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箭石类：修订间差异

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[[Image:BelemniteDB2.jpg|thumb|right|[[Paleoart|Artist's reconstruction]] of belemnoids.]]
[[Image:BelemniteDB2.jpg|thumb|right|[[Paleoart|Artist's reconstruction]] of belemnoids.]]
'''箭石類'''動物（[[學名]]：{{lang|la|'''Belemnoida'''}}），舊作'''箭石下綱'''，是一種已經滅絕[[頭足綱]]生物的分支，生活在[[泥盆紀]]至[[白堊紀]]之間。箭石在許多方面都與現代的[[魷魚]]相當接近<ref>{{cite doi|10.1666/09-018R.1}}</ref>，而且與現代的[[烏賊]]關係密切。箭石也擁有[[墨囊]]<ref>Lehmann, U. 1981. ''The Ammonites: Their life and their world''. London: Cambridge University Press.</ref>，不過牠們有10條大約相同長度的[[觸腕]]，其中並沒有特別長的觸腕<ref>{{cite doi|10.1111/j.0031-0239.2004.00395.x}}</ref>。
'''箭石類'''動物（[[學名]]：{{lang|la|'''Belemnoida'''}}），舊作'''箭石下綱'''，是一種已經滅絕[[頭足綱]]生物的分支，生活在[[泥盆紀]]至[[白堊紀]]之間。箭石在許多方面都與現代的[[魷魚]]相當接近<ref>{{cite journal|title=The Middle Eocene Belosaepia ungula (Cephalopoda: Coleoida) from Texas: structure, ontogeny and function|journal=Journal of Paleontology|url=https://www.cambridge.org/core/journals/journal-of-paleontology/article/middle-eocene-belosaepia-ungula-cephalopoda-coleoida-from-texas-structure-ontogeny-and-function/EC5F6450ED5FC7FA43696F93937FA3B4|date=2010/03|volume=84|issue=2|doi=10.1666/09-018r.1|pages=267–287|issn=0022-3360|language=en|accessdate=2018-04-02|author=Thomas E. Yancey, Christopher L. Garvie, Mary Wicksten}}</ref>，而且與現代的[[烏賊]]關係密切。箭石也擁有[[墨囊]]<ref>Lehmann, U. 1981. ''The Ammonites: Their life and their world''. London: Cambridge University Press.</ref>，不過牠們有10條大約相同長度的[[觸腕]]，其中並沒有特別長的觸腕<ref>{{cite journal|url=http://doi.wiley.com/10.1111/j.0031-0239.2004.00395.x|pages=983–998|title=The Jurassic Belemnite Suborder Belemnotheutina|journal=Palaeontology|volume=47|issue=4|date=2004-07-01|issn=1475-4983|language=en|accessdate=2018-04-02|doi=10.1111/j.0031-0239.2004.00395.x|author=Peter Doyle, Emma V. Shakides}}</ref>。


The name "belemnoid" comes from the Greek word βέλεμνον, ''belemnon'' meaning "a dart or arrow" and the Greek word είδος, ''eidos'' meaning "form".<ref>''Webster's New Universal Unabridged Dictionary.'' 2nd ed. 1979.</ref>
The name "belemnoid" comes from the Greek word βέλεμνον, ''belemnon'' meaning "a dart or arrow" and the Greek word είδος, ''eidos'' meaning "form".<ref>''Webster's New Universal Unabridged Dictionary.'' 2nd ed. 1979.</ref>
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==Anatomy==
==Anatomy==
Belemnoids possessed a central [[phragmocone]] made of [[aragonite]] and with negative buoyancy.<ref name=Monks1996>{{cite doi|10.1007/BF02988082}}</ref> To the rear of the creature was a heavy [[calcite]] guard whose main role appears to have been to counterbalance the front (towards the head) of the organism; it positions the centre of mass below the centre of buoyancy, increasing the stability of the swimming organism.<ref name=Monks1996/> The guard would account for between a third and a fifth of the length of the complete organism, arms included.<ref name=Monks1996/>
Belemnoids possessed a central [[phragmocone]] made of [[aragonite]] and with negative buoyancy.<ref name=Monks1996>{{cite journal|title=The Function of the Belemnite Guard|journal=Paläontologische Zeitschrift|doi=10.1007/bf02988082|url=https://link.springer.com/article/10.1007/BF02988082|date=1996-11-01|volume=70|issue=3-4|language=en|pages=425|issn=0031-0220|accessdate=2018-04-02|author=Neale Monks, J. David Hardwick, Andrew S. Gale}}</ref> To the rear of the creature was a heavy [[calcite]] guard whose main role appears to have been to counterbalance the front (towards the head) of the organism; it positions the centre of mass below the centre of buoyancy, increasing the stability of the swimming organism.<ref name=Monks1996/> The guard would account for between a third and a fifth of the length of the complete organism, arms included.<ref name=Monks1996/>


