The Burgess Shale

Kingdoms: Animalia

Loricicaris spinocaudatus

Loricicaris spinocaudatus, paratype, ROMIP 43188

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic assignment: Hymenocarines, Family Protocarididae (Miller 1889).
Species name: Loricicaris spinocaudatus
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 & Caron 2017; Vannier et al. 2018). Loricicaris was a close relative of Branchiocaris, both grouped within the eponymous family Protocarididae Miller, 1889—one of the oldest formal taxa from the Burgess Shale. The relationship of Protocarididae within hymenocarines, as well as the relative placement of hymenocarines within early mandibulates is still under investigation (Aria 2022; Izquierdo-López & Caron 2022).

Described by: Legg and Caron
Description date: 2014
Etymology:

Loricicaris — from the Latin “lorica,” meaning armoured or armour plating, referring to the armoured (spinose) appearance of the trunk, and “caris” meaning shrimp.

spinocaudatus — from the Latin “spinosus” and “cauda,” meaning spiny and tail respectively, in reference to the spinose trunk and tailpiece of this species.

Type Specimens: Holotype ROMIP 62143 and paratype ROMIP 43188, in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.
Other deposits: none.

Age & Localities:

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

The Collins Quarry on Mount Stephen.

History of Research:

Brief history of research:

Following the discovery and initial excavation of the Collins Quarry on Mount Stephen (initially referred as “locality 9”, (Collins et al. 1983)), the small protocaridid material from the Collins Quarry had been referred to as possible juvenile specimens of Branchiocaris (Briggs & Robison 1984). The material was formally described much later as a new genus and species by Legg and Caron (2014), alongside Nereocaris briggsi, and interpreted in the light of a very basal placement of bivalved arthropods in the evolution of the group—a view that has since given way to the mandibulate classification of these taxa (Aria 2022).

Description:

Morphology:

Loricicaris has a stout, tubular, multisegmented body largely enclosed in a broad bivalved carapace with ample, lobate corners, like other protocaridids. Eyes are very reduced or absent. The very front of the animal bears a rounded sclerite. A pair of short, stout, multisegmented antennules are the most anterior appendages. The rest of the head is poorly known, but clawed appendages are present in proximity to the antennules. The trunk limbs bear round exopods; endopods are reduced or absent. The tailpiece is a pair of caudal rami bearing setae.

Abundance:

24 specimens (Legg & Caron 2014).

Maximum Size:
About 3 cm.

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

Loricicaris was considered by its authors to be a nektobenthic deposit feeder, based on the possession of a swimmer body and three-dimensional preservation of the gut (Legg & Caron 2014). Loricicaris could be a predator or particle feeder like other hymenocarines.

References:

  • ARIA, C. 2022. The origin and early evolution of arthropods. Biological Reviews, 97, 1786–1809.
  • 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. and ROBISON, R. A. 1984. Exceptionally preserved nontrilobite arthropods and Anomalocaris from the Middle Cambrian of Utah. The University of Kansas Paleontological Contributions, 111, 1–23.
  • COLLINS, D., BRIGGS, D. E. G. and CONWAY MORRIS, S. 1983. New Burgess Shale fossil sites reveal Middle Cambrian faunal complex. Science, 222, 163–167.
  • IZQUIERDO-LÓPEZ, A. and CARON, J.-B. 2022. The problematic Cambrian arthropod Tuzoia and the origin of mandibulates revisited. Royal Society Open Science, 9.
  • LEGG, D. and CARON, J. B. 2014. New Middle Cambrian bivalved arthropods from the Burgess Shale (British Columbia, Canada). Journal of Paleontology, 57, 691–711.
  • MILLER, S. A. 1889. North American geology and palaeontology for the use of amateurs, students and scientists. Western Methodist Book Concern, Cincinnati.
  • 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.
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Kootenayscolex barbarensis

Kootenayscolex barbarensis, paratype, ROMIP 62972

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic assignment: Polychaetes
Species name: Kootenayscolex barbarensis
Remarks:

Kootenayscolex bears significant resemblance to modern polychaetes, but is currently considered outside of any extant group. It is currently considered as a stem-group polychaete, as are the other polychaetes from the Burgess Shale (Parry et al. 2016; Nanglu and Caron 2018).

Described by: Nanglu and Caron 2018
Description date: 2018
Etymology:

Kootenay — for Kootenay National Park in British Columbia, Canada, where the Marble Canyon fossil locality is located, and scolex from the Greek word for “worm,” which is a common suffix for polychaetes and reflects their general worm-shaped morphology.

barbarensis — from Barbara Polk Milstein, who is a volunteer at the Royal Ontario Museum and a long-time supporter of Burgess Shale research.

Type Specimens: Holotype ROMIP 64388; paratypes ROMIP 63099.1, and ROMIP 64389-, 64398
Other species:

Burgess Shale and vicinity: none
Other deposits: none

Age & Localities:

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

Marble Canyon and the Walcott Quarry on Fossil Ridge, British Columbia.

History of Research:

Brief history of research:

This abundant polychaete, was first reported by Caron et al. in 2014 as a species comparable to Burgessochaeta setigera from the Walcott Quarry. Kootenayscolex was formally described as its own genus by Nanglu and Caron in 2018, using hundreds of new specimens discovered from the Marble Canyon fossil site in Kootenay National Park.

