The Burgess Shale

Stephenoscolex argutus

Stephenoscolex argutus (USNM 83936b) – Holotype. Specimen showing the head (top left) followed by the trunk, which is lined by narrow parapodia and setae. Filamentous structures around the body probably represent cyanobacteria. Specimen length = 32 mm. Specimen dry – direct light (left) and wet – direct light (right). Walcott Quarry.

© SMITHSONIAN INSTITUTION – NATIONAL MUSEUM OF NATURAL HISTORY. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Class: Unranked clade (stem group polychaetes)
Remarks:

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

Species name: Stephenoscolex argutus
Described by: Conway Morris
Description date: 1979
Etymology:

Stephenoscolex – from the Greek scolex, “worm,” and Mount Stephen. Mount Stephen (3,199 m) was named after George Stephen (1829 – 1921), first president of the Canadian Pacific Railway.

argutus – from the Latin argutus, “bright,” in recognition of the shininess of the fossils.

Type Specimens: USNM – 83936b in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA. Paratype –ROM32574 in the Royal Ontario Museum, Toronto, ON, Canada.
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:

Walcott (1911; 1931) included the holotype of this species within Canadia dubia, which Simon Conway Morris, in his 1979 re-examination of Burgess Shale polychaetes, reclassified as Stephenoscolex. Conway Morris found a further partial specimen in the ROMcollections, and further specimens have since been recovered by the ROMbelow the Walcott Quarry. However, this additional material awaits detailed study; since the published description rests on two specimens, it must be treated with caution (Eibye-Jacobsen, 2004).

Description:

Morphology:

The worm has a slim body, around 1 mm wide, reaching around 3 cm in length. Its head bears two pairs of appendages extending from its front and sides. It has around forty further segments, each of which bear simple lateral projections (uniramous) called parapodia. The parapodia each bear around fifteen short and simple setae. Cirri and branchiae are absent.

Abundance:

Stephenoscolex was considered one of the rarest annelids from the Burgess Shale but additional material has now been collected from the Walcott Quarry representing 0.28% of the specimens counted in the community (Caron and Jackson, 2008).

Maximum Size:
32 mm

Ecology:

Ecological Interpretations:

There is little that can confidently be stated about the life habit of this animal, but the pattern of spines suggests that it crept or swum over or in the sediment.

References:

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.

WALCOTT, C. D. 1931. Addenda to descriptions of Burgess Shale fossils. Smithsonian Miscellaneous Collections, 85(3): 1-46.

Other Links:

None

Insolicorypha psygma

Insolicorypha psygma (USNM 198712) – Holotype, part and counterpart. Only known specimen showing the purported head (top) surrounded by a dark stain (probably representing decay fluids), setae, and gut trace. Specimen length = 12 mm. Specimen dry – polarized light (both images). Walcott Quarry.

© Smithsonian Institution – National Museum of Natural History. Photos: Jean-Bernard Caron

Taxonomy:

Class: Unranked clade (stem group polychaetes)
Remarks:

The single specimen (perhaps incomplete, Eibye-Jacobsen, 2004) of this species is too poorly known to allow detailed studies of its affinities.

Species name: Insolicorypha psygma
Described by: Conway Morris
Description date: 1979
Etymology:

Insolicorypha – from the Latin insolitus, “unusual,” and the Greek koryphe, “head,” thus, “unusual head.”

psygma – from the Greek psygma, “fan,” in reference to the fan-like arrangement of the worm’s bristles.

Type Specimens: Holotype –USNM198667 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:

Only a single specimen is known. This was originally interpreted by Conway Morris (1979) as a complete animal with an abnormal head. Eibye-Jacobsen (2004) later suggested that the specimen represented just the rear part of the animal, and that the ragged edge of the torn body wall formed the illusion of a head.

Description:

Morphology:

This tiny worm (12 mm long) had at least 19 segments, each bearing a pair of lateral projections called parapodia. On the first and perhaps second segment the parapodia are simple (uniramous), while all the other segments have biramous parapodia (divided into two sections of unequal lengths). In the third segment through to the last segment, parapodia support two main bundles of setae, the notosetae (on the upper branch) and the neurosetae (on the lower branch). The notosetae are short while the neurosetae are much longer. The branch bearing the neurosetae has three (two dorsal) and one ventral cirri (representing sensory of secretory organs) and is much longer. The purported front end of the animal has an elongate projection (prostomium) divided into two main sections.

Abundance:

Only a single specimen of Insolicorypha is known and comes from the Walcott Quarry.

