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{{Short description|Extinct genus of Isoxyid arthropod}}

{{Short description|Extinct genus of Isoxyid arthropod}}

{{Automatic taxobox

{{Automatic taxobox

| fossil_range = {{fossil_range| Cambrian stage 2|Cambrian stage 3|earliest=539}} Some specimens may be as old as 535 ma.

| fossil_range = {{fossil_range| Cambrian stage 2|Cambrian stage 3|earliest=539}} Some specimens may be as old as 535 ma.

| taxon = Sunella

| taxon = Sunella

| authority = Huo, 1965

| authority = Huo, 1965
Line 32: Line 32:

== Distribution ==

== Distribution ==

”Sunella” fossils have been found in the [[Chengjiang biota]] (exact locality cannot be determined;<ref name=”:0″ /> dated to no older than 518 Ma),<ref>{{Cite journal |last1=Yang |first1=Chuan |last2=Li |first2=Xian-Hua |last3=Zhu |first3=Maoyan |last4=Condon |first4=Daniel J. |last5=Chen |first5=Junyuan |date=2018-03-15 |title=Geochronological constraint on the Cambrian Chengjiang biota, South China |url=https://chooser.crossref.org/?doi=10.1144%2Fjgs2017-103 |journal=Journal of the Geological Society |language=en |volume=175 |issue=4 |pages=659–666 |doi=10.1144/jgs2017-103 |bibcode=2018JGSoc.175..659Y |issn=0016-7649 |archive-url=http://web.archive.org/web/20250407225828/https://chooser.crossref.org/?doi=10.1144%2Fjgs2017-103 |archive-date=2025-04-07}}</ref><ref name=”:8″ /> the [[Shuijingtuo formation]] (dated to around 526.5 Ma),<ref>{{Cite journal |last1=Yang |first1=Chuan |last2=Bowyer |first2=Fred T. |last3=Condon |first3=Daniel J. |last4=Li |first4=Xian-Hua |last5=Zhu |first5=Maoyan |date=2023-04-15 |title=New U-Pb age from the Shuijingtuo Formation (Yangtze Gorges area) and its implications for the Cambrian timescale |url=https://www.sciencedirect.com/science/article/pii/S0031018223000950 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=616 |article-number=111477 |doi=10.1016/j.palaeo.2023.111477 |bibcode=2023PPP…61611477Y |issn=0031-0182}}</ref><ref name=”:6″ /><ref name=”:4″ /><ref name=”:2″ /> the [[Qingjiang biota]] (dated to ~518 ma),<ref name=”:9″ />the [[Niutitang formation]] ( generally Meishucunian ([[Cambrian Stage 2]]) to Nangaoan ([[Cambrian Stage 3]]) but may be up to as old as the [[Fortunian]])<ref>{{Cite journal |last=Zhao |first=M.-S. |last2=Wang |first2=Y. |last3=Tian |first3=J. -C. |last4=Lei |first4=L. -F. |date=October 2013 |title=A sedimentary environment analysis of black shales based on fossil assemblage characteristics:A case study of cambrian niutitang formation in Changyang area, western Hubei |url=https://www.researchgate.net/publication/285986380_A_sedimentary_environment_analysis_of_black_shales_based_on_fossil_assemblage_characteristicsA_case_study_of_cambrian_niutitang_formation_in_Changyang_area_western_Hubei |journal=Geology in China |volume=40(5):1484-1492 |via=Researchgate.net}}</ref><ref>{{Cite web |title=Niutitang Formation |url=https://chinalex.geolex.org/formations/Niutitang%20Fm |access-date=2025-09-27 |website=chinalex.geolex.org}}</ref>and the [[Guojiaba formation]] (tentatively assigned to [[Cambrian Stage 3]]),<ref name=”:0″ /><ref>{{Cite journal |last1=Tan |first1=Yineng |last2=Xiao |first2=Xianming |last3=Gao |first3=Ping |last4=Meng |first4=Guangming |last5=Wang |first5=Qiang |last6=Liu |first6=Wei |last7=Feng |first7=Yue |date=2025-06-15 |title=Sedimentary Environment and Organic Matter Enrichment Mechanism of the Lower Cambrian Shale in the Northern Margin of the Yangtze Platform |url=http://discovery.researcher.life/article/sedimentary-environment-and-organic-matter-enrichment-mechanism-of-the-lower-cambrian-shale-in-the-northern-margin-of-the-yangtze-platform/3f062925d9a637a4aec97ad2fa0756b7 |journal=Journal of Marine Science and Engineering |language=en |volume=13 |issue=6 |page=1175 |doi=10.3390/jmse13061175 |bibcode=2025JMSE…13.1175T |doi-access=free }}</ref> all of which are in [[China]].<ref name=”:0″ /><ref name=”:2″ /> Similiar fossils have been found at other formations in [[China]] but they are relatively uncommon and poorly studied and are unable to be confidently assigned to this genus or even [[Sunellidae]].<ref name=”:0″ />

