Proarticulata

{{short description|Extinct phylum of animals}} {{Automatic taxobox | fossil_range = Ediacaran, {{fossil range|567|550}} | image = DickinsoniaCostata.jpg | image_caption = Fossil of ''Dickinsonia costata'' | image2 = Spriggina Floundensi 4.png | image2_caption = Fossil of ''Spriggina'' | taxon = Proarticulata | authority = Fedonkin, 1985 | subdivision_ranks = Classes and families | subdivision = * †Vendiamorpha Fedonkin, 1985 ** †Vendiidae Ivantsov * †Dipleurozoa Harrington & Moore, 1955 ** †Dickinsoniidae Harrington & Moore, 1955 * †Cephalozoa Ivantsov. 2004 ** †Sprigginidae Glaessner, 1958 ** †Yorgiidae Ivantsov, 2001 For more taxa, see text }}

'''Proarticulata''' is a phylum of extinct, near-bilaterally symmetrical animals known from fossils found mainly in the Ediacaran (Vendian) marine deposits, with some few possible related specimen found through Cambrian until late Devonian<ref>{{Cite journal |last=Retallack |first=Gregory J. |date=July 2018 |title=Reassessment of the Devonian problematicum Protonympha as another post-Ediacaran vendobiont |url=https://www.scup.com/doi/10.1111/let.12253 |journal=Lethaia |volume=51 |issue=3 |pages=406–423 |doi=10.1111/let.12253 |issn=0024-1164|url-access=subscription }}</ref>, and dates to approximately {{ma|567|550}}.<ref name=Maslov_2018>{{cite journal | vauthors = Maslov AV, Podkovyrov VN, Grazhdankin DV, Kolesnikov AV | date = 2018 | title = Upper Vendian in the east, northeast and north of East European Platform: Depositional processes and biotic evolution | journal = Litosfera | volume = 18 | issue = 4 | pages = 520–542 | url = https://www.researchgate.net/publication/327388718 | doi = 10.24930/1681-9004-2018-18-4-520-542 | doi-access = free }}</ref><ref name=Kolesnikov_2018>{{cite journal | vauthors = Kolesnikov AV, Liu AG, Danelian T, Grazhdankin DV | date = 2018 | title = A reassessment of the problematic Ediacaran genus Orbisiana Sokolov 1976 | journal = Precambrian Research | volume = 316 | pages = 197–205 | url = https://www.repository.cam.ac.uk/handle/1810/285052| doi = 10.1016/j.precamres.2018.08.011 | bibcode = 2018PreR..316..197K | s2cid = 134213721 }}</ref><ref>{{Cite journal|last1=Muscente|first1=A. D.|last2=Bykova|first2=Natalia|last3=Boag|first3=Thomas H.|last4=Buatois|first4=Luis A.|last5=Mángano|first5=M. Gabriela|last6=Eleish|first6=Ahmed|last7=Prabhu|first7=Anirudh|last8=Pan|first8=Feifei|last9=Meyer|first9=Michael B.|last10=Schiffbauer|first10=James D.|last11=Fox|first11=Peter|date=2019-02-22|title=Ediacaran biozones identified with network analysis provide evidence for pulsed extinctions of early complex life|journal=Nature Communications|language=en|volume=10|issue=1|pages=911|doi=10.1038/s41467-019-08837-3|pmid=30796215 |issn=2041-1723|pmc=6384941|bibcode=2019NatCo..10..911M }}</ref> The name comes from the Greek {{lang|grc|προ}} ({{Transliteration|grc|pro-}}) = "before" and Articulata, i.e. prior to animals with true segmentation such as annelids and arthropods. This phylum was established by Mikhail A. Fedonkin in 1985 for such animals as ''Dickinsonia'', ''Vendia'', ''Cephalonega'', ''Praecambridium''<ref name=Fedonkin_1985>{{cite book | vauthors = Fedonkin MA | date = 1985 | chapter = Systematic Description of Vendian Metazoa | veditors = Sokolov BS, Iwanowski AB | title = Vendian System: Historical–Geological and Paleontological Foundation | volume = 1: Paleontology | location = Moscow | publisher = Nauka | pages = 70–106 }}</ref> and currently many other Proarticulata are described (see list).<ref name=Fedonkin2003>{{cite journal | vauthors = Fedonkin MA | date = 31 March 2003 | title = The origin of the Metazoa in the light of the Proterozoic fossil record | journal = Paleontological Research | volume = 7 | issue = 1 | pages = 9–41 | url = http://www.bionet.nsc.ru/live/ppt/Fedonkin_2003.pdf | doi = 10.2517/prpsj.7.9 | bibcode = 2003PalRe...7....9F | s2cid = 55178329 }}</ref><ref name=Ivantsov_2019>{{cite journal | vauthors = Ivantsov AY, Fedonkin MA, Nagovitsyn AL, Zakrevskaya ZA |year=2019 |title=''Cephalonega'', a new generic name, and the system of Vendian Proarticulata |journal=Paleontological Journal |volume=53 |issue=5 |pages=447–454 |doi=10.1134/S0031030119050046 |bibcode=2019PalJ...53..447I |s2cid=203853224 |url=https://www.researchgate.net/publication/335988735 }}</ref>

