View source for Acipenseriformes

{{Short description|Order of fishes}}
{{Automatic taxobox
| name = Acipenseriformes
| fossil_range = {{geological range|Early Jurassic|Present|earliest=Early Triassic}}
| image = Atlantic sturgeon flipped.jpg
| image_caption = [[Atlantic sturgeon]]<br/>(''Acipenser oxyrhynchus'')
| image2 = Paddlefish (white background).jpg
| image2_caption = [[American paddlefish]]<br/>(''Polyodon spathula'')
| taxon = Acipenseriformes
| authority = [[Lev Berg|L. S. Berg]], 1940
| subdivision_ranks = Subgroups
| subdivision = * Genus †''[[Eochondrosteus]]''?
* Family †[[Chondrosteidae]] (sometimes placed in its own order)
* Family †[[Peipiaosteidae]]
* Suborder '''Acipenseroidei'''
** Family [[Acipenseridae]] (sturgeon)
** Family [[Polyodontidae]] (paddlefish)
}}
[[File:Strongylosteus hindenburgi Tubingen.JPG|thumb|Fossil of the {{extinct}}[[Chondrosteidae|chondrosteid]] {{extinct}}''[[Strongylosteus|Strongylosteus hindenburgi]]'', Tübingen]]
[[File:Yanosteus longidorsalis MHNT.jpg|thumb|Fossil of the {{extinct}}[[Peipiaosteidae|peipiaosteid]] {{extinct}}''[[Yanosteus|Yanosteus longidorsalis]]'', [[MHNT]]]]
[[File:Paddlefish underwater.jpeg|thumb|The living [[Polyodontidae|polyodontid]] ''[[Polyodon|Polyodon spathula]]'' (American paddlefish)]]
[[File:Acipenser ruthenus 1.jpg|thumb|The living [[Acipenseridae|acipenserid]] ''[[sterlet|Acipenser ruthenus]]'' (sterlet)]]
[[File:Live Pseudoscaphirhynchus kaufmanni.jpg|thumb|The living [[Acipenseridae|acipenserid]] ''[[Pseudoscaphirhynchus kaufmanni]]'' (false shovelnose sturgeon)]]

'''Acipenseriformes''' {{IPAc-en|æ|s|ᵻ|ˈ|p|ɛ|n|s|ə|r|ᵻ|f|ɔːr|m|iː|z}} is an [[order (biology)|order]] of [[basal (phylogenetics)|basal]]<ref name="Venkatesh2003">{{Cite journal |doi=10.1016/j.gde.2003.09.001 |title=Evolution and diversity of fish genomes |journal=Current Opinion in Genetics & Development |volume=13 |issue=6 |pages=588–592 |date=December 2003 |last=Venkatesh |first= B.|pmid=14638319 }}</ref> [[Actinopterygii|ray-finned fishes]] that includes living and fossil [[sturgeon]]s and [[paddlefish]]es (Acipenseroidei), as well as the [[extinct]] [[family (biology)|families]] [[Chondrosteidae]] and [[Peipiaosteidae]].<ref name="fish">{{FishBase order |order=Acipenseriformes |year=2006 |month=05}}</ref><ref name="Bemis et al. 1997">{{cite journal |last1=Bemis |first1=William E. |last2=Findeis |first2=Eric K. |last3=Grande |first3=Lance |title=An overview of Acipenseriformes |journal=Environmental Biology of Fishes |date=1997 |volume=48 |issue=1–4 |pages=25–71|doi=10.1023/A:1007370213924 |s2cid=24961905 }}</ref><ref name="Lu et al. 2020">{{cite journal|last1=Lu|first1=Liwu|last2=Tan|first2=Kai|last3=Wang|first3=Xi|date=2020|title=Redescription of ''Eochondrosteus sinensis'' (Acipenseriformes, Actinopterygii) and its geological age|url=http://www.earthsciencefrontiers.net.cn/EN/abstract/abstract6009.shtml|journal=Earth Science Frontiers|volume=27|issue=6|pages=371–381}}</ref> They are the second earliest diverging group of living ray-finned fish after the [[bichir]]s. Despite being early diverging, they are highly [[Primitive (phylogenetics)|derived]], having only weakly [[Ossification|ossified]] skeletons that are mostly made of [[cartilage]], and in modern representatives highly modified skulls.<ref name=":1">{{Citation |last1=Bemis |first1=William E. |title=An overview of Acipenseriformes |date=2002 |url=http://link.springer.com/10.1007/0-306-46854-9_4 |work=Sturgeon Biodiversity and Conservation |volume=17 |pages=25–71 |editor-last=Birstein |editor-first=Vadim J. |place=Dordrecht |publisher=Kluwer Academic Publishers |doi=10.1007/0-306-46854-9_4 |isbn=978-0-7923-4517-6 |access-date=2022-07-27 |last2=Findeis |first2=Eric K. |last3=Grande |first3=Lance |editor2-last=Waldman |editor2-first=John R. |editor3-last=Bemis |editor3-first=William E.|url-access=subscription }}</ref>

