The Burgess Shale

Titanokorys gainesi

Titanokorys gainesi, holotype ROMIP 65168

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Order Radiodonta, Family Hurdiidae
Species name: Titanokorys gainesi
Remarks:

With its single pair of jointed frontal appendages, lateral swimming flaps, and circular mouth structure, Titanokorys 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 has found it to be closely related to Cambroraster from the Burgess Shale and Zhenghecaris 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: Caron and Moysiuk
Description date: 2021
Etymology:

Titanokorys – from Titans, a group of powerful Greek deities of great sizes, in reference to the large size of the central carapace and from the Greek word Korys meaning helmet.

gainesi – after Robert R. Gaines, Professor of Geology at Pomona College, who was instrumental in the co-discovery of the Marble Canyon fossil deposit in 2012.

Type Specimens: Holotype ROMIP 65415; Paratypes ROMIP 65168, 65741, 65748, and 65749, at the Royal Ontario Museum.
Other species:

Burgess Shale and vicinity: None
Other deposits: None

Age & Localities:

Age:
Middle Cambrian, Wuliuan Stage, upper part of the ‘thick’ Stephen Formation (Burgess Shale) (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 Titanokorys were discovered at the Marble Canyon and North Tokumm sites in Kootenay National Park in 2014 and 2018. Because of their distinctive shape, large size, and resemblance to the smaller Cambroraster (nicknamed “spaceship”), the head carapaces were nicknamed the “mothership.” The genus and species were formally described in 2021 (Caron and Moysiuk 2021).

Description:

Morphology:

The defining feature of Titanokorys gainesi is its large dorsal carapace. This is roughly elliptical in overall shape. Frontally this carapace has a small spine flanked by a pair of blunt lobes. The rear sides of the carapace are developed into short, wing-like projections. Each “wing” has a small spine along its inner margin. The rear central part of the carapace extends into a bilobate projection. Between the lateral “wings” and bilobate projection are notches that presumably accommodated the eyes. 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, each of which bears a stout, downward-directed spine. All three plates are covered in longitudinal rows of small bumps. A circular, tooth-lined jaw and a pair of jointed frontal appendages with five long, curving, rake-like inner spines are located on the underside, near the front of the head. The body bears rows of stacked gill blades.

Abundance:

Titanokorys is rare in Kootenay National Park, being known from just twelve specimens. Only disarticulated frontal appendages, mouthparts, carapace elements, and gills are known.

Maximum Size:
About 500 mm.

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

Like other hurdiids, Titanokorys shows adaptations to sweep feeding. Specifically, the rake-like inner spines on its stout frontal appendages form a rigid basket-like apparatus of spines surrounding the mouth, which could have functioned to disturb the sediment, sift out burrowing organisms, and move them into the mouth for further processing. Compared to related hurdiids like Hurdia and Stanleycaris, the particularly 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 the largest animal known from the Marble Canyon and Tokumm communities, Titanokorys would have been at the top of the food chain. Titanokorys shared the environment with the slightly smaller Cambroraster, which probably employed a similar mode of feeding, although body size differences may have entailed distinct prey size niches (Moysiuk and Caron 2019; Caron and Moysiuk 2021). Respiration would have been accomplished primarily through the rows of gill blades on the body (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.
  • COLLINS, D. 1996. The “evolution” of Anomalocaris and its classification in the arthropod class Dinocarida (nov.) and order Radiodonta (nov.). Journal of Paleontology, 70: 280–293.
  • DALEY, A. C., BUDD, G. E. and CARON, J.-B. 2013. Morphology and systematics of the anomalocaridid arthropod Hurdia from the Middle Cambrian of British Columbia and Utah. Journal of Systematic Palaeontology, 11: 743–787.
  • MOYSIUK, J. and CARON, J.-B. 2019. A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources. Proceedings of the Royal Society B, 286: 20191079.
Other Links:

Surusicaris elegans

Surusicaris elegans, holotype ROMIP 62976. Specimen dry – direct light (left column), dry – polarized light (right column).

