panarthropoda
{{short description|Animal taxon}}
{{Automatic taxobox
| fossil_range = {{Fossilrange|538|0|earliest=560|Cambrian - Recent}} Molecular clock and ichnofossils indicate a possible Ediacaran origin{{Cite journal |last1=Rota-Stabelli |first1=Omar |last2=Daley |first2=Allison C. |last3=Pisani |first3=Davide |date=March 2013 |title=Molecular Timetrees Reveal a Cambrian Colonization of Land and a New Scenario for Ecdysozoan Evolution |url=https://linkinghub.elsevier.com/retrieve/pii/S0960982213000298 |journal=Current Biology |language=en |volume=23 |issue=5 |pages=392–398 |doi=10.1016/j.cub.2013.01.026|pmid=23375891 |bibcode=2013CBio...23..392R }}{{cite journal |last1=Chen |first1=Zhe |last2=Chen |first2=Xiang |last3=Zhou |first3=Chuanming |last4=Yuan |first4=Xunlai |last5=Xiao |first5=Shuhai |title=Late Ediacaran trackways produced by bilaterian animals with paired appendages |journal=Science Advances |date=6 June 2018 |volume=4 |issue=6 |pages=eaao6691 |doi=10.1126/sciadv.aao6691 |pmid=29881773 |pmc=5990303 |bibcode=2018SciA....4.6691C |hdl=10919/84444 |hdl-access=free }}
| image = Peripatopsis lawrencei 134803788 (cropped).jpg
| image_caption = Panarthropods include onychophorans such as Peripatopsis and arthropods such as polydesmid millipedes.
| taxon = Panarthropoda
| authority = Nielsen, 1995
| subdivision_ranks = Phyla
| subdivision = *Onychophora
- Arthropoda
- Tardigrada
- †Sialomorpha {{small|(possibly representing a new phylum)}}
- †"Lobopodia" {{small|(paraphyletic)}}
| display_parents = 5
}}
Panarthropoda is a clade comprising the greatest diversity of animal groups. It contains the extant phyla Arthropoda (Euarthropoda), Tardigrada (water bears) and Onychophora (velvet worms), although the precise relationships among these remained uncertain according to studies published in 2023 and 2024.{{Cite journal |last1=Wu |first1=Ruolin |last2=Pisani |first2=Davide |last3=Donoghue |first3=Philip C. J. |date=2023 |title=The unbearable uncertainty of panarthropod relationships |journal=Biology Letters |volume=19 |page=20220497 |doi=10.1098/rsbl.2022.0497 |name-list-style=amp |pmc=9832341 }}{{Cite journal |last1=Giacomelli |first1=Mattia |last2=Vecchi |first2=Matteo |last3=Guidetti |first3=Roberto |last4=Rebecchi |first4=Lorena |last5=Donoghue |first5=Philip C J |last6=Lozano-Fernandez |first6=Jesus |last7=Pisani |first7=Davide |date=December 2024 |title=CAT-Posterior Mean Site Frequencies Improves Phylogenetic Modeling Under Maximum Likelihood and Resolves Tardigrada as the Sister of Arthropoda Plus Onychophora |journal=Genome Biology and Evolution |volume=17 |issue=1 |pages=1–14 |doi=10.1093/gbe/evae273 |name-list-style=amp |pmc=11756273 }} Panarthropods also include extinct marine legged worms known as lobopodians ("Lobopodia"), a paraphyletic group where the last common ancestor and basal members (stem-group) of each extant panarthropod phylum are thought to have risen.{{cite journal |last1=Ortega-Hernández |first1=Javier |last2=Janssen |first2=Ralf |last3=Budd |first3=Graham E. |date=2017-05-01 |title=Origin and evolution of the panarthropod head – A palaeobiological and developmental perspective |journal=Arthropod Structure & Development |series=Evolution of Segmentation |language=en |volume=46 |issue=3 |pages=354–379 |doi=10.1016/j.asd.2016.10.011 |pmid=27989966 |issn=1467-8039|doi-access=free |bibcode=2017ArtSD..46..354O }}
