Xanioascus canadensis

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

Reconstruction of Xanioascus canadensis.

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.

Xanioascus canadensis (ROM 43191). Incomplete specimen, detail of the aboral region (i.e., opposite to the mouth) and presence of ovoid bodies. Specimen length = 47 mm. Specimen dry – direct light (left), wet – polarized light (right). Collins Quarry on Mount Stephen.

Taxonomy:

Kingdom: Animalia

Phylum: Ctenophora

Class: Unranked clade (stem group ctenophores)

Species name: Xanioascus canadensis

Remarks:

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

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: Nektonic, Mobile

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.