Maximum Size:
12 mm

Ecology:

Ecological Interpretations:

Insolicorypha probably had a similar mode of life to modern swimming annelids which also have sensory cirri, but the rarity of this species makes it impossible to conclude exactly how the animal fed. The fans of bristles are clear adaptations to swimming, which may contribute to the organism’s rarity in the Burgess Shale, which primarily preserves bottom-dwelling species.

References:

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: 227-274.

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

Other Links:

None

Peronochaeta dubia

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

Class: Unranked clade (stem group polychaete)
Remarks:

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:

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:

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:

None

Canadia spinosa

3D animation of Canadia spinosa.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Class: Unranked clade (stem group polychaetes)
Remarks:

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).

Species name: Canadia spinosa
Described by: Walcott
Description date: 1911
Etymology:

Canadia – from Canada, the country where the Burgess Shale is located.

spinosa – from the Latin spinosus, “full of spines,” reflecting its spiny appearance.

Type Specimens: Lectotype –USNM57654 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

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).

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:

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).

Description:

Morphology:

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.

Abundance:

Canadia is relatively rare in the Walcott Quarry representing only 0.05% of the specimens counted in the community (Caron and Jackson, 2008).

Maximum Size:
45 mm

Ecology:

Ecological Interpretations:

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.

References:

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.

ROBISON, R. A. 1969. Annelids from the Middle Cambrian Spence Shale of Utah. Journal of Paleontology, 43: 1169-1173.

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.

Other Links:

Burgessochaeta setigera

Burgessochaeta setigera (ROM 61042) – Part and counterpart. Complete specimen showing gut contents and fecal material expelled from the anus (black strand visible on the counterpart, right images). Specimen length = 26 mm. Specimen wet – direct light (top row), wet – polarized light (bottom row). Walcott Quarry.

© Royal Ontario Museum. Photos: Jean-Bernard Caron

Taxonomy:

Class: Unranked clade (stem group polychaetes)
Remarks:

Burgessochaeta bears some resemblance to modern polychaetes but it cannot be placed in any extant group (Conway Morris, 1979; Eibye-Jacobsen, 2004) suggesting a position as a stem-group polychaete (Budd and Jensen, 2000).

Species name: Burgessochaeta setigera
Described by: Walcott
Description date: 1911
Etymology:

Burgessochaeta – from Mount Burgess (2,599 m), a mountain peak in Yoho National Park. Mount Burgess was named in 1886 by Otto Klotz, the Dominion topographical surveyor, after Alexander Burgess, a former Deputy Minister of the Department of the Interior. Also from the Latin chaeta, “bristle”, a common suffix for polychaete worms, reflecting spiny structures along their body.

setigera – from the Latin saetula, “small bristle.”

Type Specimens: Lectotype –USNM57650 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:

First reported by Charles Walcott in 1911 and lumped into the genus Canadia (Walcott, 1911), Burgessochaeta was formally described as a separate genus by Simon Conway Morris in his 1979 treatise on the polychaetes of the Burgess Shale. Because it is rather common, Burgessochaeta has proven useful in calculating the extent of decay in fossil assemblages (Caron and Jackson, 2006).

Description:

Morphology:

This slender worm reached lengths of 1.8-4.9 cm (2.9 cm on average). Its width was constant (around 2 mm), except towards either end, where it tapered off. Its head bore a pair of long, smooth tentacles that reached 6 mm in length. The variation in shape seen among these tentacles suggests that the organism could contract and extend them. Its first segment also bears uniramous parapodia (paired single-branch appendages), while those of the other two dozen are biramous (divided into two). All of its body segments are similar to one another. Its parapodia bear in the range of 11-17 simple setae (usually 15), each about 2 mm in length, and which form a single plane that is inclined steeply with respect to the body. The tips of these setae form unequal forks, with one prong about half the length of the other. The animal had an unarmed eversible proboscis (prominent flexible apparatus capable of being turned inside-out like a tongue) that formed the front portion of its straight gut.

Abundance:

Burgessochaeta is relatively common in the Walcott Quarry representing 0.4% of the specimens counted in the community (Caron and Jackson, 2008).

Maximum Size:
49 mm

Ecology:

Ecological Interpretations:

Burgessochaeta probably burrowed or moved along the surface of the mud, using its short parapodia. Its tentacles are thought to have been used to collect food; the presence of sediment in its gut suggests that it might have been a deposit feeder.

References:

BUDD, G. E. AND S. JENSEN. 2000. A critical reappraisal of the fossil record of the bilaterian phyla. Biological Reviews, 75: 253-295.

CARON, J.-B. AND D. A. JACKSON. 2006. Taphonomy of the Greater Phyllopod Bed Community, Burgess Shale. PALAIOS, 21: 451-465.

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.

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

Other Links:

None