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'''''Cheungkongella''''' is a fossil organism from the ] ], the affinity of which has been the subject of debate. It was announced as a "probable" ],<ref name=Shu2001>{{harvnb|Shu|Chen|Han|Zhang|2001}}</ref> although this affinity was later disputed in a paper announcing the discovery of '']'', also from Chengjiang, as the oldest known tunicate.<ref name=Gee>{{harvnb|Gee|2018|page=99}}</ref> ''Cheungkongella'' has been accepted as a distinct taxon and possible tunicate by multiple workers not involved in its discovery,<ref name=CM2006>{{harvnb|Conway Morris|2006|page=1076}}</ref><ref name=Northcutt>{{harvnb|Northcutt|2012|page=10628}}</ref><ref name=Janvier>{{harvnb|Janvier|2015|page=484}}</ref><ref name=KML>{{harvnb|Kimmig|Meyer|Lieberman|2019|page=172}}</ref> but the dispute remains unresolved.<ref name=Gee /><ref name=Hou>{{harvnb|Hou|Siveter|Siveter|Aldridge|2017|page=256}}</ref> '''''Cheungkongella''''' is a fossil organism from the ] ], the affinity of which has been the subject of debate. It was announced as a "probable" ] while noting the lack of definitive Cambrian fossils from that group.<ref name=Shu2001>{{harvnb|Shu|Chen|Han|Zhang|2001}}</ref> However, this affinity was later disputed in a paper announcing the discovery of '']'', also from Chengjiang, as the oldest known tunicate.<ref name=Gee>{{harvnb|Gee|2018|page=99}}</ref> ''Cheungkongella'' has been accepted as a distinct taxon and possible tunicate by multiple workers not involved in its discovery,<ref name=CM2006>{{harvnb|Conway Morris|2006|page=1076}}</ref><ref name=Northcutt>{{harvnb|Northcutt|2012|page=10628}}</ref><ref name=Janvier>{{harvnb|Janvier|2015|page=484}}</ref><ref name=KML>{{harvnb|Kimmig|Meyer|Lieberman|2019|page=172}}</ref> but the dispute remains unresolved.<ref name=Gee /><ref name=Hou>{{harvnb|Hou|Siveter|Siveter|Aldridge|2017|page=256}}</ref>

==Etymology==
"Cheungkong" is "a metaphor of China" and honors the Cheungkong Scholars Programme's support for the work leading to the fossil's discovery. "Ancestralis" refers to the fossil's possible primitive taxonomic position.<ref name=Shu2001 />


==Description== ==Description==
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] ]


A 2003 paper announcing '']'' as the oldest known tunicate both disputed ''Cheungkongella'''s affinities and proposed that it is a junior synonym of ''Phlogites'', which was though to be a ] at the time<ref name=Shank>{{harvnb|Chen|Huang|Peng|Chi|2003|page=8316}}</ref> A 2003 paper announcing '']'' as the oldest known tunicate both disputed ''Cheungkongella'''s affinities and proposed that it is a junior synonym of '']'', which was though to be a ] at the time<ref name=Shank>{{harvnb|Chen|Huang|Peng|Chi|2003|page=8316}}</ref>


The paper stated that ''Cheungkongella'' is "indistinguishable" from ''Phlogites'', but proceeded to note several differences, most notably the lack of any "obvious" arms in ''Cheungkongella'' despite acknowledging that three or five such arms are a prominent feature of ''Phlogites''. The paper speculated that this is "perhaps because its arms broke off or are covered by rock." The lack of a coiled gut in ''Cheunkongella'' was dismissed by noting that not all specimens of ''Phlogites'' display one.<ref name=Shank /> The paper stated that ''Cheungkongella'' is "indistinguishable" from ''Phlogites'', but proceeded to note several differences, most notably the lack of any "obvious" arms in ''Cheungkongella'' despite acknowledging that three or five such arms are a prominent feature of ''Phlogites''. The paper speculated that this is "perhaps because its arms broke off or are covered by rock." The lack of a coiled gut in ''Cheunkongella'' was dismissed by noting that not all specimens of ''Phlogites'' display one.<ref name=Shank />


