Life Habits: Mobile



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Wiwaxia corrugata

3D animation of Wiwaxia corrugata grazing on Morania confluens.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade halwaxiids (stem group molluscs)
Species name: Wiwaxia corrugata
Remarks:

The relationship of Wiwaxia is hotly debated; its similarities to the molluscs have been highlighted (Conway Morris, 1985; Scheltema et al., 2003; Caron et al., 2006; Caron et al., 2007), but Matthew’s original view that it was related to the annelid worms (Matthew, 1899) still finds some adherents (Butterfield, 1990; Conway Morris and Peel, 1995; Butterfield, 2006; 2008). It is also possible that Wiwaxia branched off before the molluscs and annelids diverged (Eibye-Jacobsen, 2004). Wiwaxia has recently been placed in a group called the halwaxiids, along with the halkieriids, Orthrozanclus, and Odontogriphus (Conway Morris and Caron, 2007).

Described by: Matthew
Description date: 1899
Etymology:

Wiwaxia – from Wiwaxy Peaks (2,703 m) in Yoho National Park. The word wiwaxy is originally from the Stoney First Nation Nakoda language, meaning “windy.”

corrugata – from the Latin corrugis, “folded, or wrinkled,” in reference to the wrinkled aspect of the sclerites.

Type Specimens: Holotype –ROM8596 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none described, although sclerites have been reported from a number of Middle Cambrian deposits extending from northern Canada (Butterfield, 1994) to China (Zhao et al., 1994).

Age & Localities:

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

The Walcott and Raymond Quarries on Fossil Ridge. The Trilobite Beds, Tulip Beds (S7) and Collins Quarry on Mount Stephen. Additional smaller localities are known on Mount Field and Mount Odaray.

History of Research:

Brief history of research:

In an early review of fossils collected from the Trilobite Beds on Mount Stephen by Walker, Canadian palaeontologist G. F. Matthew (1899) described several forms he thought represented tubes of various annelid worms, including one he named Orthotheca corrugata. At the time, Matthew did not know this particular fossil was only part of a much larger organism. It was only when Walcott (1911) discovered articulated and much better preserved specimens from the Phyllopod Bed that the morphology of this species became clearer. Walcott placed corrugata in his new genus Wiwaxia and interpreted it as a polychaete annelid worm (Walcott, 1911). The single best specimen of Walker’s “Orthotheca corrugata” remained unrecognized until it was “rediscovered” in the ROM collections in 1977.

Walcott’s interpretation was called into question in a comprehensive reassessment of the genus (Conway Morris, 1985), and Conway Morris’s link between Wiwaxia mouthparts and the molluscan radula was built upon by Scheltema et al. (2003) and Caron et al. (2006). Butterfield (1990), however, defended an annelid affinity mostly based on the study of individual sclerites, first at the crown-, and later at the stem-group level (Butterfield, 2003; 2006), but further work suggested that the evidence does not conclusively support a close relationship with annelids (Eibye-Jacobsen, 2004). A connection with the halkieriids was drawn early on (Bengtson and Morris, 1984; Conway Morris and Peel, 1995), and expanded more recently (Conway Morris and Caron, 2007).

Other studies have dealt more specifically with the ecology and taphonomy of this animal. The finely spaced patterning of ridges on the scale may have given Wiwaxia an iridescent aspect in life (Parker, 1998). Wiwaxia has proven useful in calculating the extent of decay in fossil assemblages (Caron and Jackson, 2006) and in reconstructing the longer term taphonomic processes responsible for the preservation of the Burgess Shale fossils (Butterfield et al., 2007).

Description:

Morphology:

Wiwaxia corrugata is a slug-like organism up to 5.5 cm in length almost entirely covered (except on the ventral surface) with an array of scale-like elements referred to as sclerites and spines. The body is roughly oval, and lacks evidence of segmentation. The body-covering sclerites are arranged in about 50 rows. In addition, two rows of 7–11 blade-like spines are present on the dorsal surface. Spines and sclerites were inserted directly into the body wall. Wiwaxia’s feeding apparatus consists of two (in rare cases three) toothed plates that have been compared to a molluscan radula or annelid jaws.

Abundance:

Wiwaxia is mostly known from the Walcott Quarry where it is relatively common, representing 0.9% of the specimens counted in the community (Caron and Jackson, 2008).

Maximum Size:
55 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

The similarity of Wiwaxia’s feeding apparatus to that of Odontogriphus suggests that it too fed on the cyanobacterial Morania mats growing on the Cambrian sea floor. Its sclerite armour-plating and long spines, sometimes found broken, suggest that it was targeted by unidentified predators.

References:

BENGSTON, S. AND S. CONWAY MORRIS, 1984. A comparative study of Lower Cambrian Halkieria and Middle Cambrian Wiwaxia. Lethaia, 17:307-329.

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: 287-303.

BUTTERFIELD, N. J. 1994. Burgess Shale-type fossils from a Lower Cambrian shallow-shelf sequence in northwestern Canada. Nature, 369(6480): 477-479.

BUTTERFIELD, N. J. 2003. Exceptional fossil preservation and the Cambrian Explosion. Integrative and Comparative Biology, 43:166-177.

BUTTERFIELD, N. J. 2006. Hooking some stem-group “worms”: fossil lophotrochozoans in the Burgess Shale. BioEssays, 28: 1161-1166.

BUTTERFIELD, N. J. 2008. An early Cambrian radula. Journal of Paleontology, 82(3): 543-554.

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

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(7099): 159-163.

CARON, J.-B., A. H. SCHELTEMA, C. SCHANDER AND D. RUDKIN. 2007. Reply to Butterfield on stem-group “worms:” fossil lophotrochozoans in the Burgess Shale. BioEssays, 29:200-202.