Description:

Morphology:

Kootenayscolex ranged in size from 1mm-30mm. Its head bore two long sensory structures known as palps, as well as a short medial antenna located between them. As with other polychaetes, its body was divided into a series of segments with the widest segments being in the middle of the body. Up to 25 segments have been observed in this species, each of which possessed a pair of parapodia which are fleshy, lateral outgrowths. From these parapodia extended bristles, known as chaetae, arranged into bundles. The dorsal bundles included up to 12 bristles, while the ventral bundles included up to 16 bristles which were arranged as a wider fan. The last segment of this animal, called the pygidium, was relatively simple and possessed no appendages. The head section, called the prostomium, also possessed a single set of parapodia and chaetae, directly adjacent to the mouth.

Abundance:

Kootenayscolex is the fifth most abundant species at Marble Canyon with 833 specimens (Nanglu et al. 2020).

Maximum Size:
About 3 cm.

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

Kootenayscolex has been reconstructed as a deposit feeding organism due to some specimens preserving sediment which filled the gut. This is particularly noticeable in specimens which have an enlarge anterior part of the gut which is nearly the width of the body. The elongate dorsal bristles were likely used for defense against predators, while the ventral bristles would have allowed for movement along the seafloor.

References:

  • NANGLU, K., AND J.-B., CARON. 2018. A new Burgess Shale polychaete and the origin of the annelid head revisited. Current Biology, 28 (2): 319-326.
  • 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.
  • PARRY, L. A., EDGECOMBE, G. D., EIBYE-JACOBSEN, D., AND J. VINTHER. 2016. The impact of fossil data on annelid phylogeny inferred from discrete morphological characters. Proceedings of the Royal Society B: Biological Sciences, 283 (1837): 20161378.
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Gyaltsenglossus senis

Gyaltsenglossus senis, holotype, ROMIP 65606.1

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic assignment: No subphylum assignment
Species name: Gyaltsenglossus senis
Remarks:

Gyaltsenglossus is currently considered a stem-group hemichordate. It has features of both the modern hemichordate groups in that it has the long proboscis and worm-shaped body of the Enteropneusta (acorn worms) and the crown of feeding tentacles of the Pterobranchia.

Described by: Nanglu et al. 2020
Description date: 2020
Etymology:

Gyaltsen (pronounced “GEN-zay”) in honour of the lead author’s father, and glossus from the Greek glossa, meaning tongue, a common generic suffix for hemichordates.

Senis from the Latin senex, meaning old.

Type Specimens: Holotype ROMIP 65606.1
Other species:

Burgess Shale and vicinity: None.
Other deposits: None

Age & Localities:

Age:
Middle Cambrian, Wuliuan Stage, upper part of the Burgess Shale Formation (around 507 million years old).
Principal localities:

Odaray Mountain, Yoho National Park.

History of Research:

Brief history of research:

Gyaltsenglossus was described in 2020 based on 33 specimens, all collected from Odaray Mountain. Only the holotype preserves all major anatomical features.

Description:

Morphology:

: Gyaltsenglossus is a worm roughly 2 cm long. At the anterior end, it has an elongate, ovoid, muscular proboscis. Behind the proboscis is a set of six arms which bore roughly 15 pairs of tentacles. These arms were roughly 1.5 times as long as the proboscis, based on measurements taken from the holotype. The tentacles give the arms an overall fuzzy or foliose appearance. Behind the feeding arms is a roughly cylindrical trunk, which tapers from the largest point at the anterior and becomes smaller towards the posterior end of the animal. On the dorsal side of the trunk, directly behind the feeding arms, an elevated area leads to a set of thin, thread-like appendages. Posterior to the trunk is a bulbous structure with internal features preserved more darkly than in the surrounding tissues. This bulbous structure may constitute thickened tissue. In some specimens, a gut ending prior to the posterior bulbous structure is preserved.

Abundance:

33 specimens were described.

Maximum Size:
About 2 cm.

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

The morphology of Gyaltsenglossus suggests that it had a two-part feeding ecology. The long proboscis could have been used to feed directly from the marine mud on which the animal would have lived, in a manner similar to that of modern-day acorn worms. The feeding arms could also have been used to filter food particles from the water above the organism, as done by pterobranchs. The posterior bulbous appendage may have been used to anchor Gyaltsenglossus to the seafloor, particularly when it was feeding on small particles from the water.

References:

  • NANGLU, K., J.-B. CARON, AND C. B. CAMERON. 2020. Cambrian tentaculate worms and the origin of the hemichordate body plan. Current Biology. 30 (21): 4238-4244
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Fibulacaris nereidis

Fibulacaris nereidis, carapace ROMIP 64511

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic assignment: Hymenocarines, Family: Odaraiidae
Species name: Fibulacaris nereidis
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 Fibulacaris, determining the exact number and types of appendages on their head remains difficult, which hinders a detailed understanding of the evolutionary history of this group. Fibulacaris 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: Izquierdo-López & Caron
Description date: 2019
Etymology:

Fibulacaris – from a “fibula”, a type of brooch, the latin caris, meaning “crab” or “shrimp”

nereidis – from the Greek mythological creatures known as Nereids, the daughters of Nereus, given the similarities of Fibulacaris to the Burgess Shale odaraiid Nereocaris (Legg et al. 2012).

Type Specimens: Holotype ROMIP65380
Other species:

Burgess Shale and vicinity: None
Other deposits: None

Age & Localities:

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

Marble Canyon, Tokumm Creek.

