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Phlogites Temporal range: Lower Cambrian PreꞒ Ꞓ O S D C P T J K Pg N
Restoration of Phlogites (with tentacles extended)Phlogites longus fossil
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Superphylum:	Deuterostomia
Stem group:	Ambulacraria
Clade:	†Cambroernida
Genus:	†Phlogites Luo & Hu, 1999
Species:	†P. longus
Binomial name
†Phlogites longus Luo & Hu, 1999
Synonyms
†Phlogites brevis Luo & Hu 1999 †Cheungkongella ancestralis ? Shu et al. 2001

Phlogites is a member of the extinct ambulacrarian stem group Cambroernida, occupying an intermediate position between the basal Herpetogaster and the more derived Eldonioidea. It is known from the Lower Cambrian Haikou Chengjiang deposits of China.

Description

Phlogites was a cup-shaped animal with a branching tentacular feeding system leading to a dextrally coiled gut with a lateral anus. Sources differ as to the number of tentacles, with two, three, three or five, or four or five tentacles said to be on the anterior part of the calyx, with one source noting smooth semi-circular lobes between them.

Compared to the earlier-diverging cambroernid Herpetogaster, Phlogites lacked segmentation and had a more massive stolon that is contiguous with the body. The coiling present in the external form of Herpetogaster became internal, except for a small lobate extension with the anus opening laterally. The tentacles of Phlogites were also more massive, and seem to have branched dichotomously.

Phylogeny

The following cladogram is simpllified from Li et al. 2023:

History of interpretation

Phlogites was initially considered to be an early lophophorate. A new phylum, Dendrobrachia (Hou, Bergstrom, Ma and Zhao, 2006) was later proposed to encompass it. While some similarities were noted with the eldonioids (and phoronids), the authors were not sufficiently confident to either group Phlogites with the phoronids or include the eldonioids in the Dendrobrachia.

Since ICZN precedence rules do not apply at the phylum level, later researchers opted to propose cambroernids as an informal group rather than expanding the phylum Dendrobrachia, noting that "not only is the concept of phyla essentialist but it serves to place problematic taxa in a phylogenetic limbo, rendering them effectively immune to further evolutionary analysis." The informal group "cambroernids" was later given the formal name Cambroernida once further evidence was found to support its monophyly.

The interpretation of Phlogites has been complicated by its proposed equation (as a senior synonym) with the possible first-disovered Cambrian tunicate Cheungkongella ancestralis (sometimes misspelt Cheungkungella) by the discoverers of another candidate for the title of the oldest known Cambrian tunicate, Shankouclava.

The discoverers of Shankouclava agreed with the discovers of Phlogites that Phlogites is most likely a lophophorate, although they noted possible affinities with ambulacrarians or with Sipuncula. A different group of researchers agreed with synonymizing Cheungkongella with Phlogites, but proposed a new phylum, Dendrobrachia, with affinities to the Gnathifera.

Neither group proposed tunicate affinities for Phlogites, but later works by the discoverer of Shankouclava contain statements such as "although Lower Cambrian Phlogites (=Cheungkongella) was claimed as a tunicate (Shu et al., 2001)" that have led to confusion on this point by associating the tunicate affinity claims that only ever applied to Cheungkongella with Phlogites.

A researcher who was not part of any of the teams discovering Phlogites, Cheungkongella, or Shankouclava, or proposing Dendrobrachia, examined the fossils and concluded that the similarity between Phlogites and Cheungkongella was "superficial." The question of whether Cheungkongella is a synonym of Phlogites remains unresolved, but does not impact the current theory of Phlogites as a cambroernid.

