View source for Ecdysozoa

{{Short description|Superphylum of protostomes}}
{{Automatic taxobox
| fossil_range = [[Ediacaran]] - [[Holocene]], {{fossil range|560|0}}<ref name=uncus>{{cite journal |last1=Hughes |first1=Ian V. |last2=Evans |first2=Scott D. |last3=Droser |first3=Mary L. |title=An Ediacaran bilaterian with an ecdysozoan affinity from South Australia |journal=Current Biology |date=November 2024 |volume=34 |issue=24 |pages=5782–5788.e1 |doi=10.1016/j.cub.2024.10.030|pmid=39561775 |bibcode=2024CBio...34.5782H |doi-access=free }}</ref>
| image = Ecdysozoa.jpg
| image_caption = 
| display_parents = 5
| taxon = Ecdysozoa
| authority = Aguinaldo ''et al''., 1997
| subdivision_ranks = Phyla
| subdivision = * [[Scalidophora]]
** [[Kinorhyncha]]
** [[Priapulida]]
** [[Loricifera]]
**†''[[Qinscolex]]''<ref name="qinscolex">{{cite journal |last1=Liu |first1=Yunhuan |last2=Qin |first2=Jiachen |last3=Wang |first3=Qi |last4=Maas |first4=Andreas |last5=Duan |first5=Baichuan |last6=Zhang |first6=Yanan |last7=Zhang |first7=Hu |last8=Shao |first8=Tiequan |last9=Zhang |first9=Huaqiao |title=New armoured scalidophorans (Ecdysozoa, Cycloneuralia) from the Cambrian Fortunian Zhangjiagou Lagerstätte, South China |journal=Papers in Palaeontology |date=May 2019 |volume=5 |issue=2 |pages=241–260 |doi=10.1002/spp2.1239|bibcode=2019PPal....5..241L }}</ref>
**†''[[Shanscolex]]''<ref name="qinscolex"/>
**†''[[Xinliscolex]]''<ref>{{cite journal |last1=Zhang |first1=Hua-Qiao |title=The evolutionary relationships of the earliest known cycloneuralians and a new record from the Cambrian Fortunian of South China |journal=Palaeoworld |date=September 2022 |volume=31 |issue=3 |pages=389–401 |doi=10.1016/j.palwor.2021.09.003}}</ref>
**†''[[Dahescolex]]''<ref>{{cite journal |last1=Shao |first1=T.Q. |last2=Qin |first2=J.C. |last3=Shao |first3=Y. |last4=Liu |first4=Y.H. |last5=Waloszek |first5=D. |last6=Maas |first6=A. |last7=Duan |first7=B.C. |last8=Wang |first8=Q. |last9=Xu |first9=Y. |last10=Zhang |first10=H.Q. |title=New macrobenthic cycloneuralians from the Fortunian (lowermost Cambrian) of South China |journal=Precambrian Research |date=October 2020 |volume=349 |article-number=105413 |doi=10.1016/j.precamres.2019.105413|bibcode=2020PreR..34905413S }}</ref>
**†''[[Zhongpingscolex]]''<ref>{{cite journal |last1=Shao |first1=T.Q. |last2=Wang |first2=Q. |last3=Liu |first3=Y.H. |last4=Qin |first4=J.C. |last5=Zhang |first5=Y.N. |last6=Liu |first6=M.J. |last7=Shao |first7=Y. |last8=Zhao |first8=J.Y. |last9=Zhang |first9=H.Q. |title=A new scalidophoran animal from the Cambrian Fortunian Stage of South China and its implications for the origin and early evolution of Kinorhyncha |journal=Precambrian Research |date=October 2020 |volume=349 |article-number=105616 |doi=10.1016/j.precamres.2020.105616|bibcode=2020PreR..34905616S }}</ref>
** †''[[Dakorhachis]]''?<ref>{{cite journal |last1=Bekkouche |first1=Nicolas |last2=Gąsiorowski |first2=Ludwik |title=Careful amendment of morphological data sets improves phylogenetic frameworks: re-evaluating placement of the fossil Amiskwia sagittiformis |journal=Journal of Systematic Palaeontology |date=31 December 2022 |volume=20 |issue=1 |pages=1–14 |doi=10.1080/14772019.2022.2109217|url=https://hal.sorbonne-universite.fr/hal-03828531/file/Manuscript_Amiskwia_Bekkouche_and_Gasiorowski_Hall_version_compressed.pdf }}</ref>
* †[[Palaeoscolecida]] 
* '''Cryptovermes'''<ref name=Howard-Giacomelli-etal-2022>{{cite journal |vauthors=Howard RJ, Giacomelli M, Lozano-Fernandez J, Edgecombe GD, Fleming JF, Kristensen RM, Ma X, Olesen J, Sørensen MV, Thomsen PF, Wills MA, Donoghue PC, Pisani D |display-authors=6 |year=2022 |title=The Ediacaran origin of ecdysozoa: Integrating fossil and phylogenomic data |journal=[[Journal of the Geological Society]] |volume=179 |issue=4 |doi=10.1144/jgs2021-107 |bibcode=2022JGSoc.179..107H |s2cid=246494357 |url=https://pubs.geoscienceworld.org/jgs/article-standard/179/4/jgs2021-107/611205/The-Ediacaran-origin-of-Ecdysozoa-integrating |access-date=2023-07-30|hdl=2445/186596 |hdl-access=free }}</ref>
**[[Nematoida]]
*** [[Nematoda]]
*** [[Nematomorpha]]
***†''[[Uncus dzaugisi|Uncus]]'' ?
** [[Panarthropoda]]
*** †"[[Lobopodia]]" 
*** [[Onychophora]]
*** [[Arthropoda]]
*** [[Tardigrada]]
*** †[[Sialomorphidae]]
*†[[Saccorhytida]]<ref>{{cite journal |last1=Liu |first1=Yunhuan |last2=Carlisle |first2=Emily |last3=Zhang |first3=Huaqiao |last4=Yang |first4=Ben |last5=Steiner |first5=Michael |last6=Shao |first6=Tiequan |last7=Duan |first7=Baichuan |last8=Marone |first8=Federica |last9=Xiao |first9=Shuhai |display-authors=6 |date=2022-08-17 |df=dmy-all |title=Saccorhytus is an early ecdysozoan, and not the earliest deuterostome |journal=[[Nature (journal)|Nature]] |volume=609 |issue=7927 |pages=541–546 |lang=en |doi=10.1038/s41586-022-05107-z |pmid=35978194 |bibcode=2022Natur.609..541L |s2cid=251646316 |issn=1476-4687 |url=https://www.nature.com/articles/s41586-022-05107-z |hdl=1983/454e7bec-4cd4-4121-933e-abeab69e96c1 |hdl-access=free }}</ref>
*†''[[Acosmia]]''<ref>{{cite journal |last1=Howard |first1=Richard J. |last2=Edgecombe |first2=Gregory D. |last3=Shi |first3=Xiaomei |last4=Hou |first4=Xianguang |last5=Ma |first5=Xiaoya |date=2020-11-23 |df=dmy-all |title=Ancestral morphology of Ecdysozoa constrained by an early Cambrian stem group ecdysozoan |journal=[[BMC Evolutionary Biology]] |lang=en |volume=20 |issue=1 |page=156 |doi=10.1186/s12862-020-01720-6 |issn=1471-2148 |pmc=7684930 |pmid=33228518 |doi-access=free |bibcode=2020BMCEE..20..156H }}</ref>
*†''[[Laojieella]]''
*†''[[Saccus (genus)|Saccus]]''
}}

