The Burgess Shale

Yawunik kootenayi

Yawunik kootenayi, ROMIP 64017

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
Higher Taxonomic assignment: Megacheirans, Family Leanchoiliidae
Species name: Yawunik kootenayi
Remarks:

Yawunik is a representative of the megacheiran family Leanchoiliidae (Aria, Caron, & Gaines, 2015). Megacheirans are basal true arthropods with a frontal appendage pointing upward and made of multiple claws (the cheira, or “great appendage”). Megacheirans are generally considered to be among the first true arthropods (that is, arthropods with segmented bodies and appendages), and possibly the earliest representatives of the extended chelicerate lineage (Aria, 2022).

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

Yawunik – Latinized spelling of Yawu?nik’, the fierce monster of the Ktunaxa First Nation’s creation story.

kootenayi – After the name Kootenay National Park, representing the area where the fossil was found, a territory previously inhabited by the Ktunaxa First Nation among others.

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 Surusicaris elegans (Aria & Caron, 2015), Yawunik kootenayi is one of the first two arthropods described from the Marble Canyon locality of the Burgess Shale (Aria et al., 2015). The original study was based on 42 specimens from the 2012 Royal Ontario Museum expedition, the same year the new fossil deposit was found. Dozens more specimens have since been collected, making Yawunik one of the most abundant arthropods of the Marble Canyon quarry, next to Sidneyia (Nanglu, Caron, & Gaines, 2020). As the largest and one of the best preserved megacheiran arthropod, Yawunik has since been referenced in many studies.

Description:

Morphology:

Yawunik kootenayi was a large predator, stouter than its closest relatives. The body lacks any biomineralization. Like other leanchoiliid megacheirans, it is characterized by flagellate frontal appendages (cheirae) made of three long claws, and a body divided into two regions (tagmata): the cephalon, covered by a single shield, and the segmented trunk. At the front of the head, leanchoiliids bore a pair of large unstalked lateral eyes and a pair of smaller, mushroom-shaped median eyes. The megacheiran appendages were of similar simple morphology throughout the body, reflecting the typical arthropod biramous limb: sub-cylindrical basis with teeth for mastication (basipod), relatively strong walking legs (endopods), and paddle-like, semi-rigid flaps (exopods) fringed with lamellae. The tail is a single element called a telson, having the shape of spear’s tip (lanceolate).

Abundance:

Known through more than 180 specimens, Yawunik is one of the most abundant arthropods of Marble Canyon, and is also known from Tokumm Creek.

Maximum Size:
About 20 cm.

Ecology:

Life habits: Carnivorous
Feeding strategies: Carnivorous
Ecological Interpretations:

Like other leanchoiliid megacheirans the frontal appendages of Yawunik likely combined both sensing and grasping functions to detect and catch prey items. Food caught was brought under the body where it was rudimentarily masticated between the bases of limbs (basipods), before being channeled back to the mouth. As a leanchoiliid, Yawunik also had large glands atop its gut, presumably involved in digestion. The megacheiran body appendages, made of relatively strong walking legs (endopods) as well as paddle-like, semi-rigid flaps (exopods), would have allowed for both locomotion on the sea floor and swimming. The exopods likely served for gas exchanges (like breathing) as well, but recent studies showed that megacheirans and other Cambrian arthropods also possessed dedicated gills (Liu et al., 2021).

References:

  • 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.
  • Liu, Y., Edgecombe, G.D., Schmidt, M., Bond, A.D., Melzer, R.R., Zhai, D., Mai, H., Zhang, M. & Hou, X. (2021) Exites in Cambrian arthropods and homology of arthropod limb branches. Nature Communications 12, 4619.
  • Nanglu, K., Caron, J.-B. & Gaines, R.R. (2020) The Burgess Shale paleocommunity with new insights from Marble Canyon, British Columbia. Paleobiology 46, 58–81.
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Tokummia katalepsis