{{Cite journal |last1=Giribet |first1=Gonzalo |last2=Edgecombe |first2=Gregory D. |date=2019-06-17 |title=The Phylogeny and Evolutionary History of Arthropods |journal=Current Biology |language=English |volume=29 |issue=12 |pages=R592–R602 |doi=10.1016/j.cub.2019.04.057 |issn=0960-9822 |pmid=31211983|s2cid=189926344 |doi-access=free |bibcode=2019CBio...29.R592G }}{{cite journal |last1=Chipman |first1=Ariel D. |last2=Edgecombe |first2=Gregory D. |date=2019-10-09 |title=Developing an integrated understanding of the evolution of arthropod segmentation using fossils and evo-devo|journal=Proceedings of the Royal Society B: Biological Sciences |volume=286 |issue=1912 |pages=20191881 |doi=10.1098/rspb.2019.1881 |issn=0962-8452 |pmc=6790758 |pmid=31575373}}
{{cite journal |last=Edgecombe |first=Gregory D. |date=2020-11-02 |title=Arthropod origins: Integrating paleontological and molecular evidence |url=https://www.annualreviews.org/doi/10.1146/annurev-ecolsys-011720-124437 |journal=Annual Review of Ecology, Evolution, and Systematics |volume=51 |issue=1 |pages=1–25 |doi=10.1146/annurev-ecolsys-011720-124437 |s2cid=225478171 |issn=1543-592X|url-access=subscription }} However the term "Lobopodia" is sometimes expanded to include tardigrades and onychophorans as well.
Common characteristics of the Panarthropoda include a segmented body, paired ladder-like ventral nervous system, and the presence of paired appendages correlated with body segments.
Taxonomy
{{clade|style=font-size:100%;line-height:100%
|label1=Bilateria|1={{clade
|label1=Deuterostomia|1=Echinodermata, Chordata and relatives
|label2=Protostomia|2={{clade
|label1=Spiralia|1=Annelida, Mollusca and relatives
|label2=Ecdysozoa|2={{clade
|label1=Cycloneuralia|1=Priapulida, Nematoda and relatives
|label2=Panarthropoda|2=Onychophora, Tardigrada and Arthropoda
}} }} }} }}
Not all studies support the monophyly of Panarthropoda,{{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 | doi=10.1038/nature06614 | first10=G. D. | last11=Sørensen | first11=M. V. | last12=Haddock | first12=S. H. D. |author12-link=Steven Haddock | last13=Schmidt-Rhaesa | first13=A. | last14=Okusu | first14=A. | last15=Kristensen | first15=R. M. B. | last16=Wheeler | first16=W. C. | last17=Martindale | first17=M. Q. | last18=Giribet | first18=G. | title=Broad phylogenomic sampling improves resolution of the animal tree of life | journal=Nature | volume=452 | issue=7188 | pages=745–749 | date=10 April 2008 | pmid=18322464 | bibcode=2008Natur.452..745D | s2cid=4397099 }} but most do, including neuroanatomical,{{cite journal|last=Persson|first=Dennis K.|date=November 2012|title=Neuroanatomy of Halobiotus crispae (Eutardigrada: Hypsibiidae): Tardigrade brain structure supports the clade panarthropoda|journal=Journal of Morphology|volume=273|issue=11|pages=1227–1245|doi=10.1002/jmor.20054|pmid=22806919|s2cid=5260983}} phylogenomic{{Cite journal | last1=Rota-Stabelli | first1=O.| last2=Kayal | first2=E.| last3=Gleeson | first3=D.| last4=Daub | first4=J.| last5=Boore | first5=J. | last6=Telford | first6=M. | last7=Pisani | first7=D. | last8=Blaxter | first8=M.| last9=Lavrov | first9=D.