History of Research:

Brief history of research:

Several specimens of Fibulacaris nereidis were discovered at the Marble Canyon site in 2014 and nicknamed “epsilon-arthropod” based on the characteristic shape of its carapace. The majority of specimens were discovered at Mount Whymper and Tokumm Creek sites during the expeditions of 2016 and 2018, sometimes referred as “safety-pin”. Its genus and species were later described in 2019 (Izquierdo-López and Caron 2019).

Description:

Morphology:

Fibulacaris is generally small, with most specimens measuring around 1 cm. It has a distinct bivalved carapace enclosing its body laterally, covering up to two-thirds of its entire length. The dorsal side of the carapace is dome-shaped with a small crest that runs across the entire length, and a small spinose process on its posterior side. The frontal side of the carapace bends ventrally into a highly elongated spine, almost as long as the carapace itself. The ventral margins of the carapace are thicker, and end with a small process posteriorly on both sides. One pair of pedunculate eyes protrudes from the notches formed between the carapace and the spine. Other details about its head remain unknown, but antennae are either absent or highly reduced. The anterior side of the body is bent posteriorly, so that the eyes are facing backward. The body is multisegmented, subdivided into 30 segments, with each segment bearing limbs subdivided into two branches (biramous). Its tail has two small appendages shaped like a paddle (caudal rami).

Abundance:

Fibulacaris is rare at the Marble Canyon site, but very abundant (with more than 100 specimens) along Tokumm Creek.

Maximum Size:
About 2 cm.

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

Fibulacaris was likely a nektobenthic suspension feeder (Izquierdo-López and Caron 2019). Its gut is sometimes preserved as a three-dimensional structure, a type of preservation that has been associated with deposit feeders (Legg and Caron 2014). However, Fibulacaris’ carapace extends through its ventral side, indicating that this arthropod was not able to walk on surfaces and obtain organic material from the sediment, like a deposit feeder. Extant branchiopod crustaceans, such as many water fleas (Cladocera), have carapaces similar to that of Fibulacaris. Using their limbs, they generate small water currents carrying organic particles that pass through their limbs and carapace. Fibulacaris, could have used a similar suspension-feeding strategy. Given that the dorsal side of Fibulacaris was covered by its carapace, and that its eyes were facing towards the back of its body, it has been suggested that it was swimming upside down (Izquierdo-López and Caron 2019), as fairy shrimps do (Anostraca) (Fryer 2006). This way, Fibulacaris would have had capture organic particles falling from the water column, while being protected from predators from its back thanks to the carapace, from its ventral and posterior side thanks to the spine.

References:

  • ARIA, C. and CARON, J. B. 2017. Burgess Shale fossils illustrate the origin of the mandibulate body plan. Nature, 545: 89–92.
  • FRYER, G. 1968. Evolution and adaptive radiation in the Chydoridae (Crustacea: Cladocera): a study in comparative functional morphology and ecology. Philosophical Transactions of the Royal Society of London. B, Biological Sciences, 254: 221–382.
  • FRYER, G. 2006. The brine shrimp’s tale: a topsy turvy evolutionary fable. Biological Journal of the Linnean Society, 88(3): 377–382.
  • 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. 2021. A Burgess Shale mandibulate arthropod with a pygidium: a case of convergent evolution. Papers in Palaeontology, 7: 1877–1894.
  • 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.
  • PARI, G., BRIGGS, D. E. G. and GAINES, R. R. 2022. The soft-bodied biota of the Cambrian Series 2 Parker Quarry Lagerstätte of northwestern Vermont, USA. Journal of Paleontology, 1–21.
  • 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.
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Collinsovermis monstruosus

Collinsovermis monstruosus, holotype ROMIP 52703

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic assignment: Order Luolishaniida, Family Collinsovermidae
Species name: Collinsovermis monstruosus
Remarks:

Collinsovermis is one of a variety of lobopodian taxa from the Cambrian, which are early members of the lineage that gave rise to arthropods, and whose only modern survivors are onychophorans (velvet worms) and tardigrades (water bears). Lobopodians characteristically have annulated, unjointed bodies and bear soft limbs after which they are called: the lobopods. Collinsovermis is an armoured member of the Order Luolishaniida, along with forms such as Collinsium and Luolishania from China, or Acinocricus from Utah—together forming the family Collinsovermidae. Luolishaniids are characterized by their thin spines arranged in chevrons and the differentiation of their body into functional regions for suspension-feeding (Caron & Aria 2017, 2020).

Described by: Caron and Aria
Description date: 2020
Etymology:

Collinsovermis – Collins, patronymic, honours its discoverer, Desmond Collins, and vermis is Latin for worm.

monstruosus – From the Latin, in reference to the nickname ‘Collins’ monster’, first introduced by Delle Cave & Simonetta (1991).

Type Specimens: Holotype: ROMIP 52703, Paratypes: ROMIP 52704 and 52705 at the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: None.
Other deposits: None.

Age & Localities:

Age:
Middle Cambrian, Wuliuan stage, Bathyuriscus-Elrathina Zone of the Burgess Shale Formation (approximately 507 million years old).
Principal localities:

Mount Stephen

History of Research:

Brief history of research:

Collected by a Royal Ontario Museum expedition on Mount Stephen in 1983, the Collinsovermis animal was first revealed, unnamed and undescribed, in the non-peer-reviewed magazine Rotunda (former name of the Royal Ontario Museum Magazine), as a single picture of the holotype, with the caption: “What is it? This new spiny animal (4 cm) with hairy legs has a body plan that has not been seen before.” In 1991, Italian scientists Delle Cave and Simonetta (1991) provided a brief description of the taxon and attempted a reconstruction solely based on the photograph provided by Collins in the Rotunda magazine, coining it the “Collins’ monster”. Despite the lack of name and good documentation, the Collins’ monster have repeatedly featured in studies tackling lobopodian evolution and phylogeny (e.g., Ramsköld & Chen 1998; Budd 2001; Ou et al. 2011; Caron & Aria 2017). It was only in 2020 that the animal was formally named Collinsovermis monstruosus, in honour of Desmond Collins, and fully described based on high resolution pictures of all available material (Caron & Aria 2020).