Tokummia katalepsis, paratype, ROMIP 63826

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
Higher Taxonomic assignment: Hymenocarines, Family Protocarididae (Miller 1889).
Species name: Tokummia katalepsis
Remarks:

Hymenocarines were early arthropods with bivalved carapaces and mandibles, forming the bulk of the first mandibulates (represented today by myriapods, crustaceans and insects) (Aria & Caron 2017; Vannier et al. 2018). Tokummia was a close relative of Branchiocaris, both grouped within the eponymous family Protocarididae Miller, 1889—one of the oldest formal taxa from the Burgess Shale. The relationship of Protocarididae within hymenocarines, as well as the relative placement of hymenocarines within early mandibulates is still under investigation (Aria 2022; Izquierdo-López & Caron 2022).

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

Tokummia — from Tokumm Creek, a river of the Kootenay area, in British Columbia, running through Marble Canyon, near the outcrop where the fossil was first found.

katalapsis — from the Greek, meaning “seizing, grasping,” by reference to the well-developed pincers of the animal.

Type Specimens: Holotype ROMIP 63823; paratypes ROMIP 63014, 63081, 63824–63827, 63736 (7 specimens), in the Royal Ontario Museum, Toronto, Canada.
Other species:

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

Age & Localities:

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

The Marble Canyon and Tokumm Creek areas of the Burgess Shale, British Columbia.

History of Research:

Brief history of research:

Tokummia was discovered during the original excavation of the Marble Canyon locality in 2012, along Yawunik and other taxa characteristic of this area. Additional specimens were later discovered during quarrying operations and along Tokumm Creek. Tokummia’s description was published in 2017: Tokummia’s size and quality of preservation helped identify mandibles and other diagnostic traits of mandibulates. Mandibles were also identified in Branchiocaris in the same study. This study partially rehabilitated original interpretations by Derek Briggs recognizing mandibulate affinities of Cambrian bivalved arthropods (hymenocarines) (Briggs 1992) but were not without their issues, notably that of the presence of an intercalary segment (e.g. Edgecombe 2017). However, research on hymenocarines has since been supportive of the mandibulate affinity of these arthropods (Vannier et al. 2018; Izquierdo-López & Caron 2022). Tokummia therefore remains central to our modern understanding of early arthropod evolution as a whole (Aria 2022).

Description:

Morphology:

Like other protocaridids, Tokummia’s long, tubular, multisegmented body is largely enclosed in a broad bivalved carapace with ample, lobate corners. Small processes are present medially at the front and rear of both valves. Eyes are very reduced or absent. The very front of the animal bears a bilobed organ covered by triangular sclerite. A pair of short, stout, multisegmented antennules are the most anterior appendages. The next pair of appendages are large, round mandibles, followed by modified appendages identified as maxillules and maxillae. The first pair of thoracic limbs are very large pincers projecting at the front of the animal, and therefore called maxillipeds. Trunk limbs are composed of well-developed walking legs ending in strong claws, and of lobate flaps that get much larger starting with trunk limb pair 9. There is a total of about 50 limb pairs in the trunk, one for each segment, which gradually decrease in size towards the back. Some tergites are fused at the back of the animal, forming a plate, and the tailpiece is a pair of caudal rami, typical of mandibulates.

Abundance:

The original description was based on 21 specimens (Aria & Caron 2017), but this count has so far doubled (Nanglu et al. 2020). Tokummia is a signature taxon of both the Marble Canyon quarry and the Tokumm sites.

Maximum Size:
About 15 cm.

Ecology:

Life habits: Carnivorous
Feeding strategies: Carnivorous
Ecological Interpretations:

The combination of large pincers and strong walking appendages in Tokummia suggests it was a nektobenthic predator. However, as in Branchiocaris and Protocaris, the absence of distinct eyes in the fossils, implying they were either very reduced or absent, indicates that the predatory lifestyle of Tokummia and other Protocarididae had its own specificity. Protocaridids either relied more heavily on their other sensory organs or were perhaps more passive predators.