CONWAY MORRIS, S. 1985. The Middle Cambrian metazoan Wiwaxia corrugata (Matthew) from the Burgess Shale and Ogygopsis Shale Shale, British Columbia, Canada. Philosophical Transactions of the Royal Society of London, Series B, 307(1134): 507-582.

CONWAY MORRIS, S. AND J.-B. CARON, 2007. Halwaxiids and the Early Evolution of the Lophotrochozoans. Science, 315(5816): 1255-1258.

CONWAY MORRIS, S. AND J. S. PEEL, 1995. Articulated halkieriids from the Lower Cambrian of North Greenland and their role in early protostome evolution. Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences, 347(1321): 305-358.

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

MATTHEW, G. F. 1899. Studies on Cambrian Faunas, No. 3. Upper Cambrian fauna, Mount Stephen, British Columbia. The trilobites and worms. Transactions of the Royal Society, 5: 39-66.

PARKER, A. R. 1998. Colour in Burgess Shale animals and the effect of light on evolution in the Cambrian. Proceedings of the Royal Society B: Biological Sciences, 265(1400): 967.

SCHELTEMA, A. H., K. KERTH AND A. M. KUZIRIAN, 2003. Original molluscan radula: Comparisons among Aplacophora, Polyplacophora, Gastropoda, and the Cambrian fossil Wiwaxia corrugata. Journal of Morphology, 257(2): 219-245.

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

ZHAO, Y.-l., Y. QIAN AND X.-S. LI, 1994. Wiwaxia from Early-Middle Cambrian Kaili Formation in Taijiang, Guizhou. Acta Palaeontologica Sinica, 33:359-366.

Other Links:

http://www.paleobiology.si.edu/burgess/wiwaxia.html



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Thelxiope palaeothalassia

Thelxiope palaeothalassia (GSC 74990). Articulated specimen (close up to the right), associated with several individuals of the arthropod Canadaspis perfecta. Specimen length = 29 mm. Specimen dry – polarized light. Walcott Quarry.

© GEOLOGICAL SURVEY OF CANADA. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Thelxiope palaeothalassia
Remarks:

The affinity of Thelxiope has not been considered in detail because the appendages are unknown.

Described by: Simonetta and Delle Cave
Description date: 1975
Etymology:

Thelxiope – from the Greek thelx meaning “enchanting,” and ops, meaning “voice,” referring to the muse-like appearance of the animal.

palaeothalassia – from the Greek palaios, meaning “ancient,” and thalassios, meaning “marine,” in reference to the age and environment where the animal lived.

Type Specimens: Holotype –USNM144914 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 (1912) figured two fragmentary specimens as Mollisonia? rara; these were first reinterpreted by Simonetta (1964) within a new genus Parahabelia rara, along with three additional specimens that he thought were related. However, Simonetta and Delle Cave (1975) considered that among those five specimens, the two originally figured by Walcott as M? rara had to be synonymized with M. symmetrica and the other three had to be placed within a new genus and species called Thelxiope palaeothalassia, a name in use since then.

Description:

Morphology:

This species has a relatively wide cephalon and seven segments and resembles Habelia in overall shape. However, in T. palaeothalassia, each segment bears a single prominent spine pointing dorsally. The last segment is armed with a very long pointed telson.

Abundance:

Thelxiope is extremely rare, with only four known specimens.

Maximum Size:
43 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

Thelxiope is too poorly known to allow detailed studies of its ecology.

References:

SIMONETTA, A. M. 1964. Osservazioni sugli arthropodi non trilobiti della “Burgess Shale” (Cambriano medio). Monitore Zoologico Italiano, 72 (3-4: III Contributo: I Generi Molaria, Habelia, Emeraldella, Parahabelia (Nov.) Emeraldoides (Nov.): 215-231.

SIMONETTA, A. M. AND L. DELLE CAVE. 1975. The Cambrian non-trilobite arthropods from the Burgess shale of British Columbia: A study of their comparative morphology, taxonomy and evolutionary significance. Palaeontographia Italica, 69: 1-37.

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

Other Links:

None



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Tegopelte gigas

Tegopelte gigas (USNM 189201) – Holotype. Complete specimen showing antennae and appendages partially prepared near the back. Specimen length = 270 mm. Specimen dry – direct (top) and polarized light (bottom). Walcott Quarry.

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

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Tegopelte gigas
Remarks:

Tegopelte is usually compared to the soft-bodied “trilobites” such as Naraoia and Saperion, but the exact relationships of these taxa to the mineralized trilobites is uncertain (Whittington, 1977). The tegopeltids and other trilobite-like arthropods are sometimes referred to as Trilobitoidea, which when grouped together with the trilobites form the Lamellipedians (Hou and Bergström, 1997; Wills et al., 1998; Edgecombe and Ramsköld, 1999). This group has been variously placed in the upper stem lineage of the arthropods (Budd, 2002), or in the stem lineage of either the mandibulates (Scholtz and Edgecombe, 2006) or the chelicerates (Cotton and Braddy, 2004).

Described by: Simonetta and Delle Cave
Description date: 1975
Etymology:

Tegopelte – from the Greek tegos, “tile,” and pelte, “leather-shield,” referring to the shape of the dorsal body covering.

gigas – from the Greek gigas, “giant,” referring to the large size of the animal.

Type Specimens: Holotype –USNM189201 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:

Tegopelte was first described by Simonetta and Delle Cave (1975) to include only two relatively large specimens. This original description showed Tegopelte to have a cephalon with six or seven pairs of walking appendages, a thorax of four tergites each bearing five appendages, and a tail segment with ten appendages. Whittington (1985) re-examined the animal, reducing the number of head appendages to three, and describing the thorax as having only three tergites with three appendages each. The tail in Whittington’s (1985) reconstruction had two segments with a total of 20 appendages. Later re-examination by Ramsköld et al. (1996) suggested that the body has no tergites, but instead consists of an undivided dorsal shield. Tegopelte has been grouped together with the Chengjiang taxon Saperion to form the Tegopeltidae (Ramsköld et al., 1996; Hou and Bergström, 1997), a clade later confirmed by cladistic analysis (Edgecombe and Ramsköld, 1999; Hendricks and Lieberman, 2008).