Description:

Morphology:

Collinsovermis has a plump appearance, with an annulated, unjointed body divided into anterior and posterior regions. The entire dorsum of the body is covered in well-developed spines—three short pairs cover the first three somites (“body segments”) behind the head, while triads of longs spines cover the remaining 10 somites. The anterior region bears 6 pairs of elongate lobopods with thin spines arranged in chevrons, and a small head, as a protrusion bearing a pair of sensory filaments as well as a small dorsal plate and a frontal mouth. The posterior region is made ventrally of 8 pairs of stout annulated lobopods ending in strong, single claws.

Abundance:

Like other lobopodians, Collinsovermis is excessively rare. There are only 3 specimens known, all from the Collins Quarry on Mount Stephen (Fletcher & Collins 2003). They are housed at the Royal Ontario Museum, Department of Natural History.

Maximum Size:
32 mm.

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

Collinsovermis exemplifies suspension-feeding adaptations in lobopodians associated with strongly-developed defensive elements. Like other members of the order Luolishaniidae, and those of the family bearing its name, this animal was using its stout back limbs for anchoring (probably to sponges) and its slender spinose anterior limbs to sieve organic particles or plankton. The long dorsal spines most certainly served as deterrent to predators.

References:

  • BUDD, G. E. 2001. Tardigrades as ‘stem-group arthropods’: The evidence from the Cambrian fauna. Zoologischer Anzeiger, 240, 265–279.
  • CARON, J. and ARIA, C. 2020. The Collins’ monster, a spinous suspension‐feeding lobopodian from the Cambrian Burgess Shale of British Columbia. Palaeontology, 63, 979–994.
  • CARON, J.-B. and ARIA, C. 2017. Cambrian suspension-feeding lobopodians and the early radiation of panarthropods. BMC Evolutionary Biology, 17, 29.
  • DELLE CAVE, L. and SIMONETTA, A. M. 1991. Early Palaeozoic arthropods and problems of arthropod phylogeny; with some notes on taxa of doubtful affinities. In S, S. A. M. C. M. (ed.) The Early Evolution of Metazoa and the Significance of Problematic Taxa. Proceedings of an International Symposium Held at the University of Camerino 27-31 March 1989, Cambridge University Press, 189–244 pp.
  • FLETCHER, T. P. and COLLINS, D. 2003. The Burgess Shale and associated Cambrian formations west of the Fossil Gully Fault Zone on Mount Stephen, British Columbia. Canadian Journal of Earth Sciences, 40, 1823–1838.
  • OU, Q., LIU, J., SHU, D., HAN, J., ZHANG, Z., WAN, X. and LEI, Q. 2011. A rare onychophoran-like lobopodian from the lower Cambrian Chengjiang Lagerstätte. Journal of Paleontology, 85, 587–594.
  • RAMSKÖLD, L. and CHEN, J. Y. 1998. Cambrian lobopodians: morphology and phylogeny. In EDGECOMBE, G. D. (ed.) Arthropod Fossils and Phylogeny, Columbia University Press, New York, 107–150 pp.
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Capinatator praetermissus

Capinatator praetermissus, ROMIP 64247

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic assignment: None
Species name: Capinatator praetermissus
Remarks:

Capinatator is considered an early chaetognath unrelated to modern forms (Briggs and Caron (2017), see also Vinther and Parry (2019)). Modern chaetognaths have traditionally been difficult to classify based on morphological characters, but thanks to progress in phylogenomic techniques, they are currently viewed as members of the Gnathifera, a clade of very small organisms with complex jaws (Marlétaz et al. 2019).

Described by: Briggs and Caron
Description date: 2017
Etymology:

Capinatator — from the Latin “capere,” which means “to grasp,” and the Latin “natator,” which means “swimmer.”

praetermissus — from the Latin “praeter,” which means “besides, beyond”, and “mittere” which means “to send away, to reach out”, referring to the fact that this fossil has long been overlooked.

Type Specimens: Holotype ROMIP 64271_1, at the Royal Ontario Museum, Toronto, Canada
Other species:

Burgess Shale and vicinity: None

Other deposits: None

Age & Localities:

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

Mount Stephen (Collins Quarry locality), Walcott Quarry, British Columbia.

History of Research:

Brief history of research:

Two separate species from the Burgess Shale have previously been regarded as chaetognaths, Amiskwia sagittiformis (Walcott 1911) and Oesia disjuncta (Szaniawski 2005). Since then, Amiskwia has been redescribed as a gnathiferan (Caron and Cheung 2019; Vinther and Parry 2019) and Oesia as a hemichordate (Nanglu et al. 2020). Conway Morris (2009) illustrated the first grasping spines of a Burgess Shale chaetognath from a specimen originally discovered by Walcott. Body fossils of Cambrian chaetognaths are extremely rare, with only a few specimens known from China likely representing just one species (Vannier et al. 2007). At the time Capinatator was published, another species was also described from China with a very similar arrangement of spines but with no evidence of the body except for traces of the head (Shu et al. 2017).

