Editing Lobopodia (section)

==Phylogeny==
{{original research section|date=December 2024}}

{{cladogram
|title=
|align= right
|caption=Neutralized phylogeny between lobopodians and other [[Ecdysozoan]] taxa.<ref name="ReferenceA" /><ref name=":8" /><ref name=":2" /><ref name=":17" /><ref name=":10" /><ref name=":6" /><ref name=":11" />{{excessive citations inline|date=December 2024}} Extant panarthropod taxa are in '''bold'''. Relationship between the total-group of extant panarthropod phyla is unresolved.
|cladogram=
{{clade| style=width:45em;line-height:
|label1=<small>[[Ecdysozoa]]</small>|1={{clade
  |label1=<small>[[Cycloneuralia]]</small>|1=[[Priapulida]] [[File:Adult priapulid 2.jpg|50px]], [[Nematoda]] [[File:CelegansGoldsteinLabUNC 2.jpg|70px]] and relatives
  |label2=<small>[[Panarthropoda]]</small>|2={{clade
    |1={{clade
      |1=(Lobopodian taxa controversial)
      |2={{clade
        |1=''[[Antennacanthopodia]]'' [[File:Antennacanthopodia.jpg|80px]]
        |2=Crown-group '''[[Onychophora]]''' [[File:Velvet_worm.png|80px]]
}} }}
      |2={{clade
        |1=(Lobopodian taxa controversial)
        |2=Crown-group '''[[Tardigrada]]''' [[File:SEM image of Milnesium tardigradum in active state - journal.pone.0045682.g001-2 (white background).png|60px]]
}}
    |3=(Lobopodian taxa controversial)
      |4={{clade
        |1=''[[Megadictyon]]'' [[File:20191118_Megadictyon_cf._haikouensis.png|80px]] and ''[[Jianshanopodia]]'' [[File:20191215_Jianshanopodia_decora.png|80px]]
        |2={{clade
          |1=''[[Pambdelurion]]'' [[File:20191112_Pambdelurion_whittingtoni.png|80px]] and ''[[Kerygmachela]]'' [[File:21091022_Kerygmachela_kierkegaardi.png|80px]]
          |2={{clade
            |1=''[[Opabinia]]'' [[File:20191108_Opabinia_regalis.png|80px]]
            |2=[[Radiodonta]] [[File:20191201_Radiodonta_Amplectobelua_Anomalocaris_Aegirocassis_Lyrarapax_Peytoia_Laggania_Hurdia.png|70px]]
            |3='''[[Euarthropoda]]''' [[File:Aptostichus simus Monterey County.jpg|70 px]] [[File:Scolopendra japonica アオズムカデ 大阪府 生駒山産.jpg|80 px]] [[File:Platycheirus angustatus (Syrphidae) - (male imago), Elst (Gld), the Netherlands - 2.jpg|70 px]]
}} }} }} }} }} }} }}

The overall phylogenetic interpretation on lobopodians has changed dramatically since their discovery and first description.<ref name=":0" /> The reassignments are not only based on new fossil evidence, but also new [[Embryology|embryological]], [[Neuroanatomy|neuroanatomical]], and [[genomic]] (e.g. [[gene expression]], [[phylogenomics]]) information observed from extant [[panarthropod]] taxa.<ref name=":0" /><ref name=":10" /><ref>{{Cite journal|last=Edgecombe|first=Gregory D.|date=2009-06-01|title=Palaeontological and Molecular Evidence Linking Arthropods, Onychophorans, and other Ecdysozoa|journal=Evolution: Education and Outreach|language=en|volume=2|issue=2|pages=178–190|doi=10.1007/s12052-009-0118-3|issn=1936-6434|doi-access=free}}</ref>

