The Burgess Shale

Helmetia expansa

Reconstruction of Helmetia expansa.

© Marianne Collins

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Helmetia expansa
Remarks:

Helmetia is extremely rare and poorly known, so its phylogenetic affinity is uncertain. Some researchers have suggested it may be aligned with the arachnomorphs, as a sister group to the trilobites (Edgecombe and Ramsköld, 1999; Cotton and Braddy, 2004). If this is confirmed, Helmetia probably represents a stem group of the Mandibulata, which includes crustaceans, myriapods, and hexapods (Scholtz and Edgecombe, 2006).

Described by: Walcott
Description date: 1918
Etymology:

Helmetia – from Helmet Mountain (3,138 m) in Kootenay National Park, named by Joseph Scattergood in 1900 because of the helmet shape of the peak.

expansa – from the Latin expansa, “spread out or wide,” referring to the broad body.

Type Specimens: Lectotype –USNM83952 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: Helmetia? fastigata from the Jince Formation in the Czech Republic (Chlupáč and Kordule 2002).

Age & Localities:

Age:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge

History of Research:

Brief history of research:

Helmetia expansa was first described by Walcott in 1918, and has not been re-examined since, except for brief reviews by Conway Morris et al. (1992) and Briggs et al. (1994). It has been included in several phylogenetic analyses of the arachnomorphs (e.g. Edgecombe and Ramsköld, 1999; Cotton and Braddy, 2004).

Description:

Morphology:

The most complete specimen of Helmetia is approximately 19 cm long and has a broad, flat and thin dorsal exoskeleton. The body consists of a head shield, six thoracic segments, and a large tail shield. The head shield has a concave frontal margin with two prominent spines at each corner. An oval structure with two large spots sits in the center of the head shield anterior margin. Two eyes are preserved as reflective spots behind the oval structure on either side. The six body segments are relatively thin but broad, and have a single spine projecting from their back corners. The tail shield tapers rapidly to a point, with two posteriorly-directed spines on the sides. The central region of the body has paired reflective muscle attachment scars near the anterior, and a series of large filamentous structures.

Abundance:

Helmetia expansa is extremely rare at the Walcott Quarry and the Raymond Quarry.

Maximum Size:
190 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

Helmetia was likely free-swimming, as indicated by the lack of walking limbs, the flat carapace and the presence of filamentous appendages. The shape of the carapace might have limited sinking, but the body is not streamlined, suggesting it was a slow swimmer. It is unlikely that it actively pursued swimming prey, because there are no apparent appendages or other modifications for predation or scavenging. It may have been a suspension feeder.

References:

BRIGGS, D. E. G., D. H. ERWIN AND F. J. COLLIER. 1994. The fossils of the Burgess Shale. Smithsonian Institution Press, Washington D. C.

CHLUPÁČ, I. AND V. KORDULE. 2002. Arthropods of Burgess Shale type from the Middle Cambrian of Bohemia (Czech Republic). Bulletin of the Czech Geological Survey, 77: 167-182.

CONWAY MORRIS, S., H. B. WHITTINGTON, D. E. G. BRIGGS, C. P. HUGHES. AND D. L. BRUTON. 1992. Atlas of the Burgess Shale. Palaeontological Association, London.

COTTON, T.J. AND S. J. BRADDY. 2004. The phylogeny of arachnomorph arthropods and the origin of the Chelicerata. Transactions of the Royal Society of Edinburgh-Earth Sciences, 94: 169-193.

EDGECOMBE, G. D. AND L. RAMSKÖLD. 1999. Relationships of Cambrian Arachnata and the systematic position of Trilobita. Journal of Paleontology, 73: 263-287.

SCHOLTZ, G. AND G. D. EDGECOMBE. 2006. The evolution of arthropod heads: reconciling morphological, developmental and palaeontological evidence. Development Genes and Evolution, 216: 395-415.

WALCOTT, C. D. 1918. Geological explorations in the Canadian Rockies. Explorations and fieldwork of the Smithsonian Institution in 1917. Smithsonian Miscellaneous Collections, 68: 4-20.