== Description ==
The axial skeleton of Acipenseriformes is only partially [[ossified]], with the majority of the bones being replaced with cartilage. The [[notochord]], usually only found in fish embryos, is unconstricted and retained throughout life.<ref>{{Cite journal |last1=Leprévost |first1=A. |last2=Sire |first2=J.-Y. |date=August 2014 |title=Architecture, mineralization and development of the axial skeleton in Acipenseriformes, and occurrences of axial anomalies in rearing conditions; can current knowledge in teleost fish help? |journal=Journal of Applied Ichthyology |volume=30 |issue=4 |pages=767–776 |doi=10.1111/jai.12525|doi-access=free }}</ref> The [[premaxilla]] and [[maxilla]] bones of the skull present in other vertebrates have been lost. While larvae and early juvenile acipenseriforms have teeth, the adults are toothless, or nearly so. The [[infraorbital nerve]] is carried by a series of separate canals, rather than being within the circumorbital bones. The [[palatoquadrate]] bones of the skull possess a cartilaginous [[symphysis]] (joint), and also have a broad autopalatine plate, as well as a narrow palatoquadrate bridge, and a quadrate flange. The [[quadratojugal bone]] is three-pointed (triradiate), and the dentition on the [[Gill arch|gill-arch]] is confined to the upper part of the first arch and to only the first and second hypobranchials.<ref name=":1" /> Members of Acipenseriformes retain the ability to sense [[electric field]]s ([[Electroreception and electrogenesis|electroreception]]) using structures called [[Ampullae of Lorenzini|ampullae]]. This ability was present in the last common ancestor of all living jawed fish, but was lost in the ancestor of [[neopterygian]] fish.<ref>{{Cite journal |last=Crampton |first=William G. R. |date=July 2019 |title=Electroreception, electrogenesis and electric signal evolution |journal=Journal of Fish Biology |volume=95 |issue=1 |pages=92–134 |doi=10.1111/jfb.13922 |issn=0022-1112 |pmid=30729523 |s2cid=73442571|doi-access=free }}</ref> All acipenseriforms probably possessed [[barbels]] like modern sturgeon (which have four) and paddlefish (which have two).<ref name=":1" />

== Evolutionary history ==
Acipenseriforms are assumed to have evolved from a "[[Palaeonisciformes|palaeoniscoid]]" ancestor. Their closest relatives within the "palaeoniscoids" are uncertain and contested.<ref name=":1" /> The ancestors of Acipenseriformes are thought to have split from those of other living fish around the [[Carboniferous]] period (360–300 million years ago).<ref>{{Cite journal |last=Friedman |first=Matt |date=2022-11-02 |title=The Macroevolutionary History of Bony Fishes: A Paleontological View |url=https://www.annualreviews.org/doi/10.1146/annurev-ecolsys-111720-010447 |journal=Annual Review of Ecology, Evolution, and Systematics |language=en |volume=53 |issue=1 |pages=353–377 |doi=10.1146/annurev-ecolsys-111720-010447 |issn=1543-592X|url-access=subscription }}</ref> The last common ancestor of Acipenseriformes underwent a [[Whole-genome duplication|whole genome duplication]] event suggested to have occurred around 242–255 million years ago, with the genome subsequently undergoing [[Diploidization|rediploidization]], both before the split between sturgeons and paddlefish, and separately in both lineages after the split.<ref>{{Cite journal |last=Redmond |first=Anthony K. |last2=Casey |first2=Dearbhaile |last3=Gundappa |first3=Manu Kumar |last4=Macqueen |first4=Daniel J. |last5=McLysaght |first5=Aoife |date=2023-05-19 |title=Independent rediploidization masks shared whole genome duplication in the sturgeon-paddlefish ancestor |url=https://www.nature.com/articles/s41467-023-38714-z |journal=Nature Communications |volume=14 |issue=1 |pages=2879 |doi=10.1038/s41467-023-38714-z |issn=2041-1723|doi-access=free |hdl=20.500.11820/d45b461b-e57c-49cc-b3d2-ece367626d86 |hdl-access=free |pmc=10199039 }}</ref> 

