Life Habits: Nektonic



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Nereocaris exilis

Artistic reconstruction of Nereocaris exilis. Marianne Collins © ROM

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Hymenocarines, Family: Odaraiidae
Species name: Nereocaris exilis
Remarks:

Hymenocarines were early arthropods with bivalved carapaces and mandibles, forming the bulk of the first mandibulates (represented today by myriapods, crustaceans and insects) (Aria and Caron 2017; Vannier et al. 2018). In many hymenocarines, including Nereocaris, determining the exact number and types of appendages in their head remains difficult, which hinders a detailed understanding of the evolutionary relationships inside this group. Nereocaris most probably belongs to the family Odaraiidae, a group of hymenocarines with highly multisegmented bodies, reduced or absent antennae and highly multisegmented legs.

Described by: Legg, D. A., Sutton, M. D., Edgecombe, G. D., Caron, J-B.
Description date: 2012
Etymology:

Nereocaris – After “Nereus”, the Greek titan with a fish-like tail and the Latin caris, meaning “crab” or “shrimp”, and

exilis – from the Latin exilis, meaning “slender”.

Type Specimens: dsfsdfdsfdsfdasf
Other species:

Holotype ROMIP61831

Age & Localities:

Age:
Middle Cambrian, Wuliuan Stage, Burgess Shale Formation (around 507 million years old)
Principal localities:

Tulip Beds (S7) (N. exilis) and the Collins Quarry (N. briggsi).

History of Research:

Brief history of research:

The first description of Nereocaris exilis was published in 2012 based on specimens from the Tulip Beds site in Mount Stephen (Yoho National Park). Two years later, Nereocaris briggsi was described based on specimens from the Collins Quarry in Mount Stephen (Legg and Caron 2014). Nereocaris was originally described with a median eye protruding from a single eye peduncle located between the lateral eyes (Legg et al. 2012; Legg and Caron 2014). This structure was later reinterpreted as one of a pair of frontal filaments; short unsegmented limb-like structures with a sensorial function (Izquierdo-López and Caron 2022). Similarly, the tail fan of Nereocaris exilis was initially interpreted as having six pairs of lateral caudal rami (termed telson processes in the original study) and one medial telson process. This structure was later reinterpreted as two pairs of three-partite caudal rami borne by the terminal segment (“te” in Izquierdo-López and Caron, 2022), and was also reconstructed as such for N. briggsi (Izquierdo-López and Caron 2022). The discovery of Nereocaris and the phylogenetic analyses adjunct to the publication have been key to the interpretation of hymenocarines as earliest euarthropods (Legg et al. 2013; Fu et al. 2022) (or ‘upper stem-euarthropods’ based on Ortega-Hernández 2014). The discovery of mandibles in several hymenocarines (Aria and Caron 2017; Vannier et al. 2018; Zhai et al. 2019) has prompted the reinterpretation of this group as mandibulates, although the mandibulates affinities of Nereocaris and other odaraiids remain unclear pending clearer resolution of their head appendages.

Description:

Morphology:

The carapace of Nereocaris has a dome-like shape, compressed laterally, which becomes progressively wider towards the back of the animal. The top of the carapace bears a dorsal crest (keel) that runs across its entire length and extends posteriorly into a small process. The carapace is truncated anteriorly, and each valve extends towards the ventral side, terminating into an anterior hook. The carapace valves extend beyond the length of the legs, and in N. briggsi extend across the ventral side, similar to Odaraia alata. The head bears one pair of short pedunculate eyes and one pair of thin and small, unsegmented appendages (frontal filaments). Antennulae appear to be absent, and further cephalic specializations are unknown from the material available. The body of Nereocaris is highly multisegmented, reaching more than 90 segments in N. exilis. The trunk is subdivided into a thoracic region with limbs and a long limbless abdomen. Limbs are short, subdivided into two branches (biramous): a walking leg (endopod) and a seemingly paddle-like flap (exopod). Based on N. briggsi, the walking legs are probably subdivided into 14 or similar segments (podomeres). The exact morphology and size of the exopods is not well-preserved, but darker areas close to the legs’ base could indicate their approximate shape and length. The terminal segment is distinctly larger than the preceding segments and extends into a blunt process towards the posterior side of the animal (the “mtp” in Legg & Caron, 2014). This last segment bears one pair of caudal rami, each being partly subdivided into three smaller segments (tripartite). Each segment bears one spine on its outer edge.

Abundance:

Nereocaris exilis is rare, only known from three specimens from the same locality. Nereocaris briggsi is highly abundant in its locality, with over 190 specimens known.

Maximum Size:
About 14.2 cm (N. exilis)

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The limbs of Nereocaris exilis do not extend beyond the carapace ventral margin, indicating that they were not used for crawling. By contrast, the limbs of Nereocaris briggsi protrude from the carapace, but these were considered ill-suited to walk on the benthos (Legg and Caron 2014). For this reason, Nereocaris was reconstructed as a nektonic species, using its long abdomen as a means of propulsion (Legg et al. 2012; Perrier et al. 2015). N. exilis could have been a suspension-feeder, based on the lack of any raptorial or similar predatory limbs, but this possibility was questioned based on the lack of endites or setae on the limbs (Legg et al. 2012), which are widely used by extant filter-feeding crustaceans (Riisgård and Larsen 2010). A straight gut in N. briggsi, a simple tube filled with sediment may support the presence of a suspension or deposit feeding lifestyle, in which the animal would have consumed mud containing organic material (Legg and Caron 2014). It was also hypothesized that multiple odaraiids (Izquierdo-López and Caron 2022), most prominently Fibulacaris (Izquierdo-López and Caron 2019), could have swum upside-down, thus facilitating the capture of particles by the carapace. Whether Nereocaris could have adopted such behaviour remains uncertain.

References:

  • ARIA, C. and CARON, J. B. 2017. Burgess Shale fossils illustrate the origin of the mandibulate body plan. Nature, 545: 89–92.
  • FU, D., LEGG, D. A., DALEY, A. C., BUDD, G. E., WU, Y. and ZHANG, X. 2022. The evolution of biramous appendages revealed by a carapace-bearing Cambrian arthropod. Philosophical Transactions of the Royal Society of London B, 377.
  • IZQUIERDO-LÓPEZ, A. and CARON, J. B. 2019. A possible case of inverted lifestyle in a new bivalved arthropod from the Burgess Shale. Royal Society Open Science, 6: 191350.
  • IZQUIERDO-LÓPEZ, A. and CARON, J.-B. 2022. Extreme multisegmentation in a giant bivalved arthropod from the Cambrian Burgess Shale. IScience, 25, 104675.
  • LEGG, D., SUTTON, M. D. and EDGECOMBE, G. D. 2013. Arthropod fossil data increase congruence of morphological and molecular phylogenies. Nature Communications, 4: 1–7.
  • LEGG, D. A. and CARON, J. B. 2014. New Middle Cambrian bivalved arthropods from the Burgess Shale (British Columbia, Canada). Palaeontology, 57: 691–711.
  • LEGG, D. A., SUTTON, M. D., EDGECOMBE, G. D. and CARON, J. B. 2012. Cambrian bivalved arthropod reveals origin of arthrodization. Proceedings of the Royal Society B: Biological Sciences, 279: 4699–4704.
  • ORTEGA-HERNÁNDEZ, J. 2014. Making sense of ‘lower’ and ‘upper’ stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848. Biological Reviews, 91: 255–273.
  • PERRIER, V., WILLIAMS, M. and SIVETER, D. J. 2015. The fossil record and palaeoenvironmental significance of marine arthropod zooplankton. Earth-Science Reviews, 146: 146–162.
  • RIISGÅRD, H. U. and LARSEN, P. S. 2010. Particle capture mechanisms in suspension-feeding invertebrates. Marine Ecology Progress Series, 418: 255–293.
  • VANNIER, J., ARIA, C., TAYLOR, R. S. and CARON, J. B. 2018. Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale. Royal Society Open Science, 5:172206.
  • ZHAI, D., ORTEGA-HERNÁNDEZ, J., WOLFE, J. M., HOU, X.-G., CAO, C. and LIU, Y. 2019. Three-dimensionally preserved appendages in an early Cambrian stem-group pancrustacean. Current Biology, 29: 171–177.
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Sarotrocercus oblita

Reconstruction of Sarotrocercus oblita.

© MARIANNE COLLINS

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Sarotrocercus oblita
Remarks:

The phylogenetic affinity of Sarotrocercus is uncertain because its morphology is too poorly known to make a definitive designation. Fryer (1998) suggested it was the most primitive of all arthropods, and it was placed within the Arachnomorpha by Cotton and Braddy (2004). Sarotrocercus has also been aligned with Megacheiran taxa such as Yohoia (e.g. Briggs and Fortey, 1989) and Leanchoilia (e.g., Wills et al. 1995; 1998).

Described by: Whittington
Description date: 1981
Etymology:

Sarotrocercus – from the Greek sarotes, “sweeper”, and kerkops, “a long tailed-monkey”, in reference to the feathery aspect of the tail.

oblita – from the Latin oblitus, “forgotten”, perhaps in reference to the fact that the few specimens of this species were described as part of another species.

Type Specimens: Holotype –USNM144890 (part) and UNSM 272171 (counterpart) 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:

The genus Sarotrocercus was erected by Harry Whittington in 1981 based on seven specimens originally included within Molaria spinifera (Simonetta and Delle Cave, 1975). No further research has been performed on the fossil material since then, although Sarotrocercus has been included in many studies of arthropod relationships (e.g. Briggs and Fortey, 1989; Wills et al., 1995; Fryer, 1998).

Description:

Morphology:

Sarotrocercus has an oval body consisting of a head shield and nine overlapping trunk segments; a cylindrical posterior segment carries a relatively short, narrow spine ending in a fan-shape cluster of small spikes. The whole animal was about 1.5 cm long. Although the head shield was not very strongly developed, it did bear a pair of large, stalked eyes that poked out from beneath the margin, and a pair of jointed appendages. Each of the nine body segments bore a pair of lobate appendages, with comb-like fringes which might have functioned as gills.

Abundance:

S. oblita is rare in the Burgess Shale. It was originally described on the basis of 7 specimens (Whittington, 1981), and 28 further specimens have been recovered from the Walcott Quarry representing less than 0.1% of the community (Caron and Jackson, 2008).

Maximum Size:
16 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The absence of walking limbs combined with an inferred flexibility of the body imply that the organism swam, probably in an inverted position, using its paddle-like appendages and long tail. Its rarity in the Burgess Shale suggests that it may have spent much time in the water column, thus avoiding submarine landslides that trapped animals living on the sea floor. The absence of sediment in its gut suggest that Sarotrocercus was a filter feeder (Briggs and Whittington, 1985; Whittington, 1981).

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 H. B. WHITTINGTON, 1985. Modes of life of arthropods from the Burgess Shale, British Columbia. Transactions of the Royal Society of Edinburgh. Earth Sciences, 76(2-3): 149-160.

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

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, 94(03): 169-193.

FRYER, G. 1998. A defence of arthropod polyphyly, p. 23. In R. A. Fortey and R. H. Thomas (eds.), Arthropod relationships. Springer, London.

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. 1981. Rare arthropods from the Burgess Shale, Middle Cambrian, British Columbia. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 292(1060): 329-357.

WILLS, M. A., D. E. G. BRIGGS, R. A. FORTEY AND M. WILKINSON, 1995. The significance of fossils in understanding arthropod evolution. Verhandlungen den deutschen zoologischen Gesellschaft, 88: 203-216.

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:

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Insolicorypha psygma

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

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

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Unranked clade (stem group polychaetes)
Species name: Insolicorypha psygma
Remarks:

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

Described by: Conway Morris
Description date: 1979
Etymology:

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

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

Type Specimens: Holotype –USNM198667 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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:

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

Description:

Morphology:

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

Abundance:

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

Maximum Size:
12 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

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

References:

CONWAY MORRIS, S. 1979. Middle Cambrian Polychaetes from the Burgess Shale of British Columbia. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 285: 227-274.

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

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Pikaia gracilens

3D animation of Pikaia gracilens.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Unranked clade (stem group chordates)
Species name: Pikaia gracilens
Remarks:

Pikaia is considered to represent a primitive chordate (Conway Morris, 1979; Conway Morris et al., 1982) possibly close to craniates (Janvier, 1998); a stem-chordate (Smith et al., 2001); or a cephalochordate (Shu et al., 1999). Its exact position within the chordates is still uncertain and this animal awaits a full redescription.

Described by: Walcott
Description date: 1911
Etymology:

Pikaia – from the pika, a small alpine mammal and cousin of the rabbits. Pikas live in the Rocky Mountains, including near the Burgess Shale.

gracilens – from the Latin gracilens, “thin, simple,” in reference to the shape of the body.

Type Specimens: Syntypes –USNM57628b, 57629 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:

Pikaia was first described by Walcott based on a couple of specimens in a 1911 monograph dealing with various Burgess Shale worms. Two additional specimens were figured in a posthumous publication (Walcott, 1931). Walcott placed Pikaia in a now defunct group called the Gephyrea with other vermiform fossils such as Banffia, Ottoia and Oesia. Pikaia was later considered to be a primitive chordate (Conway Morris, 1979; Conway Morris et al., 1982), an interpretation which has since been followed to some degree in most discussions about early chordate evolution (e.g., Janvier, 1998). Pikaia played a major part in Gould’s interpretations of the Burgess Shale fossils in Wonderful Life (Gould, 1989; see also Briggs and Fortey, 2005). A full redescription of this animal is currently under way (Conway Morris and Caron, in prep.).