| title=Ecdysozoan mitogenomics: evidence for a common origin of the legged invertebrates, the Panarthropoda| journal=Genome Biology and Evolution| volume=2 | pages=425–440 | year=2010 | pmid=20624745| pmc=2998192| doi=10.1093/gbe/evq030}} and palaeontological{{cite journal | doi=10.1038/ncomms2272 | title=Cambrian lobopodians and extant onychophorans provide new insights into early cephalization in Panarthropoda | journal=Nature Communications | date=2012 | volume=3 | pages=1261 | first=Qiang | last=Ou | pmid=23232391 | pmc=3535342| bibcode=2012NatCo...3.1261O }}{{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 |url=https://www.researchgate.net/publication/264868021 |journal=Nature |volume=514 |issue=7522 |pages=363–366 |bibcode=2014Natur.514..363S |doi=10.1038/nature13576 |pmid=25132546 |s2cid=205239797}} studies. At least a close relationship between onychophorans and arthropods is widely agreed upon, but the position of tardigrades is more controversial. Some phylogenomic studies have found tardigrades to be more closely related to nematodes. Traditionally, panarthropods were considered to be closely related to the annelids, grouped together as the Articulata (animals with body segments), but subsequent phylogenomic studies consistently place them closer to cycloneuralians (nematodes, nematomorphs, loriciferans, kinorhynchas and priapulids), grouped together as Ecdysozoa.{{cite journal |last1=Aguinaldo |first1=Anna Marie A. |last2=Turbeville |first2=James M. |last3=Linford|first3=Lawrence S. |last4=Rivera |first4=Maria C.|last5=Garey|first5=James R.|last6=Raff|first6=Rudolf A. |last7=Lake |first7=James A. |date=1997 |title=Evidence for a clade of nematodes, arthropods and other moulting animals |url=https://www.nature.com/articles/387489a0 |journal=Nature |language=en |volume=387 |issue=6632 |pages=489–493|doi=10.1038/387489a0|pmid=9168109 |bibcode=1997Natur.387R.489A |s2cid=4334033 |issn=1476-4687|url-access=subscription }} While annelids are placed among the Spiralia (making them more closely related to mollusks, flatworms and such),{{Cite journal |last1=Adoutte |first1=André |last2=Balavoine |first2=Guillaume |last3=Lartillot |first3=Nicolas |last4=Lespinet |first4=Olivier |last5=Prud'homme |first5=Benjamin |last6=de Rosa |first6=Renaud |date=2000-04-25 |title=The new animal phylogeny: Reliability and implications |journal=Proceedings of the National Academy of Sciences |language=en |volume=97 |issue=9 |pages=4453–4456 |doi=10.1073/pnas.97.9.4453 |issn=0027-8424 |pmc=34321 |pmid=10781043|bibcode=2000PNAS...97.4453A |doi-access=free }} having evolved their segmented bodies convergently.{{cite journal |last1=Seaver|first1=Elaine C. |last2=Kaneshige |first2=Lori M. |date=2006-01-01 |title=Expression of 'segmentation' genes during larval and juvenile development in the polychaetes Capitella sp. I and H. elegans |journal=Developmental Biology |language=en |volume=289 |issue=1 |pages=179–194 |doi=10.1016/j.ydbio.2005.10.025 |pmid=16330020 |issn=0012-1606|doi-access=free }}
= Interrelationships =
There are three competing hyphotheses for the interrelationship between the extant panarthropod phyla, each known as Tactopoda (Arthropoda+Tardigrada), Antennopoda (Arthropoda+Onychophora), and the sister relationship between Onychophora and Tardigrada (Lobopodia sensu Smith & Goldstein 2017).{{cite journal |last1=Smith|first1=Frank W. |last2=Goldstein |first2=Bob |date=2017-05-01 |title=Segmentation in Tardigrada and diversification of segmental patterns in Panarthropoda |url=https://www.sciencedirect.com/science/article/pii/S1467803916301487 |journal=Arthropod Structure & Development |series=Evolution of Segmentation |volume=46 |issue=3 |pages=328–340 |doi=10.1016/j.asd.2016.10.005 |pmid=27725256 |bibcode=2017ArtSD..46..328S |issn=1467-8039|url-access=subscription }}
