Editing Jellyfish (section)

== Mapping to taxonomic groups ==
[[File:Sea Nettle Jelly 1.jpg|thumb|A [[purple-striped jellyfish]] at the [[Monterey Bay Aquarium]]]]

=== Phylogeny ===
==== Definition ====
The term jellyfish broadly corresponds to medusae,<ref name=etymol /> that is, a life-cycle stage in the [[Medusozoa]]. The American evolutionary biologist Paulyn Cartwright gives the following general definition:

{{blockquote|Typically, medusozoan [[cnidaria]]ns have a [[Pelagic zone|pelagic]], [[Predation|predatory]] jellyfish stage in their life cycle; [[Stauromedusae|staurozoans]] are the exceptions [as they are stalked].<ref>{{cite journal | last1=Cartwright | first1=Paulyn | last2=Halgedahl | first2=Susan L. |author-link2=Susan Halgedahl| last3=Hendricks | first3=Jonathan R. | last4=Jarrard | first4=Richard D. | last5=Marques | first5=Antonio C. | last6=Collins | first6=Allen G. | last7=Lieberman | first7=Bruce S. |display-authors=3| editor-last=Humphries | editor-first=Stuart | title=Exceptionally Preserved Jellyfishes from the Middle Cambrian | journal=PLOS ONE | volume=2 | issue=10 | year=2007 | doi=10.1371/journal.pone.0001121 | pmid=17971881 | pmc=2040521 | page=e1121| bibcode=2007PLoSO...2.1121C | doi-access=free |issn=1932-6203}}</ref>}}

The Merriam-Webster dictionary defines jellyfish as follows:

{{blockquote|A free-swimming marine [[Coelenterata|coelenterate]] that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells.<ref>{{cite dictionary |title=Jellyfish |url=https://www.merriam-webster.com/dictionary/jellyfish |dictionary=Merriam-Webster |access-date=11 September 2018 |date=1 September 2018}}</ref>}}

Given that jellyfish is a common name, its mapping to biological groups is inexact. Some authorities have called the [[Ctenophora|comb jellies]]<ref name="Perseus">{{cite web |title=Jellyfish Spotting {{!}} Species of Jellyfish |url=http://www.perseus-net.eu/en/species_of_jellyfish/index.html |publisher=Policy-oriented marine Environmental Research in the Southern Eu<!-- shd be U -->ropean Seas (PERSEUS) |access-date=28 August 2018}}</ref> and certain [[salp]]s<ref name=Perseus /> jellyfish, though other authorities state that neither of these are jellyfish, which they consider should be limited to certain groups within the medusozoa.<ref name=Mills2010>{{cite web |last1=Mills |first1=C. E. |title=Ctenophores |url=https://faculty.washington.edu/cemills/Ctenophores.html |publisher=University of Washington |access-date=28 August 2018 |date=8 November 2010}}</ref><ref name=Nereus>{{cite web |title=Our jelly-like relatives: Common misconceptions about salps |url=http://nereusprogram.org/works/our-jelly-like-relatives-common-misconceptions-about-salps/ |publisher=Nereus Program |access-date=28 August 2018}}</ref>

The non-medusozoan clades called jellyfish by some but not all authorities (both agreeing and disagreeing citations are given in each case) are indicated with "'''???'''" on the following cladogram of the animal kingdom:

{{clade
 |label1=[[Animalia]]
 |1={{clade
  |1=[[Porifera]]
  |label2=
  |2={{clade
   |1='''[[Ctenophora]]''' (comb jellies)<ref name="Perseus" /> '''???'''<ref name=Mills2010 /> [[File:LightRefractsOf comb-rows of ctenophore Mertensia ovum.jpg|55px]]
   |label2=
   |2={{clade
    |1='''[[Cnidaria]]''' [[File:Cauliflour Jellyfish, Cephea cephea at Marsa Shouna, Red Sea, Egypt SCUBA.jpg|80px]] (includes jellyfish and other jellies)
    |label2=[[Bilateria]]
    |2={{clade
     |1=[[Protostomia]]
     |label2=[[Deuterostomia]]
     |2={{clade
      |1=[[Ambulacraria]]
      |label2=[[Chordata]]
      |2={{clade
       |1='''[[Tunicata]]''' (includes [[salp]]s)<ref name="Perseus" /> '''???'''<ref name=Nereus /> [[File:Thalia democratica.jpg|55px]]
       |2=[[Vertebrata]]
      }}
     }}
    }}
   }}
  }}
 }}
}}

