Biology:Sunellidae
Sunellidae is a family of bivalved arthropods known from the Cambrian period.[1]
History of study
Sunellidae was originally made to include three genera: Sunella, Chiella and Luella but later the latter two where synonymized with Sunella. Later two other genera, Jinningella &and Combinivalvula were described and the definition of Sunellidae was strictened by adding the additional defining feature, the possession of an anterodorsal sulcus. In 2021 one species of Sunella, S. bispinata was moved to the genus Caudicaella.[2] It was assigned to Isoxyida in 2025.[1]
Liu et al, 2026 found sunellids to be basal members of Deuteropoda,[3]; Zhai et al. 2026 found them to be crown-group pancrustaceans, closely related to ostracods.[4]
Distribution
Sunellidae have been found in the Chengjiang biota (exact locality cannot be determined) [5](dated to no older than 518 Ma [6]),[5] the Guojiaba formation ( tentatively assigned to Cambrian stage 3),[5][7] the Qingjiang biota (dated to ~518 ma)[8] and the Shuijingtuo Formation (dated to ~526.5 Ma[9])[2] all of which are in China. Various more poorly documented formations also yield Sunellids. Caudicaella aff. bispinata specimens are also known from the Heatherdale Formation in Australia.[10]
Preservation
Usually the soft anatomy of sunellids is not preserved but a few examples of soft part preservation (only twenty-two times in Sunella cf. shensiella and six in Combinivalvula chenjiangensis) have been recorded in Combinivalvula chenjiangensis and Sunella cf. shensiella.[5]
Anatomy
Sunellids have a roughly semicircular carapace and have anterior and posterior carndinal spines.[5] They are distinguished from other similar arthropods by the presence of an anterodorsal sulcus (a feature shared by the unrelated bradoriids).[1][5][2] Probable sexual dimorphism has been observed in Sunella.[5]
Phylogeny
After Liu et al. 2026:[3]
| Panarthropoda |
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Cladogram of bayesian analysis after Zhai et al. 2026, with Sunella as crown-group pancrustacean:[4]
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References
- ↑ 1.0 1.1 1.2 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. https://doi.org/10.1080/08912963.2025.2529395.
- ↑ 2.0 2.1 2.2 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.
- ↑ 3.0 3.1 Liu, Cong; Pates, Stephen; Zhang, Mingjing; Wu, Yu; Ma, Jiaxin; Fu, Dongjing; Zhang, Xingliang (2026-03-21). "3D morphology of the Cambrian bivalved arthropod Sunella informs about head segmentation, arthrodization, and arthropodization" (in en). Communications Biology. doi:10.1038/s42003-026-09909-z. ISSN 2399-3642. https://www.nature.com/articles/s42003-026-09909-z.
- ↑ 4.0 4.1 Zhai, Dayou; Mai, Huijuan; Jin, Changfei; Zhang, Caixia; Hou, Xianguang (2026-08-24). "The Cambrian crown-group pancrustacean Sunella chimera sp. nov. with raptorial anteriormost appendages" (in en). Communications Biology. doi:10.1038/s42003-026-10772-1. ISSN 2399-3642. https://www.nature.com/articles/s42003-026-10772-1.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Zhang, Xingliang; Shu, Degan (November 2007). "Soft anatomy of sunellid arthropods from the Chengjiang Lagerstutte, Lower Cambrian of southwest China" (in en). Journal of Paleontology 81 (6): 1412–1422. doi:10.1666/06-031R.1. ISSN 0022-3360. Bibcode: 2007JPal...81.1412Z. https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/soft-anatomy-of-sunellid-arthropods-from-the-chengjiang-lagerstutte-lower-cambrian-of-southwest-china/BED17370D684AD13A006594258A9D643.
- ↑ Yang, Chuan; Li, Xian-Hua; Zhu, Maoyan; Condon, Daniel J.; Chen, Junyuan (2018-03-15). "Geochronological constraint on the Cambrian Chengjiang biota, South China" (in en). Journal of the Geological Society 175 (4): 659–666. doi:10.1144/jgs2017-103. ISSN 0016-7649. Bibcode: 2018JGSoc.175..659Y. https://chooser.crossref.org/?doi=10.1144%2Fjgs2017-103.
- ↑ 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" (in en). Journal of Marine Science and Engineering 13 (6): 1175. doi:10.3390/jmse13061175. Bibcode: 2025JMSE...13.1175T. 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.
- ↑ Fu, Dongjing; Tong, Guanghui; Dai, Tao; Liu, Wei; Yang, Yuning; Zhang, Yuan; Cui, Linhao; Li, Luoyang et al. (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. https://www.science.org/doi/10.1126/science.aau8800.
- ↑ 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. doi:10.1016/j.palaeo.2023.111477. ISSN 0031-0182. Bibcode: 2023PPP...61611477Y. https://www.sciencedirect.com/science/article/pii/S0031018223000950.
- ↑ 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. Bibcode: 2025Palae..3400882C. https://www.sciencedirect.com/science/article/pii/S1871174X24001161.
Wikidata ☰ Q136364196 entry
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