'''Ecdysozoa''' ({{IPAc-en|ˌ|ɛ|k|d|ɪ|s|oʊ-|ˈ|z|oʊ|ə}}) is a group of [[protostome]] animals,<ref name="TelfordBourlat2008">{{cite journal |last1=Telford |first1=Maximilian J. |last2=Bourlat |first2=Sarah J. |last3=Economou |first3=Andrew |last4=Papillon |first4=Daniel |last5=Rota-Stabelli |first5=Omar |year=2008 |title=The evolution of the Ecdysozoa |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |volume=363 |issue=1496 |pages=1529–1537 |issn=0962-8436 |doi=10.1098/rstb.2007.2243 |pmid=18192181 |pmc=2614232 }}</ref> including [[Arthropod]]a ([[insects]], [[chelicerates]] (including [[arachnids]]), [[crustaceans]], and [[myriapods]]), [[Nematoda]], and several smaller [[phylum (biology)|phyla]]. The grouping of these [[animal]] phyla into a single [[clade]] was first proposed by Eernisse ''et al.'' (1992) based on a [[phylogenetic analysis]] of 141 morphological characters of ultrastructural and [[embryological]] [[phenotypes]].<ref>{{cite journal |last1=Eernisse |first1=D.J. |last2=Albert |first2=J.S. |last3=Anderson |first3=F.E. | year=1992 |title=Annelida and Arthropoda are not sister taxa: A phylogenetic analysis of spiralian metazoan morphology |journal=[[Systematic Biology (journal)|Systematic Biology]] |volume=41 |issue=3 |pages=305–330 |doi= 10.1093/sysbio/41.3.305 }}</ref> This clade, that is, a group consisting of a [[common ancestor]] and all its descendants, was formally named by Aguinaldo ''et al.'' in 1997, based mainly on [[phylogenetic tree]]s constructed using [[18S ribosomal RNA]] genes.<ref>{{cite journal |last1=Aguinaldo |first1=A.M.A. |first2=J.M. |last2=Turbeville |first3=L.S. |last3=Linford |first4=M.C. |last4=Rivera |first5=J.R. |last5=Garey |first6=R.A. |last6=Raff |first7=J.A. |last7=Lake |date=29 May 1997 |title=Evidence for a clade of nematodes, arthropods, and other moulting animals |journal=[[Nature (journal)|Nature]] |volume=387 |pages=489–493 |doi=10.1038/387489a0 |pmid=9168109 |issue=6632 |bibcode=1997Natur.387R.489A |s2cid=4334033 }}</ref>

