The Burgess Shale

Peronochaeta dubia

A tiny, slender bristleworm

Taxonomy:

Peronochaeta dubia (ROM 61133). Complete specimen associated with an indeterminate fossil (top right). Specimen length = 8 mm. Specimen dry – polarized light. Walcott Quarry.

© ROYAL ONTARIO MUSEUM. PHOTO: JEAN-BERNARD CARON

Kingdom: Animalia
Phylum: Annelida
Class: Unranked clade (stem group polychaete)
Affinity:

Peronochaetabears some resemblance to modern polychaetes but it cannot be placed in any extant group (Conway Morris, 1979) suggesting a position as a stem-group polychaete (Eibye-Jacobsen, 2004).

Species name: Peronochaeta dubia
Described by: Walcott
Description date: 1911
Etymology:

Peronochaeta – from the Greek perone, “needle,” and khait, “long hair,” in reference to its bristles.

dubia – from the Latin dubius, “uncertain,” presumably reflecting Walcott’s uncertainty regarding his original classification of this worm as Canadia.

Type Specimens: Lectotype – UNSM 83936a; paralectotype – UNSM 83936d, 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:

This annelid worm was originally described as a species of Canadia by Charles Walcott (1911). When Simon Conway Morris (1979) re-examined these fossils, he concluded that the differences between this species and Canadia were too great to be contained within a single genus, and erected the new genus Peronochaeta.

Description:

Morphology:

This worm reached one to two centimetres in length, but its body is only 1 mm wide, or 2 mm wide, if its spines (setae) are included. The worm has approximately 25 segments, each bearing a pair of short lateral projections called parapodia. These are simple (uniramous) and the setae are short. A straight gut runs the length of its body. A pair of tentacles appears to be preserved on the sides of the head, although due to the small size and poor preservation, it is difficult to assert this with confidence.

Abundance:

Peronochaeta was considered one of the rarest annelids from the Burgess Shale but additional material has now been collected from the Walcott Quarry representing 0.03% of the specimens counted in the community (Caron and Jackson, 2008).

Maximum Size:
20 mm

Ecology:

Life habits: Endobenthic, Epibenthic, Mobile
Feeding strategies: Carnivorous
Ecological Interpretations:

On account of the scarcity of material, the ecology of this animal is difficult to ascertain. It may have been a scavenger, and its setae probably assisted in locomotion and perhaps even in burrowing.

References:

Bibliography:

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. 1979. Middle Cambrian Polychaetes from the Burgess Shale of British Columbia. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 285(1007): 227-274.

EIBYE-JACOBSEN, D. 2004. A reevaluation of Wiwaxia and the polychaetes of the Burgess Shale. Lethaia, 37(3): 317-335.

WALCOTT, C. D. 1911. Middle Cambrian annelids. Smithsonian Miscellaneous Collections, 57(2): 109-144.

Other Links:

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