Other Links:

None

Fasciculus vesanus

Reconstruction of Fasciculus vesanus.

© Marianne Collins

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Unranked clade (stem group ctenophores)
Species name: Fasciculus vesanus
Remarks:

Fasciculus is regarded as a very primitive ctenophore, possibly representing a stem-group member (Conway Morris and Collins, 1996).

Described by: Simonetta and Delle Cave
Description date: 1978
Etymology:

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.

Type Specimens: Holotype – UNSM 202151 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Age:
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 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.

Description:

Morphology:

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.

Abundance:

This species is extremely rare – one specimen is known.

Maximum Size:
114 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

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.

References:

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.

Other Links:

None

Waptia fieldensis

Reconstruction of Waptia fieldensis.

© MARIANNE COLLINS

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Waptia fieldensis
Remarks:

It has been suggested that Waptia is closely related to Canadaspis and Perspicaris (Briggs and Fortey, 1989), with the group being allied to the crustaceans (Briggs, 1983; Wills et al., 1998; Briggs et al., 2008). However, some researchers argue instead that Waptia is at most a stem-lineage crustacean (Bergström and Hou, 2005), or perhaps even in the stem lineage to the arthropods (Hou and Bergström, 1997; Walossek and Müller, 1998).

Described by: Walcott
Description date: 1912
Etymology:

Waptia – from Wapta Mountain (2,778 m), just north of Fossil Ridge, in British Columbia, Canada, named after the Stoney First Nation Nakoda word “Wapta” meaning “running water.”

fieldensis – from Field, the mountain peak (2,643 m) and small town near Fossil Ridge, British Columbia, Canada. The name was given by William Cornelius Van Horne (General Manager of the Canadian Pacific Railway), to honor Cyrus West Field a promoter of the first telegraph cable across the Atlantic Ocean.

Type Specimens: Syntypes –USNM57681 andUSNM57682 (W. fieldensis) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
Other species:

Burgess Shale and vicinity: none.

Other deposits: Waptia cf. fieldensis from the Spence Shale Member of the Langston Formation, Utah (Briggs et al. 2008).

Age & Localities:

Age:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge

History of Research:

Brief history of research:

Waptia was first described by Walcott (1912), who designated Waptia fieldensis as the type species of the type genus. Various authors have since commented on its affinities (e.g. Briggs, 1983; Briggs et al., 1994; Hou and Bergström, 1997; Walossek and Müller, 1998; Wills et al., 1998; Hou and Bergström, 2005). However, no detailed work on its morphology has since been completed. Despite this, specimens of Waptia cf. fieldensishave been described from the Spence Shale in Utah (Briggs et al., 2008), and Waptia has been compared to Pauloterminus spinodorsalis from the Sirius Passet biota in North Greenland (Taylor, 2002). Waptia-like specimens from southwest China (Li, 1975; Hou and Bergström, 1991) were at one point assigned to Waptia (Chen, 2004), but a re-examination of the specimens showed they were different enough to be assigned to their own genus, Chuandianella (Liu and Shu, 2004, 2008; Hou et al., 2009).

Description:

Morphology:

Waptia bears a bivalved head shield consisting of two roughly oval valves that narrow anteriorly and fold along a median line that functions as a hinge. Beneath this carapace, the head bears a pair of long, slender antennae and a pair of small eyes on stalks. Details of other head appendages cannot be seen due to compaction against the head and carapace. The body trunk is long and slender and bears ten pairs of appendages. The first four pairs of appendage are segmented walking limbs with terminal spines and setae on their back margin, and the next six pairs of appendages are segmented branches lined with setae (hair-like bristles) and bearing blade-shaped filaments. Behind these appendages there is an abdomen consisting of five elongated segments. The abdomen terminates in a forked tail that consists of two oval blades. The trace of a straight gut is apparent in some specimens, stretching from the head to the base of the forked tail.