Description:

Morphology:

The body is divided into a large head, short neck, an elongate trunk, and a short tail. Lateral and terminal fins did not preserve; these are the first features to decay (Casenove et al. 2011). The head has about 50 simple grasping spines, 25 on each side of the mouth. The spines are claw-shaped and each one may have been reinforced at the tip by a conical structure. A gut trace are visible in some specimens.

Abundance:

49 specimens were initially described, but only 18 preserve evidence of the body.

Maximum Size:
About 9.5 cm.

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

Like modern species, Capinatator likely swam by undulating its body, using its caudal fin for propulsion and lateral fins for added maneuverability. The rarity of specimens preserved with the body suggests that this species did not normally live along the seafloor where it would have been subject to being entrapped by rapid mudflows. Instead, it is likely that Capinatator fed in the water column using its strong grasping spines to capture small swimming prey.

References:

  • BRIGGS, D. E. G. and CARON, J. B. 2017. A large Cambrian chaetognath with supernumerary grasping spines. Current Biology, 27, 2536-2543.e1.
  • CARON, J.-B. and CHEUNG, B. 2019. Amiskwia is a large Cambrian gnathiferan with complex gnathostomulid-like jaws. Communications Biology, 2, 164.
  • CASENOVE, D., OJI, T. and GOTO, T. 2011. Experimental Taphonomy of Benthic Chaetognaths: Implications for the Decay Process of Paleozoic Chaetognath Fossils. Paleontological Research, 15, 146-153, 8.
  • CONWAY MORRIS, S. 2009. The Burgess Shale animal Oesia is not a chaetognath: A reply to Szaniawski (2005). Acta Palaeontologica Polonica, 54, 175-179.
  • MARLÉTAZ, F., PEIJNENBURG, K. T. C. A., GOTO, T., SATOH, N. and ROKHSAR, D. S. 2019. A new spiralian phylogeny places the enigmatic arrow worms among gnathiferans. Current Biology, 29, 312-318.e3.
  • NANGLU, K., CARON, J.-B. and CAMERON, C. B. 2020. Cambrian tentaculate worms and the origin of the hemichordate body plan. Current Biology, 30, 4238-4244.e1.
  • SHU, D., CONWAY MORRIS, S., HAN, J., HOYAL CUTHILL, J. F., ZHANG, Z., CHENG, M. and HUANG, H. 2017. Multi-jawed chaetognaths from the Chengjiang Lagerstätte (Cambrian, Series 2, Stage 3) of Yunnan, China. Palaeontology, 60, 763-772.
  • SZANIAWSKI, H. 2005. Cambrian chaetognaths recognized in Burgess Shale fossils. Acta Palaeontologica Polonica, 50, 1-8.
  • VANNIER, J., STEINER, M., RENVOISÉ, E., HU, S. X. and CASANOVA, J. P. 2007. Early Cambrian origin of modern food webs: evidence from predator arrow worms. Proceedings of the Royal Society B: Biological Sciences, 274, 627-633.
  • VINTHER, J. and PARRY, L. A. 2019. Bilateral jaw elements in Amiskwia sagittiformis bridge the morphological gap between gnathiferans and chaetognaths. Current Biology, 29, 881-888.e1.
  • WALCOTT, C. 1911. Cambrian Geology and Paleontology II. Middle Cambrian annelids. Smithsonian Miscellaneous Collections, 57(5), 109-145.
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Cambroraster falcatus

Cambroraster falcatus, isolated H-element ROMIP 65316

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic assignment: Order Radiodonta, Family Hurdiidae
Species name: Cambroraster falcatus
Remarks:

With its single pair of jointed frontal appendages, lateral swimming flaps, and circular mouth structure, Cambroraster 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 radiodont family Hurdiidae. Phylogenetic analysis found it to be closely related to Titanokorys from the Burgess Shale and Zenghecaris from the Chengjiang deposit, which share similarities in carapace shape and a large number of finely-spaced spines on the appendages (Caron and Moysiuk 2021).

Described by: Moysiuk and Caron
Description date: 2019
Etymology:

Cambroraster – Cambro, for Cambrian; raster, for the rake-like morphology of the inner spines on the frontal appendages.

falcatus – meaning sickle-shaped, but more specifically in reference to the dorsal carapace’s resemblance to the fictional Millennium Falcon starship in the Star Wars franchise.

Type Specimens: Holotype ROMIP 65078; Paratypes ROMIP 65079, 65081, 65083, 65084, 65092, at the Royal Ontario Museum.
Other species:

Burgess Shale and vicinity: None

Other deposits: Cambroraster sp. from the early Cambrian Chengjiang biota (Liu et al. 2020); Cambroraster cf. C. falcatus from the mid-Cambrian Mantou Formation of north China (Sun et al. 2020).

Age & Localities:

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

Marble Canyon and Mount Whymper / Tokumm Creek, Kootenay National Park, British Columbia.

History of Research:

Brief history of research:

Several specimens of Cambroraster were discovered at the Marble Canyon and North Tokumm sites in Kootenay National Park in 2014. Because of their distinctive shape, the head carapaces were nicknamed the “spaceship.” Isolated frontal appendages were initially tentatively assigned to the genus Hurdia (Caron et al. 2014). The affinities of Cambroraster were not well-understood until further finds of abundant material at North Tokumm in 2018. The genus and species were formally described in 2019 (Moysiuk and Caron 2019). 3D digital modeling of an appendage of Cambroraster found it to have the lowest potential degree of appendage articulation of any of the studied radiodontans (de Vivo et al. 2021).

