Life Habits: Epibenthic



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Spartobranchus tenuis

Artistic reconstruction of Spartobranchus tenuis. Marianne Collins © ROM

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
Higher Taxonomic assignment: Enteropneusta
Species name: Spartobranchus tenuis
Remarks:

Spartobranchus is considered a stem-group enteropneust (acorn worm), and shares many similarities with modern acorn worms (Caron et al. 2013; Nanglu et al. 2020). It shows the tripartite body characteristic of this group, consisting of an acorn-shaped proboscis, cylindrical collar, and elongate trunk.

Described by: Walcott
Description date: 1911 (redescribed in 2013)
Etymology:

Spartobranchus — from the Greek “sparte,” for cord or rope (made from the Spartium shrub), and “brankhia” for gills.

tenuis — from the Latin, meaning thin or delicate.

Type Specimens: USNM 108494; Paralectotype – USNM 553526.
Other species:

Burgess Shale and vicinity: None
Other deposits: None

Age & Localities:

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

Walcott Quarry

History of Research:

Brief history of research:

Spartobranchus tenuis was first reported by Walcott in 1911 as a priapulid worm named Ottoia tenuis. It was removed from the genus Ottoia by Conway Morris in 1979, and formally redescribed as Spartobranchus tenuis, an acorn worm, by Caron et al. in 2013.

Description:

Morphology:

Spartobanchus is a small worm with a maximum length of 10 cm. The three major components of its body are a proboscis, a collar, and a long, thin section called the trunk. The proboscis is oval or “acorn” shaped, hence the common name of the group: acorn worms. The trunk is a relatively short cylindrical section behind the proboscis. The trunk comprises roughly 90%-95% of the total body length of the animal. The entire body is highly flexible, with the trunk often being recurved onto itself. The anterior part of the trunk is known as the pharynx. Inside the pharynx are presumably collagenous bars known as gill bars, which give the pharynx a strongly striated appearance. The posterior part of the trunk is where the gut is located and is relatively featureless. It is often preserved darkly compared to the rest of the body. At the most posterior end of the trunk is a bulbous structure, which may have served as an anchor for the animal. Roughly one quarter of Spartobranchus specimens are found associated with fibrous, collagenous tubes that the worms produced. These tubes have a corrugated appearance, and can take many forms including: straight tubes, forked, spiral, and circular.

Abundance:

More than 9000 specimens, making it one of the most abundant species in the Walcott Quarry.

Maximum Size:
About 10 cm.

Ecology:

Life habits: Epibenthic
Feeding strategies: Epibenthic
Ecological Interpretations:

Spartobranchus was likely a deposit feeder, as this is the most common mode of life of extant acorn worms that are morphologically highly similar. The presence of a pre-oral ciliary organ on the proboscis also suggests that food particles were transported from the proboscis to the mouth. It may have also been able to filter feed, given the ability of some burrowing hemichordates to draw in food from interstitial water. The tubes Spartobranchus is associated with would have served as a protective dwelling and were secreted by the proboscis. These worms shared this trait with their close relatives, the graptolites. Some large tubes from the Raymond Quarry (located roughly 20m above the Walcott Quarry) appear to also contain undescribed acorn worms similar in morphology to Spartobranchus (Nanglu and Caron 2021). These tubes also possessed polychaetes, suggesting a symbiotic relationship between these worms.

References:

  • CARON, J.-B., CONWAY MORRIS, S., AND C. B. CAMERON. 2013. Tubicolous enteropneusts from the Cambrian period. Nature 495: 503-506
  • CONWAY MORRIS, S. 1979. The Burgess Shale (Middle Cambrian) fauna. Annual Review of Ecology, Evolution, and Systematics 10: 327–349.
  • NANGLU, K. AND J.-B. CARON. 2021. Symbiosis in the Cambrian: enteropneust tubes from the Burgess Shale co-inhabited by commensal polychaetes. Proceedings of the Royal Society B 288 (1951): 20210061.
  • 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
  • WALCOTT, C. 1911. Cambrian Geology and Paleontology II. Middle Cambrian annelids. Smithsonian Miscellaneous Collections, 57(5): 109-145.
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Siphusauctum gregarium

Artistic reconstruction of Siphusauctum gregarium. Marianne Collins © ROM

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
Higher Taxonomic assignment: None
Species name: Siphusauctum gregarium
Remarks:

Siphusauctum was originally compared to several fossil and living stalked animals, including ctenophores (O’Brien and Caron 2012). Despite some similarities, the authors ultimately rejected any close connections with any living or fossil groups, with the possible exception of Dinomischus, another enigmatic stemmed animal from the Burgess Shale (Conway Morris 1977) and China. More recently, Siphusauctum has been viewed as a possible stem-group ctenophore (Zhao et al. 2019).