Abundance:

Waptia is common in the Burgess Shale, with over 1,400 specimens collected from the Walcott Quarry (Conway Morris, 1986; Caron and Jackson, 2008) and 70 specimens collected from the Raymond Quarry.

Maximum Size:
80 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

Waptia lived on or near the sea floor and scavenged for food. It used its two types of appendages to both walk on the sea floor and to swim through the water column. The first four pairs of segmented walking limbs would have been used for balancing and moving around on the sea floor, and the animal could have propelled itself through the water column by waving the bladed filaments of the posterior six appendages. The tail flaps would have helped stabilize and steer Waptia while swimming. The bladed filament may also have had a use in gas exchange. The eyes and antennae were presumably used to sense the environment, and the head appendages would pick up food particles in the sediment and bring them to the mouth.

References:

BERGSTRÖM, J. AND X. HOU. 2005.Early Palaeozoic non-lamellipedian arthropods, p. 73-93. In S. Koenemann and R. A. Jenner (eds.), Crustaceans and Arthropod Relationships, Festschrift for Fredrick R. Schram. Taylor and Francis, Boca Raton, London, New York, Singapore.

BRIGGS, D. E. G. 1983. Affinities and early evolution of the Crustacea: The evidence of the Cambrian fossils, p. 1-22. In F. R. Schram (ed.), Crustacean Issues, Volume 1, Crustacean Phylogeny. Balkema, Rotterdam.

BRIGGS, D. E. G. AND R. A. FORTEY. 1989. The early radiation and relationships of the major arthropod groups. Science, 246: 241-243.

BRIGGS, D. E. G., D. H. ERWIN AND F. J. COLLIER. 1994. The fossils of the Burgess Shale. Smithsonian Institution Press, Washington D. C.

BRIGGS, D. E. G., B. S. LIEBERMAN, J. R. HENDRICKS, S. L. HALGEDAHL AND R. D. JARRARD. 2008. Middle Cambrian arthropods from Utah. Journal of Paleontology, 82(2): 238-254.

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

CHEN, J. 2004. The dawn of the animal world. Jiangsu Science and Technology Press. Nanjing.

CONWAY MORRIS, S. 1986. The community structure of the Middle Cambrian phyllopod bed (Burgess Shale). Palaeontology, 29: 423-467.

HOU, X. AND J. BERGTRÖM. 1991. The arthropods of the Lower Cambrian Chengjiang fauna, with relationships and evolutionary significance, 179-187. In A. Simonetta and S. Conway Morris (eds.), The early evolution of the Metazoa and the significance of problematic taxa. Cambridge University Press, Cambridge.

HOU, X. AND J. BERGTRÖM. 1997. Arthropods of the Lower Cambrian Chengjiang fauna, southwest China. Fossils and Strata, 45:1-116.

HOU, X., D. J. SIVETER, R. J. ALDRIDGE AND D. J. SIVETER. 2009. A new arthropod in chain-like associations from the Chengjiang lagerstätte (Lower Cambrian), Yunnan, China. Palaeontology, 52: 951-961.

LI, Y. 1975. On the Cambrian ostracods with new material from Sichuan, Yunnan and Shaanxi, China. Professional Papers on Stratigraphy & Palaeontology, 2: 37-72.

LI, H. AND D. SHU. 2004. New information on Chuandianella from the Lower Cambrian Chengjiang Fauna, Yunnan, China. Journal of Northwest University, 34: 453-456.

TAYLOR, R. S. 2002. A new bivalved arthropod from the Early Cambrian Sirius Passet fauna, North Greenland. Palaeontology, 45: 97-123.

WALCOTT, C. 1912. Cambrian Geology and Paleontology II. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57(6): 145-228.

WALOSSEK, D. AND K. J. MÜLLER. 1998. Early arthropod phylogeny in light of the Cambrian “Orsten” fossils, p. 185-231. In G. D. Edgecombe (ed.), Arthropod Fossils and Phylogeny. Columbian University Press, New York.