Due to their simplistic morphology, their affinities and mode of life are subject to debate. They are almost universally considered to be metazoans, and due to possessing a clear central axis have been suggested to be stem-bilaterians. In the traditional interpretation, the proarticulatan body is divided into transverse articulation (division) into ''isomers'' as distinct from the transverse articulation ''segments'' in annelids and arthropods, as their individual isomers occupy only half the width of their bodies, and are organized in an alternating pattern along the longitudinal axis of their bodies.<ref name=Ivantsov_2019/> In other words, one side is not the direct mirror image of its opposite (''chirality''). Opposite isomers of left and right side are located with displacement of half of their width. This phenomenon is described as the symmetry of gliding reflection.<ref name=Ivantsov2001/><ref name=Ivantsov1999/> Some recent research suggests that some proarticulatans like ''Dickinsonia'' have genuine segments, and the isomerism is superficial and due to taphonomic distortion.<ref>{{cite journal | vauthors = Dunn FS, Liu AG, Donoghue PC | title = Ediacaran developmental biology | journal = Biological Reviews of the Cambridge Philosophical Society | volume = 93 | issue = 2 | pages = 914–932 | date = May 2018 | pmid = 29105292 | pmc = 5947158 | doi = 10.1111/brv.12379 }}</ref> However, other researchers dispute this.<ref>{{cite journal | vauthors = Ivantsov AY, Zakrevskaya MA, Nagovitsyn AL |date= June 2019 |title=Morphology of integuments of the Precambrian animals, Proarticulata |journal=Invertebrate Zoology |volume=16 |issue=1 |pages=19–26 |doi=10.15298/invertzool.16.1.03 |doi-access=free }}</ref><ref>{{Cite journal| vauthors = Ivantsov Y, Fedonkin MA, Nagovitsyn AL, Zakrevskaya MA |date= September 2019 |title=Cephalonega, A New Generic Name, and the System of Vendian Proarticulata|journal=Paleontological Journal |volume=53 |issue=5 |pages=447–454 |doi=10.1134/s0031030119050046 |bibcode= 2019PalJ...53..447I |s2cid= 203853224 }}</ref> Displacement of left-right axis is known in bilaterians, notably lancelets.<ref>{{cite journal | vauthors = Blum M, Feistel K, Thumberger T, Schweickert A | title = The evolution and conservation of left-right patterning mechanisms | journal = Development | volume = 141 | issue = 8 | pages = 1603–13 | date = April 2014 | pmid = 24715452 | doi = 10.1242/dev.100560 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Soukup V | title = Left-right asymmetry specification in amphioxus: review and prospects | journal = The International Journal of Developmental Biology | volume = 61 | issue = 10–11–12 | pages = 611–620 | date = 2017 | pmid = 29319110 | doi = 10.1387/ijdb.170251vs | doi-access = free | hdl = 11104/0294582 | hdl-access = free }}</ref>

== Morphology == thumb|600px|left|Examples of the classes Proarticulata, including reconstructions of ''Vendia sokolovi'', ''Dickinsonia costata'' and ''Yorgia waggoneri''.