''[[Eochondrosteus]]'' from the [[Early Triassic]] (252–247 million years ago) of China has been suggested by some authors to be the oldest acipenseriform.<ref name="Lu et al. 20202">{{cite journal |last1=Lu |first1=Liwu |last2=Tan |first2=Kai |last3=Wang |first3=Xi |date=2020 |title=Redescription of ''Eochondrosteus sinensis'' (Acipenseriformes, Actinopterygii) and its geological age |url=http://www.earthsciencefrontiers.net.cn/EN/abstract/abstract6009.shtml |journal=Earth Science Frontiers |language=zh |volume=27 |issue=6 |pages=371–381}}</ref> The oldest unambiguous members of the order are the [[Chondrosteidae]], a group of large fish found in marine deposits from the [[Early Jurassic]] (201–175 million years ago) of Europe, which already have reduced ossification of the skeleton.<ref>{{Cite journal |last1=Hilton |first1=Eric J. |last2=Forey |first2=Peter L. |date=December 2009 |title=Redescription of † ''Chondrosteus acipenseroides'' Egerton, 1858 (Acipenseriformes, †Chondrosteidae) from the lower Lias of Lyme Regis (Dorset, England), with comments on the early evolution of sturgeons and paddlefishes |url=http://www.tandfonline.com/doi/abs/10.1017/S1477201909002740 |journal=Journal of Systematic Palaeontology |volume=7 |issue=4 |pages=427–453 |doi=10.1017/S1477201909002740 |s2cid=86821521 |issn=1477-2019|url-access=subscription }}</ref> The [[Peipiaosteidae]] are known from Middle Jurassic-Early Cretaceous freshwater deposits in Asia.<ref>{{Cite journal |last1=Hilton |first1=Eric J. |last2=Grande |first2=Lance |last3=Jin |first3=Fan |date=2020-10-08 |title=Redescription of †''Yanosteus longidorsalis'' Jin et al., (Chondrostei, Acipenseriformes, †Peipiaosteidae) from the Early Cretaceous of China |url=http://dx.doi.org/10.1017/jpa.2020.80 |journal=Journal of Paleontology |volume=95 |issue=1 |pages=170–183 |doi=10.1017/jpa.2020.80 |s2cid=225158727 |issn=0022-3360|url-access=subscription }}</ref> The estimated time of the divergence between sturgeons and paddlefish varies. An estimate based on 30 protein-encoding nuclear markers suggest 204.1 million years ago, research on mitochondrial genomes suggest 155.2 million years ago, and Bayesian dating based on the combined matrix of molecular (mitogenomes) and morphological characters set the divergence to 162 (195–137) million years ago.<ref>{{Cite journal |last=Ruban |first=G. I. |date=2023-04-01 |title=Modern Concepts on the Origin and Distribution of Acipenserids (Acipenseridae) |url=https://doi.org/10.1134/S0032945223020169 |journal=Journal of Ichthyology |language=en |volume=63 |issue=2 |pages=206–215 |doi=10.1134/S0032945223020169 |issn=1555-6425|doi-access=free }}</ref>

The oldest known paddlefish is ''[[Protopsephurus]]'' from the Early Cretaceous of China around 120 million years ago,<ref name=":0">{{Cite journal |last1=Grande |first1=Lance |last2=Jin |first2=Fan |last3=Yabumoto |first3=Yoshitaka |last4=Bemis |first4=William E. |date=2002-07-08 |title=''Protopsephurus liui'', a well-preserved primitive paddlefish (Acipenseriformes: Polyodontidae) from the Lower Cretaceous of China |url=https://doi.org/10.1671/0272-4634(2002)022[0209:PLAWPP]2.0.CO;2 |journal=Journal of Vertebrate Paleontology |volume=22 |issue=2 |pages=209–237 |doi=10.1671/0272-4634(2002)022[0209:PLAWPP]2.0.CO;2 |s2cid=86258128 |issn=0272-4634|url-access=subscription }}</ref> while the earliest known sturgeons appear in the Late Cretaceous in North America and Asia, around 100–95 million years ago.<ref>{{Cite journal |last1=Sato |first1=Hiroki |last2=Murray |first2=Alison M. |last3=Vernygora |first3=Oksana |last4=Currie |first4=Philip J. |date=2018-07-04 |title=A rare, articulated sturgeon (Chondrostei: Acipenseriformes) from the Upper Cretaceous of Dinosaur Provincial Park, Alberta, Canada |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2018.1488137 |journal=Journal of Vertebrate Paleontology |volume=38 |issue=4 |pages=(1)–(15) |doi=10.1080/02724634.2018.1488137 |s2cid=92574712 |issn=0272-4634|url-access=subscription }}</ref>