Based on their apparently [[onychophoran]]-like morphology (e.g. annulated cuticle, lobopodous appendage with claws), lobopodians were originally thought to be present a group of paleozoic onychophorans.<ref>{{Cite journal|last=Robison|first=R. A.|date=1985|title=Affinities of Aysheaia (Onychophora), with Description of a New Cambrian Species|journal=Journal of Paleontology|volume=59|issue=1|pages=226–235 |jstor=1304837}}</ref><ref name=":30">{{Cite journal|last1=Ramsköld|first1=L. |last2=Xianguang|first2=Hou|date=1991 |title=New early Cambrian animal and onychophoran affinities of enigmatic metazoans|journal=Nature |volume=351|issue=6323|pages=225–228 |doi=10.1038/351225a0|issn=1476-4687|bibcode=1991Natur.351..225R|s2cid=4309565}}</ref><ref name=":31" /><ref>{{Cite journal|last1=Bergström|first1=J. |last2=Hou |first2=Xian-Guang|date=2001-12-01|title=Cambrian Onychophora or Xenusians|url=https://www.researchgate.net/publication/248908182|journal=Zoologischer Anzeiger|volume=240|issue=3–4|pages=237–245 |doi=10.1078/0044-5231-00031|bibcode=2001ZooAn.240..237B }}</ref><ref name=":0" /> This interpretation was challenged after the discovery of lobopodians with [[arthropod]] and [[tardigrade]]-like characteristics,<ref name=":25">{{Cite journal|last=Budd|first=Graham E.|date=2001-01-01|title=Tardigrades as 'Stem-Group Arthropods': The Evidence from the Cambrian Fauna|journal=Zoologischer Anzeiger - A Journal of Comparative Zoology|volume=240|issue=3|pages=265–279 |doi=10.1078/0044-5231-00034|bibcode=2001ZooAn.240..265B |issn=0044-5231}}</ref> suggesting that the similarity between lobopodians and onychophorans represents deeper [[panarthropod]] ancestral traits ([[Plesiomorphy|plesiomorphies]]) instead of onychophoran-exclusive characteristics ([[synapomorphies]]).<ref name=":11" /> For example, The British palaeontologist [[Graham Budd]] sees the Lobopodia as representing a basal grade from which the phyla Onychophora and Arthropoda arose, with ''[[Aysheaia]]'' comparable to the ancestral plan, and with forms like ''[[Kerygmachela]]'' and ''[[Pambdelurion]]'' representing a transition that, via the [[Dinocaridida|dinocaridids]], would lead to an arthropod body plan.<ref name="Budd2001">{{Cite journal |last1=Budd |first1=G. E. |title=Why are arthropods segmented? |doi=10.1046/j.1525-142X.2001.01041.x |journal=Evolution and Development |volume=3 |issue=5 |pages=332–42 |year=2001 |pmid=11710765 |s2cid=37935884}}</ref> Aysheaia's surface ornamentation, if homologous with [[palaeoscolecid]] sclerites, may represent a deeper link connecting it with [[cycloneuralia]]n outgroups.<ref name="Budd2001" /> Lobopodians are [[paraphyletic]], and include the last common ancestor of arthropods, onychophorans and tardigrades.<ref name=":0"/>

===Stem-group arthropods===

Compared to other panarthropod stem-groups, suggestion on the lobopodian members of arthropod stem-group is relatively consistent  — siberiid like ''[[Megadictyon]]'' and ''[[Jianshanopodia]]'' occupied the basalmost position, gilled lobopodians ''[[Pambdelurion]]'' and ''[[Kerygmachela]]'' branch next, and finally lead to a clade compose of ''[[Opabinia]]'', [[Radiodonta]] and Euarthropoda (crown-group arthropods).<ref name="ReferenceA" /><ref name=":8" /><ref name=":2" /><ref name=":17" /><ref name=":10" /><ref name=":6" /><ref name=":11" />{{excessive citations inline|date=December 2024}} Their positions within arthropod stem-group are indicated by numerous arthropod groundplans and intermediate forms (e.g. arthropod-like digestive glands, radiodont-like frontal appendages and dorso-ventral appendicular structures link to arthropod biramous appendages).<ref name=":8" /><ref name=":10" /> Lobopodian ancestry of arthropods also reinforced by genomic studies on extant taxa — gene expression support the homology between arthropod appendages and onychophoran lobopods, suggests that modern less-segmented arthropodized appendages evolved from annulated lobopodous limbs.<ref name=":21" /> On the other hand, primary antennae and frontal appendages of lobopodians and [[dinocaridida|dinocaridids]] may be homologous to the [[Labrum (arthropod mouthpart)|labrum]]/hypostome complex of euarthropods, an idea support by their protocerebral origin<ref name=":8" /><ref name=":10" /><ref name=":14" /> and developmental pattern of the labrum of extant arthropods.<ref name=":21" /><ref name=":10" />