===Vendiamorpha=== {{main|Vendiamorpha}} The body is completely segmented, with all isomers curved towards the posterior, and the first isomer is normally much larger than the rest. The first two isomers at the anterior dorsal end are partly fused. (e.g., ''Vendia'', ''Paravendia'' and ''Karakhtia'').<ref name=Ivantsov2001> {{cite journal | last = Ivantsov | first = A.Yu. | year = 2001 | title = ''Vendia'' and other precambrian "Arthropods" | journal = Paleontological Journal | volume = 35 | issue = 4 | pages = 335–343 | url = https://www.academia.edu/2605872 }} </ref><ref name=Ivantsov2004> {{cite journal | last = Ivantsov | first = A.Yu. | year = 2004 | title = New Proarticulata from the Vendian of the Arkhangel'sk Region | journal = Paleontological Journal | volume = 38 | issue = 3 | pages = 247–253 | url = http://vend.paleo.ru/pub/Ivantsov_2004_eng.pdf | url-status = dead | archive-url = https://web.archive.org/web/20070927022709/http://vend.paleo.ru/pub/Ivantsov_2004_eng.pdf | archive-date = 2007-09-27 }} </ref><ref name=Ivantsov2004et_al> {{cite journal | last1 = Ivantsov | first1 = A.Yu. | last2 = Malakhovskaya | first2 = Y.E. | last3 = Serezhnikova | first3 = E.A. | year = 2004 | title = Some problematic fossils from the Vendian of the south-eastern White Sea region | journal = Paleontological Journal | volume = 38 | issue = 1 | pages = 1–9 | url = http://www.vend.paleo.ru/pub/Ivantsov_et_al_2004_eng.pdf | url-status = dead | archive-url = https://web.archive.org/web/20070704183946/http://www.vend.paleo.ru/pub/Ivantsov_et_al_2004_eng.pdf | archive-date = 2007-07-04 }} </ref><ref name=Ivantsov2004Prato> {{cite conference | last = Ivantsov | first = A.Yu. | year = 2004 | title = Vendian animals in the phylum ''Proarticulata'' | conference = The Rise and Fall of the Vendian Biota | page = 52 | id = IGSP Project 493 | location = Prato, Italy | url = https://www.monash.edu/__data/assets/pdf_file/0010/75655/ivantsov.pdf }} </ref>

===Cephalozoa=== {{main|Cephalozoa}} These proarticulatans are incompletely segmented, as the anterior zone is free of isomers, often making a "hairband" like appearance (example cephalozoans include ''Yorgia'', ''Praecambridium'', ''Andiva'', ''Archaeaspinus'', ''Ivovicia'', ''Podolimirus'', ''Tamga'', ''Spriggina'', ''Marywadea'' and ''Cyanorus'').<ref name=Ivantsov2001/><ref name=Ivantsov2004/><ref name=Ivantsov2004Prato/><ref name=Ivantsov2007> {{cite journal | last = Ivantsov | first = A.Yu. | date = April 2007 | title = Small Vendian transversely articulated fossils | journal = Paleontological Journal | volume = 41 | issue = 2 | pages=113–122 | doi = 10.1134/S0031030107020013 | bibcode = 2007PalJ...41..113I | s2cid = 86636748 | url = https://www.academia.edu/2352394 }} </ref> Some cephalozoans from the family Yorgiidae demonstrate pronounced asymmetry of the left and right parts of the body. For instance, ''Yorgia''{{'s}} initial right isomer is the only one which spreads far towards the left side of the body. ''Archaeaspinus'' has an unpaired anterior lobe confined by the furrow to the left side only.<ref name=Ivantsov2001/><ref name=Ivantsov1999> {{cite journal | last = Ivantsov | first = A.Yu. | year = 1999 | title = A new Dickinsoniid from the upper Vendian of the White Sea Winter Coast (Russia, Arkhangelsk region) | journal = Paleontological Journal | volume = 33 | issue = 3 | pages = 233–241 | url = https://www.academia.edu/2604893 }} </ref><ref name=Ivantsov2004Prato/> [[file:Cephalonega stepanovi.jpg|thumb|left|Artist's reconstruction of ''Cephalonega stepanovi''.<ref>illustration (c) Stanton F. Fink</ref>]] [[file:Lossinia_lissetski.jpg|thumb|right|Artist's reconstruction of ''Lossinia'' feeding on surface algae.]] In ''Cephalonega stepanovi'' and ''Tamga hamulifera'' the zone containing the isomers is encircled by a peripheral, undivided zone.<ref name=Ivantsov2007/> The ''Cephalonega''{{'s}} isomers are connected to each other, forming a body resembling a rubber raft; the ''Tamga''{{'s}} isomers are separated from each other, and do not touch.