Description:

Morphology:

The dorsal morphology of Tegopelte consists of an elongated oval-shaped dorsal shield that is featureless and undivided. The length of the two known specimens is 25.7 cm and 27.0 cm, making it one of the largest arthropods in the Burgess Shale. The ventral morphology consists of a pair of multi-segmented antennae at the front of the body, followed by a series of identical limbs that are segmented and branch into two (biramous), totaling approximately 33 along the entire body. The biramous limbs have a walking branch made up of six segments with a pair of spines on the terminal segment, and a filamentous branch where numerous elongated oval blades attach to a central shaft. The biramous limbs decrease in size towards the posterior end of the body.

Abundance:

Tegopelte is extremely rare, with only two known specimens.

Maximum Size:
270 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

Tegopelte probably spent much of its time walking on the seafloor, based on the presence of many appendages. It used the segmented branches of its biramous appendages for walking, and it is likely that the filamentous branches were used for oxygen exchange, and to propel the animal through the water during short bursts of swimming. The antennae would have been used to sense the environment. The lack of eyes, gut glands and feeding appendages make it difficult to allocate a feeding strategy to Tegopelte.

References:

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

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.

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.

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

HENDRICKS, J. R. AND B. S. LIEBERMAN. 2008. New phylogenetic insights into the Cambrian radiation of arachnomorph arthropods. Journal of Paleontology, 83: 585-594.

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

RAMSKÖLD, L., J. CHEN, G. D. EDGECOMBE AND G. ZHOU. 1996. Preservational folds simulating tergite junctions in tegopeltid and naraoiid arthropods. Lethaia, 29: 15-20.

SIMONETTA, A. M. AND L. DELLE CAVE. 1975. The Cambrian non-trilobite arthropods from the Burgess shale of British Columbia: A study of their comparative morphology, taxonomy and evolutionary significance. . Palaeontographia Italica, 69: 1-37.

WHITTINGTON, H. B. 1977. The Middle Cambrian trilobite Naraoia, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London, B, 280: 409-443.

WHITTINGTON, H. B. 1985. Tegopelte gigas, a second soft-bodied trilobite from the Burgess Shale, Middle Cambrian, British Columbia. Journal of Paleontology, 59: 1251-1274.

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



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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:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade (stem group polychaetes)
Species name: Stephenoscolex argutus
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).

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:

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 (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:

Life habits: Mobile
Feeding strategies: Mobile
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:

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Stanleycaris hirpex

Stanleycaris hirpex (ROM 59944) – Holotype, part and counterpart. Individual claw. Specimen length = 29 mm. Specimen dry – polarized light. Stanley Glacier.

© ROYAL ONTARIO MUSEUM. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Order Radiodonta, Family Hurdiidae
Species name: Stanleycaris hirpex
Remarks:

With its single pair of jointed frontal appendages, lateral swimming flaps, and a circular mouth structure, Stanleycaris possesses all the hallmarks of Radiodonta, part of the stem group to the true arthropods which also includes the iconic Anomalocaris (Collins 1996). The frontal appendages with comb or rake-like inner spines are characteristic of the family Hurdiidae. However, other features like the small carapace, short head, and long, streamlined body probably represent ancestral radiodontan traits. Accordingly, Stanleycaris has been recovered as the sister species to all other hurdiid radiodontans in the most recent phylogenetic analysis (Moysiuk and Caron 2022).

Described by: Caron et al.
Description date: 2010
Etymology:

Genus – From Stanley Glacier, 40 kilometres southeast of the Burgess Shale in Kootenay National Park, where the fossils come from and the Latin caris, meaning “shrimp.” The name Stanley was given after Frederick Arthur Stanley (1841-1908), Canada’s sixth Governor General.

species – from the Latin, hirpex, meaning “large rake,” in reference to the rake-like aspect of the appendage.

Type Specimens: Holotype –ROM59944 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: Stanleycaris sp. from the mid-Cambrian Wheeler Formation of Utah (Pates et al. 2017).

Age & Localities:

Age:
Middle Cambrian, Wuliuan stage, Burgess Shale Formation (approximately 505 million years ago).
Principal localities:

Stanley Glacier in Kootenay National Park and the Collins Quarry on Fossil Ridge, Yoho National Park. Smaller collections from the Walcott and Raymond Quarries on Fossil Ridge, Tokumm Creek, Mount Odaray, Mount Stephen, and Mount Field.

History of Research:

Brief history of research:

Isolated appendages and oral structures of this species were collected by the Royal Ontario Museum in 1996 from talus slopes at Stanley Glacier, but it was not until 2008, during a larger expedition, that additional specimens were discovered in their proper stratigraphic context. A description of this new genus and species soon followed (Caron et al. 2010). A single isolated appendage from the Wheeler Formation of Utah was described in 2017, representing the only possible occurrence reported outside of the Burgess Shale (Pates et al. 2017). Subsequently, it was noted that the original description of Stanleycaris did not satisfy the requirements of the International Code of Zoological Nomenclature due to its publication in an online-only repository prior to 2012 (Zhuravlev and Gámez Vintaned 2018). The name was ultimately validated by Pates, Daley, and Ortega-Hernández (2018). Moysiuk and Caron later redescribed the original type material, along with new specimens from Stanley Glacier and Tokumm Creek, in detail (2021). Most recently, a large collection of exceptional whole-body remains, mainly from ROM collections on Fossil Ridge in the 1980s and 90s, was recognized as belonging to the species, allowing the first full reconstruction (Moysiuk and Caron 2022). While there had been some debate as to whether radiodontans possessed externally developed body segmentation, the complete Stanleycaris material confirmed this, suggesting that traces of segmentation in other species are merely obscured due to preservation and weathering.