A large study in 2008 by Dunn ''et al.'' strongly supported the [[monophyly]] of Ecdysozoa.<ref name=nature_phylo>{{cite journal |last1=Dunn |first1=C.W. |last2=Hejnol |first2=A. |last3=Matus |first3=D.Q. |last4=Pang |first4=K. |last5=Browne |first5=W.E. |last6=Smith |first6=S.A. |last7=Seaver |first7=E. |last8=Rouse |first8=G.W. |last9=Obst |first9=M. |last10=Edgecombe |first10=Gregory D. |last11=Sørensen |first11=Martin V. |last12=Haddock |first12=Steven H.D. |last13=Schmidt-Rhaesa |first13=Andreas |last14=Okusu |first14=Akiko |last15=Kristensen |first15=Reinhardt Møbjerg |last16=Wheeler |first16=Ward C. |last17=Martindale |first17=Mark Q. |last18=Giribet |first18=Gonzalo |display-authors=6 |date=10 April 2008 |title=Broad phylogenomic sampling improves resolution of the animal tree of life |journal=[[Nature (journal)|Nature]] |volume=452 |issue=7188 |pages=745–749 |doi=10.1038/nature06614 |pmid=18322464 |bibcode=2008Natur.452..745D|s2cid=4397099 }}</ref>

The group Ecdysozoa is supported by many [[Morphology (biology)|morphological]] characters, including growth by [[ecdysis]], with moulting of the [[cuticle]] – without [[mitosis]] in the [[epidermis]] – under control of the [[prohormone]] [[ecdysone]], and [[internal fertilization]].<ref>{{cite book |last=Ax |first=P. |year=1985 |section=The position of the Gnathostomulida and Platyhelminthes in the phylogenetic system of the Bilateria |editor1=Conway Morris, S. |editor2=George, J.D. |editor3=Gibson, R. |editor4=Platt, H.M. |title=The Origins and Relationships of Lower Invertebrates |series=Systematics Association Special Volume |volume=28 |place=New York, NY |publisher=Clarendon / Oxford University Press |isbn=0-19-857181-X |oclc=59186778 |pages=168–180 |quote=proceedings of an international symposium held in London, September&nbsp;1983 |url=https://archive.org/details/originsrelations0000unse |via=Internet Archive (archive.org)}} {{ISBN|9780198571810}}</ref>

