Editing American paddlefish (section)

==Taxonomy, etymology and evolution==
[[File:Paddlefish underwater.jpeg|thumb|260px|An American paddlefish in a large aquarium tank]]

In 1797, French naturalist [[Bernard Germain de Lacépède]] established the genus ''Polyodon'' for paddlefish,<ref name ="Lacepede">{{cite journal |last1=Lacépède |first1=B.G.E. |title=Mémoire sur le polyodon feuille |journal=Bulletin des Sciences, par la Société Philomathique de Paris |date=1797 |volume=1 |issue=6 |page=49 |url=https://www.biodiversitylibrary.org/page/5492440}}</ref> which today includes a single extant species, ''Polyodon spathula''. Lacépède disagreed with [[Pierre Joseph Bonnaterre]]'s description in {{lang|fr|[[Tableau encyclopédique et méthodique]]}} (1788), which had suggested that paddlefish were a species of shark. When Lacépède established his [[binomial nomenclature|binomial name]] ''Polydon feuille'' he was unaware the species had already been described in 1792 by taxonomist [[Johann Julius Walbaum]], who had named it as ''Squalus spathula''.<ref name ="Walbaum"/><ref name="JStorHist">{{cite journal | jstor=1445053 | title=History of a Neglected Account of the Paddlefish, ''Polyodon spathula'' | author=Daniel McKinley | journal=Copeia | volume=1984 | issue=1 | pages=201–204| date=February 1984| doi=10.2307/1445053}}</ref><ref name="AFS">{{cite book|url=http://www.paddlefishfarming.com/files/UpdatesAug2013/Mims_2005_Aquaculture_in_the_21_century-paddlefish.pdf |title=Paddlefish |publisher=American Fisheries Society |editor1=Anita Kelly |editor2=Jeff Silverstein |author1=Steven Mims |author2=William L. Shelton |journal=Aquaculture in the 21st Century |isbn=978-1-888569-71-1 |issue=46 |pages=227–249 |date=January 2005 |access-date=November 9, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20150924063138/http://www.paddlefishfarming.com/files/UpdatesAug2013/Mims_2005_Aquaculture_in_the_21_century-paddlefish.pdf |archive-date=September 24, 2015 }}</ref> Consequently ''spathula'' has priority as the specific name (and 'Walbaum, 1792' is the taxonomic authority to be cited).<ref name=EOL>{{cite book|url=http://eol.org/pages/208600/names/synonyms|publisher=Encyclopedia of Life|title=Polyodon spathula|date=2013|access-date=October 15, 2014|url-status=live|archive-url=https://web.archive.org/web/20151208211312/http://www.eol.org/pages/208600/names/synonyms|archive-date=December 8, 2015}}</ref> But Walbaum's generic name ''[[Squalus]]'' was already in use for [[Squalidae|dogfish]], so Lacépède's ''Polyodon'' is the valid name for this paddlefish genus. Hence '''Polyodon spathula'' (Walbaum, 1792)' is the accepted full scientific name of the American paddlefish.<ref>{{cite book |last1=Fricke |first1=R. |last2=Eschmeyer |first2=W.N. |last3=Van der Laan |first3=R. |title=Eschmeyer's catalog of fishes: genera, species, references: electronic version |date=2022 |publisher=California Academy of Sciences |url=http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp |access-date=24 April 2022}}</ref>