Described by: O’Brien and Caron
Description date: 2012
Etymology:

Siphusauctum — from the Latin “siphus,” which means “cup or goblet,” and the Latin “auctus,” meaning large.

gregarium — from the Latin “gregalis,” which means “flock,” referring to large clusters of specimens recovered.

Type Specimens: Holotype ROMIP 61414; paratypes ROMIP 61413, 61415, 61421 in the Royal Ontario Museum, Toronto, Canada
Other species:

Burgess Shale and vicinity: None
Other deposits: Siphusauctum lloydguntheri from the Spence Shale of Utah (Kimmig et al. 2017)

Age & Localities:

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

Mount Stephen (Tulip Beds locality), British Columbia.

History of Research:

Brief history of research:

The Tulip Beds (initially known as “locality 8” (Collins et al. 1983) and later as “S7”(Fletcher and Collins 2003)) was discovered in 1983. It is not until a detailed overview of all material collected by ROM-led parties over multiple field seasons that a formal description of this species was published (O’Brien and Caron 2012), followed by a quantitative palaeocological study of the Tulip Beds.

Description:

Morphology:

This animal consists of three parts: a holdfast, a stem and a large calyx-shaped structure. The calyx-shaped structure is the most conspicuous part: it is composed of a continuous external sheath, perforated by the anus on top, and six holes at the bottom, and covers six comb-like internal elements arranged around a large central cavity. The comb-like elements are crescent-shaped, surrounded by a membrane with thin striae. Each comb-like element is composed of two sets of 30 transverse canals (or grooves) radiating on either side of a larger canal positioned abaxially. Following the anus, the body cavity encapsulates a digestive tract, which is composed of a narrow intestine and a wider zone, possibly representing the stomach, at the base of the tract and above a conical zone which connects to the stem. The stem is composed of an internal (inner) and external (outer) element. The inner stem connects directly to a bulbous or flat holdfast. At least one specimen suggests the presence of a tube between the stomach and the inner stem. The outer element ends sharply before the holdfast.

Abundance:

1,133 specimens, making it one of the most abundant species at the Tulip Beds (O’Brien and Caron 2016).

Maximum Size:
About 22 cm high.

Ecology:

Life habits: Epibenthic
Feeding strategies: Epibenthic
Ecological Interpretations:

The morphology and internal features of this animal strongly suggests it was a facultative stalked animal, living above the seafloor, and was an active filter feeder. The expansion and contraction of the calyx would have allowed the water and nutrients to circulate through the comb-like elements.

References:

  • 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.
  • CONWAY MORRIS, S. 1977. A new entoproct-like organism from the Burgess Shale of British Columbia. Palaeontology, 20, 833-845.
  • 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.
  • KIMMIG, J., STROTZ, L. C. and LIEBERMAN, B. S. 2017. The stalked filter feeder Siphusauctum lloydguntheri n. sp. from the middle Cambrian (Series 3, Stage 5) Spence Shale of Utah: its biological affinities and taphonomy. Journal of Paleontology, 91, 902-910.
  • O’BRIEN, L. J. and CARON, J.-B. 2012. A new stalked filter-feeder from the Middle Cambrian Burgess Shale, British Columbia, Canada. PLoS ONE, 7, e29233.
  • 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.
  • ZHAO, Y., VINTHER, J., PARRY, L. A., WEI, F., GREEN, E., PISANI, D., HOU, X., EDGECOMBE, G. D. and CONG, P. 2019. Cambrian sessile, suspension feeding stem-group ctenophores and evolution of the comb jelly body plan. Current Biology, 29, 1112-1125.e2.
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Pakucaris apatis