The group was initially contested by a significant minority of [[Biologist|biologists]]. Some argued for groupings based on more traditional taxonomic techniques,<ref>{{cite book |first=Claus |last=Nielsen |year=1995 |title=Animal Evolution: Interrelationships of the living phyla |publisher=Oxford University Press |isbn=978-0-19-850682-9}}</ref> while others contested the interpretation of the [[molecular data]].<ref name=Blair>{{cite journal |first1=J.E. |last1=Blair |first2=Kazuho |last2=Ikeo |first3=Takashi |last3=Gojobori |first4=S. Blair |last4=Hedges |date=8 April 2002 |title=The evolutionary position of nematodes |journal=[[BMC Evolutionary Biology]] |volume=2 |page=7 |doi=10.1186/1471-2148-2-7 |pmid=11985779 |pmc=102755 |doi-access=free }}</ref><ref>{{cite journal |first1=J.W. |last1=Wägele |first2=T. |last2=Erikson |first3=P. |last3=Lockhart |first4=B. |last4=Misof |date=December 1999 |title=The Ecdysozoa: Artifact or monophylum? |journal=[[Journal of Zoological Systematics and Evolutionary Research]] |volume=37 |issue=4 |pages=211–223 |doi=10.1111/j.1439-0469.1999.tb00985.x|doi-access=free }}</ref>

== Etymology ==
The name ''Ecdysozoa'' is [[International scientific vocabulary|scientific Greek]], derived from [[wikt:ἔκδυσις#Ancient Greek|{{math|ἔκδυσις}}]] (''{{grc-transl|ἔκδυσις}}'') "shedding" + [[wikt:ζῷον#Ancient Greek|{{math|ζῷον}}]] (''{{grc-transl|ζῷον}}'') "animal".

== Characteristics ==
{{See also|List of bilaterial animal orders}}

The most notable characteristic shared by ecdysozoans is a three-layered [[cuticle]] (four in [[tardigrade|Tardigrada]]<ref>{{cite book |author= Barnes, Robert D. |year=1982 |title= Invertebrate Zoology |publisher= Holt-Saunders International |location= Philadelphia, PA |pages= 877–880 |isbn=0-03-056747-5}}</ref>) composed of organic material, which is periodically molted as the animal grows. This process of molting is called [[ecdysis]], and gives the group its name. The ecdysozoans lack locomotory [[Cilium|cilia]] and produce mostly [[Amoeboid movement|amoeboid]] sperm, and their [[embryo]]s do not undergo [[spiral cleavage]] as in most other protostomes. Ancestrally, the group exhibited sclerotized teeth within the foregut, and a ring of spines around the mouth opening, though these features have been secondarily lost in certain groups.<ref>{{cite journal |last1=Smith |first1=Martin R. |last2=Caron |first2=Jean-Bernard |date=2 July 2015 |title=Hallucigenia's head and the pharyngeal armature of early ecdysozoans |journal=[[Nature (journal)|Nature]] |volume=523 |issue=7558 |pages=75–78 |bibcode=2015Natur.523...75S |s2cid=205244325 |doi=10.1038/nature14573 |pmid=26106857 |url=http://dro.dur.ac.uk/20476/1/20476.pdf}}</ref><ref>{{cite journal | url=https://onlinelibrary.wiley.com/doi/full/10.1111/pala.12256 | doi=10.1111/pala.12256 | title=The mouth apparatus of the Cambrian gilled lobopodian ''Pambdelurion whittingtoni'' | date=2016 | last1=Vinther | first1=Jakob | last2=Porras | first2=Luis | last3=Young | first3=Fletcher J. | last4=Budd | first4=Graham E. | last5=Edgecombe | first5=Gregory D. | journal=Palaeontology | volume=59 | issue=6 | pages=841–849 | bibcode=2016Palgy..59..841V | hdl=1983/16da11f1-5231-4d6c-9968-69ddc5633a8a | hdl-access=free }}</ref> An unpaired [[ventral nerve cord]], present in Priapulida and Nematoida, appear to be the ancestral condition, making the paired ventral nerve cord found in Panarthropoda, Kinorhyncha and Loricifera a derived trait.<ref>[https://www.science.org/doi/10.1126/sciadv.adr0896 Preservation and early evolution of scalidophoran ventral nerve cord]</ref> A respiratory and circulatory system is only present in [[onychophora]]ns and arthropods (often absent in smaller arthropods like mites); in the rest of the groups, both systems are missing.

