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Xanioascus canadensis

A sac-like comb-jelly with 24 comb-rows

Image of Xanioascus canadensis.

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Xanioascus canadensis (ROM 43190) – Part (left column) and counterpart (right column). Nearly complete specimen, preserved laterally with the presumed oral region at the end of the wider region. Specimen length = 75 mm. Specimen dry – direct light (top row), wet – polarized light (bottom row). Collins Quarry on Mount Stephen.

© Royal Ontario Museum. Photos: Jean-Bernard Caron

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Unranked clade (stem group ctenophores)


Xanioascus is regarded as a very primitive ctenophore, possibly representing a stem-group member (Conway Morris and Collins, 1996).

Species name:

Xanioascus canadensis

Described by:

Conway Morris and Collins

Description date:



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.

Type Specimens:

Holotype –ROM43186 in the Royal Ontario Museum, Toronto, Canada.

Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

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Middle Cambrian, Glossopleura Zone (approximately 505 million years ago).

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Principal localities:

The Collins Quarry on Mount Stephen.

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History of Research

Brief history of research:

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.

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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.

Maximum size:

125 mm

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Life habits:

Nektonic, mobile

Feeding strategies:


Ecological Interpretations:

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.

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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.

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