Reconstruction of Fasciculus vesanus.
© Marianne Collins
Fasciculus is regarded as a very primitive ctenophore, possibly representing a stem-group member (Conway Morris and Collins, 1996).
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.
Burgess Shale and vicinity: none.
Other deposits: none.
The Walcott Quarry on Fossil Ridge.
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.
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.
This species is extremely rare – one specimen is known.
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.
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.
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