The original description of ''Cheungkongella'' noted light dots in the area interpreted as a pharynx that could be gill slits, but stated that the interpretation required confirmation. The ''Shankouclava'' paper suggested that these dots are taphonomic artifacts due to their irregular pattern. However, the paper's other arguments against tunicate affinities were based on newly discovered specimens of ''Phlogites''.<ref name=Shank /> ''Phlogites'' is now known to be a ] that has never been assigned to the tunicates, except as a result of ''Cheungkongella'' being considered a synonym.<ref>{{harvnb|Giribet|Edgecombe|2020|page=105}}</ref><ref>{{harvnb|Hou|Siveter|Siveter|Aldridge|2017|page=252}}</ref> The original description of ''Cheungkongella'' noted light dots in the area interpreted as a pharynx that could be gill slits, but stated that the interpretation required confirmation. The ''Shankouclava'' paper suggested that these dots are taphonomic artifacts due to their irregular pattern. However, the paper's other arguments against tunicate affinities were based on newly discovered specimens of ''Phlogites''.<ref name=Shank /> ''Phlogites'' is now known to be a ], and has never been assigned to the tunicates except as a result of ''Cheungkongella'' being considered a synonym.<ref>{{harvnb|Giribet|Edgecombe|2020|page=105}}</ref><ref>{{harvnb|Hou|Siveter|Siveter|Aldridge|2017|page=252}}</ref>


A responding paper disputing the synonymizaion with ''Phlogites'' provided the image shown on this page in response to criticisms of poor image quality in past publications.<ref name=Shu2005>{{harvnb|Shu|2005|page=2352}}</ref> A responding paper disputing the synonymization with ''Phlogites'' provided the image shown on this page in response to criticisms of poor image quality in past publications.<ref name=Shu2005>{{harvnb|Shu|2005|page=2352}}</ref>


A paper on the affinities of ''Phlogites'' accepted the synonymization, but did not discuss the ''Cheungkongella'' fossil except to note a similar thickness of stem between it and a subset of the new ''Phlogites'' specimens.<ref>{{harvnb|Hou|Bergström|Ma|Zhao|2006|page=47–49}}</ref> The similarity of the lower section has also been noted by workers who consider the two taxa to be separate.<ref name=Shu2008 /><ref>{{harvnb|Caron|Conway Morris|Shu|Soares|2010|page=2}}</ref> A paper on the affinities of ''Phlogites'' accepted the synonymization, but did not discuss the ''Cheungkongella'' fossil except to note a similar thickness of stem between it and a subset of the new ''Phlogites'' specimens.<ref>{{harvnb|Hou|Bergström|Ma|Zhao|2006|page=47–49}}</ref> The similarity of the lower section has also been noted by workers who consider the two taxa to be separate.<ref name=Shu2008 /><ref>{{harvnb|Caron|Conway Morris|Shu|Soares|2010|page=2}}</ref>
Line 38: Line 41:
The resemblance between ''Cheunkongella'' and ''Phlogites'' has been dismissed as "superficial" by a researcher not involved with the discoveries of either of those taxa or of ''Shankcouklava''.<ref name=CM2006 /> Other sources not directly involved in the dispute have recognized both ''Cheungkongella'' (as distinct from ''Phlogites'') and ''Shankouclava'' as possible (if debatable) tunicates,<ref name=Northcutt /><ref name=Janvier /> or recognize ''Cheungkongella'' as a tunicate and ''Shankouclava'' as chordate.<ref name=KML /> The resemblance between ''Cheunkongella'' and ''Phlogites'' has been dismissed as "superficial" by a researcher not involved with the discoveries of either of those taxa or of ''Shankcouklava''.<ref name=CM2006 /> Other sources not directly involved in the dispute have recognized both ''Cheungkongella'' (as distinct from ''Phlogites'') and ''Shankouclava'' as possible (if debatable) tunicates,<ref name=Northcutt /><ref name=Janvier /> or recognize ''Cheungkongella'' as a tunicate and ''Shankouclava'' as chordate.<ref name=KML />


The dispute remains unresolved, as has been noted even by sources that accept or tentatively accept the synonymization.<ref name=Gee /><ref name=Hou /> The dispute remains unresolved, as has been noted by sources that accept or tentatively accept the synonymization.<ref name=Gee /><ref name=Hou />


==References== ==References==
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{{refbegin}} {{refbegin}}
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Latest revision as of 20:27, 24 December 2024

Extinct genus with possible tunicate affinities

Cheungkongella
Temporal range: Cambrian Stage 3, 518 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Restoration of C. ancestralis.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Subphylum: Tunicata
Class: Ascidiacea
Genus: †Cheungkongella
Shu et al., 2001
Type species
†Cheungkongella ancestralis
Shu et al., 2001
Species
  • †C. ancestralis Shu et al., 2001

Cheungkongella is a fossil organism from the lower Cambrian Chengjiang lagerstatte, the affinity of which has been the subject of debate. It was announced as a "probable" tunicate while noting the lack of definitive Cambrian fossils from that group. However, this affinity was later disputed in a paper announcing the discovery of Shankouclava, also from Chengjiang, as the oldest known tunicate. Cheungkongella has been accepted as a distinct taxon and possible tunicate by multiple workers not involved in its discovery, but the dispute remains unresolved.