”Sunella” fossils have been found in the [[Chengjiang biota]] (exact locality cannot be determined;<ref name=”:0″ /> dated to no older than 518 Ma),<ref>{{Cite journal |last1=Yang |first1=Chuan |last2=Li |first2=Xian-Hua |last3=Zhu |first3=Maoyan |last4=Condon |first4=Daniel J. |last5=Chen |first5=Junyuan |date=2018-03-15 |title=Geochronological constraint on the Cambrian Chengjiang biota, South China |url=https://chooser.crossref.org/?doi=10.1144%2Fjgs2017-103 |journal=Journal of the Geological Society |language=en |volume=175 |issue=4 |pages=659–666 |doi=10.1144/jgs2017-103 |bibcode=2018JGSoc.175..659Y |issn=0016-7649 |archive-url=http://web.archive.org/web/20250407225828/https://chooser.crossref.org/?doi=10.1144%2Fjgs2017-103 |archive-date=2025-04-07}}</ref><ref name=”:8″ /> the [[Shuijingtuo formation]] (dated to around 526.5 Ma),<ref>{{Cite journal |last1=Yang |first1=Chuan |last2=Bowyer |first2=Fred T. |last3=Condon |first3=Daniel J. |last4=Li |first4=Xian-Hua |last5=Zhu |first5=Maoyan |date=2023-04-15 |title=New U-Pb age from the Shuijingtuo Formation (Yangtze Gorges area) and its implications for the Cambrian timescale |url=https://www.sciencedirect.com/science/article/pii/S0031018223000950 |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=616 |article-number=111477 |doi=10.1016/j.palaeo.2023.111477 |bibcode=2023PPP…61611477Y |issn=0031-0182}}</ref><ref name=”:6″ /><ref name=”:4″ /><ref name=”:2″ /> the [[Qingjiang biota]] (dated to ~518 ma),<ref name=”:9″ />the [[Niutitang formation]] ( generally Meishucunian ([[Cambrian Stage 2]]) to Nangaoan ([[Cambrian Stage 3]]) but may be up to as old as the [[Fortunian]])<ref>{{Cite journal |last=Zhao |first=M.-S. |last2=Wang |first2=Y. |last3=Tian |first3=J. -C. |last4=Lei |first4=L. -F. |date=October 2013 |title=A sedimentary environment analysis of black shales based on fossil assemblage characteristics:A case study of cambrian niutitang formation in Changyang area, western Hubei |url=https://www.researchgate.net/publication/285986380_A_sedimentary_environment_analysis_of_black_shales_based_on_fossil_assemblage_characteristicsA_case_study_of_cambrian_niutitang_formation_in_Changyang_area_western_Hubei |journal=Geology in China |volume=40(5):1484-1492 |via=Researchgate.net}}</ref><ref>{{Cite web |title=Niutitang Formation |url=https://chinalex.geolex.org/formations/Niutitang%20Fm |access-date=2025-09-27 |website=chinalex.geolex.org}}</ref>and the [[Guojiaba formation]] (tentatively assigned to [[Cambrian Stage 3]]),<ref name=”:0″ /><ref>{{Cite journal |last1=Tan |first1=Yineng |last2=Xiao |first2=Xianming |last3=Gao |first3=Ping |last4=Meng |first4=Guangming |last5=Wang |first5=Qiang |last6=Liu |first6=Wei |last7=Feng |first7=Yue |date=2025-06-15 |title=Sedimentary Environment and Organic Matter Enrichment Mechanism of the Lower Cambrian Shale in the Northern Margin of the Yangtze Platform |url=http://discovery.researcher.life/article/sedimentary-environment-and-organic-matter-enrichment-mechanism-of-the-lower-cambrian-shale-in-the-northern-margin-of-the-yangtze-platform/3f062925d9a637a4aec97ad2fa0756b7 |journal=Journal of Marine Science and Engineering |language=en |volume=13 |issue=6 |page=1175 |doi=10.3390/jmse13061175 |bibcode=2025JMSE…13.1175T |doi-access=free }}</ref> all of which are in [[China]].<ref name=”:0″ /><ref name=”:2″ /> Similiar fossils have been found at other formations in [[China]] but they are relatively uncommon and poorly studied and are unable to be confidently assigned to this genus or even [[Sunellidae]].<ref name=”:0″ />