WILLS, M. A., D. E. G. BRIGGS, R. A. FORTEY, M. WILKINSON AND P. H. A. SNEATH. 1998. An arthropod phylogeny based on fossil and recent taxa, p. 33-105. In G. D. Edgecombe (ed.), Arthropod fossils and phylogeny. Columbia University Press, New York.

Other Links:

http://paleobiology.si.edu/burgess/waptia.html

Xanioascus canadensis

Reconstruction of Xanioascus canadensis.

© MARIANNE COLLINS

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Unranked clade (stem group ctenophores)
Species name: Xanioascus canadensis
Remarks:

Xanioascus is regarded as a very primitive ctenophore, possibly representing a stem-group member (Conway Morris and Collins, 1996).

Described by: Conway Morris and Collins
Description date: 1996
Etymology:

Xanioascus – from the Greek xanion, “comb,” in reference to the shape and presence of comb-rows, and askos, “a leather bag used as a bottle.”

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

Type Specimens: Holotype –ROM43186 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Age:
Middle Cambrian, Glossopleura Zone (approximately 505 million years ago).
Principal localities:

The Collins Quarry on Mount Stephen.

History of Research:

Brief history of research:

Xanioascus canadensis was described by Conway Morris and Collins in 1996 from fossils discovered by the Royal Ontario Museum at a new locality on Mount Stephen; no additional studies have been published since then.

Description:

Morphology:

Xanioascus is bag-like in overall shape and bears 24 comb-rows. The comb-rows are well developed and extend close to the presumably large, but poorly preserved, mouth area. A distinctive feature of this species is the presence of ovoid structures within the body, but their identity remains speculative.

Abundance:

Only 8 specimens of this species are known.

Maximum Size:
125 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

The presence of comb-rows suggests the animal was an active swimmer. Its mode of feeding is more conjectural as the mouth is not well preserved and there is no evidence of tentacles.

References:

CONWAY MORRIS, S. AND D. 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.

Other Links:

None

Takakkawia lineata

Reconstruction of Takakkawia lineata.

© MARIANNE COLLINS

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Demospongea (Order: Monaxonida)
Species name: Takakkawia lineata
Remarks:

Takakkawia is considered a primitive demosponge (Rigby, 1986). Demosponges, the same group that are harvested as bath sponges, represent the largest class of sponges today.

Described by: Walcott
Description date: 1920
Etymology:

Takakkawia – from Takakkaw Falls, a waterfall in Yoho National Park, British Columbia, the second tallest in Canada. From the Stoney First Nation Nakoda word “Takakkaw,” for “magnificent,” a descriptive name for the waterfall given by Cornelius Van Horne in 1897.

lineata – from the Latin lineatus, “marked with lines,” this refers to the distinctive blade-like elements along the length of this sponge.

Type Specimens: Lectotype –USNM66539, in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Age:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge, the Tulip Beds (S7) on Mount Stephen and other smaller sites on Mount Field.

History of Research:

Brief history of research:

Walcott described Takakkawia in his 1920 paper on the Burgess Shale sponges. The genus was redescribed by Rigby in 1986 and again by Rigby and Collins (2004) based on new material collected by the Royal Ontario Museum.

Description:

Morphology:

This is an elongate conical sponge with eight stiff bladelike fins that project radially from the wall of the sponge and extends from a sharp root tip. These fins are composed of fine vertical spicules. Internally the fins are connected to long twisted strands of spicules that form ribbon-like structures. These structures are connected by horizontal ladder-like bundles of spicules. Most spicules are monaxial (simple and elongate) but some could have had three spines. The eight blade-like fins form sharp tips and fan outwards at the oscular margin (the hole at the top). This sponge would have had a large central cavity (spongocoel).

Abundance:

Takakkawia is rare in most sites but abundant in the Walcott Quarry and represents 2.61 % of the community (Caron and Jackson, 2008).

Maximum Size:
40 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

Takakkawia would have lived on the sea floor. Particles of organic matter were extracted from the water as they passed through canals in the sponge’s wall.