In ''Lossinia'', the center undivided region has no visible isomers, instead having the lobe-like isomers emanate from the periphery of the undivided region as "transverse articulations."<ref name=Ivantsov2007/>

===Dipleurozoa=== {{main|Dipleurozoa}} The dipleurozoan body is subradial, divided by isomers entirely (e.g., ''Dickinsonia'' and ''Phyllozoon''). ''Dickinsonia'' juveniles show undivided anterior areas but these regions were reduced in the course of ontogeny, and in the adult stages ''Dickinsonia''-like proarticulates changed so radically that they became almost indistinguishable from isomers.<ref name=Ivantsov2004/><ref name=Ivantsov2007/><ref name=Ivantsov2002> {{cite journal | last1 = Ivantsov | first1 = A.Yu. | last2 = Malakhovskaya | first2 = Y.E. | year = 2002 | title = Giant traces of Vendian animals | journal = Doklady Earth Sciences | volume = 385 | issue = 6 | pages = 618–622 | url = http://vend.paleo.ru/pub/Ivantsov_et_Malakhovskaya_2002-e.pdf | url-status = dead | archive-url = https://web.archive.org/web/20070704183947/http://vend.paleo.ru/pub/Ivantsov_et_Malakhovskaya_2002-e.pdf | archive-date = 2007-07-04 }} </ref>

== List of proarticulates == {{multiple image | direction = vertical | width = 145 | image1 = Andiva ivantsovi.jpg | alt1 = Andiva ivantsovi | caption1 = ''Andiva ivantsovi'' ---- | image2 = DickinsoniaCostata3.png | alt2 = Dickinsonia costata | caption2 = ''Dickinsonia costata'' ---- | image3 = Spriggina Floundensi 4.png | alt3 = Spriggina floundersi | caption3 = ''Spriggina floundersi'' ---- | image4 = Ovatoscutum_concentricium_cropped.png | alt4 = Ovatoscutum concentricum | caption4 = ''Ovatoscutum concentricum'' ---- | image5 = Yorgia.jpg | alt5 = Yorgia waggoneri | caption5 = ''Yorgia waggoneri'' ---- | image6 = Tamga_hamulifera.JPG | alt6 = Tamga hamulifera | caption6 = ''Tamga hamulifera'' }}