Like some modern squid, belemnoid arms carried a series of small hooks for grabbing [[prey]]. Belemnoids were efficient [[carnivore]]s that caught small [[fish]] and other marine animals with their arms and ate them with their [[cephalopod beak|beak-like jaws]]. In turn, belemnites appear to have formed part of the diet of marine [[reptile]]s such as [[Ichthyosaur]]s, whose fossilized [[stomach]]s frequently contain [[Phosphate minerals|phosphatic]] hooks from the arms of cephalopods.
Like some modern squid, belemnoid arms carried a series of small hooks for grabbing [[prey]]. Belemnoids were efficient [[carnivore]]s that caught small [[fish]] and other marine animals with their arms and ate them with their [[cephalopod beak|beak-like jaws]]. In turn, belemnites appear to have formed part of the diet of marine [[reptile]]s such as [[Ichthyosaur]]s, whose fossilized [[stomach]]s frequently contain [[Phosphate minerals|phosphatic]] hooks from the arms of cephalopods.

2018年4月2日 (一) 13:35的版本

箭石下綱
Belemnoida
化石時期： 泥盆紀至白堊紀
Well preserved Phragmoteuthis conocauda, showing arm hooks and outline of mantle
Well preserved Phragmoteuthis conocauda, showing arm hooks and outline of mantle
保护状况
化石
科學分類
界： 動物界 Animalia
門： 軟體動物門 Mollusca
綱： 頭足綱 Cephalopoda
亞綱： 蛸亞綱 Coleoidea
下綱： 箭石下綱 Belemnoidea
目
Artist's reconstruction of belemnoids.

箭石類動物（學名：Belemnoida），舊作箭石下綱，是一種已經滅絕頭足綱生物的分支，生活在泥盆紀至白堊紀之間。箭石在許多方面都與現代的魷魚相當接近[1]，而且與現代的烏賊關係密切。箭石也擁有墨囊[2]，不過牠們有10條大約相同長度的觸腕，其中並沒有特別長的觸腕[3]。

The name "belemnoid" comes from the Greek word βέλεμνον, belemnon meaning "a dart or arrow" and the Greek word είδος, eidos meaning "form".[4]

箭石在侏儸紀與白堊紀時數量相當多，所以牠們的化石在中生代的海洋岩層中相當豐富，經常伴隨著菊石類出現。不過箭石也跟菊石一起在白堊紀末期滅絕了。

Belemnoids include belemnites (which belong to order Belemnitida proper), aulacocerids (order Aulacocerida), phragmoteuthids (order Phragmoteuthida), and diplobelids (order Diplobelida).

Occurrence

Belemnoids were numerous during the Jurassic and Cretaceous periods, and their fossils are abundant in Mesozoic marine rocks, often accompanying their cousins the ammonites. The belemnoids become extinct at the end of the Cretaceous period along with the ammonites. The belemnoids' origin lies within the bactritoid nautiloids, which date from the Devonian period; well-formed belemnoid 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.

Anatomy

Belemnoids possessed a central phragmocone made of aragonite and with negative buoyancy.[5] To the rear of the creature was a heavy calcite guard whose main role appears to have been to counterbalance the front (towards the head) of the organism; it positions the centre of mass below the centre of buoyancy, increasing the stability of the swimming organism.[5] The guard would account for between a third and a fifth of the length of the complete organism, arms included.[5]

Like some modern squid, belemnoid arms carried a series of small hooks for grabbing prey. Belemnoids 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 phosphatic hooks from the arms of cephalopods.