References:

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

RIGBY, J. K. 1986. Sponges of the Burgess shale (Middle Cambrian), British Columbia. Palaeontographica Canadiana, 2: 105 p.

RIGBY, J. K. AND D. COLLINS. 2004. Sponges of the Middle Cambrian Burgess Shale and Stephen Formations, British Columbia. Royal Ontario Museum Contributions in Science (1): 155 p.

WALCOTT, C. D. 1920. Middle Cambrian Spongiae. Cambrian Geology and Paleontology IV. Smithsonian Miscellaneous Collections, 67(6): 261-365.

Other Links:

None

Sanctacaris uncata

Reconstruction of Sanctacaris uncata.

© MARIANNE COLLINS

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Sanctacaris uncata
Remarks:

Sanctacaris was originally considered to belong to the crown-group chelicerates (Briggs and Collins, 1988), but subsequent analyses have aligned it with the arachnomorphs (Dunlop and Seldon, 1997; Wills et al., 1998; Sutton et al., 2002) or placed it in the stem lineage of the euarthropods (Budd, 2002).

Described by: Briggs and Collins
Description date: 1988
Etymology:

Sanctacaris – from the Latin sanctus, “holy, or saint,” (referring to Santa from the field name “Santa Claws”) and caris, “crab, or shrimp.”

uncata – from the Latin uncata meaning “hooked, or barbed,” referring to the numerous claws.

Type Specimens: Holotype –ROM43502 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Age:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Collins Quarry on Mount Stephen.

History of Research:

Brief history of research:

Sanctacaris was first described by Briggs and Collins in 1988, and has since been included in several studies on arthropod relationships (e.g. Briggs and Fortey, 1989; Dunlop and Seldon, 1997; Wills et al. 1998; Sutton et al. 2002; Budd, 2002).

Description:

Morphology:

Sanctacaris has a wide head shield with six pairs of head appendages projecting forward that are segmented and branch into two (biramous). The body trunk has eleven divisions, and a wide telson. Its body length ranges from 4.6 cm to 9.3 cm. The head shield is convex in the middle, and has two wide, triangular extensions on either side. A pair of eyes is located on the head shield near the lateral side of the anterior margin. The six biramous head appendages have thin, antenna-like branches in association with a spiny raptorial appendage. The rest of the body is divided into eleven segments. Each segment has a raised central region with wide lateral projections and is associated with one pair of biramous limbs. Each biramous limb consists of a wide flap with a fringe of setae and a thin, segmented walking branch. The telson is wide and paddle-shaped, with a posterior fringe of setae.

Abundance:

Sanctacaris is known from five specimens from Mount Stephen.

Maximum Size:
93 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

Sanctacaris may have lived on or just above the sea floor. The presence of the frontal appendages and eyes indicate that Sanctacaris would have been a free-swimming predator. The broad flaps of the trunk appendages would have been used to propel the animal through the water, with the telson and the lateral projections of the head and body being used to stabilize and steer. The raptorial branches of the biramous head appendages would have served to actively grab prey items, while the antennae-like branches would have been used to sense the environment.

References:

BRIGGS, D. E. G. AND D. COLLINS. 1988. A Middle Cambrian chelicerate from Mount Stephen, British Columbia. Palaeontology, 31: 779-798.

BRIGGS, D. E. G. AND R. A. FORTEY. 1989. The early radiation and relationships of the major arthropod groups. Science, 246: 241-243.

BUDD, G. E. 2002. A palaeontological solution to the arthropod head problem. Nature, 417: 271-275.

DUNLOP, J. A. AND P. A. SELDEN. 1997. The early history and phylogeny of chelicerates, pp. 221-235. In R. A Fortey and R. Thomas (eds.), Arthropod phylogeny. Chapman and Hall, London.

