Home > Canadia spinosa
3D animation of Canadia spinosa.
Animation by Phlesch Bubble © Royal Ontario Museum
3D model of Canadia spinosa.
Animation by Phlesch Bubble © Royal Ontario Museum
Reconstruction of Canadia spinosa.
© Marianne Collins
Canadia spinosa (ROM 56972). Complete specimen showing parapodia, setae and tentacles. Approximate specimen length = 32 mm. Specimen dry – direct light (left), wet – direct light (middle), wet – polarized light (left). Walcott Quarry.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Canadia spinosa (ROM 61145). Complete specimen showing parapodia, setae, gills and tentacles. Approximate specimen length = 30 mm. Specimen wet – direct light (left images), wet – polarized light (right images). Walcott Quarry.
© Royal Ontario Museum. Photos: Jean-Bernard Caron
Canadia spinosa (USNM 57654) – Lectotype. Complete specimen showing parapodia, setae and tentacles (right). Approximate specimen length = 28 mm. Specimen dry – polarized light (left); wet – direct light (right). Walcott Quarry.
© Smithsonian Institution – National Museum of Natural History. Photos: Jean-Bernard Caron
Canadia was briefly compared to modern chrysopetalids (Family: Palmyridae) but the similarities were thought to be too general to allow the inclusion of this species to this group (Conway Morris, 1979). Canadia is now regarded as a stem-group polychaete (Eibye-Jacobsen, 2004).
Canadia – from Canada, the country where the Burgess Shale is located.
spinosa – from the Latin spinosus, “full of spines,” reflecting its spiny appearance.
Burgess Shale and vicinity: none.
Other deposits: One specimen known from the Spence Shale (Middle Cambrian of Utah) and described as Canadia sp. (Robison, 1969).
The Walcott Quarry on Fossil Ridge.
Walcott (1911) described two different species of Canadia (C. setigera and C. spinosa) in his initial census of the Burgess Shale, and a more detailed description was produced from his notes after his death by Resser (Walcott, 1931) adding several additional species (C. grandis, C. irregularis, C. sparsa, C. dubia, and C. simplex). Conway Morris (1979) synonymised C. irregularis and C. grandis with C. spinosa, while the other species have all been reinterpreted as different genera. Nick Butterfield (1990) succeeded in isolating individual scales by dissolving fossils in acid. These scales were compared with the sclerites of Wiwaxia, suggesting a possible affinity between the two taxa. Wiwaxia is now regarded as a primitive mollusc (Caron et al., 2006) implying the scales of Canadia and sclerites of Wiwaxia are probably convergent. Like Burgessochaeta, Canadia has proven useful in calculating the extent of decay in fossil assemblages (Caron and Jackson, 2006).
Canadia is a bristled worm around 2 to 4 cm long and slightly dorsoventrally flattened. A long pair of smooth, tentacles protrudes from the front of its head. The variation in shape seen among these tentacles suggests that the organism could contract and extend them. The rest of the body consists of 20 to 22 trunk segments, each bearing a pair of lateral projections called parapodia. On the first segment the parapodia are simple (uniramous), while all the other segments have biramous parapodia (divided into two sections). All parapodia bear bristles called setae. In the second segment through to the last segment they form two main bundles, the notosetae (dorsal) and the neurosetae (lateral). Gills (branchiae) are situated between these two bundles of setae. The notosetae cover the organism asymmetrically, with the longest, widest setae closest to the midline. The lateral surface of the larger setae is serrated, and all the setae bear a finely spaced patterning of ridges, which may have given Canadia an iridescent lustre in life (Parker, 1998). The animal had a straight gut, and an eversible soft proboscis.
Canadia is relatively rare in the Walcott Quarry representing only 0.05% of the specimens counted in the community (Caron and Jackson, 2008).
Canadia probably lived close to the seafloor and could have swum by using its bristle-fans as paddles and by undulating its body. It would have used its tentacles primarily as sensory organs, and its proboscis for feeding on live or dead organisms.
BUTTERFIELD, N. J. 1990. A reassessment of the enigmatic Burgess Shale fossil Wiwaxia corrugata (Matthew) and its relationship to the polychaete Canadia spinosa Walcott. Paleobiology, 16(3): 287-303.
CARON, J.-B. AND D. A. JACKSON. 2006. Taphonomy of the Greater Phyllopod Bed Community, Burgess Shale. PALAIOS, 21: 451-465.
CARON, J.-B., A. H. SCHELTEMA, C. SCHANDER, AND D. RUDKIN. 2006. A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale. Nature, 442: 159-163.
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: 317-335.
PARKER, A. R. 1998. Colour in Burgess Shale animals and the effect of light on evolution in the Cambrian. Proceedings of the Royal Society of London, Biological Sciences. 265: 967-972.
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WALCOTT, C. D. 1911. Middle Cambrian annelids. Smithsonian Miscellaneous Collections, 57(2): 109-144.
WALCOTT, C. 1931. Addenda to descriptions of Burgess Shale fossils. Smithsonian Miscellaneous Collections, 85(3): 1-46.