== Phylogeny ==

The Ecdysozoa include the following phyla: [[Arthropoda]], [[Onychophora]], [[Tardigrada]], [[Kinorhyncha]], [[Priapulida]], [[Loricifera]], [[Nematoda]], and [[Nematomorpha]]. A few extinct taxa have been classified as [[stem group]] ecdysozoans, such as ''[[Uncus dzaugisi]]'' and ''[[Acosmia]]''.  Other groups such as the [[gastrotrich]]s, have been considered possible members but lack the main characters of the group, and are now placed elsewhere. The Arthropoda, Onychophora, and Tardigrada have been grouped together as the [[Panarthropoda]] because they are distinguished by segmented body plans.<ref>{{cite web |title=Panarthropoda |website=Paleos (palaeos.com) |series=Invertebrates |url=http://www.palaeos.com/Invertebrates/Arthropods/Panarthropoda.html |access-date=17 February 2007 |archive-url=https://web.archive.org/web/20070207102301/http://www.palaeos.com/Invertebrates/Arthropods/Panarthropoda.html |archive-date=2007-02-07 }}</ref> Dunn ''et al.'' in 2008 suggested that the tardigrada could be grouped along with the nematodes, leaving Onychophora as the sister group to the arthropods.<ref name="nature_phylo" /> The non-panarthropod members of Ecdysozoa have been grouped as [[Cycloneuralia]] but they are more usually considered [[paraphyly|paraphyletic]] in representing the primitive condition from which the Panarthropoda evolved.<ref>{{cite journal |last1=Webster |first1=Bonnie L. |last2=Copley |first2=Richard R. |last3=Jenner |first3=Ronald A. |last4=Mackenzie-Dodds |first4=Jacqueline A. |last5=Bourlat |first5=Sarah J. |last6=Rota-Stabelli |first6=Omar |last7=Littlewood |first7=D.T.J. |last8=Telford |first8=Maximilian J. |display-authors=6 |date=November 2006 |title=Mitogenomics and phylogenomics reveal priapulid worms as extant models of the ancestral Ecdysozoan |journal=[[Evolution & Development]] |volume=8 |issue=6 |pages=502–510 |doi=10.1111/j.1525-142X.2006.00123.x |pmid=17073934 |s2cid=22823313}}</ref>

A modern consensus [[phylogenetic tree]] for the protostomes is shown below.<ref>{{cite journal |first1=Gregory D. |last1=Edgecombe |first2=Gonzalo |last2=Giribet |first3=Casey W. |last3=Dunn |first4=Andreas |last4=Hejnol |first5=Reinhardt M. |last5=Kristensen |first6=Ricardo C. |last6=Neves |first7=Greg W. |last7=Rouse |first8=Katrine |last8=Worsaae |first9=Martin V. |last9=Sørensen |display-authors=6 |date=June 2011 |title=Higher-level metazoan relationships: Recent progress and remaining questions |journal=[[Organisms, Diversity & Evolution]] |volume=11 |issue=2 |pages=151–172 |s2cid=32169826 |doi=10.1007/s13127-011-0044-4 |bibcode=2011ODivE..11..151E |url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:27755241 |url-access=subscription }}</ref><ref name=Fröbius>{{Cite journal |last1=Fröbius |first1=Andreas C. |last2=Funch |first2=Peter |date=2017-04-04 |df=dmy-all |title=Rotiferan Hox genes give new insights into the evolution of metazoan bodyplans |journal=[[Nature Communications]] |volume=8 |issue=1 |page=9 |doi=10.1038/s41467-017-00020-w |pmid=28377584 |pmc=5431905 |bibcode=2017NatCo...8....9F }}</ref><ref>{{cite journal |last1=Smith |first1=Martin R. |last2=Ortega-Hernández |first2=Javier |year=2014 |title=Hallucigenia's onychophoran-like claws and the case for Tactopoda |journal=[[Nature (journal)|Nature]] |volume=514 |issue=7522 |pages=363–366 |doi=10.1038/nature13576 |pmid=25132546 |bibcode=2014Natur.514..363S |s2cid=205239797 |url=http://dro.dur.ac.uk/19108/1/19108.pdf}}</ref><ref name="Palaeos Metazoa: Ecdysozoa">{{Cite web |url=http://palaeos.com/metazoa/ecdysozoa/ecdysozoa.html |title=Palaeos Metazoa: Ecdysozoa |website=palaeos.com |access-date=2017-09-02}}</ref><ref>{{cite journal |last1=Yamasaki |first1=Hiroshi |last2=Fujimoto |first2=Shinta |last3=Miyazaki |first3=Katsumi |date=June 2015 |title=Phylogenetic position of Loricifera inferred from nearly complete 18S and 28S rRNA gene sequences |journal=[[Zoological Letters]] |volume=1 |page=18 |doi=10.1186/s40851-015-0017-0|pmid=26605063 |pmc=4657359 |doi-access=free }}</ref><ref>{{cite book |last=Nielsen |first=C. |year=2002 |title=Animal Evolution: Interrelationships of the Living Phyla |publisher=Oxford University Press |edition=2nd |isbn=0-19-850682-1}}</ref> It is indicated when approximately clades radiated into newer clades in millions of years ago (Mya); dashed lines show especially uncertain placements.<ref>{{cite journal |last1=Peterson |first1=Kevin J. |last2=Cotton |first2=James A. |last3=Gehling |first3=James G. |last4=Pisani |first4=Davide |date=2008-04-27 |df=dmy-all |title=The Ediacaran emergence of bilaterians: Congruence between the genetic and the geological fossil records |journal=Philosophical Transactions of the Royal Society of London B: Biological Sciences |volume=363 |issue=1496 |pages=1435–1443 |doi=10.1098/rstb.2007.2233 |pmid=18192191 |pmc=2614224}}</ref>