SUTTON, M. D., D. E. G. BRIGGS, D. J. SIVETER, D. J. SIVETER AND P. J. ORR. 2002. The arthropod Offacolus kingi (Chelicerata) from the Silurian of Herefordshire, England: computer based morphological reconstructions and phylogenetic affinities. Proceedings of the Royal Society of London, Series B, 269: 1195-1203.

WILLS, M. A., D. E. G. BRIGGS, R. A. FORTEY, M. WILKINSON AND P. H. A. SNEATH. 1998. An arthropod phylogeny based on fossil and recent taxa, p. 33-105. In G. D. Edgecombe (ed.), Arthropod fossils and phylogeny. Columbia University Press, New York.

Other Links:

None

Plenocaris plena

Reconstruction of Plenocaris plena.

© MARIANNE COLLINS

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Plenocaris plena
Remarks:

The affinity of Plenocaris is poorly known. It has been assigned to the Class Malacostraca (Whittington, 1974), but no phylogenetic analysis of this species has been carried out.

Described by: Walcott
Description date: 1912
Etymology:

Plenocaris – from the Latin plenus, “full,” and caris, “shrimp.”

plena – from the Latin plenus, “full.”

Type Specimens: Holotype –USNM57700 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Age:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge. The Collins Quarry on Mount Stephen.

History of Research:

Brief history of research:

Plenocairs was first described by Walcott (1912) as Yohoia plena. Whittington (1974) invalidated Y. plena, upgrading it to its own genus, Plenocaris plena, leaving Y. tenuis as the only species of Yohoia.

Description:

Morphology:

The body of Plenocaris is elongated and consists of a head region and 13 body segments ending in a paddle-shaped telson. The head bears a pair of simple antennae. The trunk segments 2 to 4 bear a pair of uniramous, elongate appendages whereas the other segments have no appendages. A carapace is loosely connected to the rest of the body and dorsally and laterally covers the head region and anterior of trunk.

Abundance:

Plenocaris represent a trivial proportion (0.2%) of specimens counted in the Walcott Quarry (Caron and Jackson, 2008) and is extremely rare elsewhere.

Maximum Size:
17 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

Some specimens of Plenocaris have a sediment-filled gut, suggesting that this animal lived near the benthos and was a deposit feeder. In the absence of swimming appendages, swimming and steering was only possible thanks to its long trunk and large lobate tail.

References:

WALCOTT, C. D. 1912. Cambrian Geology and Paleontology II. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57(6): 145-228.

WHITTINGTON, H. B. 1974. Yohoia Walcott and Plenocaris n. gen. arthropods from the Burgess Shale, Middle Cambrian, British Columbia. Geological Survey of Canada Bulletin, 231: 1-27.

Other Links:

None

Echmatocrinus brachiatus

Reconstruction of Echmatocrinus brachiatus.

© Marianne Collins

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Crinoidea? (stem group echinoderms)
Species name: Echmatocrinus brachiatus
Remarks:

The taxonomic position of Echmatocrinus is uncertain. This animal is either considered as a primitive crinoid (Sprinkle, 1976, Sprinkle and Collins, 1998), a cnidarian (Conway Morris, 1993) or an octocoral (Ausich and Babcock, 1998, 2000).

Described by: Sprinkle
Description date: 1973
Etymology:

Echmatocrinus – from the Greek echmatos, “holdfast, or stalk,” and krinos, “lily.” The name refers to the shape and the attachment part.

brachiatus – from the Greek brachiatus, “having arms,” in reference to the presence of arms.

Type Specimens: Holotype – GSC25962 in the Geological Survey of Canada, Ottawa, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Age:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge. A couple of specimens were also collected from the east side of Mount Field.

History of Research:

Brief history of research:

Echmatocrinus was first described by Sprinkle in 1973 as a primitive crinoid based on five specimens, four of which were originally collected by Walcott but never published. The fifth and best preserved specimen, now the holotype, was collected by the Geological Survey of Canada in 1967. Conway Morris reinterpreted Echmatocrinus as a possible cnidarian in 1993 and Ausich and Babcock (1998) suggested an octocoral affinity. Both of these newer interpretations were rejected by Sprinkle and Collins in a larger revision of all material available including new specimens collected by the Royal Ontario Museum (1998, but see Ausich and Babcock 1998).