Description:

Morphology:

Stanleycaris has a short head and a relatively long body, the latter composed of 17 well-formed segments plus four filamentous tail blades. A small, oval, domed carapace covers the front of the head. The head bears a pair a pair of stalked compound lateral eyes and a large median eye situated behind the carapace. A pair of frontal appendages project from the head. Each has a series of curving, rake like inner spines, trident-shaped medial spines, and hooked outer spines. The mouth opening, on the underside of the head, is square and surrounded by an array of tooth-bearing plates. Each body segment has a row of gill blades along the underside and a pair of swimming flaps at the sides. The digestive tract includes a long foregut and a segmentally organized midgut. Elements of the nervous system of Stanleycaris are also preserved, including a two-segmented brain, visual processing centers in the eyes, and a pair of ventral nerve cords.

Abundance:

Collectively known from about 300 specimens, the species is most common at the Collins Quarry on Fossil Ridge and Stanley Glacier. It is rare at other localities.

Maximum Size:
About 200 mm.

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

The multitool-like frontal appendages of Stanleycaris could have enabled a variety of feeding functions. They are long and flexible, allowing grappling of prey with the hooked spines at their tips. The rake-like inner spines have been hypothesized to be adapted for sediment sifting, while trident-shaped medial spines would have opposed those on the opposite appendage, together acting like a jaw to tear and crush soft prey. Additional food processing would have been accomplished by the tooth-bearing plates around the mouth (Moysiuk and Caron 2019, 2021). The large compound eyes, particularly in juveniles, show that Stanleycaris was a visual hunter, but the relatively modest number of lenses (estimated at ~1000) suggest it may have been most active in low light conditions (Moysiuk and Caron 2022, 2023). As in other radiodontans, swimming was facilitated by undulation of the lateral flaps while respiration would have been accomplished primarily through the rows of gill blades on the body (Usami 2006; Daley et al. 2013). Stanleycaris has the most completely known growth series of any radiodontan, demonstrating that segments were added to the body during early development. Specimens of Stanleycaris showing shriveling of the body and flaps, disarticulation of the appendages and mouthparts, and loss of the top portion of the head have been interpreted as moult remains, providing direct evidence that Stanleycaris moulted periodically as it grew (Moysiuk and Caron 2022, 2023).

References:

  • CARON, J.-B., GAINES, R. R., MÁNGANO, M. G., STRENG, M. and DALEY, A. C. 2010. A new Burgess Shale-type assemblage from the “thin” Stephen Formation of the southern Canadian Rockies. Geology, 38: 811–814.
  • COLLINS, D. 1996. The “evolution” of Anomalocaris and its classification in the arthropod class Dinocarida (nov.) and order Radiodonta (nov.). Journal of Paleontology, 70: 280–293.
  • DALEY, A. C., BUDD, G. E. and CARON, J.-B. 2013. Morphology and systematics of the anomalocaridid arthropod Hurdia from the Middle Cambrian of British Columbia and Utah. Journal of Systematic Palaeontology, 11: 743–787.
  • MOYSIUK, J. and CARON, J.-B. 2019. A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources. Proceedings of the Royal Society B, 286: 20191079.
  • MOYSIUK, J. and CARON, J.-B. 2021. Exceptional multifunctionality in the feeding apparatus of a mid-Cambrian radiodont. Paleobiology, 47: 704–724.
  • MOYSIUK, J. and CARON, J.-B. 2022. A three-eyed radiodont with fossilized neuroanatomy informs the origin of the arthropod head and segmentation. Current Biology, 32: 1–15.
  • MOYSIUK, J. and CARON, J.-B. 2023. A quantitative assessment of ontogeny and moulting in a Cambrian radiodont and the evolution of arthropod development. Paleobiology, 22 pg, IN REVIEW.
  • PATES, S., DALEY, A. C. and ORTEGA-HERNÁNDEZ, J. 2017. Aysheaia prolata from the Utah Wheeler Formation (Drumian, Cambrian) is a frontal appendage of the radiodontan Stanleycaris. Acta Palaeontologica Polonica, 62: 619–625.
  • PATES, S., DALEY, A. C. and ORTEGA-HERNÁNDEZ, J. 2018. Response to Comment on “Aysheaia prolata from the Utah Wheeler Formation (Drumian, Cambrian) is a frontal appendage of the radiodontan Stanleycaris” with the formal description of Stanleycaris. Acta Palaeontologica Polonica, 63: 105–110.
  • USAMI, Y. 2006. Theoretical study on the body form and swimming pattern of Anomalocaris based on hydrodynamic simulation. Journal of Theoretical Biology, 238: 11–17.
  • ZHURAVLEV, A. and GÁMEZ VINTANED, J. 2018. Comment on “Aysheaia prolata from the Utah Wheeler Formation (Drumian, Cambrian) is a frontal appendage of the radiodontan Stanleycaris” by Stephen Pates, Allison C. Daley, and Javier Ortega-Hernanández. Acta Palaeontologica Polonica, 63: 103–104.
Other Links:

http://geology.geoscienceworld.org/cgi/content/full/38/9/811?ijkey=ZQFY537sTggAw&keytype=ref&siteid=gsgeology



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Skania fragilis

Skania fragilis (ROM 60752) – Part and counterpart (first and second rows). Complete specimen showing antennae. Specimen length = 11 mm. Specimen dry – polarized light (left column) and wet (right column). Raymond Quarry.