=== Body fossils === *''Armillifera'' Fedonkin, 1980<ref name=Ivantsov2010>{{cite journal| vauthors = Ivantsov AY | date=December 2010|title=Paleontological evidence for the supposed precambrian occurrence of mollusks| journal=Paleontological Journal| volume=40| issue=12| pages=1552–1559|doi=10.1134/S0031030110120105| bibcode=2010PalJ...44.1552I| s2cid=86523806}}</ref> :''A. parva'' Fedonkin, 1980 *''Andiva'' Fedonkin, 2002<ref name="Fedonkin2002">{{Cite journal | vauthors = Fedonkin MA | title = ''Andiva ivantsovi'' gen. et sp. n. and related carapace-bearing Ediacaran fossils from the Vendian of the Winter Coast, White Sea, Russia | doi = 10.1080/11250000209356456 | journal = Italian Journal of Zoology | volume = 69 | issue = 2 | pages = 175–181 | year = 2002 | s2cid = 85352552 | doi-access = free }}</ref> :''A. ivantsovi'' Fedonkin, 2002 *''Archaeaspinus'' Ivantsov, 2007<ref name=Ivantsov2001/> (=''Archaeaspis'' Ivantsov, 2001)<ref name=Ivantsov2007/> :''A. fedonkini'' Ivantsov, 2001 *''Cephalonega'' Ivantsov ''et al.'', 2019<ref>{{Cite journal| vauthors = Ivantsov AY, Fedonkin MA, Nagovitsyn AL, Zakrevskaya MA |year=2019 |title=''Cephalonega'', a new generic name, and the system of Vendian Proarticulata |journal=Paleontological Journal |volume=53 |issue=5 |pages=447–454 |doi= 10.1134/S0031030119050046|bibcode=2019PalJ...53..447I |s2cid=203853224 |url=https://elibrary.ru/item.asp?id=39324149 |url-access=subscription }}</ref> :''C. stepanovi'' (Fedonkin, 1976)<ref name=Ivantsov2007/><ref name=Keller_Fedonkin_1976/> *''Chondroplon'' Wade, 1971 (possible =''Dickinsonia'') :''C. bilobatum'' Wade, 1971 *''Cyanorus'' Ivantsov, 2004<ref name=Ivantsov2004/> :''C. singularis'' Ivantsov, 2004 *''Dickinsonia'' Sprigg, 1947 :''D. costata'' Sprigg, 1947 :''D. menneri'' Keller 1976<ref name=Ivantsov2007/> (=''Vendomia menneri'' Keller 1976<ref name=Keller_Fedonkin_1976>{{cite journal | vauthors = Keller BM, Fedonkin MA | year = 1976 | title = New Records of Fossils in the Valdaian Group of the Precambrian on the Syuz'ma River | journal = Izvestiya Akademii Nauk SSR | series = Seriya Geologicheskaya | volume = 3 | pages = 38–44 | url = http://vend.paleo.ru/pub/Keller_Fedonkin_1976.pdf | language = ru | url-status = dead | archive-url = https://web.archive.org/web/20070927022652/http://vend.paleo.ru/pub/Keller_Fedonkin_1976.pdf | archive-date = 2007-09-27 }}</ref>) :''D. tenuis'' Glaessner & Wade, 1966 *''Ivovicia'' Ivantsov, 2007<ref name=Ivantsov2007/> :''I. rugulosa'' Ivantsov, 2007 *''Karakhtia'' Ivantsov, 2004 :''K. nessovi'' Ivantsov, 2004 *''Lossinia'' Ivantsov, 2007<ref name=Ivantsov2007/> :''L. lissetskii'' Ivantsov, 2007 *''Marywadea'' Glaessner, 1976 :''M. ovata'' Glaessner & Wade, 1966 *''Ovatoscutum'' Glaessner & Wade, 1966 :''O. concentricum'' Glaessner & Wade, 1966 *''Paravendia'' Ivantsov, 2004<ref name=Ivantsov2001/><ref name=Ivantsov2004/> :''P. janae'' Ivantsov, 2001 (=''Vendia janae'' Ivantsov, 2001) *''Podolimirus'' Fedonkin, 1983 (=''Valdainia'' Fedonkin, 1983)<ref name=Dzik2015> {{cite journal | last1 = Dzik | first1 = J. | last2 = Martyshyn | first2 = A. | year = 2015 | title = Taphonomy of the Ediacaran Podolimirus and associated dipleurozoans from the Vendian of Ukraine | journal = Precambrian Research | volume = 269 | pages = 139–146 | url = https://www.academia.edu/15860379 | doi = 10.1016/j.precamres.2015.08.015 | bibcode = 2015PreR..269..139D }}</ref> :''P. mirus'' Fedonkin, 1983 (''Valdainia plumosa'' Fedonkin, 1983) *''Praecambridium'' Glaessner & Wade, 1966 :''P. siggilum'' Glaessner & Wade, 1966 *''Spriggina'' Glaessner, 1958 :''S. floundersi'' Glaessner, 1958 *''Tamga'' Ivantsov, 2007<ref name=Ivantsov2007/> :''T. hamulifera'' Ivantsov, 2007 *''Vendia'' Keller, 1969<ref name=Ivantsov2001/><ref name=Ivantsov2004/> :''V. sokolovi'' Keller, 1969 :''V. rachiata'' Ivantsov, 2004 *? ''Windermeria'' Narbonne, 1994 :''W. aitkeni'' Narbonne, 1994<ref name="Narbonne1994">{{cite journal | vauthors = Narbonne GM |date=May 1994|title=New Ediacaran fossils from the Mackenzie Mountains, Northwestern Canada|journal=Journal of Paleontology|volume=63|issue=3|pages=411–416|jstor=1306192|doi= 10.1017/S0022336000025816|bibcode=1994JPal...68..411N |s2cid=133215767 }}</ref> *''Yorgia'' Ivantsov, 1999<ref name=Ivantsov1999/> :''Y. waggoneri'' Ivantsov, 1999

=== Trace fossils === *''Epibaion'' Ivantsov, 2002<ref name="Ivantsov2002"/><ref name="Ivantsov2011">{{Cite journal | vauthors = Ivantsov AY | title = Feeding traces of Proarticulata — the Vendian metazoa | doi = 10.1134/S0031030111030063 | journal = Paleontological Journal | volume = 45 | issue = 3 | pages = 237–248 | date = May 2011 | bibcode = 2011PalJ...45..237I | s2cid = 128741869 | url = https://www.academia.edu/2394670}}</ref> :''E. axiferus'' Ivantsov, 2002. :''E. waggoneris'' Ivantsov, 2011. This is a trace of ''Yorgia waggoneri'' :''E. costatus'' Ivantsov, 2011. This is a trace of ''Dickinsonia costata'' *''Phyllozoon'' Jenkins & Gehling, 1978 :''P. hanseni'' Jenkins & Gehling, 1978 {{Clear}}

== See also == * Articulata * List of Ediacaran genera

== References == {{reflist|25em}}

== External links == *[https://web.archive.org/web/20110725191154/http://www.complex-life.org/database Database of Ediacaran Biota] Advent of Complex Life

Category:Proarticulata Category:Bilateria phyla Category:Vendobionta