== Preservation ==

== Preservation ==

Latest revision as of 23:37, 6 October 2025

Extinct genus of Isoxyid arthropod

Sunella is an extinct genus of Stem group Cambrian arthropod[2] described by Huo Shicheng in 1965[3][4][5][6][7] as the Type genus of the family Sunellidae.[5][6][4][7] It was assigned to the order Isoxyida by Collantes & Pates, 2025.[2]

Species of Sunella include:

  • †Sunella grandis Huo, 1965[5][4][6][8][9][10] (type species)[5][4][8][11][2](subspecies: †Sunella grandis similis (Cui and Huo, 1990)[6][7])
  • †Sunella nanchengensis Huo, 1965 (may be a sexual dimorph of S. grandis)[5]
  • †Sunella shensiensis Huo, 1965[5]
  • †Sunella cf. shensiella [5](only species where soft anatomy is preserved)[5]
  • †Sunella cf. shensiensis Huo,1965[5]

A species that previously belonged to Sunella, Sunella bispinata,[7] is now included in the genus Caudicaella (Sun et al. 2021)[6][2] as Caudicaella bispinata (Cui and Huo, 1990).[6][2][7] Synonyms include Isoxys bispinata (Zhang et al., 2018)(not to be confused with Isoxys bisipinatus)[2][10] Isoxys sp. (Sun et al. 2021) (for the specimens from the Heatherdale formation, not the Shuijingtuo formation)[10][6][6]

One possible species is Sunella parva (Melnikova, 1988),[3][11] which may be the larval form of a new species of Tuzoia and is generally excluded from Sunella and may need to be assigned to its own genus.[11][5][12][13]It has also been suggested to be a Bradoriid.[11]

In the original description (Huo, 1965), Sunella was described as an arthropod of uncertain affinities ,[2][4][10]later it was considered an Ostracod-like arthropod[5] and then a species of Isoxys along with other Sunellids in Vannier & Chen 2000[10][2], in later studies such as in Sun et al. 2021 it was considered an arthropod of uncertain affinity, though similarities with Isoxys were noted and a relationship with Isoxys was suggested, [6][5] it was not until 2025 that it was assigned to Isoxyida by Collantes & Pates, 2025.[2]

Sunellidae, which Sunella belongs to originally included two other genera, Chiella and Luella,[4] but after Huo & Shu, 1985 Chiella was considered a junior synonym of Sunella and after Zhang & Shu, 2007 Luella considered a probable sexual dimorph of Sunella.[5][14]

Sunella fossils have been found in the Chengjiang biota (exact locality cannot be determined;[5] dated to no older than 518 Ma),[15][8] the Shuijingtuo formation (dated to around 526.5 Ma),[16][7][13][6] the Qingjiang biota (dated to ~518 ma),[9]the Niutitang formation ( generally Meishucunian (Cambrian Stage 2) to Nangaoan (Cambrian Stage 3) but may be up to as old as the Fortunian)[17][1]and the Guojiaba formation (tentatively assigned to Cambrian Stage 3),[5][18] all of which are in China.[5][6] Similiar fossils have been found at other formations in China but they are relatively uncommon and poorly studied and are unable to be confidently assigned to this genus or even Sunellidae.[5]