Description:

Morphology:

Pikaia resembles Metaspriggina in outline, another chordate animal from the Burgess Shale, with an elongate body and a small anterior region bearing the head. The body is laterally flattened and there is evidence of a ventral fin towards the posterior. Numerous V-shaped or ziz-zag segments interpreted as myomeres or muscle bands are visible in all specimens. A narrow dorsal structure which runs down the length of the organism might represent a notochord, but this interpretation remains to be confirmed. The head bears two equal lobes and a pair of short and slender tentacle-like structures. There is no evidence of eyes. Just behind the head, on the ventral side of the body, there is a series of up to twelve pairs of small, short, pointed structures on either side of the midline. These are thought to be related to gill openings. The gut is narrow and the anus is terminal.

Abundance:

Pikaia is relatively rare, known from more than 60 specimens, all from the Walcott Quarry where it represents 0.03% of the specimens counted in the community (Caron and Jackson, 2008).

Maximum Size:
55 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The eel-like morphology and musculature of the animal suggest that it was likely free-swimming, although it probably spent time on the sea floor. The tentacles may have had a sensory function, and the presence of mud in its gut suggests that Pikaia was potentially a deposit feeder.

References:

BRIGGS, D. E. G. AND R. A. FORTEY. 2005. Wonderful strife: Systematics, stem groups, and the phylogenetic signal of the Cambrian radiation. Paleobiology, 31(SUPPL.2 ): 94-112.

CONWAY MORRIS, S. 1979. The Burgess Shale (Middle Cambrian) fauna. Annual Review of Ecology and Systematics, 10(1): 327-349.

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. H. B. WHITTINGTON, D. E. G. BRIGGS, C. P. HUGHES AND D. L. BRUTON. 1982. Atlas of the Burgess Shale. Palaeontological Association, 31 p. + 23 pl.

GOULD, S. J. 1989. Wonderful Life. The Burgess Shale and the Nature of History. Norton, New York, 347 p.

JANVIER, P. 1998. Les vertébrés avant le Silurien. GeoBios, 30: 931-950.

SHU, D.-G,. H. L. LUO, S. CONWAY MORRIS, X. L. ZHANG, S. X. HU, L. CHEN, J. HAN, M. ZHU, Y. LI AND L. Z. CHEN. 1999. Lower Cambrian vertebrates from south China. Nature, 402(4 November 1999): 42-46.

SMITH, M. P., I. J. SANSOM AND K. D. COCHRANE. 2001. The Cambrian origin of vertebrates, p. 67-84. In P. E. Ahlberg (ed.), Major Events in Early Vertebrate Evolution: Palaeontology, Phylogeny, Genetics and Development. Taylor and Francis, London.

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

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

Other Links:

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



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Carnarvonia venosa

Carnarvonia venosa (USNM 57719) – Holotype. Complete valves attached along the hinge line showing the network of vascular-like elements as mirror-like structures, dorsal view. Specimen length = 100 mm. Specimen dry – direct light. Raymond Quarry.

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

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Hymenocarines
Species name: Carnarvonia venosa
Remarks:

Hymenocarines were early arthropods with bivalved carapaces and mandibles, forming the bulk of the first mandibulates (represented today by myriapods, crustaceans and insects) (Aria and Caron 2017; Vannier et al. 2018).

Described by: Walcott
Description date: 1912
Etymology:

Carnarvonia – from Mount Carnarvon (3,040 m), a peak in Yoho National Park. The peak was named by Alexander Burgess in 1900 in honour of Lord Henry Herbert Carnarvon (1831-1890), colonial secretary.

venosa – from the Latin vena, “vein,” referring to the vascular markings on the carapace.

Type Specimens: Holotype –USNM57719 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, Wuliuan stage, Burgess Shale Formation (approximately 505 million years ago).
Principal localities:

The Raymond Quarry in Fossil Ridge, Tokumm Creek.

History of Research:

Brief history of research:

This taxon was designated by Walcott in 1912 to describe a single specimen of a bivalved carapace that he believed was from a malacostracan crustacean. Simonetta and Delle Cave (1975) added a possible second specimen, which was later synonymized with Perspicaris recondita by Briggs (1977). The crustacean affinity has been questioned by Conway Morris (1979) and Jones and McKenzie (1980). Vannier et al. (1997) described the supposed vascular structures and compared them with modern malacostracan crustaceans. Based on our current understanding of early arthropod evolution, Carnarvonia most probably belongs to the bivalved arthropod group Hymenocarina (Aria and Caron 2017; Vannier et al. 2018), or stands among its close relatives.

Description:

Morphology:

Carnarvonia venosa has a carapace with two semi-circular and non-mineralized valves preserved flat on the shale, and joined along a straight dorsal ridge (hinge line). The outer margin of the carapace has a smooth outline. There are two globular and raised circles in a mirrored arrangement on both valves, which Walcott (1912) and Vannier et al. (1997) interpret to be adducted muscle scars (i.e., muscles attaching the carapace to the body of the animal), as well as a pair of potential eye sockets (Vannier et al., 1997). Perhaps the most striking feature preserved is a network of vascular-like elements which have left a clear imprint on the inner side of the soft carapace and now appear as raised, branching canals. No evidence of body structures, such as thorax, abdomen or limbs have been found, so far.

Abundance:

Carnarvonia is extremely rare. Only two specimens are known.

Maximum Size:
10 cm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

Based on similarities to other bivalved carapaces in the Burgess Shale, it is assumed that the carapace of Carnarvonia venosa was an external covering of an arthropod body. If the circular structures are muscle attachment scars, it may indicate that some movement, such as opening and closing of the valves, was possible. The vascular system is comparable to swimming malacostracans and might suggest a nektonic mode of life. A further description of the life habits is impossible without more complete specimens.

References:

  • ARIA, C. AND CARON, J. B. 2017. Burgess Shale fossils illustrate the origin of the mandibulate body plan. Nature, 545: 89–92.
  • BRIGGS, D. E. G. 1977. Bivalved arthropods from the Cambrian Burgess Shale of British Columbia. Palaeontology, 20: 596-612.
  • CONWAY MORRIS, S. 1979. The Burgess Shale (Middle Cambrian) fauna. Annual Review of Ecology, Evolution and Systematics, 10: 327-349.
  • JONES, P. J. AND K. G. MCKENZIE. 1980. Queensland Middle Cambrian Bradoriida (Crustacea): new taxa, palaeobiogeography and biological affinities. Alcheringa: An Australian Journal of Palaeontology, 4: 203-225.
  • 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.
  • VANNIER, J. M. WILLIAMS AND D. SIVETER. 1997. The Cambrian origin of the circulatory system of crustaceans. Lethaia, 30: 169-184.
  • VANNIER, J., ARIA, C., TAYLOR, R. S. AND CARON, J. B. 2018. Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale. Royal Society Open Science, 5:172206:
  • WALCOTT, C. 1912. Cambrian Geology and Paleontology II. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57(6): 145-228.
Other Links:

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Anomalocaris canadensis

3D animation of Anomalocaris canadensis.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Order Radiodonta, Family Anomalocarididae
Species name: Anomalocaris canadensis
Remarks:

Anomalocaris is the most iconic member of Radiodonta, the extinct group of arthropods characterized by a circular tooth-lined mouth and a single pair of jointed frontal appendages (Collins 1996). Within this group, Anomalocaris belongs to the eponymous family Anomalocarididae, which possess long, multisegmented grasping appendages with numerous trident-like spines (Vinther et al. 2014).