References

1. ^ Hou et al. 2006
2. ^ Chen et al. 2003, pp. 8316–8317
3. ^ Conway Morris 2006, p. 1076
4. ^ Caron et al. 2010
5. ^ Li et al. 2023
6. Shu 2008, p. 231
7. ^ Caron et al. 2010, p. 7
8. Li et al. 2023, p. 2363
9. Zhang et al. 2006 (Note: Cites the 1999 discovery publication Early Cambrian Chengjiang Fauna from Kunming Region China (Luo Hui-Lin, Hu Shi-Xie, Chen Liang-Zhong, Zhang Shi-Shan, Tau Yong-Shan), which is in Chinese and not available online)
10. Caron et al. 2010, pp. 1–2
11. Li et al. 2023, pp. 2361–2362
12. Shu et al. 2001
13. Shu et al. 2010
14. ^ Gee 2018, p. 99
15. Chen 2011, p. 259
16. Zhuravlev 2015, p. 427 (Note: the text includes the phrase "presumed tunicates (Cheungkongella, Phlogites, Shankouclava; Shu et al., 2001; Chen et al., 2003)" treating Phlogites as a tunicate separately from Cheungkongella, a position not supported by any known source)
17. Hou et al. 2017, p. 252
18. Caron et al. 2010, p. 2

Works cited

• Caron, J.; Conway Morris, S.; Shu, D.; Soares, D. (2010). Soares, Daphne (ed.). "Tentaculate fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) interpreted as primitive deuterostomes". PLOS ONE. 5 (3): e9586. Bibcode:2010PLoSO...5.9586C. doi:10.1371/journal.pone.0009586. PMC 2833208. PMID 20221405.
• Chen, Jun-Yuan (2011). "The origins and key innovations of vertebrates and arthropods". Palaeoworld. 20: 275–278. doi:10.1016/j.palwor.2011.07.002.
• Chen, Jun-Yuan; Huang, Di-Ying; Peng, Qing-Qing; Feng, Man (8 July 2003). "The first tunicate from the Early Cambrian of South China". Proceedings of the National Academy of Sciences of the United States of America. 100 (14): 8314–8318. doi:10.1073/pnas.1431177100. PMC 166226.
• Conway Morris, Simon (2006). "Darwin's dilemma: the realities of the Cambrian 'explosion'". Philosophical Transactions of the Royal Society B. 361: 1069–1083. doi:10.1098/rstb.2006.1846. PMC 1578734.
• Gee, Henry (2018). Across the Bridge: Understanding the Origin of the Vertebrates. The University of Chicago Press.
• Li, Yujing; Dunn, Frances S.; Murdock, Duncan J.E.; Guo, Jin; Rahman, Imran A.; Cong, Peiyun (10 May 2023). "Cambrian stem-group ambulacrarians and the nature of the ancestral deuterostome". Current Biology. 33: 2359–2366. doi:10.1016/j.cub.2023.04.048. PMID 37167976. S2CID 258592223. Retrieved 11 May 2023.
• Hou, Xian-Guang; Bergström, Jan; Ma, Xiao-Ya; Zhao, Jie (2006). "The Lower Cambrian Phlogites Luo & Hu Re-Considered". GFF. 128 (1): 47–51. doi:10.1080/11035890601281047.
• Hou, Xian-guang; Siveter, David J.; Siveter, Derek J.; Aldridge, Richard J.; Cong, Pei-yun; Gabbott, Sarah E.; Ma, Xiao-ya; Purnell, Mark A.; Williams, Mark (2017). The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life (2 ed.). Wiley Blackwell. ISBN 9781118896389.
• Shu, D. (2008). "Cambrian explosion: Birth tree of animals". Gondwana Research. 14 (1–2): 219–240. doi:10.1016/j.gr.2007.08.004.
• Shu, D.-G.; Chen, L.; Han, J.; Zhang, X.-L. (24 May 2001). "An Early Cambrian tunicate from China". Nature. 411 (6836): 472–473. doi:10.1038/35078069. PMID 11373678.
• 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. 277: 165–174. doi:10.1098/rspb.2009.0646. PMC 2842668.
• Zhang, Zhifei; Shu, Degan; Han, Jian; Liu, Jianni (2006). "New data on the rare Chengjiang (Lower Cambrian, South China) linguloid brachiopod Xianshanella haikouensis". Journal of Paleontology. 80 (2): 203–211. doi:10.1666/0022-3360(2006)080[0203:NDOTRC]2.0.CO;2.
• Zhuravlev, A. Yu. (2015). "The Early History of the Metazoa: a Paleontologist's Viewpoint". Biology Bulletin Reviews. 5 (5): 415–461. doi:10.1134/S2079086415050084.

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