The phylogenetic tree is based on Nielsen ''et al.''<ref>{{cite journal |last1=Nielsen |first1=Claus |last2=Brunet |first2=Thibaut |last3=Arendt |first3=Detlev |date=2018-08-22 |title=Evolution of the bilaterian mouth and anus |journal=[[Nature Ecology & Evolution]] |volume=2 |issue=9 |pages=1358–1376 |doi=10.1038/s41559-018-0641-0 |pmid=30135501 |bibcode=2018NatEE...2.1358N |s2cid=52067372 |issn=2397-334X }}</ref> and Howard ''et al.''.<ref>{{cite journal |last1=Howard |first1=Richard J. |last2=Giacomelli |first2=Mattia |last3=Lozano-Fernandez |first3=Jesus |last4=Edgecombe |first4=Gregory D. |last5=Fleming |first5=James F. |last6=Kristensen |first6=Reinhardt M. |last7=Ma |first7=Xiaoya |last8=Olesen |first8=Jørgen |last9=Sørensen |first9=Martin V. |last10=Thomsen |first10=Philip F. |last11=Wills |first11=Matthew A. |last12=Donoghue |first12=Philip C.J. |last13=Pisani |first13=Davide |display-authors=6 |date=2022-03-10 |df=dmy-all |title=The Ediacaran origin of Ecdysozoa: Integrating fossil and phylogenomic data |journal=[[Journal of the Geological Society]] |volume=179 |issue=4 |doi=10.1144/jgs2021-107 |bibcode=2022JGSoc.179..107H |s2cid=246494357 |issn=0016-7649|hdl=2445/186596 |hdl-access=free }}</ref>

{{clade| style=font-size:85%;line-height:85%
|label1=[[Bilateria]]
|1={{clade
   |1=[[Xenacoelomorpha]] [[File:Proporus sp.png|60 px]] 
   |label2=[[Nephrozoa]]|sublabel3=650 mya
   |2={{clade
      |1=[[Deuterostomia]] [[File:Common carp (white background).jpg|60 px]] [[File:Portugal 20140812-DSC01434 (21371237591).jpg|60 px]]
      |label2=[[Protostomia]]
      |sublabel2=610 mya
      |2={{clade
         |label1='''Ecdysozoa'''|sublabel1= 
         |1={{clade
            |label1=[[Scalidophora]]
            |1={{clade
               |label1=
               |1=[[Loricifera]] [[File:Pliciloricus enigmatus.jpg|55 px]]
               |2={{clade
                  |label1=
                  |1=[[Priapulida]] [[File:Priapulus caudatus 20150625.jpg|45 px]]
                  |2=[[Kinorhyncha]] [[File:Pycnophyes zelinkaei.jpg|35 px]]
                  }}
               }}
               |label2=[[Cryptovermes]]
               |2={{clade
                  |label1=[[Nematoida]]
                  |1={{clade
                     |label1=
                     |1=[[Nematoda]] [[File:CelegansGoldsteinLabUNC.jpg|60 px]] 
                     |2=[[Nematomorpha]] [[File:Paragordius tricuspidatus.jpeg|60 px]]
                     }}
                     |label2=[[Panarthropoda]]
                     |2={{clade
                        |1=[[Tardigrada]] [[File:Echiniscus L.png|60 px]]
                        |label2=[[Antennopoda]]
                        |2={{clade
                           |label1=
                           |1=[[Onychophora]] [[File:Velvet worm.jpg|60 px]]
                           |2=[[Arthropoda]] [[File:Long nosed weevil edit.jpg|60 px]] 
                           }}