Artistic reconstruction of Pakucaris apatis. Danielle Dufault © ROM

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
Higher Taxonomic assignment: Hymenocarines, Family: Odaraiidae
Species name: Pakucaris apatis
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 Pakucaris, 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. Pakucaris 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: 2021
Etymology:

Pakucaris – from the Japanese onomatopoeia paku, suggestive of ‘eating’, related to the video game character Pac-Man, due to the naked eye resemblance of the carapace and shield of Pakucaris to the shape of the character. Latin caris, meaning “crab” or “shrimp”, and

apatis – from the goddess of deception in Greek mythology Apate, in reference to the resemblance of Pakucaris to a trilobite.

Type Specimens: Holotype ROMIP65739
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:

The holotype of Pakucaris apatis was first discovered during the 2012 expedition to the Marble Canyon site of the Burgess Shale. A few other specimens were discovered during the following 2014 and 2016 expeditions and classified as “New arthropod E” (Nanglu et al. 2020). The 2018 expedition at the Tokumm Creek site uncovered one additional specimen. The first description of Pakucaris apatis was published in 2021 in the journal Papers in Paleontology (Izquierdo-López and Caron, 2021). Several other authors have noted the similarity between the shield of Pakucaris and pygidia (O’Flynn et al. 2022). A pygidium is a structure in which the most posterior segments of an arthropod become fused, usually into a shield. The pygidium is typically found in trilobites, but also across many other groups in the Cambrian, suggesting that this structure appeared multiple times independently.

Description:

Morphology:

Pakucaris has two morphotypes: a small one (around 1 cm) with its body subdivided into 30-35 segments, and a larger one (around 2.5 cm), with its body subdivided into 70-80 segments. The carapace of Pakucaris covers up to two-thirds of the total body length. It has a dome-like shape with a small dorsal crest that runs across its entire length. The carapace bends towards the front, extending into a small process (rostrum). Similarly, the lateral sides of the carapace also extend frontally into small lateral processes. The head has one pair of pedunculate eyes, one pair of thin small appendages, and at least one pair of larger segmented antennae. The small thin appendages are not segmented and represent a sensorial organ known as frontal filaments. The first antennae (also termed antennules) have 7 to 8 segments, with each segment bearing a small spine. Each segment of the body bears one pair of limbs, each subdivided into two branches (biramous): a walking leg (endopod) and a paddle-like flap (exopod). The endopod is thin and is subdivided into at least 20-21 segments. The exopod has an ovoid, flattened shape and is as long as half the endopod. The posterior section of the body has a shield-like structure. This shield is formed by the fusion and lateral extensions of the segments. The shield bears around 10 big spines on each of its lateral sides, as well as a series of smaller spines on its posterior side.

Abundance:

Pakucaris is rare, only known from eight specimens from the Marble Canyon and Tokumm Creek sites. The bigger morphotype is only known from one specimen.

Maximum Size:
About 2.5 cm

Ecology:

Life habits: Epibenthic
Feeding strategies: Epibenthic
Ecological Interpretations:

Pakucaris was probably a nektobenthic animal living close to the benthos (Izquierdo-López and Caron 2021). It may have used its antennae with spines to scrape rocks or other objects and may have also used its paddle-like exopods to create currents and capture organic particles, aided by its antennae and other head appendages. The tail shield (or pygidium) of Pakucaris was most probably a structure to protect against predators. The two morphotypes of Pakucaris may represent different growth stages of males and females, but the number of specimens available to date is too limited to reach a conclusion.

References:

  • ARIA, C. and CARON, J. B. 2017. Burgess Shale fossils illustrate the origin of the mandibulate body plan. Nature, 545: 89–92.
  • 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.
  • 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.
  • O’FLYNN, R. J., WILLIAMS, M., YU, M., HARVEY, T. and LIU, Y. 2022. A new euarthropod with large frontal appendages from the early Cambrian Chengjiang biota. Palaeontologia Electronica, 25(1):a6: 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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Gyaltsenglossus senis

Artistic reconstruction of Gyaltsenglossus senis. Emily Damstra © ROM

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
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: Epibenthic
Feeding strategies: Epibenthic
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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Collinsovermis monstruosus