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Family Isoxyidae?
Species name: Surusicaris elegans
Remarks:

Surusicaris is a close relative of Isoxys, as indicated by the type of carapace, eyes, and frontal pair of raptorial appendages (Aria & Caron, 2015). The presence of spines on the dorsal side of the frontal appendage is a character shared with radiodontans, such as Anomalocaris. Current evidence draws out a consensus among authors placing isoxyids as sister taxa to true arthropods (Edgecombe, 2020; Aria, 2022), although it is not clear whether Surusicaris and Isoxys are part of a single separate lineage (that is, form a monophyletic group).

Described by: Aria and Caron
Description date: 2015
Etymology:

Surusicaris – After Surus, “the Syrian,” which would have been the last elephant of Hannibal, with broad shields covering its sides and missing a tusk.

elegans – Referring to the delicate, laced appearance of the limbs.

Type Specimens: Holotype ROMIP 62977, at 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:

Marble Canyon, Kootenay National Park, British Columbia.

History of Research:

Brief history of research:

Along with Yawunik kootenayi (Aria, Caron & Gaines, 2015), Surusicaris elegans (Aria & Caron, 2015) is one of the first two new arthropods described from the Marble Canyon locality of the Burgess Shale. The original study was based on a single specimen from the original 2012 expedition. No other specimen has been confirmed so far, in the Burgess Shale or elsewhere. Surusicaris has remained a critical taxon in understanding the place of isoxyids in the transition to a euarthropod body plan (Fu et al., 2022; Aria, 2022).

Description:

Morphology:

Surusicaris elegans is about 15mm long and enclosed in a broad carapace made of two semi-circular valves, without spines. Only the posterior extremity of the body and tailpiece remain uncovered. The animal has a well-defined head composed of, at the front, a pair of large spherical eyes and a segmented predatory appendage, and, at the back of the head, under the carapace, three pairs of short limbs with a lobopod aspect. The frontal appendages show a complex ornament of spines on both the ventral and dorsal margins. The trunk limbs are clearly bipartite, forming two separate but similar branches. As for Isoxys, external segmentation of the trunk is not clearly visible. Inside the body, a bold, black trace runs alongside the gut and branches out inside one limb branch, showing similarities to hemolymphatic (“blood”) channels (Aria & Caron, 2015).

Abundance:

A single specimen from the Marble Canyon quarry.

Maximum Size:
About 15 mm.

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

The large lateral eyes and clawed frontal appendages suggest Surusicaris was an active predator, like its close relative Isoxys (Legg & Vannier, 2013). Trunk limbs lack strong functional modifications, but their lobate aspect in addition to their position underneath the carapace indicates that Surusicaris was mostly a swimmer (Aria & Caron, 2015). Although some authors implied a pelagic lifestyle (Vannier & Chen, 2000), isoxyids are commonly found among benthic/nektobenthic assemblages (Caron & Jackson, 2008) and possess general morphological characteristics of other nektobenthic Cambrian arthropods.

References:

  • Aria, C. (2022) The origin and early evolution of arthropods. Biological Reviews 97, 1786–1809.
  • Aria, C. & Caron, J.-B. (2015) Cephalic and limb anatomy of a new isoxyid from the Burgess Shale and the role of ‘stem bivalved arthropods’ in the disparity of the frontalmost appendage. PLoS ONE 10, e0124979.
  • Aria, C., Caron, J.-B. & Gaines, R. (2015) A large new leanchoiliid from the Burgess Shale and the influence of inapplicable states on stem arthropod phylogeny. Palaeontology 58, 629–660.
  • Caron, J.B. & Jackson, D.A. (2008) Paleoecology of the Greater Phyllopod Bed community, Burgess Shale. Palaeogeography, Palaeoclimatology, Palaeoecology 258, 222–256.
  • Edgecombe, G.D. (2020) Arthropod origins: Integrating paleontological and molecular evidence. Annual Review of Ecology, Evolution, and Systematics 51, 1–25.
  • Fu, D., Legg, D.A., Daley, A.C., Budd, G.E., Wu, Y. & Zhang, X. (2022) The evolution of biramous appendages revealed by a carapace-bearing Cambrian arthropod. Philosophical Transactions of the Royal Society B: Biological Sciences 377, 20210034.
  • Legg, D.A. & Vannier, J. (2013) The affinities of the cosmopolitan arthropod Isoxys and its implications for the origin of arthropods. Lethaia 46, 540–550.
  • Vannier, J. & Chen, J.Y. (2000) The Early Cambrian colonization of pelagic niches exemplified by Isoxys (Arthropoda). Lethaia 33, 295–311.
Other Links:

Pakucaris apatis

Pakucaris apatis, holotype ROMIP 65739

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
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: Mobile
Feeding strategies: Mobile
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.
Other Links:

Nereocaris exilis

Nereocaris briggsi, holotype ROMIP 62153

Taxonomy:

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

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

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

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

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

Type Specimens: dsfsdfdsfdsfdasf
Other species:

Holotype ROMIP61831

Age & Localities:

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

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

History of Research:

Brief history of research:

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

Description:

Morphology:

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

Abundance:

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

Maximum Size:
About 14.2 cm (N. exilis)

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

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

References:

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

Collinsovermis monstruosus

Collinsovermis monstruosus, holotype ROMIP 52703

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
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: Mobile
Feeding strategies: Mobile
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.
Other Links:

Capinatator praetermissus

Capinatator praetermissus, ROMIP 64247

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
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: Mobile
Feeding strategies: Mobile
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.
Other Links:

Cambroraster falcatus

Cambroraster falcatus, isolated H-element ROMIP 65316

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
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 Zhenghecaris 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:

CambrorasterCambro, 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: Mobile
Feeding strategies: Mobile
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:

Zacanthoides romingeri

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

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
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: Mobile
Feeding strategies: Mobile
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:

Yohoia tenuis

3D animation of Yohoia tenuis.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Mobile
Phylum: Mobile
Higher Taxonomic assignment: Unranked clade Megacheira? (stem group arthropods)
Species name: Yohoia tenuis
Remarks:

Yohoia was originally considered to be a branchiopod crustacean (Walcott, 1912; Simonetta, 1970), but was also described as being closely related to the chelicerates (Briggs and Fortey, 1989; Wills et al., 1998; Cotton and Braddy, 2004). Other analyses suggest that Yohoia belongs in the group of “great appendage” arthropods, the Megacheira, together with LeanchoiliaAlalcomenaeus and Isoxys (Hou and Bergström, 1997; Budd, 2002). The megacheirans have been suggested to either be stem-lineage chelicerates (Chen et al. 2004; Edgecombe, 2010), or stem-lineage euarthropods (Budd, 2002).

Described by: Walcott
Description date: 1912
Etymology:

Yohoia – from the Yoho River, Lake, Pass, Glacier, Peak (2,760 m) and Park, British Columbia, Canada. “Yoho” is a Cree word expressing astonishment.

tenuis – from the Latin tenuis, “thin,” referring to its slender body.

Type Specimens: Lectoype –USNM57699 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott, Raymond and Collins Quarries on Fossil Ridge.

History of Research:

Brief history of research:

Yohoia was first described by Walcott (1912), who designated the type species Y. tenuis based on six specimens, and a second species, Y. plena, based on one specimen. Additional specimens of Y. tenuis were described by Simonetta (1970), and a major redescription of Yohoia tenuis was then undertaken by Whittington (1974), based on over 400 specimens of this species. Whittington (1974) invalidated Y. plena, upgrading it to its own genus, Plenocaris plena, leaving Y. tenuis as the only species of YohoiaYohoia has since been included in several studies on arthropod phylogeny and evolution (e.g., Briggs and Fortey, 1989; Hou and Bergström, 1997; Wills et al., 1998; Budd, 2002; Chen et al., 2004; Cotton and Braddy, 2004).

Description:

Morphology:

The body of Yohoia consists of a head region encapsulated in a cephalic shield and 14 body segments, ending in a paddle-shaped telson. The dorsal head shield is roughly square and extends over the dorsal and lateral regions of the head. There is a pair of great appendages at the front of the head. Each appendage consists of two long, thin segments that bend like an elbow at their articulation, with four long spines at the tip. Three pairs of long, thin, segmented appendages project from beneath the head shield behind the great appendages.

