The Burgess Shale

Xanioascus canadensis

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

Reconstruction of Xanioascus canadensis.

© MARIANNE COLLINS

Taxonomy:

Kingdom: Animalia
Phylum: Ctenophora
Class: Unranked clade (stem group ctenophores)
Remarks:

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: 1996
Etymology:

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.

Age & Localities:

Period:
Middle Cambrian, Glossopleura Zone (approximately 505 million years ago).
Principal localities:

The Collins Quarry on Mount Stephen.

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.

Description:

Morphology:

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.

Abundance:

Only 8 specimens of this species are known.

Maximum Size:
125 mm

Ecology:

Life habits: Mobile, Nektonic
Feeding strategies: Unknown
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.

References:

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.

Other Links:

None