The Burgess Shale

Kootenayscolex barbarensis

A small worm with long bristles and tentacles

Kootenayscolex barbarensis, paratype, ROMIP 62972


Kingdom: Animalia
Phylum: Annelida
Higher Taxonomic assignment: Polychaetes
Species name: Kootenayscolex barbarensis

Kootenayscolex bears significant resemblance to modern polychaetes, but is currently considered outside of any extant group. It is currently considered as a stem-group polychaete, as are the other polychaetes from the Burgess Shale (Parry et al. 2016; Nanglu and Caron 2018).

Described by: Nanglu and Caron 2018
Description date: 2018

Kootenay — for Kootenay National Park in British Columbia, Canada, where the Marble Canyon fossil locality is located, and scolex from the Greek word for “worm,” which is a common suffix for polychaetes and reflects their general worm-shaped morphology.

barbarensis — from Barbara Polk Milstein, who is a volunteer at the Royal Ontario Museum and a long-time supporter of Burgess Shale research.

Type Specimens: Holotype ROMIP 64388; paratypes ROMIP 63099.1, and ROMIP 64389-, 64398
Other species:

Burgess Shale and vicinity: none
Other deposits: none

Age & Localities:

Middle Cambrian, Wuliuan Stage, upper part of the Burgess Shale Formation (around 507 million years old)
Principal localities:

Marble Canyon and the Walcott Quarry on Fossil Ridge, British Columbia.

History of Research:

Brief history of research:

This abundant polychaete, was first reported by Caron et al. in 2014 as a species comparable to Burgessochaeta setigera from the Walcott Quarry. Kootenayscolex was formally described as its own genus by Nanglu and Caron in 2018, using hundreds of new specimens discovered from the Marble Canyon fossil site in Kootenay National Park.



Kootenayscolex ranged in size from 1mm-30mm. Its head bore two long sensory structures known as palps, as well as a short medial antenna located between them. As with other polychaetes, its body was divided into a series of segments with the widest segments being in the middle of the body. Up to 25 segments have been observed in this species, each of which possessed a pair of parapodia which are fleshy, lateral outgrowths. From these parapodia extended bristles, known as chaetae, arranged into bundles. The dorsal bundles included up to 12 bristles, while the ventral bundles included up to 16 bristles which were arranged as a wider fan. The last segment of this animal, called the pygidium, was relatively simple and possessed no appendages. The head section, called the prostomium, also possessed a single set of parapodia and chaetae, directly adjacent to the mouth.


Kootenayscolex is the fifth most abundant species at Marble Canyon with 833 specimens (Nanglu et al. 2020).

Maximum Size:
About 3 cm.


Life habits: Nektobenthic
Feeding strategies: Deposit feeder
Ecological Interpretations:

Kootenayscolex has been reconstructed as a deposit feeding organism due to some specimens preserving sediment which filled the gut. This is particularly noticeable in specimens which have an enlarge anterior part of the gut which is nearly the width of the body. The elongate dorsal bristles were likely used for defense against predators, while the ventral bristles would have allowed for movement along the seafloor.


  • NANGLU, K., AND J.-B., CARON. 2018. A new Burgess Shale polychaete and the origin of the annelid head revisited. Current Biology, 28 (2): 319-326.
  • NANGLU, K., CARON, J.-B. and GAINES, R. R. 2020. The Burgess Shale paleocommunity with new insights from Marble Canyon, British Columbia. Paleobiology, 46, 58-81.
  • PARRY, L. A., EDGECOMBE, G. D., EIBYE-JACOBSEN, D., AND J. VINTHER. 2016. The impact of fossil data on annelid phylogeny inferred from discrete morphological characters. Proceedings of the Royal Society B: Biological Sciences283 (1837): 20161378.
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