The Burgess Shale

Fasciculus vesanus

Reconstruction of Fasciculus vesanus.

© Marianne Collins

Taxonomy:

Class: Unranked clade (stem group ctenophores)
Remarks:

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

Species name: Fasciculus vesanus
Described by: Simonetta and Delle Cave
Description date: 1978
Etymology:

Fasciculus – from the Latin fasciculus, “a bundle,” in reference to the large number of comb-rows.

vesanus – from the Latin vesanus, “wild,” in reference to the unusual morphology of this animal.

Type Specimens: Holotype – UNSM 202151 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Walcott discovered the single known specimen of this species in 1917, but it was not described, albeit briefly, until about 60 years later (Simonetta and Delle Cave, 1978). The specimen was redescribed in more detail by Conway Morris and Collins in 1996.

Description:

Morphology:

Fasciculus is apparently dome-shaped but the overall outline of this animal is unknown since the only known specimen of this species is broken along the widest side. The oral region is unknown. There are two sets of rows which are thought to be bilaterally symmetrical, giving a roughly bilateral symmetry to the entire organism. One set has 16 comb-rows, the other about 64, for a total of 80 comb-rows. Two, perhaps four lobate internal organs, roughly parallel to the margins, are present. These organs are made of imbricated elements and are difficult to identify with certainty, but they may correspond to feeding tentacles.

Abundance:

This species is extremely rare – one specimen is known.

Maximum Size:
114 mm

Ecology:

Ecological Interpretations:

The presence of comb-rows suggests the animal was an active swimmer. Its mode of feeding is more conjectural as the mouth region is not preserved. Potential tentacles however, could imply that this animal was a predator, or a suspension feeder, feeding on small organisms or food particles present in the water column.

References:

CONWAY MORRIS, S. AND D. H. 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.

SIMONETTA, A. M. AND L. DELLE CAVE. 1978. Notes on new and strange Burgess Shale fossils (Middle Cambrian of British Columbia). Atti della Società Toscana di Scienze Naturali, Serie A, 85: 45-49.

Other Links:

None

Xanioascus canadensis

Reconstruction of Xanioascus canadensis.

© MARIANNE COLLINS

Taxonomy:

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:

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

Ctenorhabdotus capulus

Reconstruction of Ctenorhabdotus capulus.

© Marianne Collins

Taxonomy:

Class: Unranked clade (stem group ctenophores)
Remarks:

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

Species name: Ctenorhabdotus capulus
Described by: Conway Morris and Collins
Description date: 1996
Etymology:

Ctenorhabdotus – from the Greek ktenos, “comb,” and rhabdotos, “striped,” in reference to the pronounced striped-like appearance of the comb-rows.

capulus – from the Latin capulus, “a handle,” in reference to the prominent aboral capsule-like element.

Type Specimens: Holotype –ROM50822 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott and Raymond Quarries on Fossil Ridge.

History of Research:

Brief history of research:

Ctenorhabdotus capulus was described by Conway Morris and Collins in 1996 and no additional studies have been published since then.

Description:

Morphology:

Ctenorhabdotus is ovoid in shape and bears 24 comb-rows. The top (aboral) and bottom (oral) surfaces are relatively flat. The comb-rows are organised in 8 sets of three, with the central row being much shorter than the two flanking ones. Each group of three comb rows converges towards the aboral side to form 8 strands. The oral region is well developed with an undulating margin. There is a small capsule-like structure on the aboral side of the animal which is thought to include an apical organ and statocysts.

Abundance:

Ctenorhabdotus is rare, known from about two dozen specimens, mostly from the Raymond Quarry. In the Walcott Quarry, this species comprises only 0.01% of the specimens counted (Caron and Jackson, 2008).

Maximum Size:
70 mm

Ecology:

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:

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

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