Artistic reconstruction of Collinsovermis monstruosus. Danielle Dufault © ROM

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
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: Epibenthic
Feeding strategies: Epibenthic
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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Ovatiovermis cribratus

Artistic reconstruction of Ovatiovermis cribratus. Danielle Dufault © ROM

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
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: Epibenthic
Feeding strategies: Epibenthic
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.
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Balhuticaris voltae

Balhuticaris voltae, holotype ROMIP 66238

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
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: Epibenthic
Feeding strategies: Epibenthic
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:


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Yuknessia simplex

3D animation of Yuknessia simplex.
© Phlesch Bubble

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
Higher Taxonomic assignment: Pterobranchia
Species name: Yuknessia simplex
Remarks:

Yuknessia consists of the tubes of miniature colonial animals called pterobranchs (Hemichordata). The tubes were formed as clustered colonies, with the tubes themselves possessing the zig-zagging growth marks that are diagnostic of the Pterobranchia.

Described by: Walcott
Description date: 1919
Etymology:

Yuknessia – from Yukness Mountain (2,847m), a Peak in Yoho National Park, east of the Burgess Shale.

simplex – from the Latin simplex, meaning “simple,” in reference to its simple morphology.

Type Specimens: Holotype –USNM35406 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: Yuknessia stephenensis from the Trilobite Beds on Mount Stephen (LoDuca et al. 2015)

Other deposits: Yuknessia stephenensis from the Wheeler Shale (Utah) and Spence Shale (Utah) (Conway Morris and Robison, 1988;  LoDuca et al. 2015). Yuknessia sp. from the Lower Cambrian Niutitan Formation in China (Yang et al., 2003).

Age & Localities:

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

Burgess Shale and vicinity: The Walcott Quarry on Fossil Ridge and the Trilobite Beds on Mount Stephen.

Other deposits: none

History of Research:

Brief history of research:

This genus was described by Charles Walcott (1919) as a possible green alga. It was redescribed by LoDuca et al. (2015) as the tubes of a hemichordate.

Description:

Morphology:

Yuknessia consists of a colony of branching tubes that were constructed by pterobranch individuals known as zooids. While the zooids themselves are not preserved, the growth mode of the tubes, in particular a series of zig-zagging growth marks known as fuselli, are diagnostic of the hemichordate class Pterobranchia. The tubes are thin, and range from 4mm-13mm, although 6mm is more common.

Abundance:

Yuknessia is very rare and represents only 0.04% of the Walcott Quarry community (Caron and Jackson, 2008).

Maximum Size:
30 mm

Ecology:

Life habits: Epibenthic
Feeding strategies: Epibenthic
Ecological Interpretations:

All pterobranchs, including Yuknessia, were suspension feeders. The zooids possessed tentacle-laden feeding arms which would have extended into the surrounding water. The tentacles would then trap passing food particles and transport them down to the mouth. The actual zooids themselves would have been attached to zooids in adjacent tubes with a system of tissues called the stolon system. In this way, Yuknessia actually represents a colony of related individuals rather than a single animal. The tubes of Yuknessia would have been attached directly to the seafloor or a hard substrate such as a rock or fragments of biomineralizing animals. While the zooids could move up and down within their individual tubes, the colony itself was immobile.

References:

  • CARON, J.-B. AND D. A. JACKSON. 2008. Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology, 258: 222-256.
  • CONWAY MORRIS, S. AND R. A. ROBISON. 1988. More soft-bodied animals from the Middle Cambrian of Utah and British Columbia. University of Kansas Paleontological Contributions, 122 p.
  • WALCOTT, C. 1919. Cambrian Geology and Paleontology IV. Middle Cambrian Algae. Smithsonian Miscellaneous Collections, 67(5): 217-260.
  • YANG, R., W. ZHANG, L. JIANG AND H. GAO. 2003. Chengjiang biota from the Lower Cambrian Niutitang Formation, Zunyi County, Guizhou Province, China. Acta Palaeontologica Sinica, 77: 145-150.
Other Links:

None

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Acanthotretella spinosa

Reconstruction of Acanthotretella spinosa.