References:

  • ARIA, C. 2022. The origin and early evolution of arthropods. Biological Reviews, 97, 1786–1809.
  • ARIA, C. and CARON, J. B. 2017. Burgess Shale fossils illustrate the origin of the mandibulate body plan. Nature, 545, 89–92.
  • BRIGGS, D. E. G. 1992. Phylogenetic significance of the Burgess Shale crustacean Canadaspis. Acta Zoologica, 73, 293–300.
  • EDGECOMBE, G. D. 2017. Palaeontology: The cause of jaws and claws. Current Biology, 27, R796–R815.
  • IZQUIERDO-LÓPEZ, A. and CARON, J.-B. 2022. The problematic Cambrian arthropod Tuzoia and the origin of mandibulates revisited. Royal Society Open Science, 9.
  • MILLER, S. A. 1889. North American geology and palaeontology for the use of amateurs, students and scientists. Western Methodist Book Concern, Cincinnati.
  • NANGLU, K., CARON, J.-B. and GAINES, R. R. 2020. The Burgess Shale paleocommunity with new insights from Marble Canyon, British Columbia. Paleobiology, 46, 58–81.
  • 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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Titanokorys gainesi

Titanokorys gainesi, holotype ROMIP 65168

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
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: Carnivorous
Feeding strategies: Carnivorous
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.
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Surusicaris elegans

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

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
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: Carnivorous
Feeding strategies: Carnivorous
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.
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Misszhouia canadensis

Misszhouia canadensis, two specimens, ROMIP 65408

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
Higher Taxonomic assignment: Subphylum Artiopoda (Hou & Bergström 1997), Class Nektaspida (Raymond 1920), Family Naraoiidae (Walcott 1912).
Species name: Misszhouia canadensis
Remarks:

Artiopoda is the clade including trilobites and their non-biomineralized relatives. The placement of Artiopoda relative to other arthropod groups, and particularly extant lineages, has been the subject of a long and ongoing debate (e.g. Aria et al. 2015; Paterson 2020). Misszhouia is the closest relative of Naraoia, together forming the family Naraoiidae, typified notably by having both cephalon and trunk forming smooth, articulating shields. Naraoiidae could be derived taxa among artiopodans (Mayers et al. 2019), but the internal relationships of Artiopoda have been difficult to resolve and continue to remain at odds between phylogenetic studies (e.g. Lerosey-Aubril et al. 2017; Moysiuk & Caron 2019).

Described by: Mayers, Aria and Caron
Description date: 2018
Etymology:

Misszhouia — in honour of Miss Guiqing Zhou, fossil preparator and technical assistant to Prof. Junyuan Chen from the Nanjing Institute of Geology and Palaeontology, Academia Sinica, China.

canadensis — from being discovered in Canada.

Type Specimens: dsfsdfdsfdsfdasf
Other species:

Holotype ROMIP 64408; paratypes ROMIP 64411, 64438, 64450, 64451, 64509, 64510, 64511, in the Royal Ontario Museum, Toronto, Canada.

Age & Localities:

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

The Marble Canyon and Tokumm Creek areas of the Burgess Shale, British Columbia.

History of Research:

Brief history of research:

Chen and colleagues created the genus Misszhouia mostly based on the distinction that these individuals of “Naraoialongicaudata did not possess gut ramifications inside the head, compared to Naraoia species from the Chengjiang biota and Burgess Shale. The morphoanatomy and taxonomy of Naraoiidae from China were later thoroughly revised by Zhang and colleagues (2007). Misszhouia canadensis was one of the first taxa found on talus when the Marble Canyon outcrop was discovered in 2012 (Caron et al. 2014). Although these fossils do possess extensive digestive ramifications in the head, morphometric analyses of body shape showed that specimens from both Canada and China formed a genus distinct from Naraoia (Mayers et al. 2019). Morphometric data also allowed for the identification of putative sexual morphs (Zhang et al. 2007; Mayers et al. 2019).