The American paddlefish is the sole surviving species in the paddlefish family, the [[Polyodontidae]]. This is the [[sister group]] to the [[sturgeons]] (family Acipenseridae); evidence from DNA sequences suggest that their [[Most recent common ancestor|last common ancestor]] lived roughly 140 million years ago.<ref name="Peng2007">{{cite journal |last1=Peng |first1=Z. |last2=Ludwig |first2=A. |last3=Wang |first3=D. |last4=Diogo |first4=R. |last5=Wei |first5=Q. |last6=He |first6=S. |title=Age and biogeography of major clades in sturgeons and paddlefishes (Pisces: Acipenseriformes) |journal=Molecular Phylogenetics and Evolution |date=March 2007 |volume=42 |issue=3 |pages=854–862 |doi=10.1016/j.ympev.2006.09.008|pmid=17158071 |bibcode=2007MolPE..42..854P }}</ref> Together these families compose the [[Acipenseriformes]], an order of [[basal (phylogenetics)|basal]] [[ray-finned fish]]es.<ref name="RSPB">{{cite journal |title=A New Time-Scale for Ray-Finned Fish Evolution |author=Imogen A. Hurley |author2=Rachel Lockridge Mueller |author3=Katherine A. Dunn |author4=Eric J. Schmidt |author5=Matt Friedman |author6=Robert K. Ho |author7=Victoria E. Prince |author8=Ziheng Yang |author9=Mark G. Thomas |author10=Michael I. Coates |journal=  Proceedings of the Royal Society B: Biological Sciences|date=February 2007 |volume=274 |issue=1609 |pages=489–498 |doi=10.1098/rspb.2006.3749 |pmid=17476768 |pmc=1766393 }}</ref> Paddlefish have a long fossil record dating back to the [[Early Cretaceous]] 125 million years ago.<ref name="Murray2020"/> American paddlefish are often referred to as [[primitive fish]], or [[relict species]], because of morphological characteristics that they retain from some of their early fossil ancestors.<ref name="INHS">{{cite web | url=http://wwx.inhs.illinois.edu/resources/inhsreports/spring-02/padfish/ | title=Species Spotlight: Paddlefish | publisher=University of Illinois at Urbana-Champaign | work=Illinois Natural History Survey | access-date=June 18, 2014 | author=Susan Post | url-status=live | archive-url=https://web.archive.org/web/20140529051611/http://wwx.inhs.illinois.edu/resources/inhsreports/spring-02/padfish/ | archive-date=May 29, 2014 }}</ref> These characteristics include a skeleton composed primarily of [[cartilage]], and a deeply forked [[heterocercal]] (spine extending into the upper lobe) [[caudal fin]] similar to that of [[shark]]s, although they are not closely related.<ref name=UMESC>{{cite web | url=http://www.umesc.usgs.gov/aquatic/fish/paddlefish/faq.html | publisher=Upper Midwest Environmental Sciences Center, US Geological Survey | title=Paddlefish Study Project | date=March 13, 2014 | author=Steven Zigler | access-date=October 15, 2014 | url-status=dead | archive-url=https://web.archive.org/web/20141006120107/http://www.umesc.usgs.gov/aquatic/fish/paddlefish/faq.html | archive-date=October 6, 2014 }}</ref>