© ROYAL ONTARIO MUSEUM. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Skania fragilis
Remarks:

The affinity of Skania is controversial, but most agree it is related to the arthropods. It is similar to Primicaris (Lin et al., 2006; Zhang et al., 2007), and both taxa have been compared to soft-bodied trilobites like Naraoia (Walcott, 1931; Zhang et al., 2007; Hou and Bergström, 1997). Other researchers suggest these taxa are related to the enigmatic Ediacaran taxon Parvancorina (Delle Cave and Simonetta, 1975; Gehling, 1991; Conway Morris, 1993; Simonetta and Insom, 1993), with all three taxa forming a clade in sister group position relative to the trilobites (Lin et al., 2006).

Described by: Walcott
Description date: 1931
Etymology:

Skania – from Skana, the name of a glacier near Mount Robson, British Columbia, Canada.

fragilis – from the Latin fragilis, “brittle,” referring to the delicate nature and small size of the animal.

Type Specimens: Holotype –USNM83950 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: Skania sundbergi Lin et al. 2006 from the Kaili Formation, China.

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:

Skania fragilis was first described by Walcott (1931) in a posthumous monograph published by his assistant Charles Resser. Resser compared Skania to the trilobites and Naraoia. However in a redescription by Delle Cave and Simonetta (1975), it was suggested instead that Skania was closely related to the Ediacaran taxon Parvancorina minchami Glaessner 1958. This affinity has been much discussed (Gehling, 1991; Conway Morris, 1993; Simonetta and Insom, 1993; Lin et al. 2006), and Skania has also been compared extensively with Primicaris Zhang et al. 2003. Skania and Primicaris have also been interpreted as juveniles (protaspides) of naraoiids (Hou and Bergström, 1997).

Description:

Morphology:

Skania has a single, undifferentiated, soft dorsal shield that is roughly kite-shaped. The dorsal shield is rounded at the front of the head, and tapers towards the posterior of the body, ending in a pair of short margin spines at the posterior end. At the point of maximum width there are sharp genal spines directed posteriorly. The posterior margin of the head is delineated by a narrow rim that is strongly arched forward, with the cephalic region occupying one-quarter of the exoskeletal length. A midgut is preserved in the axial region of the body trunk. Appendages are poorly preserved but consist of a pair of anterior antennae and ten or more paired body limbs.

Abundance:

Skania fragilis is known from fewer than 40 specimens in total.

Maximum Size:
17 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

The ecology of Skania is poorly known because the details of its morphology remain enigmatic. The form of the appendages is assumed to be biramous based on the overall similarity with Primicaris, which possesses biramous appendages, meaning that both animals may have walked on the seafloor, using their filamentous appendages for oxygen exchange and occasional swimming. Skania lacks eyes, so it likely used its antennae to sense the environment. The feeding strategy is unknown.

References:

CONWAY MORRIS, S. 1993. Ediacaran-like fossil in Cambrian Burgess Shale-type faunas of North America. Palaeontology, 36: 593-635.

DELLE CAVE, L. AND A. M. SIMONETTA. 1975. Notes on the morphology and taxonomic position of Aysheaia (Onycophora?) and of Skania (undetermined phylum). Monitore Zoologico Italiano New Series, 9: 67-81.

GEHLING, J. G. 1991. The case for Ediacaran fossil roots to the metazoan tree, p. 181-223. In B. P. Radhakrishna (ed.), The world of Martin F. Glaessner. Geological Society of India, Bangalore.

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

LIN, J., S. M. GON III, J. G. GEHLING, L. E. BABCOCK, Y. ZHAO, X. ZHANG, S. HU, J. YUAN M. YU AND J. PENG. 2006. A Parvancorina-like arthropod from the Cambrian of South China. Historical Biology, 18: 33-45.

SIMONETTA, A. M. AND E. INSOM. 1993. New animals from the Burgess Shale (Middle Cambrian) and their possible significance for the understanding of the Bilateria. Bolletino di Zoologia, 60: 97-107.

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

ZHANG, X., D. SHU AND D. H. ERWIN. 2007. Cambrian naraoiids (Arthropoda): morphology, ontogeny, systematics, and evolutionary relationships. Palaeontological Society Memoir, 68: 1-52.

Other Links:

None



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Sidneyia inexpectans

3D animation of Sidneyia inexpectans.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Sidneyia inexpectans
Remarks:

Sidneyia is usually considered to be closely related to the chelicerates, but its exact position relative to this group remains unclear (Budd and Telford, 2009). Sidneyia has been variously placed as the sister group to the chelicerates (Hou and Bergström, 1997), close to the crown on the chelicerate stem lineage (Bruton, 1981; Edgecombe and Ramsköld, 1999; Hendricks and Lieberman, 2008), or basal in the chelicerate stem lineage (Briggs and Fortey, 1989; Wills et al., 1998; Cotton and Braddy, 2004).

Described by: Walcott
Description date: 1911
Etymology:

Sidneyia – after Walcott’s son Sidney, who discovered the first specimen in August of 1910.

inexpectans – from the Latin inexpectans, “unexpected,” since Walcott did not expect to find such a fossil in strata older than the Ordovician.

Type Specimens: Lectotype –USNM57487 (S. inexpectans) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: A single specimen from the Chengjiang Fauna in China was used to describe a second species, Sidneyia sinica (Zhang et al. 2002), however this was later shown to be incorrectly attributed to Sidneyia (Briggs et al. 2008).

Age & Localities:

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

Burgess Shale and vicinity: The Walcott, Raymond and Collins Quarries on Fossil Ridge, Mount Field and Mount Stephen – Tulip Beds (S7) and other smaller localities – Odaray Mountain and Stanley Glacier.

Other deposits: Sidneyia has been described from the Wheeler Formation (Briggs and Robison, 1984) and the Spence Shale (Briggs et al. 2008) in Utah, and the Kinzers Formation in Pennsylvania (Resser and Howell, 1938).