Described by: Whiteaves
Description date: 1892
Etymology:

Anomalocaris – from the Greek anomoios, “unlike,” and the Latin caris, “crab” or “shrimp,” thus, “unlike other shrimp.”

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

Type Specimens: Lectotype – GSC3418 in the Geological Survey of Canada, Ottawa, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits:

Other deposits: Several species have been described from widely distributed deposits, including Anomalocaris pennsylvanica from the Kinzers Formation, USA (Pates and Daley 2018), Anomalocaris magnabasis from the Pioche and Carrara Formations (Pates et al. 2019), A. cf. canadensis from the Emu Bay Shale, Australia (Daley et al. 2013), A. cf. canadensis. from the Eager Formation (Briggs 1979), British Columbia, Canada, and possibly A. sp. from the Balang Formation of China (Liu 2013). As a consequence of the complex history of research on Anomalocaris (see below), several species previously assigned to this genus likely belong to other genera (e.g., Daley et al., 2013; Wang et al., 2013; Wu et al., 2021), but not all have yet been reassigned.

Age & Localities:

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

The Collins, Raymond and Walcott Quarries on Fossil Ridge. The Trilobite Beds, Tulip Beds (S7) and the Collins Quarry on Mount Stephen. Additional localities on Mount Field, Mount Stephen, and near Stanley Glacier.

History of Research:

Brief history of research:

Anomalocaris famously has a complex history of description because parts of its body were described in isolation before it was realized they all belonged to the same animal. The frontal appendage of Anomalocaris was described by Whiteaves (1892) as the body of a shrimp. The mouth parts were described by Walcott (1911) as a jellyfish called Peytoia nathorsti. A full body radiodontan specimen was originally described as the sea cucumber Laggania cambria (Walcott 1911), and re-examined by Conway Morris (1978) who concluded it was a superimposition of the “jellyfish” Peytoia nathorsti on top of a sponge. Henriksen (1928) attached Anomalocaris to the carapace of Tuzoia, but Briggs (1979) suggested instead that it was the appendage of an unknown arthropod, an idea that turned out to be correct. In the early 1980s, Harry Whittington was preparing an unidentified Burgess Shale fossil from the Geological Survey of Canada by chipping away layers of rock to reveal underlying structures, when he solved the mystery of Anomalocaris‘s identity. Much to his surprise, Whittington uncovered two Anomalocaris “shrimp” attached to the head region of a large body, which also had the “jellyfish” Peytoia as the mouth apparatus. Similar preparations of other fossils from the Smithsonian Institution in Washington DC revealed the same general morphology, including the Laggania cambria specimen studied by Conway Morris (1978), which was reinterpreted as a second species of Anomalocaris. Thus, Whittington and Briggs (1985) were able to describe two species: Anomalocaris canadensis, which had a pair of Anomalocaris appendages, and Anomalocaris nathorsti, which had a different type of frontal appendage and includes the original specimen of Laggania cambria and Peytoia nathorsti. Bergström (1986) re-examined the morphology and affinity of Anomalocaris and suggested it had similarities to the arthropods. Collecting at the Burgess Shale by the Royal Ontario Museum in the early 1990s led to the discovery of several complete specimens, which Collins (1996) used to reconstruct Anomalocaris canadensis with greater accuracy. This also led to a name change of Anomalocaris nathorsti to Laggania cambria, although it was later argued that the name Peytoia nathorsti had priority (Daley and Bergström 2012). Daley and Bergström (2012) re-examined the material and were the first to recognize that the mouthpart of A. canadensis was triradially organized, distinct from prior interpretations of a tetraradial organization as in Peytoia. Daley and Edgecombe (2014) conducted the most recent comprehensive revision of A. canadensis based on all available material. Anomalocaris has been the subject of many studies discussing its morphology (e.g. Moysiuk and Caron 2019; Paterson et al. 2020; Zeng et al. 2022), affinity (e.g., Chen et al., 2004; Daley et al., 2009; Hou et al., 1995; Vinther et al., 2014), ecology (e.g., Nedin, 1999; Rudkin, 1979; Vannier et al., 2014) and functional morphology (e.g., de Vivo et al., 2021; Sheppard et al., 2018; Usami, 2006).

Description:

Morphology:

Anomalocaris is a dorsoventrally flattened animal with a relatively flexible exoskeleton. It has a segmented body, with sixteen lateral swimming flaps bearing gills, and a prominent tail fan, which consists of three pairs of prominent fins that extend upward from the body (Daley and Edgecombe 2014). Repeated paired gut glands are associated with the body segments in some specimens. The head region bears one pair of frontal jointed appendages, two large dorsal eyes on stalks, three small rounded plates, and a ventrally oriented circular mouth apparatus (Whittington and Briggs 1985; Daley and Edgecombe 2014; Moysiuk and Caron 2019). The mouthparts are composed of three large, tubercle-covered plates separated by a series of smaller plates, all with orally-directed teeth (Daley and Bergström 2012). The frontal appendages are elongated and have fourteen segments, each with a pair of trident-like spikes projecting from the ventral surface (Briggs 1979). The most complete Anomalocaris specimen is 25 cm in length, although isolated fragments suggest individuals could reach a larger size, perhaps up to 100 cm.

Abundance:

The Anomalocaris frontal appendage is extremely common at the Mount Stephen Trilobite Beds, and several hundred specimens of isolated frontal appendages and mouth parts have been collected from Mount Stephen and the Raymond Quarry on Fossil Ridge (O’Brien and Caron 2016; Nanglu et al. 2020). These parts are relatively rare at Walcott Quarry, where fewer than 50 specimens are known (Caron and Jackson 2008). About ten complete body specimens are known from the Raymond Quarry.

Maximum Size:
About 100 cm.