Ecology

Belemnoids were effectively neutrally buoyant, and swam in near-shore to mid-shelf oceans.[5] Their fins could be used to their advantage in all water speeds; in a gentle current they could be flapped for propulsion; in a stronger current they could be held erect to generate lift; and when swimming rapidly by jet propulsion they could be tucked in to the body for streamlining.[5]

Preservation

A belemnoid fossil with preserved guard, mantle remnants, and arm hooks
Guard of Hibolites hastatus from the Jurassic near Moneva Teruel, Spain. Note the barnacle borings (Rogerella) showing that it spent considerable time on the seafloor after death.

Normally with fossil belemnoids only the back part of the shell (called the guard or rostrum) is found. The guard is usually elongated and bullet-shaped (though in some subgroups the rostrum may only exist as a thin layer coating the phragmocone). 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 belemnoid phragmocones are homologous with the shells of other cephalopods and are similarly composed of aragonite, belemnoid guards are evolutionarily novel and are composed of calcite or aragonite, thus tending to preserve well. Broken guards show a structure of radiating calcite fibers and may also display concentric growth rings.

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 belemnoid Megateuthis gigantea, which is found in Europe and Asia, can measure up to 46厘米（18英寸） in length, giving the living animal an estimated length of 3米（9.8英尺）.

Very exceptional belemnoid 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.

Thunderstones

The name "thunderbolt" or "thunderstone" has also been traditionally applied to the fossilised rostra of belemnoids. The origin of these bullet-shaped stones was not understood, and thus a mythological explanation of stones created where lightning struck has arisen.[6]

Uses

The stable isotope composition of a belemnoid rostrum from the Peedee Formation (Cretaceous, southeast USA) has long been used as a global standard (Peedee Belemnite, "PDB") against which other isotope geochemistry samples are measured, for both carbon isotopes and oxygen isotopes.

Some belemnoids (such as Belemnites of Belemnitida) 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.

分類

現時箭石目只包含下列三個亞目：

以下三個亞目原來屬於箭石目，現時已分往其他分類：

  • Aulacocerida
  • Phragmoteuthida
  • Diplobelida

Note: all families extinct

Belemnoid from the very top bedding plane of the Zohar Formation (Jurassic) near Neve Atif, the Golan. Note the central fold along the axis characteristic of some genera.
Opalized belemnite rostrum under UV illumination, from Cairn Hill mine, Coober Pedy, South Australia
Fossil of Hybodus, with belemnites in the stomach region

参见

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參考資料

  1. ^ Thomas E. Yancey, Christopher L. Garvie, Mary Wicksten. The Middle Eocene Belosaepia ungula (Cephalopoda: Coleoida) from Texas: structure, ontogeny and function. Journal of Paleontology. 2010/03, 84 (2): 267–287 [2018-04-02]. ISSN 0022-3360. doi:10.1666/09-018r.1 （英语）. 
  2. ^ Lehmann, U. 1981. The Ammonites: Their life and their world. London: Cambridge University Press.
  3. ^ Peter Doyle, Emma V. Shakides. The Jurassic Belemnite Suborder Belemnotheutina. Palaeontology. 2004-07-01, 47 (4): 983–998 [2018-04-02]. ISSN 1475-4983. doi:10.1111/j.0031-0239.2004.00395.x （英语）. 
  4. ^ Webster's New Universal Unabridged Dictionary. 2nd ed. 1979.
  5. ^ 5.0 5.1 5.2 5.3 5.4 Neale Monks, J. David Hardwick, Andrew S. Gale. The Function of the Belemnite Guard. Paläontologische Zeitschrift. 1996-11-01, 70 (3-4): 425 [2018-04-02]. ISSN 0031-0220. doi:10.1007/bf02988082 （英语）. 
  6. ^ Vendetti, Jan. The Cephalopoda: Squids, octopuses, nautilus, and ammonites. UC Berkeley. 2006 [2013-06-07]. 

外部連結

维基共享资源上的相关多媒体资源：箭石类
检索自“https://zh.wikipedia.org/zhwiki/w/index.php?title=箭石类&oldid=48945467”