History of Research:

Brief history of research:

Sidneyia was the first fossil to be described by Walcott (1911) from the Burgess Shale. Further details were added by Walcott the following year (Walcott, 1912), and Strømer (1944) and Simonetta (1963) made minor revisions to Walcott’s reconstruction. A large appendage found in isolation was originally suggested to be the large frontal appendage of Sidneyia (Walcott, 1911), but this was later found to belong to the anomalocaridid Laggania (Whittington and Briggs, 1985). A major study by Bruton (1981) redescribed the species based on the hundreds of available specimens.

Description:

Morphology:

Sidneyia has a short, wide head shield that is convexly domed and roughly square. The two front lateral corners are notched to allow an antenna and a stalked eye to protrude. Other than the pair of antennae, which are long and thin with at least 20 segments, there are no cephalic appendages. The hemispherical and highly reflective eyes are above and posterior to the antennae.

The thorax of Sidneyia has nine wide, thin body segments that widen from the first to the fourth segment and then get progressively narrower posteriorly. The first four thoracic segments bear appendages with a large, spiny basal segment (the coxa) and 8 thinner segments, ending in a sharp claw. The next five thoracic appendages have a similar appendage but also have flap-like filaments in association with the limbs.

The abdomen consists of three circular rings that are much narrower than the thorax, with a terminal, triangular telson. The last segment of the abdomen has a pair of wide flaps that articulate with the telson to form a tail fan. A trace of the straight gut can be seen in some specimens extending from the anterior mouth to the anus on the telson, and pieces of broken trilobites are sometimes preserved in the gut.

Abundance:

Sidneyia is a relatively common arthropod in the Walcott Quarry, comprising 0.3% of the specimens counted (Caron and Jackson, 2008). Hundreds of specimens have been collected from the Walcott Quarry (Bruton, 1981) and in other nearby localities.

Maximum Size:
160 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

Sidneyia walked and swam above the sea floor. Its anterior four thoracic appendages were used for walking, and the spiny basal coxa would crush food items and move them towards the mouth. The posterior five thoracic appendages were used for swimming, with the flap-like filaments undulating through the water column to create propulsion. These filaments were also likely used for breathing, like gills.

The predatory nature of Sidneyia is indicated by its spiny coxa used to masticate food, and the presence of crushed fossil debris in its gut. Sidneyia would have walked or swam above the sea floor, using its eyes and antennae to seek out prey, which it would capture and crush with its anterior appendages.

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. AND R. A. ROBISON. 1984. Exceptionally preserved non-trilobite arthropods and Anomalocaris from the Middle Cambrian of Utah. The University of Kansas Paleontological Contributions, 111: 1-24.

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.

BRUTON, D. L. 1981. The arthropod Sidneyia inexpectans, Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London B, 295: 619-653.

BUDD, G. E. AND M. J. TELFORD. 2009. The origin and evolution of arthropods. Nature, 457(7231): 812-817.

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

CARON, J.-B., R. GAINES, G. MANGANO, M. STRENG, AND A. DALEY. 2010. A new Burgess Shale-type assemblage from the “thin” Stephen Formation of the Southern Canadian Rockies. Geology, 38: 811-814.

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. Jounral of Paleontology, 73: 263-287.

HENDRICKS , J. R. AND B. S. LIEBERMAN. 2008. Phylogenetic insights into the Cambrian radiation of arachnomorph arthropods. Journal of Paleontology, 82: 585-594.

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

RASSER, C. E. AND B. F. HOWELL. 1938. Lower Cambrian Olenellus zone of the Appalachians. Bulletin of the Geological Society of America, 49: 195-248.

SIMONETTA, A. M. 1963. Osservazioni sugli artropodi non trilobiti della Burgess Shale (Cambriano medio). II. Contributo: I Generai Sidneyia ed Amiella Walcott 1911. Monitore Zoologico Italiano, 70: 97-108.

STØMER, L. 1944. On the relationships and phylogeny of fossil and recent Arachnomorpha. Norsk Videnskaps-Akademi Skrifter I. Matematisk-Naturvidenskaplig Klasse, 5: 1-158.

WALCOTT, C. D. 1911. Middle Cambrian Merostomata. Cambrian geology and paleontology II. Smithsonian Miscellaneous Collections, 57: 17-40.

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. AND D. E. G. BRIGGS. 1985. The largest Cambrian animal, Anomalocaris, Burgess Shale, British-Columbia. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences, 309: 569-609.

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, pp. 33-105. In G. D. Edgecombe (ed.), Arthropod fossils and phylogeny. Columbia University Press, New York.

ZHU, X., H. JIAN AND S. DEGAN. 2002. New occurrence of the Burgess Shale arthropod Sidneyia in the Early Cambrian Chengjiang Lagerstätte (South China), and revision of the arthropod Urokodia. Alcheringa: An Australasian Journal of Palaeontology, 26: 1-18.

Other Links:

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



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Selkirkia columbia

3D animation of Selkirkia columbia.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade (stem group priapulids)
Species name: Selkirkia columbia
Remarks:

Selkirkia has been compared to the nemathelminth worms (Maas et al., 2007), but most analyses support a relationship with the priapulids at a stem-group level (Harvey et al., 2010; Wills, 1998).

Described by: Walcott
Description date: 1911
Etymology:

Selkirkia – from the Selkirk Mountains, a mountain range in southeastern British Columbia.

columbia – from British Columbia, where the Burgess Shale is located.

Type Specimens: Holotype –USNM57624 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: The genus Selkirkia ranges from the Lower to the Middle Cambrian and is represented by several species, including S. sinica from the Lower Cambrian Chengjiang Biota (Luo et al., 1999; Maas et al., 2007), S. pennsylvanica from the Lower Cambrian Kinzers Formation (Resser and Howell, 1938), Selkirkia sp. cf. and S. spencei from the Middle Cambrian Spence Shale of Utah (Resser, 1939; Conway Morris and Robison, 1986, 1988), and S. willoughbyi from the Middle Cambrian Marjum Formation of Utah (Conway Morris and Robison, 1986).

