Shankouclava

Shankouclava; Temporal range: Cambrian Stage 3,
	Restoration of S. anningense.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Tunicata
Genus:	†Shankouclava; Chen et al., 2003
Type species
	†Shankouclava anningense; Chen et al., 2003
Species
	†S. anningense Chen et al., 2003; †S. shankouense Chen et al., 2003;

Shankouclava is an extinct genus of tunicates. It represents the oldest candidate member of this group, dating to 518 million years ago. It has been found in the Lower Cambrian Maotianshan Shale at Shankou village, Anning, near Kunming (South China). Each of the eight specimens found and used for description were isolated, suggesting that the genus was solitary and not colonial.[2]

Morphology

Shankouclava had a soft, sac-like body that was elongated and pointed proximally. The body lengths of individuals vary from 2 cm (0.8 in) to 4 cm (1.6 in).[2]

Degan Shu asserts that some fossil specimens exhibit tentacles, which would make the genus similar to the deuterostome Phlogites.[3] Expanding on this idea, Shu and colleagues argue against a tunicate affinity for Shankouclava.[4]

Etymology

The generic name is composed of the fossil locality, Shankou, and the Latin word clava (club-shaped).[2]

Classification

A stem group tunicate affinity for Shankouclava has been broadly accepted, though some authors have expressed reservations that the evidence in favour of this affinity is not conclusive.[5]

Another Cambrian tunicate, Megasiphon, known from a single specimen, resembles more closely the morphology of surviving tunicates.[6]

References

Yang, C.; Li, X.-H.; Zhu, M.; Condon, D. J.; Chen, J. (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. S2CID 135091168.
Chen, Jun-Yuan; Huang, Di-Ying; Peng, Qing-Qing; Chi, Hui-Mei; Wang, Xiu-Qiang; Feng, Man (2003). "The first tunicate from the Early Cambrian of South China". Proceedings of the National Academy of Sciences. 100 (14): 8314–8318. Bibcode:2003PNAS..100.8314C. doi:10.1073/pnas.1431177100. PMC 166226. PMID 12835415.
Shu (2008). "Cambrian explosion: Birth of tree of animals". Gondwana Research. 14 (1–2): 219–240. Bibcode:2008GondR..14..219S. doi:10.1016/j.gr.2007.08.004.
Shu, D.-G.; Conway Morris, S.; Zhang, Z.-F.; Han, J. (2010). "The earliest history of the deuterostomes: The importance of the Chengjiang Fossil-Lagerstätte". Proceedings of the Royal Society B: Biological Sciences. 277 (1679): 165–174. doi:10.1098/rspb.2009.0646. PMC 2842668. PMID 19439437.
Conway Morris (29 June 2006). "Darwin's dilemma: the realities of the Cambrian 'explosion'". Philos Trans R Soc Lond B Biol Sci. 361 (1470): 1069–1083. doi:10.1098/rstb.2006.1846. PMC 1578734. PMID 16754615.
Nanglu, Karma; Lerosey-Aubril, Rudy; Weaver, James C.; Ortega-Hernández, Javier (2023). "A mid-Cambrian tunicate and the deep origin of the ascidiacean body plan". Nature Communications. 14 (1): 3832. doi:10.1038/s41467-023-39012-4. PMC 10325964. PMID 37414759.

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[1] Yang, C.; Li, X.-H.; Zhu, M.; Condon, D. J.; Chen, J. (2018). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (PDF). Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. S2CID 135091168.

[:1-2] Chen, Jun-Yuan; Huang, Di-Ying; Peng, Qing-Qing; Chi, Hui-Mei; Wang, Xiu-Qiang; Feng, Man (2003). "The first tunicate from the Early Cambrian of South China". Proceedings of the National Academy of Sciences. 100 (14): 8314–8318. Bibcode:2003PNAS..100.8314C. doi:10.1073/pnas.1431177100. PMC 166226. PMID 12835415.

[3] Shu (2008). "Cambrian explosion: Birth of tree of animals". Gondwana Research. 14 (1–2): 219–240. Bibcode:2008GondR..14..219S. doi:10.1016/j.gr.2007.08.004.

[4] Shu, D.-G.; Conway Morris, S.; Zhang, Z.-F.; Han, J. (2010). "The earliest history of the deuterostomes: The importance of the Chengjiang Fossil-Lagerstätte". Proceedings of the Royal Society B: Biological Sciences. 277 (1679): 165–174. doi:10.1098/rspb.2009.0646. PMC 2842668. PMID 19439437.

[5] Conway Morris (29 June 2006). "Darwin's dilemma: the realities of the Cambrian 'explosion'". Philos Trans R Soc Lond B Biol Sci. 361 (1470): 1069–1083. doi:10.1098/rstb.2006.1846. PMC 1578734. PMID 16754615.

[6] Nanglu, Karma; Lerosey-Aubril, Rudy; Weaver, James C.; Ortega-Hernández, Javier (2023). "A mid-Cambrian tunicate and the deep origin of the ascidiacean body plan". Nature Communications. 14 (1): 3832. doi:10.1038/s41467-023-39012-4. PMC 10325964. PMID 37414759.