Editing Lobopodia (section)

== Definitions ==
[[File:20210817 Lobopodia Lobopodian Lobopod definitions.png|thumb|left|300px|Various definitions of lobopodians within [[Panarthropoda]].<ref name=":8" />]]

The Lobopodian concept varies from author to author.<ref name=":8" /> Its most general sense refers to a suite of mainly [[Cambrian]] worm-like panarthropod taxa possessing lobopods – for example, ''[[Aysheaia]]'', ''[[Hallucigenia]]'', and ''[[Xenusion]]'' – which were traditionally united as "Xenusians" or "Xenusiids" (class Xenusia).<ref name=":19" /><ref name=":30" /><ref name=":31">{{Cite journal|last1=HOU|first1=XIANGUANG|last2=BERGSTRÖM|first2=JAN|date=1995-05-01|title=Cambrian lobopodians-ancestors of extant onychophorans?|url=https://doi.org/10.1111/j.1096-3642.1995.tb00110.x|journal=Zoological Journal of the Linnean Society|volume=114|issue=1|pages=3–19|doi=10.1111/j.1096-3642.1995.tb00110.x|issn=0024-4082}}</ref> Certain [[Dinocaridida|Dinocaridid]] genera, such as ''[[Opabinia]]'', ''[[Pambdelurion]]'', and ''[[Kerygmachela]]'', may also be regarded as lobopodians,<ref name=":1">{{cite journal|last=Budd|first=Graham E.|year=1998|title=The morphology and phylogenetic significance of ''Kerygmachela kierkegaardi'' Budd (Buen Formation, Lower Cambrian, N Greenland)|journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh|language=en|volume=89|issue=4|pages=249–290|doi=10.1017/S0263593300002418|s2cid=85645934 |issn=1473-7116}}</ref><ref name=":13"/> sometimes referred to more specifically as "gilled lobopodians" or "gilled lobopods".<ref name=":18">{{Cite journal |last=Budd |first=Graham |date=August 1993 |title=A Cambrian gilled lobopod from Greenland |journal=Nature |language=en |volume=364 |issue=6439 |pages=709–711 |doi=10.1038/364709a0 |issn=1476-4687 |bibcode=1993Natur.364..709B|s2cid=4341971}}</ref> This traditional, informal usage of "Lobopodia" treats it as an [[evolutionary grade]], including only extinct Panarthropods near the base of [[crown group|crown]] Panarthropoda. Crown Panarthropoda comprises the three extant Panarthropod phyla – [[Onychophora]] (velvet worms), [[Tardigrada]] (waterbears), and [[Arthropoda]] (arthropods) – as well as their [[most recent common ancestor]] and all of its descendants. Thus, in this usage, Lobopodia consists of various basal Panarthropods.<ref name=":0" /><ref name="ReferenceA">{{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=http://dro.dur.ac.uk/19108/1/19108.pdf |archive-url=https://ghostarchive.org/archive/20221010/http://dro.dur.ac.uk/19108/1/19108.pdf |archive-date=2022-10-10 |url-status=live |journal=Nature |volume=514 |issue=7522 |pages=363–366 |bibcode=2014Natur.514..363S |doi=10.1038/nature13576 |pmid=25132546|s2cid=205239797}}</ref><ref name=":2"/><ref name=":8"/><ref name=":10">{{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 |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 }}</ref><ref name=":11" /> This corresponds to "A" in the image to the left.

An alternative, broader definition of Lobopodia would also incorporate Onychophora and Tardigrada,<ref name=":19">{{cite journal |last1=Dzik |first1=Jerzy |last2=Krumbiegel |first2=Günter |date=1989 |title=The oldest 'onychophoran' Xenusion: a link connecting phyla? |journal=Lethaia |language=en |volume=22 |issue=2 |pages=169–181 |issn=1502-3931 |doi=10.1111/j.1502-3931.1989.tb01679.x|bibcode=1989Letha..22..169D }}</ref><ref name=":1"/><ref name="Cavalier-Smith"/> the two living panarthropod phyla which still bear lobopodous limbs. This definition, corresponding to "C", is a [[morphology (biology)|morphological]] one, depending on the superficial similarity of appendages (the "lobopods"). Thus, it is [[paraphyletic]], excluding the Euarthropods, which are descendants of certain Lobopodians, on the basis of their highly divergent limb morphology.<ref name=":0" /> "Lobopodia" has also been used to refer to a proposed sister [[clade]] to Arthropoda, consisting of the extant Onychophora and Tardigrada, as well as their most recent common ancestor and all of its descendants. This definition renders Lobopodia a [[monophyletic]] taxon, if indeed it is valid (that is, if Tardigrades and Onychophora are closer to one another than either is to Arthropoda), but would exclude all the Euarthropod-line taxa traditionally considered Lobopodians. Its validity is uncertain, however, as there are a number of hypotheses regarding the internal phylogeny of Panarthropoda.<ref>{{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 |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}}</ref> The broadest definition treats Lobopodia as a monophyletic superphylum equivalent in [[circumscription (taxonomy)|circumscription]] to [[Panarthropoda]]. By this definition, represented by "D" in the image, Lobopodia is no longer treated as an evolutionary grade but as a clade, containing not only the early, superficially "Lobopodian" forms but also all of their descendants, including the extant Panarthropods.<ref name=":20">{{cite book |url=https://books.google.com/books?id=Pj-q9eHyIx0C&pg=PA125 |title=Arthropod Relationships |last1=Fortey |first1=Richard A. |last2=Thomas |first2=Richard H. |date=1997-12-31 |publisher=Springer Science & Business Media |isbn=978-0-412-75420-3 |language=en}}</ref><ref name=":16" />

