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Fasciculus vesanus

A very rare comb-jelly with two sets of comb-rows

Reconstruction of Fasciculus vesanus.

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Reconstruction of Fasciculus vesanus.

© Marianne Collins

Media 1 of 2 for Fasciculus vesanus 2D Model
Media 2 of 2 for Fasciculus vesanus Photo

Taxonomy

Kingdom:

Animalia

Phylum:

Ctenophora

Class:

Unranked clade (stem group ctenophores)

Affinity:

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.

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Age

Period:

Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).

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Localities

Principal localities:

The Walcott Quarry on Fossil Ridge.

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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.

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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

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Ecology

Life habits:

Nektonic, mobile

Feeding strategies:

Carnivorous?, suspension feeder

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.

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References

Bibliography:

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

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