== Classification ==
* Order '''Acipenseriformes''' <small>[[Lev Berg|Berg]], 1940</small>
** Genus †''[[Eochondrosteus]]''? <small>Lu, Li & Yang, 2005</small>
** '''Family''' †'''[[Chondrosteidae]]''' <small>[[Sir Philip Grey Egerton, 10th Baronet|Egerton]], 1858</small> (Also placed in the separate order Chondrosteiformes<ref name=":022">{{Cite book |last=Nelson |first=Joseph S. |url=http://dx.doi.org/10.1002/9781119174844 |title=Fishes of the World |last2=Grande |first2=Terry C. |last3=Wilson |first3=Mark V. H. |date=2016-02-22 |publisher=Wiley |isbn=978-1-118-34233-6}}</ref>)
*** Genus †''[[Chondrosteus]]'' <small>[[Louis Agassiz|Agassiz]], 1833–1844</small>
*** Genus †''[[Gyrosteus]]'' <small>Agassiz, 1833–1844</small>
*** Genus †''[[Strongylosteus]]'' <small>Agassiz, 1833–1844</small>
** '''Family''' †'''[[Peipiaosteidae]]''' <small>Liu & Zhou, 1965</small>
*** Genus †''[[Spherosteus]]'' <small>Jakovlev, 1968</small>
*** Genus †''[[Yanosteus]]'' <small>Jin et al., 1995</small>
*** Genus †''[[Liaosteus]]'' <small>Lu, 1995</small>
*** Genus †''[[Peipiaosteus]]'' <small>Liu & Zhou, 1965</small> 
*** Genus †''[[Stichopterus]]'' <small>Reis, 1909</small>
**'''Suborder Acipenseroidei''' <small>Grande & Bemis, 1991</small><ref name="Grande & Bemis, 1996">{{cite book |author1=Grande, L. |author2=Bemis, W.E. |name-list-style=amp |year=1996 |chapter=Interrelationships of Acipenseriformes, with Comments on 'Chondrostei' |chapter-url=https://books.google.com/books?id=H20q9rqZENsC&pg=PA112 |editor1=Stiassny, M.L.J. |editor2=Parenti, L.R. |editor3=Johnson, G.D. |title=Interrelationships of Fishes |url=https://books.google.com/books?id=H20q9rqZENsC&pg=PP1 |publisher=[[Academic Press]] |place=San Diego, California |pages=85–115 |isbn=0-12-670950-5 |lccn=96028224 |oclc=34990143 |ol=989905M |doi=10.1016/B978-012670950-6/50006-0}}</ref>
*** '''Family [[Polyodontidae]]''' <small>[[Charles Lucien Bonaparte|Bonaparte]], 1838</small> (paddlefish)
**** Genus †''[[Protopsephurus]]'' <small>Lu, 1994</small>
**** Genus †''[[Paleopsephurus]]'' <small>MacAlpin, 1941a</small>
**** Genus †''[[Pugiopsephurus]]'' <small>Hilton et al., 2023</small>
**** Genus †''[[Parapsephurus]]'' <small>Hilton et al., 2023</small>
**** '''Subfamily''' '''[[Paddlefish#Classification|Polyodontinae]]''' <small>Grande & Bemis, 1991 non Pflugfelder, 1934</small>
***** Genus †''[[Crossopholis]]'' <small>[[Edward Drinker Cope|Cope]], 1883</small>
***** Genus ''[[Polyodon]]'' <small>[[Bernard Germain de Lacépède|Lacépède]], 1797</small> (American paddlefish)
***** Genus †''[[Psephurus]]'' <small>[[Albert Günther|Günther]], 1873</small> (Chinese paddlefish)
*** '''Family [[Acipenseridae]]''' <small>[[Charles Lucien Bonaparte|Bonaparte]], 1831 sensu Bemis et al., 1997</small> (sturgeons)
**** Genus †''[[Boreiosturion]]'' <small>Murray et al. 2023</small>
**** Genus †''[[Protoscaphirhynchus]]'' <small>Wilimovsky, 1956</small>
**** Genus † ''[[Engdahlichthys]]'' <small>Murray et al. 2020</small>
**** Genus †''[[Anchiacipenser]]'' <small>Sato, Murray, Vernygora and Currie, 2019</small>
**** Genus †''[[Priscosturion]]'' <small>Grande & Hilton, 2009</small> [''Psammorhynchus'' <small>Grande & Hilton, 2006</small>]
**** Genus ''[[Acipenser]]'' <small>[[Carl Linnaeus|Linnaeus]], 1758</small>
**** Genus ''[[Huso]]'' <small>[[Johann Friedrich von Brandt|J. F. Brandt]] & [[Julius Theodor Christian Ratzeburg|Ratzeburg]], 1833</small>
**** Genus ''[[Scaphirhynchus]]'' <small>[[Johann Jakob Heckel|Heckel]], 1835</small>
**** Genus ''[[Pseudoscaphirhynchus]]'' <small>[[Alexander Mikhailovich Nikolsky|Nikolskii]], 1900</small>