                        }}
                    }}
                 }}
          |2=[[Spiralia]] [[File:Grapevinesnail 01.jpg|60 px]] [[File:Polychaeta (no).JPG|75 px]]
          |3=''[[Kimberella]]'' †
          }}
       }}
   }}
}}

== Older alternative groupings ==

=== Articulata hypothesis ===
The grouping proposed by Aguinaldo ''et al.'' is almost universally accepted, replacing an older hypothesis that [[Panarthropoda]] should be classified with [[Annelida]] in a group called the [[Articulata Hypothesis|Articulata]], and that Ecdysozoa are [[polyphyletic]]. Nielsen has suggested that a possible solution is to regard Ecdysozoa as a sister-group of [[Annelida]],<ref>{{cite journal | last1 = Nielsen | first1 = C. | date = September 2003 | title = Proposing a solution to the Articulata–Ecdysozoa controversy | journal = [[Zoologica Scripta]] | volume = 32 | issue = 5| pages = 475–482 | s2cid = 1416582 | doi=10.1046/j.1463-6409.2003.00122.x}}</ref> though later considered them unrelated.<ref>{{cite book |first=Claus |last=Nielsen |year=2012 |title=Animal Evolution: Interrelationships of the living phyla |edition=3rd |publisher=Oxford University Press |isbn=978-0-19-960603-0}}</ref>
Inclusion of the [[roundworm]]s within the Ecdysozoa was initially contested<ref name=Blair/><ref>{{cite journal |last=Zrzavý |first=J. |date=12 January 2002 |title=Ecdysozoa versus Articulata: Clades, artifacts, prejudices |journal=[[Journal of Zoological Systematics and Evolutionary Research]] |volume=39 |issue=3 |pages=159–163 |doi=10.1046/j.1439-0469.2001.00168.x|doi-access=free }} — in support of clade Ecdysozoa</ref><ref>{{cite journal |last1=Wägele |first1=J.W. |first2=B. |last2=Misof |date=September 2001 |title=On quality of evidence in phylogeny reconstruction: A reply to Zrzavý's defence of the 'Ecdysozoa' hypothesis |journal=[[Journal of Zoological Systematics and Evolutionary Research]] |volume=39 |issue=3 |pages=165–176 |doi=10.1046/j.1439-0469.2001.00177.x|doi-access=free }}</ref><!-- Would be good to cite the exact critique (criticising Ecdysozoa) and Zrzavy, (2001) here instead. --> but since 2003, a broad consensus has formed supporting the Ecdysozoa<ref>{{cite journal |first1=Maximilian J. |last1=Telford |first2=D. Timothy J. |last2=Littlewood |date=27 April 2008 |title=The evolution of the animals: Introduction to a Linnean tercentenary celebration |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |volume=363 |issue=1496 |pages=1421–1424 |doi=10.1098/rstb.2007.2231 |pmid=18192193 |pmc=2394567}}</ref> and in 2011 the [[Darwin–Wallace Medal]] was awarded to [[James Lake]] for the discovery of the New Animal Phylogeny consisting of the Ecdysozoa, the [[Lophotrochozoa]], and the Deuterostomia.<ref name="Darwin–Wallace Medal">{{cite press release |title=The Darwin-Wallace Medal |publisher=The Linnean Society of London |url=https://www.linnean.org/the-society/medals-awards-prizes-grants/the-darwin-wallace-medal |access-date=28 February 2018}}</ref>