Usually the only part of Sunella that is preserved is the carapace, but rarely (only twenty-two times in Sunella cf. shensiella and only six in the related Combinivalvula chenjiangensis) soft tissue is also preserved. When this occurs, the carapace usually adopts a “butterfly” position, possibly due to the decay of the adductor muscles that hold it together.[5] Only the soft parts of Sunella cf. shensiella and the related Combinivalvula chenjiangensis (Hou, 1987) have been preserved.[5]

Carapace morphology

[edit]

Sunella grandis has a bivalved[19] roughly semicircular carapace with an anterodorsal sulcus and cardinal spines, a typical bodyplan for a Sunellid, while Sunella cf. shensiella had a more oval shaped carapace, shorter cardinal spines and an anterodorsal sulcus pointing at a slightly lower angle.[5][6] Both species have shorter cardinal spines than Caudicaella bispinata also Caudicaella bispinata had a longer carapace in relation to the height of the carapace relative to S. grandis, otherwise Caudicaella bispinata appears to be more similar to S. grandis and Jinningella communis than S. cf. shensiella.[5][6][10]

S. grandis specimens are typically 6.5-8.5 mm[5][6] and the largest specimen is 15mm which is the largest recorded for a Sunellid.[6][2]

  1. ^ a b “Niutitang Formation”. chinalex.geolex.org. Retrieved 2025-09-27.
  2. ^ a b c d e f g h i j Collantes, Luis; Pates, Stephen (2025). “Isoxys carbonelli and the palaeoenvironmental disparity of Isoxys during Cambrian Stage 3″. Historical Biology. 0: 1–9. doi:10.1080/08912963.2025.2529395. ISSN 0891-2963.
  3. ^ a b Melnikova, L. M. (1988). “Some Bradoriids (Crustacea) from the Bostonian stage of Eastern Transbaikalia”. Paleontol Zh. (Moscow).
  4. ^ a b c d e f Huo, Shicheng (1965). “The Early Cambrian ostracods from Shaanxi and Yunnan”. Acta Palaeontologica Sinica (in Chinese and English). 13 (1965).
  5. ^ a b c d e f g h i j k l m n o p q r s t u v Zhang, Xingliang; Shu, Degan (2007). “Soft anatomy of sunellid arthropods from the Chengjiang Lagerstutte, Lower Cambrian of southwest China”. Journal of Paleontology. 81 (6): 1412–1422. Bibcode:2007JPal…81.1412Z. doi:10.1666/06-031R.1.
  6. ^ a b c d e f g h i j k l m n o Sun, Ao. “Taxonomy and ontogeny of bivalved arthropods from the lower member of the Shuijingtuo Formation, Series 2 and Stage 3, Eastern Three Georges Area, South China”. Acta Palaeontologica Sinica. doi:10.19800/j.cnki.aps.2021019.
  7. ^ a b c d e f Cui, Zhilin; Huo, Shicheng (1990). “New discoveries of Lower Cambrian crustacean fossils from western Hubei”. Acta Palaeontologica Sinica (in Chinese and English). 29(3) 1990: 321-330.
  8. ^ a b c “Chengjiang Maotianshan Shales”. www.fossilmuseum.net. Archived from the original on 9 March 2021. Retrieved 10 September 2015.
  9. ^ a b Fu, Dongjing; Tong, Guanghui; Dai, Tao; Liu, Wei; Yang, Yuning; Zhang, Yuan; Cui, Linhao; Li, Luoyang; Yun, Hao; Wu, Yu; Sun, Ao; Liu, Cong; Pei, Wenrui; Gaines, Robert R.; Zhang, Xingliang (2019-03-22). “The Qingjiang biota—A Burgess Shale–type fossil Lagerstätte from the early Cambrian of South China”. Science. 363 (6433): 1338–1342. doi:10.1126/science.aau8800.