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The streamlined body would have been ideal for swimming. Undulatory movements of the lateral flaps propelled the animal through the water column and might have also served in gill ventilation (Whittington and Briggs 1985; Usami 2006). The tail fan would have enabled rapid turning, allowing Anomalocaris to chase fast-moving prey (Sheppard et al. 2018). A predatory lifestyle is suggested by the large eyes, frontal appendages with spines, gut glands, and spiny mouth apparatus (Whittington and Briggs 1985; Vannier et al. 2014). The frontal appendages are highly flexible, suggesting an ability to precisely manipulate prey items (de Vivo et al. 2021). The circular ring of plates around the mouth, shared with other radiodontans, is unique in the animal kingdom. Although the precise functioning of these mouthparts remains unclear, it seems likely that the plates could be pivoted to bring the teeth into contact with prey or to create suction to draw prey into the mouth (Daley and Bergström 2012). It has been suggested that Anomalocaris may have preyed on trilobites because some Cambrian trilobites have round or W-shaped healed wounds, interpreted as bite marks (Rudkin 1979), and large fecal pellets composed of trilobite parts have been found in the Cambrian rock record (Nedin 1999). It was proposed that Anomalocaris could have fed by grasping one end of the trilobite in the mouth apparatus and rocking the other end back and forth with the frontal appendages until the exoskeleton cracked (Nedin 1999). However, the non-biomineralized mouth apparatus of Anomalocaris was arguably too weak to penetrate the calcified shell of trilobites and it never shows any sign of breakage or wear, rendering this hypothesis less plausible (Whittington and Briggs 1985; Daley and Bergström 2012). Other Cambrian predators, such as larger trilobites, have been proposed as alternative candidates responsible for coprolites and trilobite injuries (Bicknell et al. 2021, 2022). It remains conceivable that Anomalocaris could have fed on freshly moulted “soft-shell” trilobites as well as other soft bodied organisms (Rudkin 2009).

References:

  • BERGSTRÖM, J. 1986. Opabinia Anomalocaris, unique Cambrian ‘arthropods’. Lethaia, 19: 241–246.
  • BICKNELL, R. D. C., HOLMES, J. D., PATES, S., GARCÍA-BELLIDO, D. C. and PATERSON, J. R. 2022. Cambrian carnage: Trilobite predator-prey interactions in the Emu Bay Shale of South Australia. Palaeogeography, Palaeoclimatology, Palaeoecology, 591: 110877.
  • BICKNELL, R. D. C., HOLMES, J. D., EDGECOMBE, G. D., LOSSO, S. R., ORTEGA-HERNÁNDEZ, J., WROE, S. and PATERSON, J. R. 2021. Biomechanical analyses of Cambrian euarthropod limbs reveal their effectiveness in mastication and durophagy. Proceedings of the Royal Society B, 288: 20202075.
  • BRIGGS, D. E. G. 1979. Anomalocaris: The largest known Cambrian arthropod. Palaeontology, 22: 631–664.
  • CARON, J.-B. and JACKSON, D. A. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222–256.
  • CHEN, J., WALOSZEK, D. and MAAS, A. 2004. A new ‘great-appendage’ arthropod from the Lower Cambrian of China and homology of chelicerate chelicerae and raptorial antero-ventral appendages. Lethaia, 37: 3–20.
  • 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.
  • CONWAY MORRIS, S. 1978. Laggania cambria Walcott: a composite fossil. Journal of Paleontology, 52: 126–131.
  • DALEY, A. C. and BERGSTRÖM, J. 2012. The oral cone of Anomalocaris is not a classic ‘peytoia’. Naturwissenschaften, 99: 501–504.
  • DALEY, A. C.  and EDGECOMBE, G. D. 2014. Morphology of Anomalocaris canadensis from the Burgess Shale. Journal of Paleontology, 88: 68–91.
  • DALEY, A. C., BUDD, G. E., CARON, J.-B., EDGECOMBE, G. D. and COLLINS, D. 2009. The Burgess Shale anomalocaridid Hurdia and its significance for early euarthropod evolution. Science, 323: 1597–1600.
  • DALEY, A. C., PATERSON, J. R., EDGECOMBE, G. D., GARCÍA-BELLIDO, D. C. and JAGO, J. B. 2013. New anatomical information on Anomalocaris from the Cambrian Emu Bay Shale of South Australia and a reassessment of its inferred predatory habits. Palaeontology, 56: 971–990.
  • HENRIKSEN, K. L. 1928. Critical notes upon some Cambrian arthropods described from Charles D. Walcott. Videnskabelige Meddelelser fra Dansk Naturhistorisk Forening: Khobenhavn, 86: 1–20.
  • HOU, X., BERGSTRÖM, J. and AHLBERG, P. 1995. Anomalocaris and other large animals in the Lower Cambrian Chengjiang fauna of southwest China. GFF, 117: 163–183.
  • LIU, Q. 2013. The first discovery of anomalocaridid appendages from the Balang Formation (Cambrian Series 2) in Hunan, China. Alcheringa, 37: 338–343.
  • 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.
  • NANGLU, K., CARON, J.-B. and GAINES, R. R. 2020. The Burgess Shale paleocommunity with new insights from Marble Canyon, British Columbia. Paleobiology, 46: 58–81.
  • NEDIN, C. 1999. Anomalocaris predation on nonmineralized and mineralized trilobites. Geology, 27: 987–990.
  • O’BRIEN, L. J. and CARON, J. B. 2016. Paleocommunity analysis of the Burgess Shale Tulip Beds, Mount Stephen, British Columbia: Comparison with the Walcott Quarry and implications for community variation in the Burgess Shale. Paleobiology, 42: 27–53.
  • PATERSON, J. R., EDGECOMBE, G. D. and GARCÍA-BELLIDO, D. C. 2020. Disparate compound eyes of Cambrian radiodonts reveal their developmental growth mode and diverse visual ecology. Science Advances, 6: eabc6721.
  • PATES, S. and DALEY, A. C. 2018. The Kinzers Formation (Pennsylvania, USA): The most diverse assemblage of Cambrian Stage 4 radiodonts. Geological Magazine, 156: 1233–1246.
  • PATES, S. and DALEY, A. C, EDGECOMBE, G. D., CONG, P. and LIEBERMAN, B. S. 2019. Systematics, preservation and biogeography of radiodonts from the southern Great Basin, USA, during the upper Dyeran (Cambrian Series 2, Stage 4). Papers in Palaeontology, 7: 235–262.
  • RUDKIN, D. M. 1979. Healed injuries in Ogygosis klotzi (Trilobita) from the Middle Cambrian of British Columbia. Royal Ontario Museum, Life Sciences Occasional Paper, 32: 1–8.
  • RUDKIN, D. M. 2009. The Mount Stephen Trilobite Beds. In CARON, J.-B. and RUDKIN, D. M. (eds.) A Burgess Shale Primer – History, Geology, and Research Highlights, The Burgess Shale Consortium, Toronto, 90–102 pp.
  • SHEPPARD, K. A., RIVAL, D. E. and CARON, J. B. 2018. On the Hydrodynamics of Anomalocaris Tail Fins. Integrative and comparative biology,.
  • 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.
  • VANNIER, J., LIU, J., LEROSEY-AUBRIL, R., VINTHER, J. and DALEY, A. C. 2014. Sophisticated digestive systems in early arthropods. Nature Communications, 5: 3641.
  • VINTHER, J., STEIN, M., LONGRICH, N. R. and HARPER, D. A. T. 2014. A suspension-feeding anomalocarid from the Early Cambrian. Nature, 507: 496.
  • DE VIVO, G., LAUTENSCHLAGER, S. and VINTHER, J. 2021. Three-dimensional modelling, disparity and ecology of the first Cambrian apex predators. Proceedings of the Royal Society B, 288: 20211176.
  • WALCOTT, C. D. 1911. Middle Cambrian holothurian and medusae. Smithsonian Miscellaneous Collections, 57: 41–68.
  • WANG, Y. Y., HUANG, D. Y. and HU, S. X. 2013. New anomalocardid frontal appendages from the Guanshan biota, eastern Yunnan. Chinese Science Bulletin, 58: 3937–3942.
  • WHITEAVES, J. F. 1892. Description of a new genus and species of phyllocarid Crustacea from the Middle Cambrian of Mount Stephen, B.C. Canadian Record of Science, 5: 205–208.
  • WHITTINGTON, H. B. and BRIGGS, D. E. G. 1985. The largest Cambrian animal, Anomalocaris, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society B: Biological Sciences, 309: 569–609.
  • WU, Y., FU, D., MA, J., LIN, W., SUN, A. and ZHANG, X. 2021. Houcaris gen. nov. from the early Cambrian (Stage 3) Chengjiang Lagerstätte expanded the palaeogeographical distribution of tamisiocaridids (Panarthropoda: Radiodonta). PalZ, 95: 209–221.
  • ZENG, H., ZHAO, F. and ZHU, M. 2022. Innovatiocaris, a complete radiodont from the early Cambrian Chengjiang Lagerstätte and its implications for the phylogeny of Radiodonta. Journal of the Geological Society, jgs2021-164:.
Other Links:

www.trilobites.info/anohome.html

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



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Amplectobelua stephenensis

Amplectobelua stephenensis (ROM 59492) – Holotype. Individual claw. Specimen length = 51 mm. Specimen wet – polarized light. Tulip Beds (S7) on Mount Stephen.

© Royal Ontario Museum. Photo: Jean-Bernard Caron

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Order Radiodonta, Family Amplectobeluidae
Species name: Amplectobelua stephenensis
Remarks:

Amplectobelua is a member of Radiodonta, the group of arthropods which also includes the more famous Anomalocaris (Collins 1996). The appendages bear a pair of greatly enlarged spines near their bases which form a pincer-like apparatus with the appendage tip. This provides a link with better preserved fossils from China (Chen et al. 1994; Liu et al. 2018), demonstrating membership to the genus Amplectobelua (Hou et al. 1995) of the Family Amplectobeluidae (Vinther et al. 2014).

Described by: Daley and Budd
Description date: 2010
Etymology:

Amplectobelua – from the Latin amplectus, “embrace,” and belua, “monster.”

stephenensis – from Mount Stephen (3,199 m), the mountain peak in Yoho National Park from which the specimens were collected. Named in 1886 for George Stephen, the first president of the Canadian Pacific Railway.

Type Specimens: Holotype –ROM59492 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: Amplectobelua cf. stephenensis is known from the Wheeler Formation of Utah (Lerosey-Aubril et al. 2020). A second species, A. symbrachiata, is known from the Chengjiang Fauna in China (Hou et al. 1995) and possibly from the Kinzers Formation of Pennsylvania (Pates and Daley 2018).

Age & Localities:

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

The Tulip Beds (S7) on Mount Stephen.

History of Research:

Brief history of research:

The specimens of Amplectobelua from the Chinese Chengjiang deposits were first described as “anomalocaridid animal 2” (Chen et al. 1994) and given a formal designation as Amplectobelua symbrachiata by Hou et al. (1995). The Burgess Shale species A. stephenensis was described by Daley and Budd (2010) from six isolated appendages in the Royal Ontario Museum collections. Several papers have subsequently discussed the functional morphology of the appendages of Amplectobelua based on comparisons with modern arthropods and 3D modeling (Liu et al. 2018; de Vivo et al. 2021) as well as the homology of different appendage regions (Moysiuk and Caron 2021). Other discoveries in China have yielded new anatomical information about the genus, particularly related to the feeding apparatus which has been argued to include spinous plates associated with three anterior body segments in addition to the circlet of oral plates shared with other radiodontans (Cong et al. 2017, but see Moysiuk and Caron 2021).

Description:

Morphology:

Amplectobelua stephenensis is known only from isolated appendages that have thirteen segments including a hooked terminal spine (Moysiuk and Caron 2021). The segment nearest to the body has a pair of thick spines nearly as long as the whole appendage which are directed at an angle towards the tip of the appendage, forming a pincer. Segments 2 to 9 have tiny paired inner spines. The appendages range in size from 2.8 cm to 5.1 cm (Daley and Budd 2010). There are also paired outer spines on the three furthest segments, which are long and curved towards the end of the appendage. No full-body specimens of A. stephenensis have yet been found, but it may have had a similar morphology to A. symbrachiata and Anomalocaris, with wide swimming flaps on a dorsoventrally flattened body and a head with eyes on stalks (Chen et al. 1994).

Abundance:

Six specimens of Amplectobelua have been described from a single locality, the Tulip Beds (S7), on Mount Stephen.

Maximum Size:
51 mm (appendage)

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

Amplectobelua is considered a predator, based on the morphology of its frontal appendage. The pincer-like, many-segmented appendage would have been ideal for gripping and manipulating prey items (de Vivo et al. 2021). The distal podomeres could be used to grasp prey with a scissor-like motion when brought into opposition against the proximal endites (Liu et al. 2018). Like other anomalocaridids, Amplectobelua has a streamlined body and would swim through the water column by undulating its lateral flaps to propel itself forward (Usami 2006).

References:

  • CHEN, J. Y., RAMSKÖLD, L. and ZHOU, G. Q. 1994. Evidence for monophyly and arthropod affinity of Cambrian giant predators. Science, 264: 1304–1308.
  • 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.
  • CONG, P., DALEY, A. C., EDGECOMBE, G. D. and HOU, X. 2017. The functional head of the Cambrian radiodontan (stem-group Euarthropoda) Amplectobelua symbrachiata. BMC Evolutionary Biology, 17: 208.
  • DALEY, A. C. and BUDD, G. E. 2010. New anomalocaridid appendages from the Burgess Shale, Canada. Palaeontology, 53: 721–738.
  • HOU, X., BERGSTRÖM, J. and AHLBERG, P. 1995. Anomalocaris and other large animals in the Lower Cambrian Chengjiang fauna of southwest China. GFF, 117: 163–183.
  • LEROSEY-AUBRIL, R., KIMMIG, J., PATES, S., SKABELUND, J., WEUG, A. and ORTEGA-HERNÁNDEZ, J. 2020. New exceptionally preserved panarthropods from the Drumian Wheeler Konservat-Lagerstätte of the House Range of Utah. Papers in Palaeontology, 6: 501–531.
  • LIU, J., LEROSEY-AUBRIL, R., STEINER, M., DUNLOP, J. A., DEGAN, S. and PATERSON, J. R. 2018. Origin of raptorial feeding in juvenile euarthropods revealed by a Cambrian radiodontan. National Science Review, 5: 863–869.
  • MOYSIUK, J. and CARON, J.-B. 2021. Exceptional multifunctionality in the feeding apparatus of a mid-Cambrian radiodont. Paleobiology, 47: 704–724.
  • PATES, S. and DALEY, A. C. 2018. The Kinzers Formation (Pennsylvania, USA): The most diverse assemblage of Cambrian Stage 4 radiodonts. Geological Magazine, 156: 1233–1246.
  • 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.
  • VINTHER, J., STEIN, M., LONGRICH, N. R. and HARPER, D. A. T. 2014. A suspension-feeding anomalocarid from the Early Cambrian. Nature, 507: 496.
  • DE VIVO, G., LAUTENSCHLAGER, S. and VINTHER, J. 2021. Three-dimensional modelling, disparity and ecology of the first Cambrian apex predators. Proceedings of the Royal Society B, 288: 20211176.
Other Links:

None



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Amiskwia sagittiformis

Reconstruction of Amiskwia sagittiformis.

© Marianne Collins

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Non applicable
Species name: Amiskwia sagittiformis
Remarks:

The phylogenetic position of Amiskwia is uncertain. Despite significant objections to its traditional interpretation as a chaetognath (Conway Morris, 1977; Owre and Bayer, 1962), some workers still hold this view (Butterfield, 1990). Nemertine (Owre and Bayer, 1962) and molluscan (Chen and Huang, 2002; Chen et al., 2005) affinities have also been suggested, but not substantiated.

Described by: Walcott
Description date: 1911
Etymology:

Amiskwia – from the Cree amiskwi, “beavertail,” a name given to various topographical features in Yoho National Park.

sagittiformis – from the Latin sagitta, “arrow,” and formis, “shape,” in reference to the general outline of the animal.

Type Specimens: Lectotype – UNSM 57644 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: A. sinica (Chen et al., 2002) from the Lower Cambrian Chengjiang deposits, Yunnan, China.

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:

Described by Walcott in 1911, Amiskwia was originally interpreted as an arrow-worm (Walcott, 1911). Originally popular, this interpretation fell into disrepute after further studies (Conway Morris, 1977; Owre and Bayer, 1962), but it has more recently been reconsidered as a possible arrow-worm (Butterfield, 1990).

Description:

Morphology:

Amiskwia is a symmetrical, flattened worm. It bears a pair of lateral fins in addition to a paddle-like tail fin. A pair of small tentacles is situated on the bottom of its head, just in front of its mouth. The trace of a gut and other internal organs are preserved in the fossils.

Abundance:

A. saggitiformis is known from only a couple dozen specimens from the Walcott Quarry, comprising only 0.025% of the specimens counted (Caron and Jackson, 2008).

Maximum Size:
25 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The presence of fins demonstrates that Amiskwia was well adapted for swimming. Its rarity in the Burgess Shale suggests that it may have spent much of its time well above the sea bed, above the depth at which it could be caught in submarine mudslides.

References:

BUTTERFIELD, N. J. 1990. Organic preservation of non-mineralizing organisms and the Taphonomy of the Burgess Shale. Paleobiology, 16(3): 272-286.

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.-Y. AND D.-Y. HUANG. 2002. A possible Lower Cambrian chaetognath (arrow worm). Science, 298(5591): 187.

CHEN, J.-Y., D.-Y. HUANG AND D. J. BOTTJER. 2005. An Early Cambrian problematic fossil: Vetustovermis and its possible affinities. Proceedings of the Royal Society B: Biological Sciences, 272(1576): 2003-2007.

CHEN, L., H. LUO, S. HU, J. YIN, Z. JIANG, Z. WU, F. LI AND A. CHEN. 2002. Early Cambrian Chengjiang fauna in Eastern Yunnan, China. Yunnan Science and Technology Press, Kunming, China, 199 p.

CONWAY MORRIS, S. 1977. A redescription of the Middle Cambrian worm Amiskwia sagittiformis Walcott from the Burgess Shale of British Columbia. Palaontologische Zeitschrift, 51(3): 271-287.

OWRE, H. B. AND F. M. BAYER. 1962. The systematic position of the Middle Cambrian fossil Amiskwia Walcott. Journal of Paleontology, 36(6): 1361-1363.

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

Other Links:

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



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Metaspriggina walcotti

Metaspriggina walcotti (USNM 198611) – Holotype, part and counterpart. Lateral specimen showing clear myomeres; anterior to the right. Specimen length = 43 mm. Specimen dry – direct light (left column), dry – polarized light (right column). Walcott Quarry.

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

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Unranked clade (stem group chordates)
Species name: Metaspriggina walcotti
Remarks:

Metaspriggina is considered to represent a primitive chordate, possibly transitional between cephalochordates and the earliest vertebrates (Conway Morris, 2008).

Described by: Simonetta and Insom
Description date: 1993
Etymology:

Metaspriggina – from the Greek meta, “in company with, or later in time,” and the morphologically similar Ediacaran organism Spriggina (which is no longer thought to be related). Spriggina honours Reg Sprigg, discoverer of the Precambrian fossils of the Ediacara Hills in Australia.

walcotti – after Charles Walcott, discoverer of the Burgess Shale.

Type Specimens: Lectotype –USNM198612 and former holotype 198611 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:

Set aside by Walcott for further study, the two known specimens of this species were briefly examined by Conway Morris (1979). Simonetta and Insom (1993) described one of the two specimens (the original holotype specimen) as a potential relative of the Ediacaran organism Spriggina, whereas the second specimen (now the lectotype) was interpreted as a potential chordate. A chordate interpretation for both specimens was proposed (Janvier, 1998; Smith et al., 2001) and a detailed redescription was eventually instigated by Conway Morris (2008) with both specimens being included in the same genus and species.

Description:

Morphology:

Metaspriggina is elongate in shape with a small anterior cranial region and a long triangular and laterally flattened trunk; there is no evidence of fins. The larger of the two known fossil specimens is around 7 cm in length. Both specimens possess numerous V-shaped or zig-zag segments interpreted as myomeres or muscle bands. A narrow central structure runs down the length of the organism and is interpreted as a gut. The front of one specimen appears to show a rudimentary cranium which is poorly preserved and seems to have lacked eyes.

Abundance:

M. walcotti is very rare in the Walcott Quarry, known from just two specimens.

Maximum Size:
69 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

With only two specimens, and poor preservation of the head, the diet and feeding habits of Metaspriggina remain a mystery. The rarity of fossils suggests that the animal was likely free-swimming, which is consistent with its musculature, although it is possible that it also spent some time on the sea floor.

