Editing Lobopodia (section)

==Morphology==
[[File:Aysheaia Walcott 1911.png|thumb|140px|Complete fossil of ''[[Aysheaia]] pedunculata'', showing overall morphology.]]
<gallery mode="packed" heights="200">
File:20210000 Hallucigenia diagrammatic reconstruction.png|Maximum size of the 3 species of ''[[Hallucigenia]]'' (from top, ''H. fortis'', ''H. hongmeia'' and ''H. sparsa'') in scale.
File:Xenusion auerswaldae.jpg|Fossils of ''[[Xenusion]]'', a lobopodian that might have grown up to 20&nbsp;centimeters. 
</gallery>

Most lobopodians were only a few centimeters in length, while some genera grew up to over 20&nbsp;centimeters.<ref name="Liu2006"/> Their bodies are [[Annulus (zoology)|annulated]], although the presence of annulation may differ between position or taxa, and sometimes difficult to discern due to their close spacing and low relief on the fossil materials.<ref name='Hou2004'/> Body and appendages are circular in cross-section.<ref name='Hou2004'/>

=== Head ===
{{multiple image
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| image1 = 20210822 Onychodictyon ferox anterior.png
| caption1 = Anterior section of ''[[Onychodictyon]] ferox'', showing head structures.
| image2 = Jianshanopodia decora 1.jpg
| caption2 = Fossil of ''[[Jianshanopodia]] decora'', showing head region (upper left) compose of robust frontal appendage (right) and pharynx with rows of teeth (bottom left).
}}