The family Polyodontidae comprises six known species: three fossil species from western North America, one fossil species from China,<ref name="Murray2020">{{cite journal |last1=Murray |first1=Alison M. |last2=Brinkman |first2=Donald B. |last3=DeMar |first3=David G. |last4=Wilson |first4=Gregory P. |title=Paddlefish and sturgeon (Chondrostei: Acipenseriformes: Polyodontidae and Acipenseridae) from lower Paleocene deposits of Montana, U.S.A. |journal=Journal of Vertebrate Paleontology |date=3 March 2020 |volume=40 |issue=2 |pages=e1775091 |doi=10.1080/02724634.2020.1775091|bibcode=2020JVPal..40E5091M |s2cid=222213273 }}</ref> one recently extinct species from China (the [[Chinese paddlefish]], ''Psephurus gladius''; last recorded 2003),<ref name="Zhang Jarić Roberts He 2020 p=136242">{{cite journal | last1=Zhang | first1=Hui | last2=Jarić | first2=Ivan | last3=Roberts | first3=David L. | last4=He | first4=Yongfeng | last5=Du | first5=Hao | last6=Wu | first6=Jinming | last7=Wang | first7=Chengyou | last8=Wei | first8=Qiwei | title=Extinction of one of the world's largest freshwater fishes: Lessons for conserving the endangered Yangtze fauna | journal=Science of the Total Environment | publisher=Elsevier BV | volume=710 | year=2020 | issn=0048-9697 | doi=10.1016/j.scitotenv.2019.136242 | page=136242| pmid=31911255 | bibcode=2020ScTEn.71036242Z | s2cid=210086307 }}</ref><ref name="Oceanographic 2020">{{cite web | title=Study declares ancient Chinese paddlefish extinct | website=Oceanographic | date=2020-01-09 | url=https://www.oceanographicmagazine.com/news/chinese-paddlefish-extinct/ | access-date=2022-04-23}}</ref> and the single extant species, the American paddlefish, native to the Mississippi River Basin in the United States.<ref name=MnDNR>{{cite web|url=http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=AFCAB01010|publisher=Minnesota Department of Natural Resources|title=''Polyodon spathula'' (Walbaum, 1792)|date=2014|access-date=October 14, 2014|url-status=live|archive-url=https://web.archive.org/web/20141019133739/http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=AFCAB01010|archive-date=October 19, 2014}}</ref> DNA sequences suggest the Chinese and American paddlefishes diverged about 68 million years ago.<ref name ="Peng2007"/> The oldest fossils of paddlefish belonging to ''[[Polyodon]]'' are those of ''[[Polyodon tuberculata|P. tuberculata]]'' from the Lower [[Paleocene]] Tullock Member of the [[Fort Union Formation]] in Montana, dating to around 65 million years ago.<ref name="Murray2020"/><ref name="Warren">{{cite book|author1=M.L. Warren|url=https://books.google.com/books?id=iUrcAwAAQBAJ&q=Freshwater+Fishes+of+North+America%3A+Volume+1%3A+Petromyzontidae+to+Catostomidae|title=Freshwater Fishes of North America: Volume 1: Petromyzontidae to Catostomidae|author2=B.M. Burr|author3=J.R. Tomelleri|publisher=Johns Hopkins University Press|year=2014|isbn=978-1-4214-1202-3|page=211|oclc=883820201}}</ref> An elongated rostrum is a morphological characteristic of Polyodontidae, but only the genus ''Polyodon'' has characteristics adapted specifically for filter feeding, including the jaw, gill arches, and cranium. The gill rakers of American paddlefish are composed of extensive comb-like filaments believed to have inspired the [[etymology]] of the genus name, ''Polyodon'', a Greek compound word meaning "many toothed". Adult American paddlefish are actually toothless, although numerous small teeth less than {{cvt|1|mm|in}} were found in a juvenile paddlefish measuring {{cvt|630|mm|in}}. The name ''spathula'' references the elongated, paddle-shaped snout or rostrum.<ref name="HelfmanCollette2009">{{cite book|author=Gene Helfman|author2=Bruce B. Collette|author3=Douglas E. Facey|author4=Brian W. Bowen|title=The Diversity of Fishes: Biology, Evolution, and Ecology|url=https://books.google.com/books?id=FyehAR6hsUUC&pg=PA254|date=April 3, 2009|publisher=John Wiley & Sons|isbn=978-1-4443-1190-7|page=254|url-status=live|archive-url=https://web.archive.org/web/20160617190622/https://books.google.com/books?id=FyehAR6hsUUC&pg=PA254|archive-date=June 17, 2016}}</ref><ref name="TSU">{{cite web |url=http://txstate.fishesoftexas.org/polydon%20spathula.htm |title=Polyodon spathula |publisher=Texas National History Collection, a division of Texas Natural Science Center, University of Texas at Austin |work=Fishes of Texas Project and Online Database |date=2007 |access-date=June 19, 2014 |author1=Carla Hassan-Williams |author2=Timothy H. Bonner |url-status=live |archive-url=https://web.archive.org/web/20140726121402/http://txstate.fishesoftexas.org/polydon%20spathula.htm |archive-date=July 26, 2014 }}</ref> Compared to Chinese paddlefish and fossil genera, American paddlefish (and the fossil relative ''P. tuberculata'') are considered to be highly [[Derived (phylogenetics)|derived]] because of their specialised adaptations.<ref name="BioScience">{{cite journal | journal=BioScience | title=The paddlefish rostrum as an electrosensory organ: a novel adaptation for plankton feeding | volume=57 | issue=5 | author=Lon A. Wilkens Michael | author2=H. Hofmann | name-list-style=amp | pages=399–407 | date=2007 | doi=10.1641/B570505 | doi-access=free }}</ref>

Unlike the [[planktivorous]] American paddlefish, Chinese paddlefish were strong swimmers, grew larger, and were opportunistic [[piscivore]]s that fed on small fishes and crustaceans. Some distinct morphological differences of Chinese paddlefish include a narrower, sword-like rostrum, and a protrusible mouth. They also had fewer, thicker gill rakers than American paddlefish.<ref name="HelfmanCollette2009"/><ref name="TSU"/>