© MARIANNE COLLINS

Taxonomy:

Kingdom: Epibenthic
Phylum: Epibenthic
Higher Taxonomic assignment: Lingulata (Order: Siphonotretida, stem group brachiopods)
Species name: Acanthotretella spinosa
Remarks:

Acanthotretella spinosa is probably related to a primitive group of brachiopods of the Order Siphonotretida (Holmer and Caron, 2006).

Described by: Holmer and Caron
Description date: 2006
Etymology:

Acanthotretella – from the Greek akantha, “thorn,” and tretos, “perforated,” and the Latin diminutive ella, describing the small, perforated, spiny shell.

spinosa – from the Latin spinosus, referring to the exterior spines.

Type Specimens: Holotype –ROM57749 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: Acanthotretella decaius from the early Cambrian Guanshan fauna, 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:

Specimens were first illustrated as Lingulella sp. by Jin, et al. (1993), and formally described as Acanthotretella spinosa by Holmer and Caron (2006). New characters preserved in a related species from China (Acanthotretella decaius, Zhifei et al., 2010) reinforce the probable position of this genus within the Order Siphonotretida.

Description:

Morphology:

The shell of Acanthotretella is mainly organic in composition with probably only minor organo-phosphatic mineralization, and is ventri-biconvex. Both valves are covered in long, slender spines that penetrate the shell and are posteriorly inclined, angled obliquely away from the anterior margin. A long, flexible pedicle emerges from an external tube that extends from the pedicle foramen along the ventral valve. The pedicle is at least three to four times the length of the valves. The visceral area of both valves is short and triangular, and does not extend to mid-valve. Other interior features are poorly known.

Abundance:

Most specimens come from the Walcott Quarry and represent one of the rarest brachiopods with less than 0.05% of the entire fauna (Caron and Jackson, 2008).

Maximum Size:
8 mm

Ecology:

Life habits: Epibenthic
Feeding strategies: Epibenthic
Ecological Interpretations:

The long, thin pedicle and overall shell shape probably preclude an infaunal habit. Pedicles of several specimens were found attached at the terminal bulb to organic structures, suggesting that Acanthotretella spinosa was epibenthic. The pedicle was likely able to maintain the shell in an upright position well above the sediment-water interface. Extraction of food particles from the water would have been possible thanks to a filter-feeding apparatus (located between the shells) called a lophophore.

References:

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

HU, S. X., Z. F. ZHANG, L. E. HOLMER AND C. B. SKOVSTED. 2010. Soft-part preservation in a linguliform brachiopod from the lower Cambrian Wulongqing Formation (Guanshan Fauna) of Yunnan, South China. Acta Palaeontologica Polonica, 55: 495-505.

HOLMER, L. E. AND J.-B. CARON. 2006. A spinose stem-group brachiopod with pedicle from the Middle Cambrian Burgess Shale. Acta Zoologica (Stockholm), 87: 273-290.

JIN, Y. G, X. G. HOU. AND H. Y. WANG. 1993. Lower Cambrian pediculate lingulids from Yunnan, China. Journal of Paleontology, 67: 788-798.

Other Links:

http://onlinelibrary.wiley.com/doi/10.1111/j.1463-6395.2006.00241.x/abstract



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Wiwaxia corrugata

3D animation of Wiwaxia corrugata grazing on Morania confluens.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

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

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

Described by: Matthew
Description date: 1899
Etymology:

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

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

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

Burgess Shale and vicinity: none.

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

Age & Localities:

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

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

History of Research:

Brief history of research:

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

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

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

Description:

Morphology:

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

Abundance:

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

Maximum Size:
55 mm

Ecology:

Life habits: Epibenthic
Feeding strategies: Epibenthic
Ecological Interpretations:

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

References:

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

BUTTERFIELD, N. J. 1990. A reassessment of the enigmatic Burgess Shale fossil Wiwaxia corrugata (Matthew) and its relationship to the polychaete Canadia spinosa Walcott. Paleobiology: 287-303.

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

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

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

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

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

CARON, J.-B., A. H. SCHELTEMA, C. SCHANDER AND D. RUDKIN, 2006. A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale. Nature, 442(7099): 159-163.

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

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

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

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

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

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

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

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

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

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

Other Links:

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