Amiskwia
| Amiskwia Temporal range:
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| Fossil of Amiskwia sagittiformis from the Burgess Shale | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Total group: | Gnathifera |
| Genus: | †Amiskwia Walcott, 1911 |
| Type species | |
| Amiskwia sagittiformis Walcott, 1911
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| Species | |
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Amiskwia is a genus of soft-bodied
Etymology
The scientific name Amiskwia sagittiformis derives from the Cree amiskwi, "beavertai", a name of various objects in Yoho National Park, and from the Latin sagitta ("arrow") and formis ("shape"), in reference to the general appearance of the animal. "Sinica", of A. sinica, refers to that species' origin from China.
Description
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Known specimens of Amiskwia vary in length from 7.4 to 31.3 millimetres (0.29 to 1.23 in) and in width from 0.5 to 5.5 millimetres (0.020 to 0.217 in). The body was somewhat flattened. The head had a pair of tentacles that emerged from the midline of the head. The tentacles had a relatively thick base and tapered to a point. Along the sides of the trunk were a pair of lateral fins, which were around one third of the total body length. The trunk terminated with a flat, rounded caudal fin. The gut was straight, and ran from the mouth to the anus, which was located on the underside of the body near the caudal fin. Within the mouth is a pair of semi-circular structures, described as "jaws" each bearing 8-10 conical spikes, which increased in size away from the midline of the structure. Two other structures, dubbed the "dorsal plate" and "ventral plate", are also present in the mouth.[1]
Phylogeny
The following dendrogram shows the evolutionary relationships of Amiskwia as in Park et al. 2024.[4]
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- a A yet undescribed chaetognath, as of January 2024, from Sirius Passet
Ecology
Amiskwia was likely a freely swimming (nektonic) organism that was either a predator or a scavenger.[1]
History of research
Amiskwia was originally categorized by
Two studies published in 2019 redescribed Amiskwia. Vinther and Parry (2019) argued that Amiskwia was a stem-group chaetognath,[2] while Caron and Cheung (2019) suggested that the organism was a total group gnathiferan, based on the presence of gnathiferan-like jaws and ventral plates within the mouth. Its precise affinity within this group is difficult to resolve, they suggested that if it fell in the stem lineage of any extant phylum then it would be a gnathostomulid.[1] A 2022 study supported a stem-chaetognath interpretation, suggesting that gnathiferan-like jaws were lost in the ancestor of chaetognaths.[3] A 2024 study again supported a stem-chaetognath position.[4]
See also
References
- ^ PMID 31069273.
- ^ S2CID 72332845.
- ^ S2CID 252747552.
- ^ PMID 38170772.
- ^ S2CID 84554285.
- S2CID 133486523.
- ^ Kasatkina, A. P. 1982. Ŝetinkočelustnyje morej SSSR i sopredel'nyh vod.
136 pp. Nauka, Leningrad.
- Cited in Doguzhaeva, L. A.; Mutvei, H.; Mapes, R. H. (2002). "Chaetognath grasping spines from the Upper Mississippian of Arkansas (USA)" (PDF). Acta Palaeontologica Polonica. 47 (3): 421–430. Retrieved 2007-08-19.
External links
- "Amiskwia sagittiformis". Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. Archived from the original on 2020-11-12. Retrieved 2023-01-21.
- Graphic of Amiskwia in motion