=== Coelomata hypothesis ===

Before Aguinaldo's Ecdysozoa proposal, one of the prevailing theories for the evolution of the [[Bilateria|bilateral animals]] was based on the morphology of their [[body cavity|body cavities]]. There were three types, or [[evolutionary grade|grades]] of organization: the [[Acoelomata]] (no [[coelom]]), the [[Pseudocoelomata]] (partial coelom), and the [[Eucoelomata]] (true [[coelom]]). Adoutte and coworkers were among the first to strongly support the Ecdysozoa.<ref>{{cite journal |last1=Adoutte |first1=A. |author2=Balavoine, G. |author3=Lartillot, N. |author4=Lespinet, O. |author5=Prud'homme, B. |author6=de Rosa, R. |date=25 April 2000 |title=The new animal phylogeny: Reliability and implications |department=Special feature |journal=[[Proceedings of the National Academy of Sciences of the USA]] |volume=97 |issue=9 |pages=4453–4456 |doi=10.1073/pnas.97.9.4453 |doi-access=free |pmid=10781043 |pmc=34321 |bibcode=2000PNAS...97.4453A }}</ref> With the introduction of molecular phylogenetics, the coelomate hypothesis was abandoned, although some molecular, phylogenetic support for the Coelomata continued until as late as 2005.<ref>{{cite journal |first1=G.K. |last1=Philip |first2=C.J. |last2=Creevey |first3=J.O. |last3=McInerney |date=9 February 2005 |title=The Opisthokonta and the Ecdysozoa may not be clades: Stronger support for the grouping of plant and animal than for animal and fungi, and stronger support for the Coelomata than Ecdysozoa |journal=Molecular Biology and Evolution |volume=22 |issue=5 |pages=1175–1184 |doi=10.1093/molbev/msi102 |doi-access=free |pmid=15703245}}</ref>

==References==
<!-- Cladistics23:130. ZoolSci23:943. -->
{{reflist|25em}}

== Further reading ==
* {{Cite conference |first1=James R. |last1=Garey |first2=Andreas |last2=Schmidt-Rhaesa |date=December 1998 |orig-date=3–7 January 1998 |title=Essential Role of 'Minor' Phyla in Understanding Animal Evolution |conference=Symposium on Evolutionary Relationships of Metazoan Phyla: Advances, Problems, and Approaches (Annual Meeting of the Society for Integrative and Comparative Biology) |location=Boston, Massachusetts |journal=[[American Zoologist]] |volume=38 |issue=6 |pages=907–917 |doi=10.1093/icb/38.6.907 |jstor=4620218 |via=chuma.cas.usf.edu/~garey |url=http://chuma.cas.usf.edu/~garey/essential.html |access-date=2023-07-30 |archive-url=https://web.archive.org/web/20030313065540/http://chuma.cas.usf.edu/~garey/essential.html |archive-date=2003-03-13 |doi-access=free }}
* {{Cite journal |first1=Andreas |last1=Schmidt-Rhaesa |first2=Thomas |last2=Bartolomaeus |first3=Christian |last3=Lemburg |first4=Ulrich |last4=Ehlers |first5=James R. |last5=Garey |date=December 1998 |orig-date=6 January 1999 (online publication) |title=The Position of the Arthropoda in the phylogenetic system |journal=[[Journal of Morphology]] |volume=238 |issue=3 |pages=263–285 |doi=10.1002/(SICI)1097-4687(199812)238:3<263::AID-JMOR1>3.0.CO;2-L|pmid=29852696 |s2cid=46920478 }}
** {{cite web |title=Abstract & images |website=chuma.cas.usf.edu/~garey |url=http://chuma.cas.usf.edu/~garey/articulata.html |archive-url=https://web.archive.org/web/20100510081324/http://chuma.cas.usf.edu/~garey/articulata.html |archive-date=2010-05-10 }}

== External links ==
{{Wikispecies|Ecdysozoa}}
* {{Cite web |title=Ecdysozoa introduction |url=http://www.ucmp.berkeley.edu/phyla/ecdysozoa.html |department=Phyla |publisher=[[University of California Museum of Paleontology]] (ucmp.berkeley.edu) |place=Berkeley, CA}}
* {{Cite web |title=Ecdysozoa |url=http://www.palaeos.com/Kingdoms/Animalia/Ecdysozoa.html |archive-url=https://web.archive.org/web/20030313115747/http://www.palaeos.com/Kingdoms/Animalia/Ecdysozoa.html |archive-date=2003-03-13 |department=Kingdoms / Animalia |website=palaeos.com}}
* {{Cite web |title=Tardigrades and Ecdysozoa |department=Tardigrades |website=nematodes.org |url=http://www.nematodes.org/tardigrades/Tardigrades_and_Ecdysozoa.html |archive-url=https://web.archive.org/web/20080618211750/http://www.nematodes.org/tardigrades/Tardigrades_and_Ecdysozoa.html |archive-date=2008-06-18 }}
* [http://www.nematomorpha.net Nematomorpha]

{{Animalia}}
{{Tardigrades}}
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[[Category:Ecdysozoa| ]]
[[Category:Extant Cambrian first appearances]]
[[Category:Superphyla]]