<gallery mode="packed" heights="160">
File:20191201 Radiodonta Amplectobelua Anomalocaris Aegirocassis Lyrarapax Peytoia Laggania Hurdia.png|[[Radiodonta|Radiodonts]] are stem-group [[arthropod]]s with gilled lobopodian-like body flaps, arthropodized frontal appendages and [[Eyestalk|stalked]] [[compound eye]]s.
File:20191112 Pambdelurion whittingtoni.png|Restoration of ''[[Pambdelurion]]'' a "gilled lobopodian" related to arthropods, which has both pairs of lobopods and lateral flaps.
</gallery>

''[[Diania]]'', a genus of armoured lobopodian with stout and spiny legs, were originally thought to be associated within the arthropod stem-group based on its apparently arthropod-like (arthropodized) trunk appendages.<ref name=":24" /> However, this interpretation is questionable as the data provided by the original description are not consistent with the suspected phylogenic relationships.<ref>{{Cite journal|last1=Mounce|first1=Ross C. P.|last2=Wills|first2=Matthew A.|date=August 2011|title=Phylogenetic position of Diania challenged|url=https://www.researchgate.net/publication/51563233|journal=Nature |volume=476|issue=7359|pages=E1; discussion E3–4|doi=10.1038/nature10266|pmid=21833044|issn=1476-4687|bibcode=2011Natur.476E...1M|s2cid=4417903|doi-access=free}}</ref><ref>{{Cite journal|last1=Legg|first1=David|last2=Ma |first2=Xiaoya |last3=Wolfe|first3=Joanna|last4=Ortega-Hernández|first4=Javier |last5=Edgecombe |first5=Gregory|last6=Sutton |first6=Mark|date=2011-08-11 |title=Lobopodian phylogeny reanalysed |url=https://www.researchgate.net/publication/51563234 |journal=Nature |volume=476|issue=7359|pages=E2–3; discussion E3|doi=10.1038/nature10267|pmid=21833046 |bibcode=2011Natur.476Q...1L|s2cid=4310063|doi-access=free}}</ref> Further re-examination even revealed that the suspected arthropodization on the legs of ''Diania'' was a misinterpretation — although the spine may have hardened, the remaining cuticle of ''Diania''<nowiki/>'s legs were soft (not harden nor scleritzed), lacking any evidence of pivot joint and arthrodial membrane, suggest the legs are lobopods with only widely spaced annulations.<ref name=":12" /><ref name=":13" /> Thus, the re-examination eventually reject the evidence of arthropodization (sclerotization, segmentation and articulation) on the appendages as well as the fundamental relationship between ''Diania'' and arthropods.<ref name=":12" /><ref name=":13" />

===Stem-group onychophorans===

[[File:Antennacanthopodia.jpg|thumb|''[[Antennacanthopodia]] gracilis'', a lobopodian suggested to be a stem-group onychophoran.]]