The body behind the head consists of ten segments with tough plates, or tergites, that extend over the back and down the side of the animal, ending in backward-facing triangular points. The first of these body segments may have an appendage that is segmented and branches into two (biramous), with a segmented walking limb bearing a flap-like extension. The following nine body segments have only simple flap-shaped appendages fringed with short spines or setae. The next three body segments have no appendages, and the telson is a paddle-shaped plate with distal spines.

Abundance:

Over 700 specimens of Yohoia are known from the Walcott Quarry, comprising 1.3% of the specimens counted (Caron and Jackson, 2008) but only few specimens are known from the Raymond and Collins Quarries.

Maximum Size:
23 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

Yohoia is thought to have used its three pairs of cephalic appendages, and possibly the biramous limb on the first body segment, to walk on the sea floor. The animal could also swim by waving the flap-like appendage on the body trunk. The setae on these appendages may have been used for respiration. The pair of frontal appendages were likely used to capture prey or scavenge food particles from the sea floor.

References:

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

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

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

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

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

EDGECOMBE, G. D. 2010. Arthropod phylogeny: An overview from the perspectives of morphology, molecular data and the fossil record. Arthropod Structure and Development, 39: 74-87.

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

SIMONETTA, A. M. 1970. Studies on non trilobite arthropods of the Burgess Shale (Middle Cambrian). Palaeontographia Italica, 66 (New series 36): 35-45.

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

WHITTINGTON, H. B. 1974. Yohoia Walcott and Plenocaris n. gen. arthropods from the Burges

Other Links:

None

Worthenella cambria

Worthenella cambria (USNM 57643) – Holotype, part and counterpart. Left, plate 22 of Walcott (1911), showing a retouched image of the original specimen described (figure 2) together with other “worms.” Right, images of the same specimen. Specimen length = 60 mm. Specimen wet – direct light (left column), dry – polarized light (right column). Walcott Quarry.

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

Taxonomy:

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

This animal is related to arthropods, but its systematic status within this group is unknown (Briggs and Conway Morris, 1986).

Described by: Walcott
Description date: 1911
Etymology:

Worthenella – Possibly after the American palaeontologist Amos Henry Worthen, who died in 1888, just as Walcott’s career was taking off.

cambria – from the Welsh Cambria meaning Wales, in reference to the age of the fossil.

Type Specimens: Holotype –USNM57643 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none

Other deposits: none

Age & Localities:

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

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Worthenella was first described by Walcott from a single specimen in a 1911 monograph dealing with various Burgess Shale worms. Walcott interpreted this animal as a polychaete annelid (or bristle worm), in the same family as the animal Wiwaxia (which is now interpreted as a primitive mollusc). However, this interpretation was questioned (Conway Morris, 1979), and the affinities of Worthenella have remained difficult to establish because this singular fossil is too poorly known (Briggs and Conway Morris, 1986).

Description:

Morphology:

The animal is elongate with a small head and bears at least 46 segments of similar dimensions. Appendages or tentacles are present beneath the head, but their preservation is poor and it is difficult to know their precise nature and arrangement. The anterior 34 segments seem to bear filamentous branches on their ventral sides, with the following 8 segments equipped with longer appendages. The gut is straight and the anus is terminal.

Abundance:

This animal is known from a single specimen.

Maximum Size:
60 mm

Ecology:

Life habits: Mobile
Feeding strategies: Mobile
Ecological Interpretations:

Not enough is known about this organism to interpret its ecology.

References:

BRIGGS, D. E. G. AND S. CONWAY MORRIS. 1986. Problematica from the Middle Cambrian Burgess Shale of British Columbia, p. 167-183. In A. Hoffman and M. H. Nitecki (eds.), Problematic fossil taxa (Oxford Monographs on Geology and Geophysics No. 5). Oxford University Press & Clarendon Press, New York.

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

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

Other Links:

None