Isoxyida
| Isoxyida Temporal range:
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| Restoration of Isoxys volucris | |
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| Restoration of Surusicaris elegans | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Order: | †Isoxyida Simonetta & Delle Cave, 1975 |
| Family: | †Isoxyidae Vogdes, 1893 |
| Genera | |
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Isoxyids are members of the order Isoxyida and the family Isoxyidae, a group of basal arthropods that existed during the Cambrian period.
Description
They are considered to be one of the most basal lineages of arthropods, with a combination of features seen in both stem-group arthropods, as well as more advanced taxa. They are often defined by their semicircular bivalved carapaces, long raptorial appendages, and their large, spherical eyes. Currently only two genera have been accepted to be members of this family. These being Isoxys, which has an almost cosmopolitan distribution, and Surusicaris, which is known from the Burgess shale site in British Columbia. These arthropods are thought to have been predators, hunting soft-bodied prey in either the water column, or close to the seabed.[1][2][3]
Taxonomy
The true classification of the isoxyids has been somewhat controversial. Although they are often regarded as basal arthropods, where they actually fit into the arthropod family tree has been contested. Originally, it was thought that Isoxys was related to another bivalved arthropod from the Cambrian, Tuzoia, due to the similar aspects of their carapaces. However, a study in 2022 found that Tuzoia to belong to the hymenocarina grouping, and that it was not closely related to the isoxyids. Currently the group has been placed into the Deuteropoda a proposed clade of arthropods whose members are distinguished by an anatomical reorganization of the head region, including the appearance of a differentiated first appendage pair (the 'deutocerebral' pair), a multisegmented head, and a hypostome/labrum complex.[4][5][6]
References
- ^ Aria, Cédric; Caron, Jean-Bernard (2015-06-03). Friedman, Matt (ed.). "Cephalic and Limb Anatomy of a New Isoxyid from the Burgess Shale and the Role of "Stem Bivalved Arthropods" in the Disparity of the Frontalmost Appendage". PLOS ONE. 10 (6): e0124979. Bibcode:2015PLoSO..1024979A. doi:10.1371/journal.pone.0124979. ISSN 1932-6203. PMC 4454494. PMID 26038846.
- ^ Vannier, J.; Garcia-Bellido, C.; Hu, X.; Chen, L. (Jul 2009). "Arthropod visual predators in the early pelagic ecosystem: evidence from the Burgess Shale and Chengjiang biotas". Proceedings: Biological Sciences. 276 (1667): 2567–2574. doi:10.1098/rspb.2009.0361. ISSN 0962-8452. PMC 2686666. PMID 19403536.
- ^ Pates, Stephen; Daley, Allison C.; Legg, David A.; Rahman, Imran A. (2021-06-30). "Vertically migrating Isoxys and the early Cambrian biological pump". Proceedings of the Royal Society B: Biological Sciences. 288 (1953): 20210464. doi:10.1098/rspb.2021.0464. PMC 8220267. PMID 34157876.
- ^ Ortega-Hernández, Javier (2016), "Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848", Biol. Rev., 91 (1): 255–273, doi:10.1111/brv.12168, PMID 25528950, S2CID 7751936
- ^ Ma, Jiaxin; Lin, Weiliang; Liu, Cong; Sun, Ao; Wu, Yu; Wu, Yuheng; Fu, Dongjing (January 2022). "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. Bibcode:2022JGSoc.179..229M. doi:10.1144/jgs2020-229. ISSN 0016-7649. S2CID 236289449.
- ^ 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.