Amiskwia is a genus of soft-bodied marine animals known from fossils of the Middle Cambrian Lagerstätten both in the Burgess Shale in British Columbia, Canada and the Maotianshan shales of Yunnan Province, China. It is interpreted as a member of the clade Gnathifera sensu lato or as a basal cucullophoran.
:<small>A yet undescribed chaetognath, as of January 2024, from Sirius Passet</small>
Ecology
Amiskwia was likely a freely swimming (nektonic) organism that was either a predator or a scavenger. Conway Morris, on re-examining of the Burgess Shale fauna in the 1970s, described it as being the single known species in an otherwise unknown phylum, given that it has two tentacles near its mouth, rather than the characteristic single tentacle of true nemerteans. (Nemerteans do not have a single tentacle. However, a pair of antero-lateral tentacles is present in two of the many genera of pelagic nemerteans. Nemerteans do have a single eversible—normally internal—proboscis, which when everted could resemble an anterior median tentacle if fossilized. Whether retracted or everted, the proboscis is the only structure in pelagic nemerteans likely to fossilize, as it is the only structure with substantial connective tissue and muscle. The body wall has almost no muscle or connective tissue and is exceedingly unlikely to fossilize; hence, a pelagic nemertean fossil would be only the proboscis). while this is also true of the nemerteans, these organisms lack a coelom and are thus unlikely to fossilise. He goes on to argue that the absence of cuticle is characteristic of the chaetognaths; whilst teeth would be expected, a similar fossil, Wiwaxia, shows such structures in only 10% of the expected instances, and anomalocaridids are often found detached from their mouthparts, so the absence may be taphonomic rather than genuine. The absence of spines could simply mean that the fossils represent young organisms — or that later chaetognath evolution involved paedomorphosis.
Two studies published in 2019 redescribed Amiskwia. Vinther and Parry (2019) argued that Amiskwia was a stem-group chaetognath, 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. A 2024 study again supported a stem-chaetognath position.