  10. ^ a b c d e f Chen, Fei-Yang; Betts, Marissa J.; Zhang, Zhi-Liang; Brock, Glenn A. (2025-06-01). “The bivalved arthropod Caudicaella aff. bispinata from the Heatherdale Shale (Cambrian Stage 3), South Australia”. Palaeoworld. 34 (3): 100882. doi:10.1016/j.palwor.2024.09.006. ISSN 1871-174X.
  11. ^ a b c d L.m, Melnikova (1998). “REVISION OF SOME CAMBRIAN BRADORIIDS (CRUSTACEA) FROM THE SIBERIAN PLATFORM”. Paleontologicheskii zhurnal. ISSN 0031-031X.
  12. ^ Izquierdo-López, Alejandro; Caron, Jean-Bernard (December 2022). “The problematic Cambrian arthropod Tuzoia and the origin of mandibulates revisited”. Royal Society Open Science. 9 (12) 220933. Bibcode:2022RSOS….920933I. doi:10.1098/rsos.220933. ISSN 2054-5703. PMC 9727825. PMID 36483757.
  13. ^ a b Ma, Jiaxin; Lin, Weiliang; Liu, Cong; Sun, Ao; Wu, Yu; Wu, Yuheng; Fu, Dongjing (6 July 2021). “A new bivalved arthropod from the Cambrian (Stage 3) Qingjiang biota expands the palaeogeographical distribution and increases the diversity of Tuzoiidae”. Journal of the Geological Society. 179 (1) jgs2020–229. doi:10.1144/jgs2020-229.
  14. ^ Huo, S. C.; Shu, D. G. (1985). Cambrian bradoriids from South China (in Chinese). China: Northwest University press.
  15. ^ Yang, Chuan; Li, Xian-Hua; Zhu, Maoyan; Condon, Daniel J.; Chen, Junyuan (2018-03-15). “Geochronological constraint on the Cambrian Chengjiang biota, South China”. Journal of the Geological Society. 175 (4): 659–666. Bibcode:2018JGSoc.175..659Y. doi:10.1144/jgs2017-103. ISSN 0016-7649. Archived from the original on 2025-04-07.
  16. ^ Yang, Chuan; Bowyer, Fred T.; Condon, Daniel J.; Li, Xian-Hua; Zhu, Maoyan (2023-04-15). “New U-Pb age from the Shuijingtuo Formation (Yangtze Gorges area) and its implications for the Cambrian timescale”. Palaeogeography, Palaeoclimatology, Palaeoecology. 616 111477. Bibcode:2023PPP…61611477Y. doi:10.1016/j.palaeo.2023.111477. ISSN 0031-0182.
  17. ^ Zhao, M.-S.; Wang, Y.; Tian, J. -C.; Lei, L. -F. (October 2013). “A sedimentary environment analysis of black shales based on fossil assemblage characteristics:A case study of cambrian niutitang formation in Changyang area, western Hubei”. Geology in China. 40(5):1484-1492 – via Researchgate.net.
  18. ^ Tan, Yineng; Xiao, Xianming; Gao, Ping; Meng, Guangming; Wang, Qiang; Liu, Wei; Feng, Yue (2025-06-15). “Sedimentary Environment and Organic Matter Enrichment Mechanism of the Lower Cambrian Shale in the Northern Margin of the Yangtze Platform”. Journal of Marine Science and Engineering. 13 (6): 1175. Bibcode:2025JMSE…13.1175T. doi:10.3390/jmse13061175.
  19. ^ Castle Jones, Jack; M. Jackquet, Sarah; Chen, Feiyang; J. Betts, Marissa; Zhang, Zhiliang; Anthony Hall, Philip; A. Brock, Glenn; Klaebae, Robert (April 2025). “A new integrated lower Cambrian chronostratigraphy for the Normanville Group, eastern Stansbury Basin, with definition of the oldest small shelly fossil zones in South Australia” (PDF). Australasian Palaeontological Memoirs – via Researchgate.

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