Description:

Morphology:

As an artiopodan, Misszhouia possesses a flattened body divided into a circular cephalon and a trunk, a pair of sensory antennules, and robust walking limbs with masticatory gnathobases, oriented parallel to the ventral surface of the body. Both cephalon and trunk form single smooth shields articulating to one another. In the cephalon, the gut ramifies into extensive diverticula; it is completed by lateral extensions called caeca in the trunk. In addition to the frontal antennules, the head bears another three pairs of limbs. The trunk represents 65% of total body length, with at least 30 limb pairs. The appendages are likely similar to M. longicaudata, with an inner walking branch and an outer, rod-shaped respiratory branch bearing packed lamellae.

Abundance:

Misszhouia is relatively rare at the Marble Canyon Quarry proper, but can be common along Tokumm Creek sites (Mayers et al. 2019).

Maximum Size:
About 8 cm.

Ecology:

Life habits: Carnivorous
Feeding strategies: Carnivorous
Ecological Interpretations:

Misszhouia was construed to be a predator or scavenger based on the presence of long antennules and well-developed gnathobases (masticatory surfaces at the base of the limbs) (Chen et al. 1997). The absence of digestive ramifications in the head of the Burgess Shale species, compared to the one from Chengjiang, suggests either different diets or different frequencies of feeding (Mayers et al. 2019).

References:

  • ARIA, C., CARON, J.-B. and 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., GAINES, R. R., ARIA, C., MANGANO, M. G. and STRENG, M. 2014. A new phyllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies. Nature Communications, 5.
  • CHEN, J. Y., EDGECOMBE, G. D. and RAMSKÖLD, L. 1997. Morphological and ecological disparity in naraoiids (Arthropoda) from the Early Cambrian Chengjiang fauna, China. Records of the Austalian Museum, 49, 1–24.
  • HOU, X. G. and BERGSTRÖM, J. 1997. Arthropods of the Lower Cambrian Chengjiang fauna, southwest China. Fossils and Strata, 45, 1–116.
  • LEROSEY-AUBRIL, R., ZHU, X. and ORTEGA-HERNÁNDEZ, J. 2017. The Vicissicaudata revisited – insights from a new aglaspidid arthropod with caudal appendages from the Furongian of China. Scientific Reports, 7, Article number: 11117.
  • MAYERS, B., ARIA, C. and CARON, J. B. 2019. Three new naraoiid species from the Burgess Shale, with a morphometric and phylogenetic reinvestigation of Naraoiidae. Palaeontology, 62, 19–50.
  • MOYSIUK, J. and CARON, J. B. 2019. Burgess Shale fossils shed light on the agnostid problem. Proc Biol Sci, 286, 20182314.
  • PATERSON, J. R. 2020. The trouble with trilobites: classification, phylogeny and the cryptogenesis problem. Geological Magazine, 157, 35–46.
  • RAYMOND, P. E. 1920. The appendages, anatomy and relationships of trilobites. Memoirs of the Connecticut Academy of Arts and Sciences, 7, 1–169.
  • WALCOTT, C. 1912. Cambrian Geology and Paleontology II. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57(6), 145–228.
  • ZHANG, X. L., SHU, D. G. and ERWIN, D. H. 2007. Cambrian naraoiids (Arthropoda): morphology, ontogeny, systematics, and evolutionary relationships. Journal of Paleontology, 81, 1–52.
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Capinatator praetermissus

Capinatator praetermissus, ROMIP 64247

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
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: Carnivorous
Feeding strategies: Carnivorous
Ecological Interpretations:

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

References:

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

Cambroraster falcatus, isolated H-element ROMIP 65316

Taxonomy:

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

Balhuticaris voltae, holotype ROMIP 66238

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
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:

Balhuticarisfrom 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: Carnivorous
Feeding strategies: Carnivorous
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.
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Zacanthoides romingeri

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

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
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: Carnivorous
Feeding strategies: Carnivorous
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.

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Yohoia tenuis

3D animation of Yohoia tenuis.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Carnivorous
Phylum: Carnivorous
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: Carnivorous
Feeding strategies: Carnivorous
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.

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