Lobopodia has, historically, sometimes included [[Pentastomida]],<ref name=":9" /> a group of parasitic panarthropod which were traditionally thought to be a unique [[phylum]],<ref>[http://sea-entomologia.org/IDE@/revista_98B.pdf Pentastomida - Sociedad Entomológica Aragonesa]</ref><ref>[https://books.google.com/books?id=JHm9BwAAQBAJ&dq=%22Pentastomes+do+not+display+simplified+morphology+due+to+parasitism%22&pg=PA17 Treatise on Zoology - Anatomy, Taxonomy, Biology. The Crustacea, Volum 5]</ref> but revealed by subsequent [[phylogenomic]] and anatomical studies to be a highly specialized taxon of [[crustacean]]s.<ref>{{Cite journal|last1=Riley|first1=J.|last2=Banaja|first2=A. A.|last3=James|first3=J. L.|date=1978-08-01|title=The phylogenetic relationships of the pentastomida: The case for their inclusion within the crustacea|url=https://dx.doi.org/10.1016/0020-7519%2878%2990087-5|journal=International Journal for Parasitology|language=en|volume=8|issue=4|pages=245–254|doi=10.1016/0020-7519(78)90087-5|issn=0020-7519}}</ref><ref>{{Cite journal|last1=Lavrov|first1=Dennis V.|last2=Brown|first2=Wesley M.|last3=Boore|first3=Jeffrey L.|date=2004-03-07|title=Phylogenetic position of the Pentastomida and (pan)crustacean relationships|journal=Proceedings of the Royal Society of London. Series B: Biological Sciences|volume=271|issue=1538|pages=537–544|doi=10.1098/rspb.2003.2631|pmc=1691615|pmid=15129965}}</ref><ref>{{Cite journal|last1=Regier|first1=Jerome C.|last2=Shultz|first2=Jeffrey W.|last3=Zwick|first3=Andreas|last4=Hussey|first4=April|last5=Ball|first5=Bernard|last6=Wetzer|first6=Regina|last7=Martin|first7=Joel W.|last8=Cunningham|first8=Clifford W.|date=2010|title=Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences|url=https://www.nature.com/articles/nature08742|journal=Nature|language=en|volume=463|issue=7284|pages=1079–1083|doi=10.1038/nature08742|pmid=20147900|bibcode=2010Natur.463.1079R|s2cid=4427443|issn=1476-4687}}</ref><ref>{{Cite journal|last1=Lozano-Fernandez|first1=Jesus|last2=Giacomelli|first2=Mattia|last3=Fleming|first3=James F|last4=Chen|first4=Albert|last5=Vinther|first5=Jakob|last6=Thomsen|first6=Philip Francis|last7=Glenner|first7=Henrik|last8=Palero|first8=Ferran|last9=Legg|first9=David A|last10=Iliffe|first10=Thomas M|last11=Pisani|first11=Davide|date=2019-08-01|title=Pancrustacean Evolution Illuminated by Taxon-Rich Genomic-Scale Data Sets with an Expanded Remipede Sampling|url=https://doi.org/10.1093/gbe/evz097|journal=Genome Biology and Evolution|volume=11|issue=8|pages=2055–2070|doi=10.1093/gbe/evz097|issn=1759-6653|pmc=6684935|pmid=31270537}}</ref><ref>{{Citation|last=Rabet|first=Nicolas|title=Crustaceans|date=2021|work=Handbook of Marine Model Organisms in Experimental Biology|pages=271–287|publisher=CRC Press|doi=10.1201/9781003217503-15|isbn=978-1-003-21750-3|s2cid=239958264|doi-access=free}}</ref>