{{clade|style=font-size:100%;line-height:100%
|label1=Panarthropoda
|1={{clade
|1=Onychophora
|label2=Tactopoda
|2={{clade
|1=Tardigrada
|2=Arthropoda
}} }} }}
{{clade|style=font-size:100%;line-height:100%
|label1=Panarthropoda
|1={{clade
|1=Tardigrada
|label2=Antennopoda
|2={{clade
|1=Onychophora
|2=Arthropoda
}} }} }}
{{clade|style=font-size:100%;line-height:100%
|label1=Panarthropoda
|1={{clade
|1=Arthropoda
|label2=Lobopodia
sensu Smith & Goldstein 2017
|2={{clade
|1=Tardigrada
|2=Onychophora
}} }} }}
Tactopoda had been supported by mitochondrial gene arrangements,{{Cite journal |last1=Ryu |first1=Shi Hyun |last2=Lee |first2=Ji Min |last3=Jang |first3=Kuem-Hee |last4=Choi |first4=Eun Hwa |last5=Park |first5=Shin Ju |last6=Chang |first6=Cheon Young |last7=Kim |first7=Won |last8=Hwang |first8=Ui Wook |date=2007-12-31 |title=Partial mitochondrial gene arrangements support a close relationship between Tardigrada and Arthropoda |journal=Molecules and Cells |volume=24 |issue=3 |pages=351–357 |doi=10.1016/S1016-8478(23)07350-8 |issn=1016-8478 |pmid=18182850|doi-access=free }} palaeontological{{Cite journal |last=Budd|first=Graham E. |date=2001-01-01 |title=Tardigrades as 'Stem-Group Arthropods': The Evidence from the Cambrian Fauna |url=https://www.sciencedirect.com/science/article/pii/S004452310470025X |journal=Zoologischer Anzeiger - A Journal of Comparative Zoology |language=en |volume=240 |issue=3 |pages=265–279 |doi=10.1078/0044-5231-00034 |bibcode=2001ZooAn.240..265B |issn=0044-5231|url-access=subscription }} and neuroanatomical evidences, specifically the presence of segmented ganglia shared by arthropods and tardigrades.{{cite journal |last1=Mayer |first1=Georg |last2=Martin |first2=Christine |last3=Rüdiger|first3=Jan |last4=Kauschke |first4=Susann |last5=Stevenson |first5=Paul A. |last6=Poprawa |first6=Izabela |last7=Hohberg |first7=Karin |last8=Schill |first8=Ralph O. |last9=Pflüger|first9=Hans-Joachim |last10=Schlegel |first10=Martin |date=2013-10-24 |title=Selective neuronal staining in tardigrades and onychophorans provides insights into the evolution of segmental ganglia in panarthropods |journal=BMC Evolutionary Biology |volume=13 |issue=1 |pages=230 |doi=10.1186/1471-2148-13-230 |issn=1471-2148 |pmc=4015553 |pmid=24152256 |doi-access=free |bibcode=2013BMCEE..13..230M }} Antennopodia united by the presence of specialized head appendages and deutocerebrum (additional second section of the brain), but subsequent anatomical studies suggest these features were convergently evolved between onychophoran and arthropod lineages.{{cite journal |last1=Martin |first1=Christine |last2=Mayer |first2=Georg |date=2015-08-25 |title=Insights into the segmental identity of post-oral commissures and pharyngeal nerves in Onychophora based on retrograde fills |journal=BMC Neuroscience |volume=16 |issue=1 |page=53 |doi=10.1186/s12868-015-0191-1 |issn=1471-2202 |pmc=4549126 |pmid=26303946 |doi-access=free }} Onychophorans and tardigrades shared some lobopodian traits (e.g. soft cuticle, lobopodous appendages and peripheral nerve roots), but these were generally considered to be plesiomorphies traced back to the last common ancestor of Panarthropoda or Ecdysozoa.
