| Belemnites Fossil range: Devonian-Cretaceous |
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 Small Belemnite fossils
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Aulacocerida |
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. The Devonian is a geologic period and system of the Paleozoic era spanning from to million years ago. The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by Subclass Coleoidea is the grouping of Cephalopods containing all the primarily soft-bodied creatures This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used Aulacocerida is an extinct order of Belemnoids The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by Squid are marine Cephalopods of the order Teuthida, which comprises around 300 species Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes Squid, Octopuses Like them, the belemnites possessed an ink sac, but, unlike the squid, they possessed ten arms of roughly equal length and no tentacles.
Belemnites were numerous during the Jurassic and Cretaceous periods, and their fossils are abundant in Mesozoic marine rocks, often accompanying their cousins the ammonites. The Jurassic is a geologic period and system that extends from about Ma (million years ago to Ma that is from the end of the Triassic to the beginning The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum The belemnites become extinct at the end of the Cretaceous period along with the ammonites. The belemnites' origin lies within the bactritoid nautiloids, which date from the Devonian period; well-formed belemnite guards can be found in rocks dating from the Mississippian (or Early Carboniferous) onward through the Cretaceous. The Bactritida form a small order of more or less straight-shelled (orthoconic Cephalopods that first appeared during the Emsian Stage of the Devonian The Devonian is a geologic period and system of the Paleozoic era spanning from to million years ago. The Carboniferous is a geologic period and system that extends from the end of the Devonian period about 359 Other fossil cephalopods include baculites, nautiloids and goniatites. The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by Baculites ("walking stick rock" is a Genus of extinct marine animals in the Phylum Mollusca and Class 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 Goniatites are an extinct group of ammonoid, which are shelled Cephalopods related to Squids Belemnites Octopuses
Normally with fossil belemnites only the back part of the shell (called the guard or rostrum) is found. The guard is elongated and bullet-shaped, being cylindrical and either pointed or rounded at one end. The hollow region at the front of the guard is termed the alveolus, and this houses a chambered conical-shaped part of the shell (called the phragmocone). The phragmocone is the chambered portion of the shell of a Cephalopod. The phragmocone is usually only found with the better preserved specimens. Projecting forwards from one side of the phragmocone is the thin pro-ostracum.
While belemnite phragmocones are homologous with the shells of other cephalopods and are similarly composed of aragonite, belemnite guards are evolutionarily novel and are composed of calcite, thus tending to preserve well. The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by Aragonite is a Carbonate mineral, one of the two common naturally occurring polymorphs of Calcium carbonate, Ca[[carbon C]] O 3 Calcite is a carbonate mineral and the most stable polymorph of Calcium carbonate ( Ca[[carbon C]] O 3 Broken guards show a structure of radiating calcite fibers and may also display concentric growth rings. Dendrochronology (from Greek grc δένδρον dendron, "tree" grc χρόνος khronos, "time" and grc -λογία The bulk geochemical signature contained within belemnite guards of the Peedee Formation (Cretaceous, southeast USA) has long been used as a global standard ("PDB") against which all other geochemical samples are measured, for both carbon isotopes and oxygen isotopes. Isotope geochemistry is an aspect of Geology based upon study of the relative and absolute concentrations of the elements and their Isotopes in the The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of Isotope geochemistry is an aspect of Geology based upon study of the relative and absolute concentrations of the elements and their Isotopes in the Carbon ( C)Standard atomic mass 120107(8 u Natural isotopes See also Carbon-12, Carbon-13, Carbon-14 There are three stable isotopes of oxygen that lead to Oxygen ( O) having a standard atomic mass of 15
The guard, phragmocone and pro-ostracum were all internal to the living creature, forming a skeleton which was enclosed entirely by soft muscular tissue. The original living creature would have been larger than the fossilized shell, with a long streamlined body and prominent eyes. The guard would have been in place toward the rear of the creature, with the phragmocone behind the head and the pointed end of the guard facing backward.
The guard of the belemnite Megateuthis gigantea, which is found in Europe and Asia, can measure up to 46 cm in length (18 inches), giving the living animal an estimated length of 3 metres (10 feet). Megateuthis gigantea is the largest known Belemnite species The guard of M
Very exceptional belemnite specimens have been found showing the preserved soft parts of the animal. Elsewhere in the fossil record, bullet-shaped belemnite guards are locally found in such profusion that such deposits are referred to semi-formally as "belemnite battlefields" (cf. "orthocone orgies"). Orthoceras ("straight horn" is a Genus of extinct Nautiloid Cephalopod. It remains unclear whether these deposits represent post-mating mass death events as are common among modern cephalopods and other semelparous creatures. The cephalopods ( Greek plural (kephalópoda "head-feet" are the Mollusc class Cephalopoda characterized by Reproduction is the Biological process by which new individual Organisms are produced
Some belemnites (such as Belemnites) serve as index fossils, particularly in the Cretaceous Chalk Formation of Europe, enabling geologists to date the age the rocks in which they are found. Index fossils (also known as guide fossils or zone fossils are Fossils used to define and identify geologic periods (or faunal stages The Chalk Formations of Europe are thick deposits of Chalk, a soft porous white Limestone, deposited in a marine environment during the upper Cretaceous A geologist is a contributor to the Science of Geology, studying the physical structure and processes of the Earth and planets of the solar system In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere
Like some modern squid, belemnite arms carried a series of small hooks for grabbing prey. Belemnites were efficient carnivores that caught small fish and other marine animals with their arms and ate them with their beak-like jaws. A carnivore (ˈkɑrnɪvɔər meaning 'meat eater' ( Latin carne meaning 'flesh' and vorare meaning 'to devour' is any animal with a diet consisting Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two In turn, belemnites appear to have formed part of the diet of marine reptiles such as Ichthyosaurs, whose fossilized stomachs frequently contain phosphatic hooks from the arms of cephalopods. Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Ichthyosaurs ( Greek for 'fish lizard' - ιχθυς / ichthyos meaning 'fish' and σαυρος / sauros meaning 'lizard' were giant In Human anatomy, the stomach is a J-shaped hollow muscular organ of the Gastrointestinal tract involved in the second phase of Digestion, following Phosphate minerals are those Minerals that contain the tetrahedrally coordinated Phosphate (PO43- Anion along with the freely substituting
Classification
Note: all families extinct
- Cohort Belemnoidea
- Basal and unresolved
- Genus Jeletzkya
- Order Aulacocerida
- Family Aulacoceratidae
- Family Dictyoconitidae
- Family Hematitidae
- Family Palaeobelemnopseidae
- Family Xiphoteuthididae
- Order Belemnitida
- Suborder Belemnitina
- Family Cylindroteuthididae
- Family Hastitidae
- Family Oxyteuthididae
- Family Passaloteuthididae
- Family Salpingoteuthididae
- Suborder Belemnopseina
- Family Belemnitellidae
- Family Belemnopseidae
- Family Dicoelitidae
- Family Dimitobelidae
- Family Duvaliidae
- Suborder Belemnitina
- Order Belemnoteuthina
- Family Belemnotheutididae
- Family Chitinobelidae
- Family Sueviteuthididae
- Order Diplobelida
- Family Chondroteuthididae
- Family Diplobelidae
- Order Phragmoteuthida
- Family Phragmoteuthididae
- Basal and unresolved
See also
External links
- Fossil cephalopod topics for non-specialists
- TONMO.com Cephalopod Fossils articles and discussion forums
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