Xanioascus is regarded as a very primitive ctenophore, possibly representing a stem-group member (Conway Morris and Collins, 1996).
Xanioascus – from the Greek xanion, “comb,” in reference to the shape and presence of comb-rows, and askos, “a leather bag used as a bottle.”
canadensis – from Canada, the country where the Burgess Shale is located.
Burgess Shale and vicinity: none.
Other deposits: none.
The Collins Quarry on Mount Stephen.
Xanioascus canadensis was described by Conway Morris and Collins in 1996 from fossils discovered by the Royal Ontario Museum at a new locality on Mount Stephen; no additional studies have been published since then.
Xanioascus is bag-like in overall shape and bears 24 comb-rows. The comb-rows are well developed and extend close to the presumably large, but poorly preserved, mouth area. A distinctive feature of this species is the presence of ovoid structures within the body, but their identity remains speculative.
Only 8 specimens of this species are known.
The presence of comb-rows suggests the animal was an active swimmer. Its mode of feeding is more conjectural as the mouth is not well preserved and there is no evidence of tentacles.
CONWAY MORRIS, S. AND D. COLLINS. 1996. Middle Cambrian ctenophores from the Stephen Formation, British Columbia, Canada. Philosophical Transactions of the Royal Society of London, Series B, 351: 279-308.