- Belemnite
Ext link
- Photo; Article english. Hamites ("Hook-stone" is a Genus of heteromorph Ammonite that evolved late in the Aptian stage of the Early Cretaceous Lituites is an extinct Genus of the Nautiloids and is one of the most primitive known Cephalopods It originated in the Ordovician Belemnites (or belemnoids are an extinct group of marine Cephalopod, very similar in many ways to the modern Squid and closely related to the modern Cuttlefish fossiel. net–"Explanation of Fossil Types"
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