Age & Localities:

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

Burgess Shale and vicinity: The Walcott, Raymond and Collins Quarries on Fossil Ridge, and smaller localities on Mount Field and Mount Odaray. The Trilobite Beds, the Collins Quarry, the Tulip Beds (S7) and smaller localities on Mount Stephen.

Other deposits: The Middle Cambrian Spence Shale of Utah (Resser, 1939; Conway Morris and Robison, 1986, 1988).

History of Research:

Brief history of research:

Charles Walcott (1908) illustrated a single specimen of a simple tube that he named “Orthotheca major.” He interpreted the fossil as the tube of a polychaete worm, along with another famous species, “O. corrugata,” described by Matthew a decade earlier. O. corrugata is now referred to as Wiwaxia corrugata, which is not the tube of a worm but the scale of an armoured mollusc! The original specimen of “O. major” came from the Trilobite Beds on Mount Stephen, but it was not until the discovery of complete specimens from Fossil Ridge showing soft-bodied worms within the tubes that more details about this animal became available. Walcott (1911) created a new genus name Selkirkia to accommodate the new fossil material. In addition to the type species, S. major, he named two new species, S. gracilis and S. fragilis. In a revision of Walcott’s collections and other fossils discovered by the Geological Survey of Canada, Conway Morris (1977) synonymised Walcott’s three species into one that he called S. columbia, which is still in use today. S. columbia was described as a primitive priapulid worm (Conway Morris, 1977); later studies showed that it belongs to the priapulid stem group (Wills, 1998; Harvey et al., 2010).

Description:

Morphology:

Selkirkia lived in a tube and could reach up to 6 centimetres in length. The body of the worm itself is similar to most priapulids in having a trunk (which remained in the tube) and an anterior mouthpart that could be inverted into the trunk, called a proboscis. The proboscis has different series of spines along its length and is radially symmetrical. Small body extensions called papillae are present along the anterior part of the trunk and probably helped in anchoring the trunk in the tube. The gut is straight and the anus is terminal. The unmineralized tube is slightly tapered, open at both ends, and bears fine transverse lineations.

Abundance:

Selkirkia is the most abundant priapulid in the Walcott Quarry community, representing 2.7% of the entire community (Caron and Jackson, 2008); thousands of specimens are known, mostly isolated tubes.

Maximum Size:
60 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

The well developed proboscis and strong spines suggest a carnivorous feeding habit. Comparisons with modern tube-building priapulids suggest Selkirkia was capable of only limited movement, and spend most of the time buried vertically or at an angle to the sediment-water interface, where they might have “trap fed” on live prey. Empty tubes were often used as a substrate for other organisms to colonize, for example, brachiopods, sponges and primitive echinoderms (see Echmatocrinus).

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. 1977. Fossil priapulid worms. Special Papers in Palaeontology, 20: 1-95.

CONWAY MORRIS, S. AND R. A. ROBISON. 1986. Middle Cambrian priapulids and other soft-bodied fossils from Utah and Spain. The University of Kansas paleontological contributions, 117: 1-22.

CONWAY MORRIS, S. AND R. A. ROBISON. 1988. More soft-bodied animals and algae from the Middle Cambrian of Utah and British Columbia. University of Kansas Paleontological Contributions, Paper, 122: 23-48.

HARVEY, T. H. P., X. DONG AND P. C. J. DONOGHUE. 2010. Are palaeoscolecids ancestral ecdysozoans? Evolution & Development, 12(2): 177-200.

LUO, H., S. HU, L. CHEN, S. ZHANG AND Y. TAO. 1999. Early Cambrian Chengjiang fauna from Kunming region, China. Yunnan Science and Technology Press, Kunming, 162 p.

MAAS, A., D. HUANG, J. CHEN, D. WALOSZEK AND A. BRAUN. 2007. Maotianshan-Shale nemathelminths – Morphology, biology, and the phylogeny of Nemathelminthes. Palaeogeography, Palaeoclimatology, Palaeoecology, 254(1-2): 288-306.

RESSER, C. E. AND B. F. HOWELL. 1938. Lower Cambrian Olenellus Zone of the Appalachians. Geological Society of America, Bulletin, 49: 195-248.

RESSER, C. E. 1939. The Spence Shale and its fauna. Smithsonian Miscellaneous Collections, 97(12):1-29.

WALCOTT, C. 1908. Mount Stephen rocks and fossils. Canadian Alpine Journal, 1: 232-248.

WALCOTT, C. 1911. Cambrian Geology and Paleontology II. Middle Cambrian annelids. Smithsonian Miscellaneous Collections, 57(5): 109-145.

WILLS, M. A. 1998. Cambrian and Recent disparity: the picture from priapulids. Paleobiology, 24(2): 177-199.

Other Links:

None



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Scolecofurca rara

Scolecofurca rara (GSC 45331) – Holotype (part and counterpart). Only known specimen of the species showing the pair tentacles in direct light (anterior to the right). Specimen length = 65 mm. Specimen wet – direct light (top), dry – polarized light (middle and bottom). Raymond Quarry.

© GEOLOGICAL SURVEY OF CANADA. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade (stem group priapulids)
Species name: Scolecofurca rara
Remarks:

Scolecofurca belongs to the priapulid worm stem group (Harvey et al., 2010; Wills, 1998).

Described by: Conway Morris
Description date: 1977
Etymology:

Scolecofurca – from the Greek skolex, meaning “worm,” and the Latin furca, “fork,” in reference to the fork-like anterior of this worm.

rara – from the Latin rarus, “infrequent,” in reference to the rarity of the species.

Type Specimens: Holotype – GSC45331 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 Raymond Quarry on Fossil Ridge.