Due to the usually poor preservation, detailed reconstructions of the head region are only available for a handful of lobopodian species.<ref name=":22" /><ref name=":2" /> The head of a lobopodian is more or less bulbous,<ref name=":0" /> and sometime possesses a pair of pre-ocular, presumely protocerebral<ref name=":10" /> appendages – for example, primary antennae<ref name=":3" /><ref name=":4">{{cite journal|last1=Ma|first1=Xiaoya|last2=Hou|first2=Xianguang|last3=Bergström|first3=Jan|year=2009|title=Morphology of ''Luolishania longicruris'' (Lower Cambrian, Chengjiang Lagerstätte, SW China) and the phylogenetic relationships within lobopodians|url=https://www.academia.edu/4124153|journal=Arthropod Structure & Development|language=en|volume=38|issue=4|pages=271–291|doi=10.1016/j.asd.2009.03.001|issn=1467-8039|pmid=19293001|bibcode=2009ArtSD..38..271M }}</ref><ref name=":10" /><ref name=":28" /> or well-developed frontal appendages,<ref name=":32">{{Cite journal|last=Whittington|first=Harry Blackmore|date=1978-11-16|title=The Lobopod Animal ''Aysheaia Pedunculata'' Walcott, Middle Cambrian, Burgess Shale, British Columbia|url=https://royalsocietypublishing.org/doi/10.1098/rstb.1978.0061|journal=Philosophical Transactions of the Royal Society of London. B, Biological Sciences|volume=284|issue=1000|pages=165–197|doi=10.1098/rstb.1978.0061|bibcode=1978RSPTB.284..165W}}</ref><ref name=":1" /><ref name="Liu2007" /><ref name="Liu2006" /><ref name=":0"/> which are individualized from the trunk lobopods<ref name=":10" /><ref name=":21">{{Cite journal |last=Jockusch |first=Elizabeth L. |date=2017-09-01 |title=Developmental and Evolutionary Perspectives on the Origin and Diversification of Arthropod Appendages |journal=Integrative and Comparative Biology |language=en |volume=57 |issue=3 |pages=533–545 |doi=10.1093/icb/icx063 |pmid=28957524 |issn=1540-7063|doi-access=free}}</ref> (with the exception of ''[[Antennacanthopodia]]'', which have two pairs of head appendages instead of one<ref name=":3" />). Mouthparts may consist of rows of teeth<ref name="Hou2004"/><ref name=":2"/><ref name="Liu2007" /><ref name="Liu2006" /><ref name=":7">{{Cite journal|last1=Vinther|first1=Jakob|last2=Porras|first2=Luis|last3=Young|first3=Fletcher|last4=Budd|first4=Graham|last5=Edgecombe|first5=Gregory|date=2016-09-01|title=The mouth apparatus of the Cambrian gilled lobopodian ''Pambdelurion whittingtoni''|url=https://www.researchgate.net/publication/309090813|journal=Palaeontology|volume=59|issue=6|pages=841–849|doi=10.1111/pala.12256|bibcode=2016Palgy..59..841V |hdl=1983/16da11f1-5231-4d6c-9968-69ddc5633a8a|s2cid=88758267 |hdl-access=free}}</ref> or a conical proboscis.