{{Cite journal |last1=Yang |first1=Jie |last2=Ortega-Hernández |first2=Javier |last3=Butterfield |first3=Nicholas J. |last4=Liu |first4=Yu |last5=Boyan |first5=George S. |last6=Hou |first6=Jin-bo |last7=Lan |first7=Tian |last8=Zhang |first8=Xi-guang |date=2016-03-15 |title=Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda |journal=Proceedings of the National Academy of Sciences |language=en |volume=113 |issue=11 |pages=2988–2993 |doi=10.1073/pnas.1522434113 |issn=0027-8424 |pmc=4801254 |pmid=26933218|bibcode=2016PNAS..113.2988Y |doi-access=free }} While most phylogenomic analyses support the monophyly of Panarthropoda, the results of interrelationship between the three phyla are less correlated—some of them inconsistently placing Tardigrada within Arthropoda, while the others mostly recovering either Antennopoda or Onychophora+Tardigrada.{{Cite journal |last1=Rota-Stabelli |first1=Omar |last2=Daley |first2=Allison C. |last3=Pisani |first3=Davide |date=2013-03-04 |title=Molecular Timetrees Reveal a Cambrian Colonization of Land and a New Scenario for Ecdysozoan Evolution|journal=Current Biology |language=English |volume=23 |issue=5 |pages=392–398 |doi=10.1016/j.cub.2013.01.026 |issn=0960-9822 |pmid=23375891|s2cid=2510415 |doi-access=free |bibcode=2013CBio...23..392R }}{{Cite journal |last1=Marlétaz |first1=Ferdinand |last2=Peijnenburg |first2=Katja T.C.A. |last3=Goto |first3=Taichiro |last4=Satoh |first4=Noriyuki |last5=Rokhsar |first5=Daniel S. |date=2019-01-21 |title=A New Spiralian Phylogeny Places the Enigmatic Arrow Worms among Gnathiferans |journal=Current Biology |language=English |volume=29 |issue=2 |pages=312–318.e3 |doi=10.1016/j.cub.2018.11.042 |issn=0960-9822 |pmid=30639106|s2cid=58562919 |doi-access=free |bibcode=2019CBio...29E.312M }} A study published in December 2024 supported the sister relationship of Onychophora and Arthropoda (the second cladogram above).
File:Britannica 1911 Arthropoda - Peripatus head.png|Anatomy of onychophoran anterior region, showing specialized appendages (ant, md) and deutocerebrum (D)
File:Tardigrade zenuw.jpg|Nervous system of a tardigrade, showing ventral nerve cord with segmented ganglia (ga1-4)
File:20200213 Remipedia Nectiopoda central nervous system.png|Nervous system of a remipede arthropod, showing the presence of both deutocerebrum (dc) and ventral nerve cord (vnc) organized by segmented ganglia
The "Lobopodia" are paraphyletic; they include the last common ancestor of arthropods, onychophorans and tardigrades.{{cite journal |last=Ortega-Hernández |first=Javier |date=2015-10-05 |title=Lobopodians |journal=Current Biology |volume=25 |issue=19 |pages=R873–R875 |doi=10.1016/j.cub.2015.07.028 |pmid=26439350 |doi-access=free}}
Sialomorpha, a genus of microinvertebrate discovered in Dominican amber in 2019, is also considered to be a panarthropod. However, due to the unusual combination of tardigrade and mite-like characteristics, its exact placement is uncertain.{{Cite journal |last1=Poinar |first1=George |last2=Nelson |first2=Diane R. |date=2019 |title=A new microinvertebrate with features of mites and tardigrades in Dominican amber |journal=Invertebrate Biology |volume=138 |issue=4 |pages=e12265 |doi=10.1111/ivb.12265 |s2cid=204157733 |issn=1744-7410}}
See also
References
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{{Animalia}}
{{Tardigrades}}
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