Etymology

"Cheungkong" is "a metaphor of China" and honors the Cheungkong Scholars Programme's support for the work leading to the fossil's discovery. "Ancestralis" refers to the fossil's possible primitive taxonomic position.

Description

Cheungkongella has a club-shaped body similar to the extant ascidian Styela, with a bucket-shaped main body with thick, tapering stem beneath it. A large oral siphon with short tentacles at the top of the animal leads to a pharynx occupying two-thirds of the main body, with a structure presumed to ben an alimentary canal beneath it. A small cloacal siphon emerges from the side above the transition to the stem.

Classification

Cheungkongella was placed in the class Ascidiacea based on its resemblance Styela. This classification was initially accepted by other workers.

Proposal to synonomize with Phlogites

Cheungkongella ancestralis (left) and Phlogites (right) fossils for comparison
(BT: branching tentacles; CIS: Complex internal organs; Os: Oral siphon; S: Stem; Sp: Simple pharynx; St: Stomach)

A 2003 paper announcing Shankouclava as the oldest known tunicate both disputed Cheungkongella's affinities and proposed that it is a junior synonym of Phlogites, which was though to be a lophophorate at the time

The paper stated that Cheungkongella is "indistinguishable" from Phlogites, but proceeded to note several differences, most notably the lack of any "obvious" arms in Cheungkongella despite acknowledging that three or five such arms are a prominent feature of Phlogites. The paper speculated that this is "perhaps because its arms broke off or are covered by rock." The lack of a coiled gut in Cheunkongella was dismissed by noting that not all specimens of Phlogites display one.

The original description of Cheungkongella noted light dots in the area interpreted as a pharynx that could be gill slits, but stated that the interpretation required confirmation. The Shankouclava paper suggested that these dots are taphonomic artifacts due to their irregular pattern. However, the paper's other arguments against tunicate affinities were based on newly discovered specimens of Phlogites. Phlogites is now known to be a cambroernid, and has never been assigned to the tunicates except as a result of Cheungkongella being considered a synonym.

A responding paper disputing the synonymization with Phlogites provided the image shown on this page in response to criticisms of poor image quality in past publications.

A paper on the affinities of Phlogites accepted the synonymization, but did not discuss the Cheungkongella fossil except to note a similar thickness of stem between it and a subset of the new Phlogites specimens. The similarity of the lower section has also been noted by workers who consider the two taxa to be separate.

The resemblance between Cheunkongella and Phlogites has been dismissed as "superficial" by a researcher not involved with the discoveries of either of those taxa or of Shankcouklava. Other sources not directly involved in the dispute have recognized both Cheungkongella (as distinct from Phlogites) and Shankouclava as possible (if debatable) tunicates, or recognize Cheungkongella as a tunicate and Shankouclava as chordate.

The dispute remains unresolved, as has been noted by sources that accept or tentatively accept the synonymization.

References

  1. Yang et al. 2018
  2. ^ Shu et al. 2001
  3. ^ Gee 2018, p. 99
  4. ^ Conway Morris 2006, p. 1076
  5. ^ Northcutt 2012, p. 10628
  6. ^ Janvier 2015, p. 484
  7. ^ Kimmig, Meyer & Lieberman 2019, p. 172
  8. ^ Hou et al. 2017, p. 256
  9. ^ Shu 2008, p. 230–231
  10. Chen et al. 2003, p. 285
  11. ^ Chen et al. 2003, p. 8316
  12. Giribet & Edgecombe 2020, p. 105
  13. Hou et al. 2017, p. 252
  14. Shu 2005, p. 2352
  15. Hou et al. 2006, p. 47–49
  16. Caron et al. 2010, p. 2

Works cited

Tunicate genera
Tunicata
Appendicularia
(Larvacea)
Fritillariidae
Oikopleuridae
Stolidobranchia
(Pleurogona)¹
Molgulidae
Pyuridae
Styelidae
Thaliacea
Pyrosomatidae
Salpidae
Doliolida
Doliopsidae
Doliolidae
Enterogona¹
    • see below↓
Halocynthia roretzi

Microcosmus sabatieri

Pyrosoma
Enterogona
Aplousobranchia
Clavelinidae
Diazonidae
Didemnidae
Holozoidae
Polycitoridae
Polyclinidae
Protopolyclinidae
Pseudodistomidae
Ritterellidae
Phlebobranchia
Agneziidae
Ascidiidae
Cionidae
Corellidae
Octacnemidae
Perophoridae
Plurellidae
Pycnoclavella diminuta

Didemnum molle

Megalodicopia hians
Tunicate-like fossils
Ediacaran
Cambrian
Later
Khmeriamorpha
Ichnotaxa
Megasiphon thylakos
Taxon identifiers
Cheungkongella
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