<ref name=":22">{{Cite journal |last1=Ou |first1=Qiang |last2=Shu |first2=Degan |last3=Mayer |first3=Georg |date=2012-12-11 |title=Cambrian lobopodians and extant onychophorans provide new insights into early cephalization in Panarthropoda |journal=Nature Communications |language=en |volume=3 |issue=1 |pages=1261 |doi=10.1038/ncomms2272 |pmid=23232391 |pmc=3535342 |issn=2041-1723 |bibcode=2012NatCo...3.1261O}}</ref><ref name=":0" /><ref name=":6" /> The eyes may be represented by a single ocellus or by numerous<ref name=":23" /> pairs of simple ocelli,<ref name=":0" /> as has been shown in ''[[Luolishania]]''<ref name=":4" /> (=''[[Miraluolishania]]''<ref name=":23">{{Cite journal|last1=Schoenemann|first1=Brigitte|last2=Liu|first2=Jian-Ni|last3=Shu|first3=De-Gan|last4=Han|first4=Jian|last5=Zhang|first5=Zhi-Fei|date=2009|title=A miniscule optimized visual system in the Lower Cambrian|journal=Lethaia|language=en|volume=42|issue=3|pages=265–273|doi=10.1111/j.1502-3931.2008.00138.x|bibcode=2009Letha..42..265S |issn=1502-3931}}</ref><ref name=":27" />), ''[[Ovatiovermis]]'',<ref name=":6" /> ''[[Onychodictyon]]'',<ref name=":22" /> ''[[Hallucigenia]]'',<ref name=":2" /> ''[[Facivermis]]'',<ref name=":27" /> and less certainly ''[[Aysheaia]]'' as well.<ref name=":22" /> However, in gilled lobopodians like ''[[Kerygmachela]]'', the eyes are relatively complex reflective patches<ref>{{Cite journal|last1=Fleming|first1=James F.|last2=Kristensen|first2=Reinhardt Møbjerg|last3=Sørensen|first3=Martin Vinther|last4=Park|first4=Tae-Yoon S.|last5=Arakawa|first5=Kazuharu|last6=Blaxter|first6=Mark|last7=Rebecchi|first7=Lorena|last8=Guidetti|first8=Roberto|last9=Williams|first9=Tom A.|last10=Roberts|first10=Nicholas W.|last11=Vinther|first11=Jakob|date=2018-12-05|title=Molecular palaeontology illuminates the evolution of ecdysozoan vision|journal=Proceedings of the Royal Society B: Biological Sciences|volume=285|issue=1892|pages=20182180|doi=10.1098/rspb.2018.2180|issn=0962-8452|pmc=6283943|pmid=30518575}}</ref> that may had been [[Compound eye|compound]] in nature.<ref name=":14">{{Cite journal|last1=Park|first1=Tae-Yoon S.|last2=Kihm|first2=Ji-Hoon|last3=Woo|first3=Jusun|last4=Park|first4=Changkun|last5=Lee|first5=Won Young|last6=Smith|first6=M. Paul|last7=Harper|first7=David A. T.|last8=Young|first8=Fletcher|last9=Nielsen|first9=Arne T.|date=2018-03-09|title=Brain and eyes of ''Kerygmachela'' reveal protocerebral ancestry of the panarthropod head|journal=Nature Communications|language=En|volume=9|issue=1|pages=1019|bibcode=2018NatCo...9.1019P|doi=10.1038/s41467-018-03464-w|issn=2041-1723|pmc=5844904|pmid=29523785}}</ref>

=== Trunk and lobopods ===
{{multiple image
| align = right
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| image1 = 20210829 Paucipodia inermis diagrammatic reconstruction.png
| caption1 = ''[[Paucipodia]] inermis'', a lobopodian with featureless, undifferentiated trunk region.
| image2 = 20210902 Luolishania longicruris Miraluolishania haikouensis diagrammatic reconstruction.png
| caption2 = ''[[Luolishania]] longicruris'', showing clear differentiation between trunk segments and lobopods.
}}

