Editing Tunicate (section)

===Fossil record===
[[Image:Catellocaula.jpg|thumb|right|The star-shaped holes (''[[Catellocaula vallata]]'') in this Upper Ordovician bryozoan may represent a tunicate preserved by [[Fossil#Bioimmuration|bioimmuration]] in the [[bryozoa]]n skeleton.]]
Undisputed fossils of tunicates are rare. The best known and earliest unequivocally identified species is ''[[Shankouclava|Shankouclava shankouense]]'' from the Lower [[Cambrian]] [[Maotianshan Shale]] at Shankou village, Anning, near [[Kunming]] ([[Northern and southern China|South China]]).<ref name=Jun-Yuan2003>{{cite journal|author1=Chen, Jun-Yuan |author2=Huang, Di-Ying |author3=Peng, Qing-Qing |author4=Chi, Hui-Mei |author5=Wang,Xiu-Qiang |author6=Feng, Man |year=2003 |title=The first tunicate from the Early Cambrian of South China |journal=[[Proceedings of the National Academy of Sciences]] |volume=100 |pmid=12835415 |issue=14 |pages=8314–8318 |pmc=166226 |doi=10.1073/pnas.1431177100 |bibcode=2003PNAS..100.8314C |doi-access=free }}</ref> There is also a common [[Fossil#Bioimmuration|bioimmuration]], (''Catellocaula vallata''), of a possible tunicate found in Upper [[Ordovician]] [[bryozoa]]n skeletons of the upper midwestern United States.<ref>{{cite journal |author1=Palmer, T. J. |author2=Wilson, M. A. |year=1988 |title=Parasitism of Ordovician bryozoans and the origin of pseudoborings |journal=Palaeontology |volume=31 |pages=939–949 |url=http://palaeontology.palass-pubs.org/pdf/Vol%2031/Pages%20939-949.pdf |access-date=7 April 2013 |archive-url=https://web.archive.org/web/20130927070328/http://palaeontology.palass-pubs.org/pdf/Vol%2031/Pages%20939-949.pdf |archive-date=27 September 2013 |url-status=usurped }}</ref> A well-preserved Cambrian fossil, ''Megasiphon thylakos'', shows that the tunicate basic body design had already been established 500 million years ago.<ref>{{Cite web |url=https://www.techexplorist.com/500-million-year-old-fossil-reveals-amazing-secrets-tunicate-origins/63818/ |title=A 500 million-year-old fossil reveals the amazing secrets of tunicate origins |first=Vidya |last=Nagalwade |date=7 July 2023 |website=Tech Explorist}}</ref>

Three enigmatic species were also found from the [[Ediacaran]] period – ''[[Ausia (animal)|Ausia fenestrata]]'' from the Nama Group of [[Namibia]], the sac-like ''[[Yarnemia|Yarnemia ascidiformis]]'', and one from a second new ''Ausia''-like genus from the Onega Peninsula of northern [[Russia]], ''[[Burykhia|Burykhia hunti]]''. Results of a new study have shown possible affinity of these Ediacaran organisms to the ascidians.<ref name=Vickers-Rich>Vickers-Rich P. (2007). "Chapter 4. The Nama Fauna of Southern Africa". In: Fedonkin, M. A.; Gehling, J. G.; Grey, K.; Narbonne, G. M.; Vickers-Rich, P. "The Rise of Animals: Evolution and Diversification of the Kingdom Animalia", Johns Hopkins University Press. pp. 69–87</ref><ref name=Oslo_2008>Fedonkin, M. A.; Vickers-Rich, P.; Swalla, B.; Trusler, P.; Hall, M. (2008). "A Neoproterozoic chordate with possible affinity to the ascidians: New fossil evidence from the Vendian of the White Sea, Russia and its evolutionary and ecological implications". HPF-07 Rise and fall of the Ediacaran (Vendian) biota. International Geological Congress - Oslo 2008.</ref> ''Ausia'' and ''Burykhia'' lived in shallow coastal waters slightly more than 555 to 548&nbsp;million years ago, and are believed to be the oldest evidence of the chordate lineage of metazoans.<ref name=Oslo_2008/> The Russian Precambrian fossil ''[[Yarnemia]]'' is identified as a tunicate only tentatively, because its fossils are nowhere near as well-preserved as those of ''Ausia'' and ''Burykhia'', so this identification has been questioned.

Fossils of tunicates are rare because their bodies decay soon after death, but in some tunicate families, microscopic spicules are present, which may be preserved as microfossils. These spicules have occasionally been found in Jurassic and later rocks, but, as few palaeontologists are familiar with them, they may have been mistaken for [[sponge spicule]]s.<ref>{{cite web |url=http://www.ucmp.berkeley.edu/chordata/urochordata.html |title=Introduction to the Urochordata |publisher=University of California Museum of Paleontology |access-date=2013-04-07 |archive-url=https://web.archive.org/web/20090421215035/http://www.ucmp.berkeley.edu/chordata/urochordata.html |archive-date=21 April 2009 |url-status=dead }}</ref>

In the Permian and the Triassic, there were also forms with a calcareous exoskeleton. At first, they were mistaken for corals.<ref>[https://www.cambridge.org/core/services/aop-cambridge-core/content/view/0FE5DCCCDFDD464B92DCA4AF68F36F2B/S0022336019001094a.pdf/rare_case_of_an_evolutionary_late_and_ephemeral_biomineralization_tunicates_with_composite_calcareous_skeletons.pdf A rare case of an evolutionary late and ephemeral biomineralization: tunicates with composite calcareous skeletons]</ref><ref>{{Cite journal |url=https://onlinelibrary.wiley.com/doi/10.1111/pala.12356 |title=The first tunicate with a calcareous exoskeleton (Upper Triassic, northern Italy) |first=Jobst |last=Wendt |editor-first=Michael |editor-last=Hautmann |date=25 July 2018 |journal=Palaeontology |volume=61 |issue=4 |pages=575–595 |via=CrossRef |doi=10.1111/pala.12356|bibcode=2018Palgy..61..575W |s2cid=135456629 |url-access=subscription }}</ref>