Description:

Morphology:

The defining feature of Cambroraster falcatus is its large, horseshoe-shaped dorsal carapace. This carapace is rounded frontally and projects along the rear sides into elongate wing-like projections lined along their margins with small spines. The rear central part of the carapace extends into a bilobate projection. Between the lateral “wings” and central projection are deep notches that accommodate the elliptical eyes, which are directed upwards. On the underside, the head is protected by two additional plates, shaped like elongate paddles and joined together at the front by their narrow ends. A circular, tooth-lined jaw and a pair of jointed frontal appendages with five long, curving, strong rake-like inner spines are located on the underside, near the front of the head. The body is stout, shorter than the dorsal carapace, and composed of 11 segments bearing rows of stacked gill blades and short lateral swimming flaps plus four short tail blades.

Abundance:

Cambroraster is abundant in Kootenay National Park, being known from over 100 specimens. It is particularly abundant around the North Tokumm locality, and may occur by the dozens on certain bedding planes, suggesting gregarious mass moulting behaviour. Rarer remains are known from Marble Canyon and single, isolated carapace fragments are known from Mount Stephen and Mount Field.

Maximum Size:
About 300 mm

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

Like other hurdiids, Cambroraster shows adaptations to sweep feeding. Specifically, the stout and rigid frontal appendages are ill-suited to grasping large, mobile prey (de Vivo et al. 2021). Instead, the rake-like inner spines on the appendages form a rigid, basket-like apparatus of spines surrounding the mouth. Sideways movements of the appendages could have disturbed the sediment, sifting out burrowing organisms, and transferring them to the mouth for further processing (Moysiuk and Caron 2019). Compared to related hurdiids like Hurdia and Stanleycaris, the particularly numerous and finely-spaced, strong, hooked secondary spines on the inner spines could have enabled capture of minute benthic organisms, although larger prey may also have been consumed. As one of the largest animals in the Marble Canyon and Tokumm communities, Cambroraster would have been near the top of the food chain. The broad dorsal carapace, upward facing eyes, and stubby body suggest it spent most of its time near the sea floor (Moysiuk and Caron 2019). 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).

References:

  • CARON, J.-B. and MOYSIUK, J. 2021. A giant nektobenthic radiodont from the Burgess Shale and the significance of hurdiid carapace diversity. Royal Society Open Science, 8: 210664.
  • CARON, J.-B., GAINES, R. R., ARIA, C., MÁNGANO, M. G. and STRENG, M. 2014. A new phyllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies. Nature communications, 5: 1–6.
  • 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.
  • LIU, Y., LEROSEY-AUBRIL, R., AUDO, D., ZHAI, D., MAI, H. and ORTEGA-HERNÁNDEZ, J. 2020. Occurrence of the eudemersal radiodont Cambroraster in the early Cambrian Chengjiang Lagerstätte and the diversity of hurdiid ecomorphotypes. Geological Magazine, 157: 1200–1206.
  • 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.
  • SUN, Z., ZENG, H. and ZHAO, F. 2020. Occurrence of the hurdiid radiodont Cambroraster in the middle Cambrian (Wuliuan) Mantou Formation of North China. Journal of Paleontology, 94: 881–886.
  • 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.
  • 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.
Other Links:

Ovatiovermis cribratus

Artistic reconstruction of Ovatiovermis cribratus. Danielle Dufault © ROM

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic Assignment: Order Luolishaniida
Species name: Ovatiovermis cribratus
Remarks:

Ovatiovermis is one of a variety of lobopodian taxa from the Cambrian, which are early members of the lineage that gave rise to arthropods, and whose only modern survivors are onychophorans (velvet worms) and tardigrades (water bears). Lobopodians characteristically have annulated, unjointed bodies and bear soft limbs after which they are called: the lobopods. Ovatiovermis groups with Facivermis as a peculiar “unarmoured” lineage within the Order Luolishaniida, notably characterized by their thin spines arranged in chevrons and the differentiation of their body into functional regions for suspension-feeding (Caron & Aria 2017, 2020).

Described by: Caron and Aria
Description date: 2017
Etymology:

Ovatiovermis – from the Latin ovatio (ovation) and vermis (worm) owing to the inferred upward-reaching, limb-waving posture of these animals.
cribratus – from the Latin cribrare, to sieve.

Type Specimens: Holotype ROMIP 52707 and Paratype ROMIP 64006 at the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: None

Other deposits: None

Age & Localities:

Age:
Middle Cambrian, Wuliuan stage, Bathyuriscus-Elrathina Zone of the Burgess Shale Formation (approximately 507 million years old).
Principal localities:

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Although the first and most complete specimen was discovered in 1994 by one of the ROM expeditions, Ovatiovermis was not described until 2017 by Caron and Aria. The animal served to exemplify suspension-feeding strategies early in panarthropod evolution, and prompted an analysis of the extent and significance of such lifestyle among other lobopodians.

Description:

Morphology:

Ovatiovermis has a worm-like, tubular body divided into three sections: An anterior section with two pairs of very long lobopods bearing thin spines arranges in chevrons and ending in paired claws; a middle section with four pairs of similar but smaller lobopods; and a posterior section with three pairs of very stout lobopods ending in single strong claws. The head is small and bears a pair of simple visual organs and an eversible pharynx. The surface of the body is devoid of any sclerite or spine. Cuticular folds are visible in the space in between lobopods.