The trunk is elongated and composed of numerous body segments ([[somites]]), each bearing a pair of legs called lobopods<ref name=":0" /> or lobopodous limbs.<ref name=":1" /> The segmental boundaries are not as externally significant as those of arthropods, although they are indicated by heteronomous annulations (i.e., the alternation of annulation density corresponding to the position of segmental boundaries) in some species.<ref name=":33">Chen, J.Y., Zhou, G.Q., Ramsköld, L. (1995a). [https://www.academia.edu/3776072 The Cambrian lobopodian ''Microdictyon sinicum'']. Bulletin of the National Museum of Natural Science 5, 1–93 (Taichung, Taiwan).</ref><ref name=":4" /><ref name="ReferenceA" /> The trunk segments may bear other external, segment-corresponding structures such as nodes (e.g. ''[[Hadranax]]'',<ref name=":16" /> ''[[Kerygmachela]]''<ref name=":1" />), papillae (e.g. ''[[Onychodictyon]]''<ref name=":22" />), spine/plate-like sclerites (e.g. armoured lobopodians<ref name=":0" />) or lateral flaps (e.g. gilled lobopodians<ref name=":1" /><ref name=":7" />). The trunk may terminate with a pair of lobopods (e.g. ''[[Aysheaia]]'', ''[[Hallucigenia]] sparsa'')<ref name=":2" /> or a tail-like extension (e.g. ''[[Paucipodia]]'', ''[[Siberion]]'', ''[[Jianshanopodia]]'').<ref name=":33" /><ref name="Hou2004" /><ref name="Liu2006" /><ref name=":9" />

The lobopods are flexible and loosely conical in shape, tapering from the body to tips that may <ref name="ReferenceA" /><ref name=":0" /> or may not <ref name=":3">{{cite journal |last1=Ou |first1=Qiang |last2=Liu |first2=Jianni |last3=SHU |first3=DEGAN |last4=Han |first4=Jian |last5=Zhang |first5=Zhifei |last6=Wan |first6=Xiaoqiao |last7=Lei |first7=Qianping |date=2011-05-01 |title=A Rare Onychophoran-Like Lobopodian from the Lower Cambrian Chengjiang Lagerstätte, Southwestern China, and its Phylogenetic Implications |url=https://www.researchgate.net/publication/259887599 |journal=Journal of Paleontology |volume=85 |issue=3 |pages=587–594 |doi=10.1666/09-147R2.1 |jstor=23020193|bibcode=2011JPal...85..587O |s2cid=53056128}}</ref><ref name=":12">{{cite journal|last1=Ma|first1=Xiaoya|last2=Edgecombe|first2=Gregory|last3=Legg|first3=David|last4=Hou|first4=Xianguang|date=2013-05-08|title=The morphology and phylogenetic position of the Cambrian lobopodian ''Diania cactiformis''|url=https://www.researchgate.net/publication/247777382|journal=Journal of Systematic Palaeontology|volume=12|issue=4|pages=445–457|doi=10.1080/14772019.2013.770418|s2cid=220463025}}</ref><ref name=":13">{{cite journal|last1=Ou|first1=Qiang|last2=Mayer|first2=Georg|date=2018-12-01|title=A Cambrian unarmoured lobopodian, †''Lenisambulatrix humboldti'' gen. et sp. nov., compared with new material of †''Diania cactiformis''|url=https://www.researchgate.net/publication/327777757|journal=Scientific Reports|volume=8|issue=1|pages=13667|bibcode=2018NatSR...813667O|doi=10.1038/s41598-018-31499-y|pmc=6147921|pmid=30237414|doi-access=free}}</ref> bear claws. The claws, if present, are hardened structures with a shape resembling a hook or gently-curved spine.<ref name="Hou2004" /><ref name=":36">{{Cite journal|last1=Steiner|first1=M.|last2=Hu|first2=S.X.|last3=Liu|first3=J.|last4=Keupp|first4=H.|date=2012-02-02|title=A new species of ''Hallucigenia'' from the Cambrian Stage 4 Wulongqing Formation of Yunnan (South China) and the structure of sclerites in lobopodians|journal=Bulletin of Geosciences|pages=107–124|doi=10.3140/bull.geosci.1280|issn=1802-8225|doi-access=free}}</ref><ref name=":4" /><ref name="ReferenceA" /><ref name=":0" /> Claw-bearing lobopods usually have two claws, but single claws are known (e.g. posterior lobopods of [[luolishaniids]]<ref name=":4" /><ref name=":6" /><ref name=":28" />), as are more than two (e.g. three in ''[[Tritonychus]]'',<ref name=":34" /> seven in ''[[Aysheaia]]''<ref name=":32" />) depending on its segmental or taxonomical association.<ref name="ReferenceA" /> In some genera, the lobopods bear additional structures such as spines (e.g. ''[[Diania]]''<ref name=":12" />), fleshy outgrowths (e.g. ''[[Onychodictyon]]''<ref name=":22" />), or tubercules (e.g. ''[[Jianshanopodia]]''<ref name="Liu2006" />). There is no sign of [[Arthropod leg|arthropodization]] (development of a hardened exoskeleton and segmental division on panarthropod appendages) in known members of lobopodians, even for those belonging to the [[arthropod]] stem-group (e.g. gilled lobopodians and siberiids), and the suspected case of arthropodization on the limbs of ''[[Diania]]''<ref name=":24">{{cite journal |last1=Liu |first1=Jianni |last2=Steiner |first2=Michael |last3=Dunlop |first3=Jason A. |last4=Keupp |first4=Helmut |last5=Shu |first5=Degan |last6=Ou |first6=Qiang |last7=Han |first7=Jian |last8=Zhang |first8=Zhifei |last9=Zhang |first9=Xingliang |date=February 2011 |title=An armoured Cambrian lobopodian from China with arthropod-like appendages |journal=Nature |language=en |volume=470 |issue=7335 |pages=526–530 |doi=10.1038/nature09704 |pmid=21350485 |issn=1476-4687 |bibcode=2011Natur.470..526L|s2cid=4324509}}</ref> is considered to be a misinterpretation.<ref name=":12" /><ref name=":13" />

