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Information about Belemnite

Belemnites
Fossil range: Devonian-Cretaceous
Enlarge picture
Small Belemnite fossils

Small Belemnite fossils
Scientific classification
Kingdom:Animalia
Phylum:Mollusca
Class:Cephalopoda
Subclass:Coleoidea
(unranked)Cohort †Belemnoidea
Extinct Orders


Aulacocerida
Phragmoteuthida
Belemnitida
Diplobelida
Belemnoteuthina


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. 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 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. Other fossil cephalopods include baculites, nautiloids and goniatites.

Enlarge picture
A belemnite fossil from the Franconian Jura.


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 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. Broken guards show a structure of radiating calcite fibers and may also display concentric growth rings. 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.

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).

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"). It remains unclear whether these deposits represent post-mating mass death events as are common among modern cephalopods and other semelparous creatures.

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.

Unlike the modern squid, whose arms have suckers, 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. In turn, belemnites appear to have formed part of the diet of marine reptiles such as Ichthyosaurs, whose fossilized stomachs frequently contain many phosphatic hooks from the arms of cephalopods.

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
  • Order Belemnoteuthina
  • Family Belemnotheutididae
  • Family Chitinobelidae
  • Family Sueviteuthididae
  • Order Diplobelida
  • Family Chondroteuthididae
  • Family Diplobelidae
  • Order Phragmoteuthida
  • Family Phragmoteuthididae

See also

External links

Devonian is a geologic period of the Paleozoic era spanning from roughly 416 to 359 million years ago. It is named after Devon, England, where rocks from this period were first studied.
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The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i.e. from 145.5 ± 4.0 million years ago (Ma)) to the beginning of the Paleocene epoch of the Tertiary Period (about 65.5 ± 0.3 Ma).
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Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
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Mollusca
Linnaeus, 1758

Classes

Caudofoveata
Aplacophora
Polyplacophora
Monoplacophora
Bivalvia
Scaphopoda
Gastropoda
Cephalopoda
† Rostroconchia
† Helcionelloida
† ?Bellerophontida
The molluscs
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Cephalopoda
Cuvier, 1797

Orders

Subclass Nautiloidea
  • †Plectronocerida
  • †Ellesmerocerida
  • †Actinocerida
  • †Pseudorthocerida
  • †Endocerida
  • †Tarphycerida
  • †Oncocerida

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Coleoidea
Bather, 1888

Orders
  • †Belemnoidea
  • †Aulacocerida
  • †Belemnitida

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order (Latin: ordo, plural ordines) is a rank between class and family (termed a taxon at that rank). The superorder is a rank between class and order. Exact details of formal nomenclature depend on the Nomenclature Code which applies.
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Aulacocerida
Stolley, 1919

Families

†Aulacoceratidae †Dictyoconitidae †Hematitidae †Palaeobelemnopseidae †Xiphoteuthididae

Aulacocerida is an extinct order of belemnoids.
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Cephalopoda
Cuvier, 1797

Orders

Subclass Nautiloidea
  • †Plectronocerida
  • †Ellesmerocerida
  • †Actinocerida
  • †Pseudorthocerida
  • †Endocerida
  • †Tarphycerida
  • †Oncocerida

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For other uses, see Squid (disambiguation).


Superconducting Quantum Interference Devices (SQUID) are very sensitive magnetometers used to measure extremely small magnetic fields, based on superconducting loops
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Sepiida
Zittel, 1895

Suborders and Families
  • †Vasseuriina
  • †Vasseuriidae
  • †Belosepiellidae
  • Sepiina

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The Jurassic Period is a major unit of the geologic timescale that extends from about 199.6 ± 0.6 Ma (million years ago) to 145.4 ± 4.0 Ma, the end of the Triassic to the beginning of the Cretaceous.
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The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i.e. from 145.5 ± 4.0 million years ago (Ma)) to the beginning of the Paleocene epoch of the Tertiary Period (about 65.5 ± 0.3 Ma).
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For other uses of the term, see Fossil (disambiguation)


FOSSIL is a standard for allowing serial communication for telecommunications programs under the DOS operating system.
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The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. The division of time into eras dates back to Giovanni Arduino, in the 18th century, although his original name for the era now called the 'Mesozoic' was 'Secondary' (making the modern era the 'Tertiary').
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Bactritida

Bactritida are a small and poorly studied order of more or less straight-shelled ("orthocone") nautiloids which first appeared during the Emsian Stage of the Devonian Period (390 million years ago) and persisted until the Carnian Stage of the
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Devonian is a geologic period of the Paleozoic era spanning from roughly 416 to 359 million years ago. It is named after Devon, England, where rocks from this period were first studied.
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Mississippian was an epoch of the Carboniferous period lasting from roughly 360 to 325 Ma (million years ago). As with most other geologic periods, the rock beds that define the period are well identified, but the exact start and end dates are uncertain by a few million years.
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The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359.2 ± 2.5 Ma (million years ago), to the beginning of the Permian period, about 299.0 ± 0.8 Ma (ICS 2004).
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Cephalopoda
Cuvier, 1797

Orders

Subclass Nautiloidea
  • †Plectronocerida
  • †Ellesmerocerida
  • †Actinocerida
  • †Pseudorthocerida
  • †Endocerida
  • †Tarphycerida
  • †Oncocerida

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Baculites

Species

all extinct

Baculites ("walking stick rock") is a genus of extinct marine animals in the phylum Mollusca and class Cephalopoda.
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Nautiloidea
Agassiz, 1847

Orders

Palcephalopoda
  • †Plectronocerida
  • †Ellesmerocerida
  • †Actinocerida
  • †Pseudorthocerida
  • †Endocerida
  • †Tarphycerida
  • †Oncocerida

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Goniatitida
Hyatt, 1884

Suborder
  • Goniatitina
  • Tornoceratatina


Goniatites are an extinct group of ammonoid, which are shelled cephalopods related to squids, belemnites, octopi, and cuttlefish, and more distantly to the nautiloids.
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phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae.

In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a siphuncle which determines
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Homology may refer to:
  • Homology (anthropology), analogy between human beliefs, practices or artifacts due to genetic or historical connections.
  • Homology (biology): analogy of structures due to shared ancestry.

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Cephalopoda
Cuvier, 1797

Orders

Subclass Nautiloidea
  • †Plectronocerida
  • †Ellesmerocerida
  • †Actinocerida
  • †Pseudorthocerida
  • †Endocerida
  • †Tarphycerida
  • †Oncocerida

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Aragonite is a carbonate mineral, one of the two common, naturally occurring polymorphs of calcium carbonate, CaCO3. The other is the mineral calcite. Aragonite's crystal lattice differs from that of calcite, resulting in a different crystal shape, an orthorhombic
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calcite]] The carbonate mineral, calcite, is a chemical or biochemical calcium carbonate corresponding to the formula CaCO3 and is one of the most widely distributed minerals on the Earth's surface.
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