Abundance:

Only two specimens. The holotype specimen (ROMIP 52707) was collected in 1994 from bed assemblage −120 (about 1.2 m below the base of the original Walcott Quarry floor), which is distinct from other bed assemblages in that it has particularly well-preserved specimens across a range of taxa (92 species). The paratype specimen (ROMIP 64006) was found in 2016 by a guest on a guided hike to the Walcott Quarry and forwarded to Dr. Jean-Bernard Caron by the Parks Interpreter office.

Maximum Size:
Maximum Size: 25 mm.

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

With its anterior sieving and posterior anchoring appendages, Ovatiovermis exemplifies suspension-feeding specialization among lobopodians. It was likely anchored to sponges and stood erect in the water to catch food particles or plankton.

References:

  • CARON, J. and ARIA, C. 2020. The Collins’ monster, a spinous suspension‐feeding lobopodian from the Cambrian Burgess Shale of British Columbia. Palaeontology, 63, 979–994.
  • CARON, J.-B. and ARIA, C. 2017. Cambrian suspension-feeding lobopodians and the early radiation of panarthropods. BMC Evolutionary Biology, 17, 29.
Other Links:

Balhuticaris voltae

Balhuticaris voltae, holotype ROMIP 66238

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic Assignment: Hymenocarines, Family: Odaraiidae
Species name: Balhuticaris voltae
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 Balhuticaris, 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. Balhuticaris 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: Izquierdo-López & Caron
Description date: 2022
Etymology:

Balhuticaris–from the mythological creature Balhut, a giant aquatic animal in some Persian cosmologies, and the latin caris, meaning “crab” or “shrimp”, and voltae- from the Catalan word volta, an arch-like structure.

Type Specimens: Holotype ROMIP66238
Other species:

Burgess Shale and vicinity: None
Other deposits: None

Age & Localities:

Age:
Middle Cambrian, Wuliuan Stage, upper part of the Burgess Shale Formation (Burgess Shale) (around 505 million years old)
Principal localities:

Marble Canyon, Tokumm Creek

History of Research:

Brief history of research:

Balhuticaris has been found from both the Marble Canyon and the Tokumm Creek localities of the Burgess Shale during several expeditions between 2012 to 2022. The different specimens of Balhuticaris were originally not recognized as belonging to the same organism. Instead, these were identified as different undescribed euarthropods or potential radiodonts (Nanglu et al. 2020). Balhuticaris was formally described in 2022 (Izquierdo-López and Caron 2022).

Description:

Morphology:

Balhuticaris is a large bivalved arthropod that can reach up to 25 cm in length. The carapace only covers the first quarter of the total body length. It has a dome-like shape. In frontal view, the carapace looks like an arch: each valve extends towards the ventral side of the animal, surpassing the length of the legs. The dorsal side of the carapace extends towards the posterior side of the animal, giving the valves a “bean-like” shape in lateral view. The head bears a pair of well-developed, pedunculate, bilobate eyes. The head also bears one pair of short antennulae and a sclerotized structure that may represent a head sclerite. The body is highly multisegmented, with approximately 110 segments posterior to the head. Approximately the first ten segments are longer, and bear legs that become smaller towards the head. All segments bear a pair of legs, each subdivided into two branches (biramous): a walking leg (endopod) and a paddle-like flap (exopod). The endopod is thin and subdivided into around 14 segments. The exopod is ovoid, almost as long as the endopod. The last segment is longer than the rest, and has a flattened triangular shape. This segment bears two paddle-like legs (caudal rami). Each of these is subdivided into three segments, bears three spines on their outer edge and elongated filaments (setae) on their posterior edge.

Abundance:

Balhuticaris is rare, only known from a dozen specimens from the Marble Canyon and Tokumm Creek sites.

Maximum Size:
About 25 cm

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

Balhuticaris is the largest bivalved arthropod to date, surpassing in length Tuzoia (Vannier et al. 2007) and Nereocaris exilis (Legg et al. 2012), and rivalling other arthropods from the Burgess Shale, such as radiodonts, including the largest complete Anomalocaris (Briggs 1975) and Cambroraster (Moysiuk and Caron 2019), but smaller than the estimated 50 cm long Titanokorys (Caron and Moysiuk 2021). The general anatomy of Balhuticaris, including its elongated body and large segmented caudal rami, indicates that it was probably a good swimmer. It was hypothesized that it could be swimming upside-down (Izquierdo-López and Caron 2022), similar to its relatives Fibulacaris and Odaraia (Briggs 1981; Izquierdo-López and Caron 2019). Balhuticaris’ feeding could have ranged from suspension-feeder to predator (Izquierdo-López and Caron 2022), similar to some of the largest fairy shrimps today (Fryer 1966).

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. 1975. Anomalocaris, the largest known Cambrian arthropod. Palaeontology, 22: 631–664.
  • BRIGGS, D. E. G. 1981. The arthropod Odaraia alata Walcott, middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London. B, Biological Sciences, 291: 541–582.
  • CARON, J.-B. and MOYSIUK, J. 2021. A giant nektobenthic radiodont from the Burgess Shale and the significance of hurdiid carapace diversity. Royal Society Open Science, 8: 210664.
  • FRYER, G. 1966. Branchinecta gigas Lynch, a non‐filter‐feeding raptatory anostracan, with notes on the feeding habits of certain other anostracans. Proceedings of the Linnean Society of London, 177: 19–34.
  • 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. 2021. A Burgess Shale mandibulate arthropod with a pygidium: a case of convergent evolution. Papers in Palaeontology, 7: 1877–1894.
  • 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. 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.
  • 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: Biological Sciences, 286:201910.
  • NANGLU, K., CARON, J. and GAINES, R. 2020. The Burgess Shale paleocommunity with new insights from Marble Canyon, British Columbia. Paleobiology, 46(1): 58–81.
  • 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.
  • VANNIER, J. CARON, J. B., YUAN, J., BRIGGS, D. E. G., COLLINS, D., ZHAO, Y. and ZHU, M. 2007. Tuzoia: morphology and lifestyle of a large bivalved arthropod of the Cambrian seas. Journal of Paleontology, 81(3): 445–471.
Other Links:

Zacanthoides romingeri

Zacanthoides romingeri (figure 3) illustrated by Rominger (1887) as Embolimus spinosa.