==== Medusozoan jellyfish ====

Jellyfish are not a [[clade]], as they include most of the Medusozoa, barring some of the Hydrozoa.<ref name=Zapata2015>{{cite journal |doi=10.1371/journal.pone.0139068 |pmid=26465609 |pmc=4605497 |title=Phylogenomic Analyses Support Traditional Relationships within Cnidaria |journal=PLOS ONE |volume=10 |issue=10 |page=e0139068 |year=2015 |last1=Zapata |first1=Felipe |last2=Goetz |first2=Freya E. |last3=Smith |first3=Stephen A. |last4=Howison |first4=Mark |last5=Siebert |first5=Stefan |last6=Church |first6=Samuel H. |last7=Sanders|first7=Steven M. |last8=Ames |first8=Cheryl Lewis |last9=McFadden |first9=Catherine S. |last10=France |first10=Scott C. | last11=Daly |first11=Marymegan |last12=Collins |first12=Allen G. |last13=Haddock| first13=Steven H. D. |author13-link=Steven Haddock |last14=Dunn |first14=Casey W. | last15=Cartwright |first15=Paulyn|display-authors=3|bibcode=2015PLoSO..1039068Z |doi-access=free }}</ref><ref>{{cite journal |doi=10.1186/s12862-018-1142-0 |title=Phylogenomics provides a robust topology of the major cnidarian lineages and insights on the origins of key organismal traits |journal=BMC Evolutionary Biology |volume=18 |pages=68 |year=2018 |last1=Kayal |first1=Ehsan |last2=Bentlage |first2=Bastian |last3=Sabrina Pankey |first3=M. |last4=Ohdera |first4=Aki H. |last5=Medina |first5=Monica |last6=Plachetzki |first6=David C. |last7=Collins |first7=Allen G. |last8=Ryan |first8=Joseph F.|issue=1 |display-authors=3|pmc=5932825 |doi-access=free |bibcode=2018BMCEE..18...68K }}</ref> The medusozoan groups included by authorities are indicated on the following [[phylogenetic tree]] by the presence of citations. Names of included jellyfish, in English where possible, are shown in boldface; the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish.