While ''[[Antennacanthopodia]]'' is widely accepted as a stem-group onychophoran,<ref name="ReferenceA" /><ref name=":2" /><ref name=":34" /><ref name=":6" /><ref name=":11" /><ref name=":27" /> the position of other xenusiid genera that were previously thought to be onychophoran-related is controversial — in further studies, most of them were either suggested to be stem-group onychophorans<ref name="ReferenceA" /><ref name=":2" /><ref name=":34" /><ref name=":27" /> or basal panarthropods,<ref name=":6" /><ref name=":11">{{Cite journal|last1=Siveter|first1=Derek J.|last2=Briggs|first2=Derek E. G.|last3=Siveter|first3=David J.|last4=Sutton|first4=Mark D.|last5=Legg|first5=David |title=A three-dimensionally preserved lobopodian from the Herefordshire (Silurian) Lagerstätte, UK|journal=Royal Society Open Science|volume=5|issue=8|pages=172101 |doi=10.1098/rsos.172101|pmc=6124121|pmid=30224988|year=2018}}</ref><ref name=":28" /> with a few species (''[[Aysheaia]]''<ref name=":6" /><ref name=":11" /><ref name=":28" />{{excessive citations inline|date=December 2024}} or ''[[Onychodictyon]] ferox''<ref name="ReferenceA" /><ref name=":2" />) occasionally suggested to be stem-group tardigrades. A study in 2014 suggested that ''[[Hallucigenia]]'' are stem-group onychophorans based on their claws, which have overlapped internal structures resembling those of an extant onychophoran.<ref name="ReferenceA" /> This interpretation was questioned by later studies, as the structures may be a [[panarthropod]] plesiomorphy.<ref name=":11" /><ref name=":28" />

===Stem-group tardigrades===

[[File:OrstenTardigrade.jpg|thumb|Artistic reconstruction of the “[[Orsten]]” tardigrade, a parasitic stem-lineage tardigrade, known from fossils recovered from the Cambrian Kuonamka Formation of Siberia.<ref>{{Cite journal |last1=Maas |first1=Andreas |last2=Waloszek |first2=Dieter |date=2001-01-01 |title=Cambrian Derivatives of the Early Arthropod Stem Lineage, Pentastomids, Tardigrades and Lobopodians An 'Orsten' Perspective |url=https://www.sciencedirect.com/science/article/pii/S0044523104700443 |journal=Zoologischer Anzeiger - A Journal of Comparative Zoology |language=en |volume=240 |issue=3 |pages=451–459 |doi=10.1078/0044-5231-00053 |bibcode=2001ZooAn.240..451M |issn=0044-5231}}</ref>]]

Lobopodian taxa of the tardigrade stem-group is unclear.<ref name=":0" /> ''[[Aysheaia]]''<ref name=":6" /><ref name=":11" /><ref name=":28" /> or ''[[Onychodictyon]] ferox''<ref name="ReferenceA" /><ref name=":2" /> had been suggest to be a possible member, based on the high claw number (in ''Aysheaia'') and/or terminal lobopods with anterior-facing claws  (in both taxa).<ref name="ReferenceA" /> Although not widely accepted, there are even suggestions that Tardigrada itself representing the basalmost panarthropod or branch between the arthropod stem-group.<ref name=":25" /> However, a paper in 2023 found luolishaniids to be the closest relatives of tardigrades using various morphological characteristics. <ref name="Kihm2023">{{cite journal |doi=10.1073/pnas.2211251120 |title=Cambrian lobopodians shed light on the origin of the tardigrade body plan |year=2023 |last1=Kihm |first1=Ji-Hoon |last2=Smith |first2=Frank W. |last3=Kim |first3=Sanghee |last4=Rho |first4=Hyun Soo |last5=Zhang |first5=Xingliang |last6=Liu |first6=Jianni |last7=Park |first7=Tae-Yoon S. |journal=Proceedings of the National Academy of Sciences |volume=120 |issue=28 |pages=e2211251120 |pmid=37399417 |doi-access=free |pmc=10334802|bibcode=2023PNAS..12011251K }}</ref>

===Stem-group panarthropods===

It is unclear that which lobopodians represent members of the panarthropod stem-group, which were branched just before the last common ancestor of extant panarthropod phyla. ''[[Aysheaia]]'' may have occupied this position based on its apparently basic morphology;<ref name="Budd2001" /><ref name="ReferenceA" /><ref name=":2" /><ref name=":27" /> while other studies rather suggest luolishaniid and hallucigenid,<ref name=":6" /><ref name=":11"/><ref name=":28" /> two lobopodian taxa which had been resolved as members of stem-group onychophorans as well.<ref name=":0" /><ref name="ReferenceA" /><ref name=":2" /><ref name=":34" /><ref name=":27" />