Description:

Morphology:

The body consists of a small attachment disk (holdfast), a conical stalk ending into a wide cup (theca) with 7 to 10 short arms attached to the edge of it. Soft appendages are present on alternate sides of each arm. The stalk is at least the length of the cup and arms combined. A number of plates, presumably originally weakly mineralized cover the entire body. The plates are irregular in shape and might have sutures along them. Plates are more regular and pronounced in the arms. The arms are uniserial (i.e., they do not branch) and could fold on themselves. A surface texture or ornament is also present on the external parts of the plates. This ornament is interpreted by some authors as evidence of a stereom, the characteristic mineralized skeleton of all echinoderms. The locations of the mouth and anus are uncertain.

Abundance:

Echmatocrinus is very rare in the Walcott Quarry, where it makes up a negligible percentage (0.01%) of the community (Caron and Jackson, 2008). About two dozen specimens are known in total from three different localities.

Maximum Size:
185 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

Echmatocrinus was attached to skeletal debris on the seafloor and evidently it needed hard substrates for growth. It is often found in clusters of several individuals thus showing a gregarious habit. Food particles were likely transported along the arms to a central mouth near the summit of the cup.

References:

AUSICH, W. I. AND L. E. BABCOCK. 1998. The phylogenetic position of Echmatocrinus brachiatus, a probable octocoral from the Burgess shale. Palaeontology, 41: 193-202.

AUSICH, W. I. AND L. E. BABCOCK. 2000. Echmatocrinus, a Burgess Shale animal reconsidered. Lethaia, 33: 92-94.

SPRINKLE, J. 1976. Biostratigraphy and paleoecology of Cambrian echinoderms from the Rocky Mountains, p. 61-73. In R. A. Robison and A. J. Rowell (eds.), Paleontology and depositional environments: Cambrian of Western North America. 23. Brigham Young University Geology Studies.

SPRINKLE, J. AND D. COLLINS. 1998. Revision of Echmatocrinus from the Middle Cambrian Burgess Shale of British Columbia. Lethaia, 31: 269-282.

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Molaria spinifera

Taxonomy:

Reconstruction of Molaria spinifera.

© MARIANNE COLLINS

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Molaria spinifera
Remarks:

The phylogenetic position of Molaria is uncertain because the taxon is rather poorly known. It may be belong within Lamellipedia, as closely related to Naraoia and the trilobites (Briggs and Fortey, 1989; Wills et al., 1998), or it could also be aligned with the chelicerates (Briggs et al., 1992).

Described by: Walcott
Description date: 1912
Etymology:

Molaria – from Molar Mountain (3,022 m), a peak near the Valley of the Ten Peaks, named by James Hector in 1859 because the shape of the mountain resembles a molar tooth.

spinifera – from the Latin word spinifer, “spine-bearing.”

Type Specimens: Lectotype –USNM57688 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Age:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge.

History of Research:

Brief history of research:

This taxon was designated by Walcott in 1912 and revised by Simonetta in 1964. A major re-description was undertaken by Whittington in 1981. Molaria has since been included in several studies of arthropod relationships (e.g. Briggs and Fortey, 1989; Briggs et al., 1992, Wills et al., 1998).

Description:

Morphology:

Body sizes range from 0.8 cm to 2.6 cm (3.6 cm with tail spine). The body consists of a semi-circular head shield, eight body segments and an elongated tail. The head shield is smooth, with no ornamentation or eyes. A pair of tiny antennae extends forward from the anterior of the head, and three pairs of biramous appendages are located under the head shield behind them. These appendages have a large basal segment, to which are attached a walking branch with five segments and an outer lobe with a fringe of lamellae. Posterior to the head, there are eight trunk segments, each with a pair of limbs that are segmented and branch into two (biramous), similar to those on the head. The subcylindrical tail segment is small, and has an elongated, tapering posterior spine extending from it. This posterior spine is segmented and flexible. The trace of the gut can be seen in some lateral specimens.