Taxonomy:

Kingdom: Animalia
Phylum: Animalia
Higher Taxonomic assignment: Trilobita (Order: Corynexochida)
Species name: Zacanthoides romingeri
Remarks:

Trilobites are extinct euarthropods, probably stem lineage representatives of the Mandibulata, which includes crustaceans, myriapods, and hexapods (Scholtz and Edgecombe, 2006).

Described by: Rominger
Description date: 1887
Etymology:

Zacanthoides – probably from the Greek z(a), “very,” and akanthion, “thistle” or “porcupine” or “hedgehog,” and oides, “resembling;” thus, very thistle- or porcupine-like.

romingeri – after Carl Rominger, a Michigan paleontologist who in 1887 published the first descriptions of trilobites from Mount Stephen.

Type Specimens: Type status under review – UMMP 4871 (2 specimens), University of Michigan Museum of Paleontology, Ann Arbor, Michigan, USA.
Other species:

Burgess Shale and vicinity: Zacanthoides sexdentatus, Z. submuticus, Z. longipygus, Z. planifrons, Z. divergens, all from older and younger Middle Cambrian rocks on Mount Stephen, Mount Odaray, and Park Mountain (Rasetti, 1951).

Other deposits: other species elsewhere in North America.

Age & Localities:

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

The Trilobite Beds on Mount Stephen.

History of Research:

Brief history of research:

In 1887 Carl Rominger published an engraving of a nearly complete and markedly spiny trilobite and named it Embolimus spinosa. In 1908 Charles Walcott introduced the combination Zacanthoides spinosus for the Mount Stephen species and for a similar trilobite from Nevada. The next change came in 1942, when Charles Resser at the United States National Museum asserted that the Mount Stephen species was sufficiently distinct that it required a new name. Resser chose to honour the man who first formally described many of the common Mount Stephen trilobites, and Zacanthoides romingeri remains the combination in use today.

Description:

Morphology:

Hard parts: adult dorsal exoskeletons can reach up to 6 cm in length, tapering back from a large crescentic cephalon through a thorax of nine segments, to a relatively small rounded-triangular pygidium with long marginal spines.

The wide free cheeks bear strong genal spines; short, thorn-like intragenal spines mark the posterior corners of the fixed cheeks. The glabella is long and narrow, slightly expanded forwards. There are four pairs of lateral glabellar furrows; the anterior two pairs are weaker and angled to the front, the stronger posterior two are angled back. Very long narrow eyes that bow strongly outward are located far back on the cephalon. The occipital ring extends rearward into a strong, broad-based spine. Long, blade-shaped terminal spines on the wide pleurae curve progressively more backwards. A slender needle-like spine arises from the axial ring of the eighth thoracic segment. There are four pygidial axial rings; five pairs of marginal spines, each successively shorter, are directed rearwards and extend beyond the tip of the pygidium.

Unmineralized anatomy: not known.

Abundance:

Zacanthoides romingeri is moderately abundant at the Mount Stephen Trilobite Beds but absent from Fossil Ridge. Complete trilobites with the free cheeks in place are very scarce, and this species is mostly found as disarticulated sclerites. Its distinctive characteristics, however, usually allow even isolated pieces to be readily identified.

Maximum Size:
60 mm

Ecology:

Life habits: Animalia
Feeding strategies: Animalia
Ecological Interpretations:

Zacanthoides romingeri adults very likely walked along the sea bed. The overall spinosity of this species may have served as a deterrent to predators, or possibly helped to break up the visual outline of the animal, making it harder to see on the sea floor (Rudkin, 1996).

References:

RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116 (5): 1-277.

RESSER, C. E. 1942. Fifth contribution to nomenclature of Cambrian trilobites. Smithsonian Miscellaneous Collections, 101 (15): 1-58.

ROMINGER, C. 1887. Description of primordial fossils from Mount Stephens, N. W. Territory of Canada. Proceedings of the Academy of Natural Sciences of Philadelphia, 1887: 12-19.

RUDKIN, D. M. 1996. The Trilobite Beds of Mount Stephen, Yoho National Park, p. 59-68. In R. Ludvigsen (ed.), Life in Stone – A Natural History of British Columbia’s Fossils. UBC Press, Vancouver.

RUDKIN, D. M. 2009. The Mount Stephen Trilobite Beds, p. 90-102. In J.-B. Caron and D. Rudkin (eds.), A Burgess Shale Primer – History, Geology, and Research Highlights. The Burgess Shale Consortium, Toronto.

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

WALCOTT, C. D. 1888. Cambrian fossils from Mount Stephens, Northwest Territory of Canada. American Journal of Science, Series 3, 36: 163-166.

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

Other Links:

http://www.trilobites.info/ordcorynexochida.htm