History of Research:

Brief history of research:

This worm was described by Conway Morris in 1977 as a possible primitive priapulid. Later analyses showed that S. rara belongs to the priapulid stem group (Harvey et al., 2010; Wills, 1998).

Description:

Morphology:

Scolecofurca is known from a single incomplete specimen, which is estimated to have reached nine centimeters in total length. Like other priapulids, the body is divided into a proboscis and a trunk. The proboscis is fringed with small extensions called papillae, and tipped with a pair of conspicuous tentacles giving the appearance of a two-pronged fork. The trunk is annulated and the gut appears to be represented by a simple tube. Contrary to all the other species of priapulids from the Burgess Shale, this form does not have spines or hooks on the proboscis or body.

Abundance:

This species is known from a single specimen.

Maximum Size:
90 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

The general body-shape and presence of a proboscis suggests Scolecofurca was a burrower. The tentacles might have had a sensory function rather than being used for prey manipulation, but the mode of feeding of this species is unknown.

References:

CONWAY MORRIS, S. 1977. Fossil priapulid worms. Special Papers in Palaeontology, 20: 1-95.

HARVEY, T. H. P., X. DONG AND P. C. J. DONOGHUE. 2010. Are palaeoscolecids ancestral ecdysozoans? Evolution & Development, 12(2): 177-200.

WILLS, M. A. 1998. Cambrian and Recent disparity: the picture from priapulids. Paleobiology, 24(2): 177-199.

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Scenella amii

3D animation of Scenella amii.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade (stem group molluscs)
Species name: Scenella amii
Remarks:

Scenella is generally classified as a monoplacophoran mollusc (Knight, 1952; Runnegar and Jell, 1976). A position possibly ancestral to brachiopods (Dzik, 2010), or within the Cnidaria, has also been proposed (Babcock and Robison, 1988; Yochelson and Gil Cid, 1984).

Described by: Matthew
Description date: 1902
Etymology:

Scenella – from the Greek word skene, “tent, or shelter,” in reference to its shape.

amii – after Marc Henri Ami from the Geological Survey of Canada.

Type Specimens: Holotype –ROM8048 in the Royal Ontario Museum, Toronto, ON, Canada.
Other species:

Burgess Shale and vicinity: none

Other deposits: Dozens of species are known from the Lower Cambrian to the Lower Ordovician.

Age & Localities:

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

The Walcott and Raymond Quarries on Fossil Ridge. The Trilobite Beds and smaller localities on Mount Stephen.

History of Research:

Brief history of research:

The limpet-like appearance of Scenella led to its original classification as a mollusc, initially as a pteropod, then as a gastropod (Walcott, 1886). The first fossils of this genus known from the Burgess Shale were collected from the Trilobite Beds on Mount Stephen. These were described as Metoptoma amii by Matthew (1902), but Walcott (1908) considered other specimens from the same locality (and from the Walcott Quarry) to belong to Scenella varians, an earlier named species. Resser (1938) recognized that both species were identical and proposed a new combination, Scenella amii. In the same publication, Resser named a second species from the Trilobite Beds S. columbiana; this was based on a single specimen, originally recognized as a brachiopod with possible spines (Walcott, 1912), and remains highly dubious.

Description:

Morphology:

Each cone-shaped fossil has the form of a flat disc with a central peak, here termed “shell.” Concentric rings surround this peak, and sometimes the shell is also corrugated. The shells are stretched along one axis, making them elliptical rather than circular.

The fossils are often preserved in dense clusters and are usually oriented point-up.

No soft tissue is ever found associated with Scenella. The shell was evidently mineralized as indicated by the three-dimensional preservation and the presence of small cracks suggesting brittleness.

Abundance:

Hundreds of specimens of S. amii are known in the Walcott Quarry (2.27% of the community, Caron and Jackson, 2008). Many of these are found in dense clusters on single slabs.

Maximum Size:
10 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

If a mollusc, Scenella would have been a creeping bottom-dweller, potentially a grazer.

References:

BABCOCK, L. E. AND R. A. ROBISON. 1988. Taxonomy and paleobiology of some Middle Cambrian Scenella (Cnidaria) and hyolithids (Mollusca) from western North America. University of Kansas Paleontological Contributions, Paper, 121: 1-22.

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

DZIK, J. 2010. Brachiopod identity of the alleged monoplacophoran ancestors of cephalopods. Malacologia, 52:97-113.

KNIGHT, J. B. 1952. Primitive fossil gastropods and their bearing on gastropod evolution. Smithsonian Miscellaneous Collections, 117(13): 1–56.

MATTHEW, G. F. 1902. Notes on Cambrian Faunas: Cambrian Brachiopoda and Mollusca of Mt. Stephen, B.C. with the description of a new species of Metoptoma. Transactions of the Royal Society of Canada, 4:107-112.

RASETTI, F. 1954. Internal shell structures in the Middle Cambrian gastropod Scenella and the problematic genus Stenothecoides. Journal of Paleontology, 28: 59-66.

RESSER, C. E. 1938. Fourth contribution to nomenclature of Cambrian fossils. Smithsonian Miscellaneous Collections, 97:1-43.

Runnegar, B. AND P. A. JELL. 1976. Australian Middle Cambrian molluscs and their bearing on early molluscan evolution. Alcheringa: An Australasian Journal of Palaeontology, 1(2): 109-138.

WALCOTT, C. D. 1886. Second contribution to the studies on the Cambrian faunas of North America. Bulletin of the United States Geological Survey, (30): 11-356.

WALCOTT, C. 1908. Mount Stephen rocks and fossils. Canadian Alpine Journal, 1: 232-248.

WALCOTT, C. 1912. Cambrian Brachiopoda. United States Geological Survey Monograph, 51: Part 1: 1-872, Part 872: 871-363.

YOCHELSON, E. L. AND D. GIL CID. 1984. Reevaluation of the systematic position of Scenella. Lethaia, 17: 331-340.

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