Abundance:

A total of 111 specimens of Molaria were originally described from Walcott Quarry. This arthropod comprises 0.28% of the Walcott Quarry community (Caron and Jackson, 2008).

Maximum Size:
36 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

The presence of walking limbs in Molaria suggests it lived and moved around on the sea floor, perhaps using its head shield to plough through the sediment. It fed on detritus or scavenged on the sea floor, using the large basal segment with spines to scrape up food and pass it forwards to the backward-directed mouth. Molaria may also have been able to launch itself off of the sea floor for short bursts of swimming, using the branches of its limbs for propulsion and the posterior spine for balance and steering.

References:

BRIGGS, D. E. G. AND R. A. FORTEY. 1989. The early radiation and relationships of the major arthropod groups. Science, 246: 241-243.

BRIGGS, D. E. G., R. A. FORTEY, M. A. WILLS. 1992. Morphological disparity in the Cambrian. Science, 256: 1670-3.

CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.

SIMONETTE, A. M. 1964. Osservazioni sugli artropodi non trilobiti della ‘Burgess Shale’ (Cambriano medio). III conributo. Monitore Zoologico Italiano, 72: 215-231.

WALCOTT, C. D. 1912. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57: 145-228.

WHITTINGTON, H. B. 1981. Rare arthropods from the Burgess Shale, Middle Cambrian, British Columbia. Philosophical Transactions of the Royal Society of London Series B – Biological Sciences, 292: 329-357.

WILLS, M. A., D. E. G. BRIGGS, R. A. FORTEY, M. WILKINSON AND P. H. A. SNEATH. 1998. An arthropod phylogeny based on fossil and recent taxa, p. 33-105. In G. D. Edgecombe (ed.), Arthropod fossils and phylogeny. Columbia University Press, New York.

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Ctenorhabdotus capulus

Reconstruction of Ctenorhabdotus capulus.

© Marianne Collins

Taxonomy:

Kingdom: 2D Model
Phylum: 2D Model
Higher Taxonomic assignment: Unranked clade (stem group ctenophores)
Species name: Ctenorhabdotus capulus
Remarks:

Ctenorhabdotus is regarded as a very primitive ctenophore, possibly representing a stem-group member (Conway Morris and Collins, 1996).

Described by: Conway Morris and Collins
Description date: 1996
Etymology:

Ctenorhabdotus – from the Greek ktenos, “comb,” and rhabdotos, “striped,” in reference to the pronounced striped-like appearance of the comb-rows.

capulus – from the Latin capulus, “a handle,” in reference to the prominent aboral capsule-like element.

Type Specimens: Holotype –ROM50822 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

Age:
Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).
Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge.

History of Research:

Brief history of research:

Ctenorhabdotus capulus was described by Conway Morris and Collins in 1996 and no additional studies have been published since then.

Description:

Morphology:

Ctenorhabdotus is ovoid in shape and bears 24 comb-rows. The top (aboral) and bottom (oral) surfaces are relatively flat. The comb-rows are organised in 8 sets of three, with the central row being much shorter than the two flanking ones. Each group of three comb rows converges towards the aboral side to form 8 strands. The oral region is well developed with an undulating margin. There is a small capsule-like structure on the aboral side of the animal which is thought to include an apical organ and statocysts.

Abundance:

Ctenorhabdotus is rare, known from about two dozen specimens, mostly from the Raymond Quarry. In the Walcott Quarry, this species comprises only 0.01% of the specimens counted (Caron and Jackson, 2008).

Maximum Size:
70 mm

Ecology:

Life habits: 2D Model
Feeding strategies: 2D Model
Ecological Interpretations:

The presence of comb-rows suggests the animal was an active swimmer. Its mode of feeding is more conjectural as the mouth is not well preserved and there is no evidence of tentacles.

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. AND D. 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.

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