{{clade
| label1=[[Cnidaria]]
| 1={{clade
   |1=[[Anthozoa]] (corals)
   |2={{clade
      |1=[[Polypodiozoa]] and [[Myxozoa]] (parasitic cnidarians)
      |label2=[[Medusozoa]]
      |2={{clade
         |label1=[[Acraspeda]]
         |1={{clade
            |1=[[Staurozoa]] ('''stalked jellyfish''')<ref>{{cite web |title=STAUROMEDUSAE UK An online guide to the Stalked jellyfish (Stauromedusae) found around the coastal waters of the United Kingdom and Ireland. Includes notes on their identification, and where and how to find them. BACK UK Checklist for Stalked jellyfish (Stauromedusae) |url=http://www.stauromedusae.co.uk/stauromedusae_checklist_uk.html |website=Stauromedusae UK |access-date=28 August 2018}}</ref> [[File:Haliclystus stejnegeri 1.jpg|55px]]
            |label2=[[Rhopaliophora]]
            |2={{clade
               |1=[[Cubozoa]] ('''box jellyfish''')<ref name="Perseus" /> [[File:Carybdea marsupialis screenshot 6.png|80px]]
               |label2=[[Scyphozoa]]
               |sublabel2=('''true jellyfish'''<ref name=Zapata2015 />)
               |2={{clade
                  |1='''[[Discomedusae]]'''<ref name="Perseus" /> [[File:Phyllorhiza punctata macro II.jpg|80px]]
                  |2=[[Coronatae]] ('''crown jellyfish''')<ref>{{cite journal |last1=Schierwater |first1=Bernd |last2=Helm |first2=Rebecca R. |last3=Dunn |first3=Casey W. |title=Indoles induce metamorphosis in a broad diversity of jellyfish, but not in a crown jelly (Coronatae) |journal=PLOS ONE |volume=12 |issue=12 |year=2017 |pages=e0188601 |doi=10.1371/journal.pone.0188601|pmid=29281657 |pmc=5744923 |bibcode=2017PLoSO..1288601H |doi-access=free }}</ref> [[File:Nausithoe aurea.jpg|80px]]                     }}
                  }}
               }}
         |label2=[[Hydrozoa]]
         |2={{clade
            |1={{clade
               |1=[[Aplanulata]] [[File:Hydra-Foto.jpg|55px]]
               |2={{clade
                  |1=[[Siphonophorae]] [[File:Portuguese Man-O-War (Physalia physalis).jpg|55px]]
                  |2={{clade
                     |1=Some '''[[Leptothecata]]'''<ref name="Perseus" /> e.g. [[Aequorea victoria|crystal jelly]] [[File:Aequorea3.jpeg|80px]]
                     |2='''[[Filifera]]'''<ref name="Perseus" /> e.g. [[red paper lantern jellyfish]]<ref>{{cite magazine |title=Red Paper Lantern Jellyfish |url=https://ocean.si.edu/holding-tank/images-hide/red-paper-lantern-jellyfish |author=Osborn, K. J. |magazine=Smithsonian |access-date=13 October 2018 |year=2014}}</ref> [[File:Red-paper-lantern-jellyfish-Karen-Osborn-Smithsonian-Institution.png|80px]]
                     }}
                  }}
               }}
            |label2=[[Trachylinae]]
            |2={{clade
               |1='''[[Limnomedusae]]''', e.g. [[flower hat jelly]]<ref name="Perseus" /> [[File:Olindias formosa1.jpg|80px]]
               |2='''[[Narcomedusae]]''', e.g. cosmic jellyfish<ref>{{cite magazine |title=Take a Peek at the Mesmerizing 'Cosmic Jellyfish' |author=Daley, Jason |date=1 March 2017 |url=https://www.smithsonianmag.com/smart-news/take-peek-mesmerizing-cosmic-jellyfish-180962326/ |magazine=Smithsonian |access-date=28 August 2018}}</ref> [[File:Expl0393 - Flickr - NOAA Photo Library.jpg|80px]]
               }}
            }}
         }}
      }}
   }}
}}

=== Taxonomy ===
The subphylum Medusozoa includes all cnidarians with a medusa stage in their life cycle. The basic cycle is egg, [[planula]] larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, [[Scyphozoa]] (large jellyfish), [[Cubozoa]] (box jellyfish) and [[Hydrozoa]] (small jellyfish), and excludes [[Anthozoa]] (corals and sea anemones).<ref name=Ruppert>{{cite book |title=Invertebrate Zoology, 7th edition |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard, S. |last3=Barnes |first3=Robert D. |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |pages=148–174 }}</ref> This suggests that the medusa form evolved after the polyps.<ref name="treeoflife">[http://tolweb.org/Cnidaria/ Cnidaria] {{webarchive|url=https://web.archive.org/web/20120921151117/http://tolweb.org/Cnidaria |date=2012-09-21 }}, Tree of Life.</ref> Medusozoans have tetramerous symmetry, with parts in fours or multiples of four.<ref name=Ruppert />

The four major classes of medusozoan Cnidaria are:

* [[Scyphozoa]] are sometimes called true jellyfish, though they are no more truly jellyfish than the others listed here. They have tetra-radial symmetry. Most have tentacles around the outer margin of the bowl-shaped bell, and long, oral arms around the mouth in the center of the subumbrella.<ref name=Ruppert />
* [[Cubozoa]] (box jellyfish) have a (rounded) box-shaped bell, and their velarium assists them to swim more quickly. Box jellyfish may be related more closely to scyphozoan jellyfish than either are to the Hydrozoa.<ref name="treeoflife" />
* [[Hydrozoa]] medusae also have tetra-radial symmetry, nearly always have a velum (diaphragm used in swimming) attached just inside the bell margin, do not have oral arms, but a much smaller central stalk-like structure, the manubrium, with terminal mouth opening, and are distinguished by the absence of cells in the mesoglea. Hydrozoa show great diversity of lifestyle; some species maintain the polyp form for their entire life and do not form medusae at all (such as [[Hydra (genus)|Hydra]], which is hence not considered a jellyfish), and a few are entirely medusal and have no polyp form.<ref name=Ruppert />
* [[Staurozoa]] (stalked jellyfish) are characterized by a medusa form that is generally sessile, oriented upside down and with a stalk emerging from the apex of the "calyx" (bell), which attaches to the substrate. At least some Staurozoa also have a polyp form that alternates with the medusoid portion of the life cycle. Until recently, Staurozoa were classified within the Scyphozoa.<ref name=Ruppert />

There are over 200 species of Scyphozoa, about 50 species of Staurozoa, about 50 species of Cubozoa, and the Hydrozoa includes about 1000–1500 species that produce medusae, but many more species that do not.<ref>{{Cite journal |doi=10.1111/j.1744-7410.2004.tb00139.x |last=Marques |first=A.C. |author2=A. G. Collins |s2cid=28342963 |year=2004 |title=Cladistic analysis of Medusozoa and cnidarian evolution |journal=Invertebrate Biology|volume=123|pages=23–42}}</ref><ref>{{Cite journal |last=Kramp |first=P.L. |year=1961 |title=Synopsis of the Medusae of the World|journal=Journal of the Marine Biological Association of the United Kingdom |volume=40 |pages=1–469 |doi=10.1017/s0025315400007347|doi-broken-date=1 November 2024 |bibcode=1961JMBUK..40....7K }}</ref>

=== Fossil history ===
[[File:A guide to the fossil invertebrate animals in the Department of geology and palaeontology in the British museum (Natural history) (1907) (14799088733).jpg|thumb|Fossil jellyfish, ''[[Rhizostomites lithographicus]]'', one of the Scypho-medusae, from the [[Kimmeridgian]] (late Jurassic, 157 to 152 mya) of [[Solnhofen]], Germany]]
[[File:Stranded Cambrian scyphozoans.jpg|thumb|Stranded scyphozoans on a Cambrian tidal flat at [[Blackberry Hill]], Wisconsin]]
[[File:Conularia milwaukeensis.jpg|thumb|right|The [[conulariid]] ''Conularia milwaukeensis'' from the Middle [[Devonian]] of [[Wisconsin]]]]

Since jellyfish have no hard parts, fossils are rare. The oldest unambiguous fossil of a free-swimming medusa is ''[[Burgessomedusa]]'' from the mid-Cambrian [[Burgess Shale]] of Canada, which is likely either a [[Stem-group|stem group]] of box jellyfish (Cubozoa) or [[Acraspeda]] (the clade including Staurozoa, Cubozoa, and Scyphozoa). Other claimed records from the Cambrian of China and Utah in the United States are uncertain, and possibly represent [[Ctenophora|ctenophores]] instead.<ref name="Moon-2023">{{Cite journal |last1=Moon |first1=Justin |last2=Caron |first2=Jean-Bernard |last3=Moysiuk |first3=Joseph |date=2023-08-09 |title=A macroscopic free-swimming medusa from the middle Cambrian Burgess Shale |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=290 |issue=2004 |doi=10.1098/rspb.2022.2490 |issn=0962-8452 |pmc=10394413 |pmid=37528711 }}</ref>