Differentiation (tagmosis) between trunk somites barely occurs, except in [[hallucigenids]] and luolishaniids, where numerous pairs of their anterior lobopods are significantly slender (hallucigenids) or setose (luolishaniids) in contrast to their posterior counterparts.<ref name=":0" /><ref name=":2" /><ref name=":6" /><ref name=":11" /><ref name=":28" />

=== Internal structures ===

[[File:Jianshanopodia decora.jpg|thumb|Fossilized posterior trunk region of ''[[Jianshanopodia]] decora'', showing traces of lobopods, gut diverculae and lobe-like terminal extension.]]

The gut of lobopodians is often straight, undifferentiated,<ref name=":5">{{Cite journal|last1=Vannier|first1=Jean|last2=Liu|first2=Jianni|last3=Lerosey-Aubril|first3=Rudy|last4=Vinther|first4=Jakob|last5=Daley|first5=Allison C.|date=2014-05-02|title=Sophisticated digestive systems in early arthropods|journal=Nature Communications|language=en|volume=5|issue=1|pages=3641|doi=10.1038/ncomms4641|pmid=24785191|issn=2041-1723|bibcode=2014NatCo...5.3641V|doi-access=free}}</ref> and sometimes preserved in the fossil record in three dimensions. In some specimens the gut is found to be filled with sediment.<ref name="Hou2004">{{cite journal|author=Hou, Xian-Guang|last2=Ma|first2=Xiao-Ya|last3=Zhao|first3=Jie|last4=Bergström|first4=Jan|year=2004|title=The lobopodian ''Paucipodia inermis'' from the Lower Cambrian Chengjiang fauna, Yunnan, China|url=https://www.academia.edu/4190258|journal=Lethaia|volume=37|issue=3|pages=235–244|doi=10.1080/00241160410006555|bibcode=2004Letha..37..235H }}</ref> The gut consists of a central tube occupying the full length of the lobopodian's trunk,<ref name="Liu2006">{{cite journal |title=A large xenusiid lobopod with complex appendages from the Lower Cambrian Chengjiang Lagerstätte|author1=Jianni Liu |author2=Degan Shu |author3=Jian Han |author4=Zhifei Zhang |author5=Xingliang Zhang  |name-list-style=amp |journal=Acta Palaeontol. Pol. |volume=51 |issue=2 |pages=215–222 |year=2006 |url=http://www.app.pan.pl/archive/published/app51/app51-215.pdf |archive-url=https://ghostarchive.org/archive/20221010/http://www.app.pan.pl/archive/published/app51/app51-215.pdf |archive-date=2022-10-10 |url-status=live |access-date=9 February 2011}}</ref> which does not change much in width - at least not systematically. However, in some groups, specifically the gilled lobopodians and siberiids, the gut is surrounded by pairs of serially repeated, kidney-shaped gut diverticulae (digestive glands).<ref name="Liu2006" /><ref name="Liu2007">{{cite journal| first1 = J. |first2=D. |first3=J. |first4=Z. | first5=X. |title=Morpho-anatomy of the lobopod Magadictyon cf. Haikouensis from the Early Cambrian Chengjiang Lagerstätte, South China |journal=Acta Zoologica |volume=88 |issue=4 |pages=279–288 |year=2007 |last1=Liu |doi=10.1111/j.1463-6395.2007.00281.x |last2=Shu |last3=Han |last4=Zhang |last5=Zhang}}</ref><ref name=":5" /> In some specimens, parts of the lobopodian gut can be preserved in three dimensions. This cannot result from phosphatisation, which is usually responsible for 3-D gut preservation,<ref name="LeancholiaGuts">{{cite journal |first1=N. J. |title=Leanchoilia guts and the interpretation of three-dimensional structures in Burgess Shale-type fossils |journal=Paleobiology |volume=28 |pages=155–171 |year=2002 |issn=0094-8373 |last1=Butterfield |issue=1 |doi=10.1666/0094-8373(2002)028<0155:LGATIO>2.0.CO;2 |bibcode=2002Pbio...28..155B |s2cid=85606166}}</ref> because the phosphate content of the guts is under 1%; the contents comprise quartz and muscovite.<ref name="Hou2004" /> The gut of the representative ''[[Paucipodia]]'' is variable in width, being widest at the centre of the body. Its position in the body cavity is only loosely fixed, so flexibility is possible.

[[File:20191029 Kerygmachela brain and digestive system.png|thumb|Eyes (deep blue), brain (light blue) and digestive system (yellow) of ''[[Kerygmachela]]''.]]

Not much is known about the neural anatomy of lobopodians due to the spare and mostly ambiguous fossil evidence. Possible traces of a nervous system were found in ''[[Paucipodia]]'', ''[[Megadictyon]]'' and ''[[Antennacanthopodia]]''.<ref name="Liu2007" /><ref name="Hou2004" /><ref name=":3" /> The first and so far the only confirmed evidence of lobopodian neural structures comes from the gilled lobopodian ''[[Kerygmachela]]'' in Park et al. 2018 — it presents a brain composed of only a protocerebrum (the frontal-most cerebral [[ganglion]] of [[panarthropods]]) that is directly connected to the nerves of eyes and frontal appendages, suggesting the protocerebral ancestry of the head of lobopodians as well as the whole [[Panarthropoda]].<ref name=":14" />

In some extant [[ecdysozoa]]n such as [[priapulid]]s and [[onychophora]]ns, there is a layer of outermost circular muscles and a layer of innermost longitudinal muscles. The onychophorans also have a third, intermediate, layer of interwoven oblique muscles. Musculature of the gilled lobopodian ''[[Pambdelurion]]'' shows a similar anatomy,<ref name=":29" /> but that of the lobopodian ''[[Tritonychus]]'' shows the opposite pattern: it is the outermost muscles that are longitudinal and the innermost layer that consists of circular muscles.<ref name=":34">{{Cite journal|last1=Zhang|first1=Xi-Guang|last2=Smith|first2=Martin R.|last3=Yang|first3=Jie|last4=Hou|first4=Jin-Bo|date=2016|title=Onychophoran-like musculature in a phosphatized Cambrian lobopodian|journal=Biology Letters|language=en|volume=12|issue=9|pages=20160492|doi=10.1098/rsbl.2016.0492|pmid=27677816|pmc=5046927|issn=1744-9561}}</ref>