References:

CONWAY MORRIS, S. 1979. The Burgess Shale (Middle Cambrian) fauna. Annual Review of Ecology and Systematics, 10(1): 327-349.

CONWAY MORRIS, S. 2008. A redescription of a rare chordate, Metaspriggina walcottiSimonetta and Insom, from the Burgess Shale (Middle Cambrian), British Columbia, Canada. Journal of Paleontology, 82(2): 424-430.

JANVIER, P. 1998. Les vertébrés avant le Silurien. GeoBios, 30: 931-950.

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(1): 97 – 107.

SMITH, M. P., I. J. SANSOM AND K. D. COCHRANE. 2001. The Cambrian origin of vertebrates, p. 67-84. In P. E. Ahlberg (ed.), Major Events in Early Vertebrate Evolution: Palaeontology, Phylogeny, Genetics and Development. Taylor and Francis, London.

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Laggania cambria

Reconstruction of Laggania cambria.

© Marianne Collins

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Higher Taxonomic assignment: Dinocarida (Order: Radiodonta, stem group arthropods)
Species name: Laggania cambria
Remarks:

Laggania is an anomalocaridid. Anomalocaridids have been variously regarded as basal stem-lineage euarthropods (e.g., Daley et al., 2009), basal members of the arthropod group Chelicerata (e.g., Chen et al., 2004), and as a sister group to the arthropods (e.g., Hou et al., 2006).

Described by: Walcott
Description date: 1911
Etymology:

Laggania – from Laggan, the name given to a now defunct railway station on the Canadian Pacific Railway in Banff National Park, now known as Lake Louise Village. The name Laggan comes from a location of a 1655 battle in the Great Glen of Scotland.

cambria – from the Welsh Cambria meaning Wales.

Type Specimens: Holotype –USNM57555 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: A possible new species from the Tulip Beds (S7) on Mount Stephen (Daley and Budd, 2010).

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:

The anomalocaridids, including Laggania, have a complex history of description, because parts of their bodies were preserved in isolation from each other, resulting in the body part fossils being given their own generic names before they were identified as different parts of the same animal. The name Laggania cambria was first applied to a single specimen of a “sea cucumber” (Walcott, 1911a), which was later re-described as a superimposition of the “jellyfish” Peytoia nathorsti on top of a sponge (Conway Morris, 1978). The frontal appendages of Laggania were first described as “Appendage F”, the feeding appendages of the arthropod Sidneyia (Walcott, 1911b), but they were later removed from that genus and described as the appendage of an unknown arthropod (Briggs, 1979).

A critical revelation was made by Harry Whittington early in the 1980s when he discovered the basic body plan of the anomalocaridids by preparing specimens of Anomalocaris and Laggania. He revealed that the anomalocaridids had the “jellyfish” Peytoia as a mouth part and a pair of large frontal appendages at the front of the head. Whittington and Briggs (1985) first described Laggania under the name Anomalocaris nathorsti. Bergström (1986) re-described some aspects of the morphology of the anomalocaridids.

The discovery of several more complete specimens during Royal Ontario Museum fieldwork in the 1990s allowed Collins (1996) to reconstruct the genus Anomalocaris with greater accuracy. This led to a reversal of names from Anomalocaris nathorsti to Laggania cambria. Laggania has since been the subject of many studies discussing anomalocaridid affinity (e.g., Hou et al., 1995; Chen et al., 2004; Daley et al., 2009).

Description:

Morphology:

The body of Laggania consists of a posterior body region with a series of lateral swimming flaps, and a head region with circular mouth parts, a pair of frontal appendages, two large eyes, and a head shield. Full body specimens are no longer than 15 cm in length, but isolated parts suggest that body lengths could be much longer, perhaps up to 50 cm. The frontal appendages have eleven robust segments with short dorsal and lateral spines and five elongated ventral spines.

A pair of these appendages is found on the ventral surface of the head, flanking the mouth parts. They consist of 32 rectangular plates, four large and 28 small, arranged in a circle with sharp spines pointing into a square central opening. The large, oval eyes are located on either side of the head, and a thin carapace shield covers the dorsal head region. The trunk of Laggania has a central region of eleven segments bearing rows of gills, and elongated, wide swimming flaps extending out to either side. The body trunk is tapering, and ends in a blunt tail.

Abundance:

Ten whole-body specimens of Laggania and dozens of isolated frontal appendages are known from the Walcott Quarry on Fossil Ridge.

Maximum Size:
500 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

Laggania was an active swimmer, as indicated by the lack of walking limbs and the presence of numerous gills. It probably propelled itself through the water column by undulating its swimming flaps along the sides of its body. The large eyes, sharp mouth parts and spiny appendages would have made Laggania a formidable predator. It may have used its frontal appendages as a sieve to sift prey out from the sediment or entangle swimming prey and sweep them towards its mouth parts. The mouth parts likely operated by pivoting the plates outwards and contracting them inward to bring prey further into the mouth. Like other anomalocaridids, Laggania probably ingested mostly soft-bodied prey. It swam through the water column just above the sea floor, using its large eyes to seek out prey.

References:

BERGSTRÖM, J. 1986. Opabinia and Anomalocaris, unique Cambrian ‘arthropods’. Lethaia, 19: 241-46.

BRIGGS, D. E. G. 1979. Anomalocaris, the largest known Cambrian arthropod. Palaeontology, 22: 631-663.

CHEN, J. Y., D. WALOSZEK AND A. MAAS. 2004. A new ‘great-appendage’ arthropod from the Lower Cambrian of China and homology of chelicerate chelicerae and raptorial antero-ventral appendages. Lethaia, 37: 3-20.

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.

CONWAY MORRIS, S. 1978. Laggania cambria Walcott: a composite fossil. Journal of Paleontology, 52: 126-131.

DALEY, A. C. AND G. E. BUDD. 2010. New anomalocaridid appendages from the Burgess Shale, Canada. Palaeontology, 53: 721-738.

DALEY, A. C., G. E. BUDD, J. B. CARON, G. D. EDGECOMBE AND D. COLLINS. 2009. The Burgess Shale anomalocaridid Hurdia and its significance for early euarthropod evolution. Science, 323: 1597-1600.

HOU, X., J. BERGSTRÖM AND P. AHLBERG. 1995. Anomalocaris and other large animals in the Lower Cambrian Chengjiang fauna of Southwest China. GFF, 117: 163-183.

HOU, X., J. BERGSTRÖM AND Y. JIE. 2006. Distinguishing anomalocaridids from arthropods and priapulids. Geological Journal, 41: 259-269.

WALCOTT, C. D. 1911a. Middle Cambrian holothurians and medusae. Cambrian geology and paleontology II. Smithsonian Miscellaneous Collections, 57: 41-68.

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

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.

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