==Conservation==
Most living [[species]] of Acipenseriformes are classified as [[threatened species|threatened]] (mostly [[endangered]] or [[critically endangered]]) by the [[International Union for Conservation of Nature]].

The [[Chinese paddlefish]] was last seen alive in 2003, and was considered to have gone extinct sometime between 2005 and 2010 by the [[Yangtze River Fisheries Research Institute]] in their 2019 report.

== Hybridization ==
A study published in 2020 reported a successful [[Hybrid (biology)|hybridization]] between a [[Russian sturgeon]] (''Acipenser gueldenstaedtii'') and an [[American paddlefish]] (''Polyodon spathula''), indicating that the two species can breed with one another despite their lineages having been separated for hundreds of millions of years. This has marked the first successful hybridization between members of [[Sturgeon|Acipenseridae]] and [[Paddlefish|Polyodontidae]].<ref>{{Cite journal|last1=Káldy|first1=Jenő|last2=Mozsár|first2=Attila|last3=Fazekas|first3=Gyöngyvér|last4=Farkas|first4=Móni|last5=Fazekas|first5=Dorottya Lilla|last6=Fazekas|first6=Georgina Lea|last7=Goda|first7=Katalin|last8=Gyöngy|first8=Zsuzsanna|last9=Kovács|first9=Balázs|last10=Semmens|first10=Kenneth|last11=Bercsényi|first11=Miklós|date=July 2020|title=Hybridization of Russian Sturgeon (''Acipenser gueldenstaedtii'', Brandt and Ratzeberg, 1833) and American Paddlefish (''Polyodon spathula'', Walbaum 1792) and Evaluation of Their Progeny|journal=Genes|volume=11|issue=7|pages=753|doi=10.3390/genes11070753|pmid=32640744|pmc=7397225|doi-access=free}}</ref>

== References ==
{{Portal|fish}}
{{Reflist}}
* [[Martin Hochleithner]] and [[Joern Gessner]], ''The Sturgeons and Paddlefishes of the World: Biology and Aquaculture''
* [[Martin Hochleithner]], [[Joern Gessner]], and [[Sergej Podushka]], ''The Bibliography of Acipenseriformes''
* {{cite journal|last=Sepkoski |first=Jack |title=A compendium of fossil marine animal genera |journal=Bulletins of American Paleontology |volume=364 |pages=560 |year=2002 |url=http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |access-date=2011-05-17 |url-status=dead |archive-url=https://web.archive.org/web/20110723131237/http://strata.ummp.lsa.umich.edu/jack/showgenera.php?taxon=611&rank=class |archive-date=2011-07-23 }}

==External links==
*[http://animaldiversity.ummz.umich.edu/site/accounts/pictures/Acipenseriformes.html Photos and illustrations of Acipenseriformes]
*[http://www.cites.org/eng/news/press_release.shtml CITES finalizes 2006 caviar export quotas]

{{Actinopterygii}}
{{Chondrostei|state=collapsed}}
{{Acipenseriformes}}
{{Diversity of fish}}
{{Taxonbar|from=Q192422}}
{{Authority control}}

[[Category:Acipenseriformes| ]]
[[Category:Ray-finned fish orders]]
[[Category:Taxa named by Lev Berg]]
[[Category:Articles which contain graphical timelines]]
[[Category:Extant Late Jurassic first appearances]]