Creatures: Scavengers



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Peronopsis columbiensis

Artistic reconstruction of Peronopsis columbiensis. Danielle Dufault © ROM

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Artiopoda, Order: Agnostida
Species name: Peronopsis columbiensis
Remarks:

Owing to their distinctive appearance, agnostids have been classified either as trilobites, related to Eodiscina, or as stem group “crustaceans” (Müller and Walossek 1987; Cotton and Fortey 2005; Haug et al. 2009). The most recent phylogenetic analysis finds that agnostids form a grouping with trilobites, supported by shared features of the dorsal exoskeleton, such as mineralization, the expression of segmental boundaries, and the form of the thoracic joints (Moysiuk and Caron 2019). More taxonomically inclusive analyses will be needed to determine whether they belong inside or outside the group of true trilobites.

Described by: Rasetti
Description date: 1951
Etymology:

Peronopsis – From the Greek perone, “pin, brooch ” and opsis, “looking like.”

columbiensis – No etymology provided, but presumably in reference to the occurrence of the species in British Columbia, Canada.

Type Specimens: Holotype – USNM 116267; paratypes – USNM 116268-9; in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: P. montis

Other deposits: other species occur throughout the world in the middle Cambrian.

Age & Localities:

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

Mount Stephen, Mount Odaray, Marble Canyon.

History of Research:

Brief history of research:

Burgess Shale material was originally named Peronopsis columbiensis by Rasetti (1951). Naimark (2012) proposed to reassign the species to the genus Quadragnostus based on published images, but we maintain it here under Peronopsis pending taxonomic restudy of Burgess Shale specimens. Moysiuk and Caron (2019) recently described the appendages, digestive tract, and other soft tissues from exceptionally preserved specimens.

Description:

Morphology:

Adult dorsal exoskeletons reach about 20 mm in length. The semicircular cephalon has a narrow marginal rim around the front and sides and rounded genal angles. There are no dorsal eyes and no facial sutures. The narrow glabella comes to an ogival point, with no anterior median furrow; a transverse furrow crosses the glabella near its anterior. A pair of short genal spines are present. Two short thoracic segments carry lateral nodes on the axial rings. A narrowly rimmed pygidium, the same size and general shape as the cephalon, has abruptly angled anterolateral corners and a pair of short, backwards-directed marginal spines posterolaterally. The pygidial axis is broader than the glabella, but of similar outline, with a median tubercle between two transverse furrows. The pointed tip of the axis is separated by a gap from the pygidial rim posteriorly, without a median furrow. A saddle-shaped hypostome is present ventrally, unfused to the headshield. Unmineralized anatomy: The head probably bears six pairs of appendages, including one pair of elongate sensory antennules, two pairs of appendages with oar-like outer branches, and probably three pairs of stout walking limbs with a row of club-like projections. Additional walking limbs were present beneath the thorax (2) and pygidium (probably 4). The digestive tract curves dorsally from the mouth before emitting two pairs of branching gut glands, the first of which is the largest and occupies much of the space below the headshield. Behind this, the cylindrical midgut extends back to the pygidium. The hindgut begins roughly below the pygidial tubercle, and narrows considerably before reaching the anus below the tip of the pygidial axis.

Abundance:

Specimens likely assignable to this species are very common at Tokumm Creek and in the upper levels of the Marble Canyon quarry, where it is the most abundant artiopodan (Nanglu et al. 2020). Peronopsis columbiensis also occurs in notable numbers at Mount Odaray, Mount Stephen, and a few smaller localities (Rasetti 1951).

Maximum Size:
About 20 mm.

Ecology:

Life habits: Scavengers
Feeding strategies: Scavengers
Ecological Interpretations:

The mode of life of agnostids has been extensively debated (Fortey and Owens 1999). With the oar-like appendages capable of protruding while the animal was partially enrolled, agnostids certainly appear well-adapted for swimming (Müller and Walossek 1987). Together with their occurrence in mass mortality beds with wide geographic range, this evidence has been proposed to support a pelagic lifestyle (Fortey 1985). However, most specimens at the Burgess Shale are found in unrolled position, suggesting they did not live permanently enrolled. Further, Peronopsis is sometimes found in groups, associated with the remains of other Burgess Shale organisms, where it was potentially feeding on carrion or bacterial films, providing evidence for a benthic habitat. The huge, branching gut glands in the head likely acted as a food storage organ, possibly enabling a feast-and-famine lifestyle. The club-like outgrowths on the walking legs may have functioned in respiration (Moysiuk and Caron 2019).

References:

  • COTTON, T. J. and FORTEY, R. A. 2005. Comparative morphology and relationships of the Agnostida. In KOENEMANN, S. and JENNER, R. (eds.) Crustacea and Arthropod Relationships, CRC Press, 95–136 pp.
  • FORTEY, R. A. 1985. Pelagic trilobites as an example of deducing the life habits of extinct arthropods. Earth and Environmental Science Transactions of The Royal Society of Edinburgh, 76: 219–230.
  • FORTEY, R. A. and OWENS, R. M. 1999. Feeding habits in trilobites. Palaeontology, 42: 429–465.
  • HAUG, J. T., MAAS, A. and WALOSZEK, D. 2009. †Henningsmoenicaris scutula, †Sandtorpia vestrogothiensis gen. et sp. nov. and heterochronic events in early crustacean evolution. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 100: 311–350.
  • MOYSIUK, J. and CARON, J.-B. 2019. Burgess Shale fossils shed light on the agnostid problem. Proceedings of the Royal Society B: Biological Sciences, 286: 20182314.
  • MÜLLER, K. J. and WALOSSEK, D. 1987. Morphology, ontogeny, and life habit of Agnostus pisiformis from the Upper Cambrian of Sweden. Fossils and Strata, 19: 1–124.
  • NAIMARK, E. B. 2012. Hundred species of the genus Peronopsis Hawle et Corda, 1847. Paleontological Journal, 46: 945–1057.
  • 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.
  • RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116: 1–277.
Other Links:


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Misszhouia canadensis

Misszhouia canadensis, holotype, ROMIP 64408

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
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 “Naraoia” longicaudata 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: Scavengers
Feeding strategies: Scavengers
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.
Other Links:


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Zacanthoides romingeri

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

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Class Trilobita, Order Corynexochida
Species name: Zacanthoides romingeri
Remarks:

Trilobites are, by a large margin, the most diverse of extinct arthropod classes, encompassing more than 2000 species, although the biomineralization of their cuticle is likely largely responsible for their much better-known diversity. A recent probabilistic analysis of trilobite relationships suggests that many of the diagnostic traits used for the taxonomy of the main groups remain highly variable across lineages (Paterson, Edgecombe & Lee, 2019), which explains long-standing difficulties in resolving the trilobite evolutionary tree. The kinship of trilobites relative to other arthropod groups has been a historical dilemma also (Cotton & Braddy, 2004; Aria, Caron & Gaines, 2015; Paterson, 2020). Antennules and some other characters, on the one hand, would ally them with mandibulate arthropods (the Gnathomorpha or Antennulata hypothesis), while others would place them within the chelicerate lineage (the Arachnomorpha hypothesis). Recent phylogenetic results have brought increased support to Arachnomorpha, but there is still no consensus on the question (Aria, 2022).

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: Scavengers
Feeding strategies: Scavengers
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:

  • ARIA, C. (2022) The origin and early evolution of arthropods. Biological Reviews 97, 1786–1809.
  • 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.
  • COTTON, T.J. & BRADDY, S.J. (2004) The phylogeny of arachnomorph arthropods and the origin of the Chelicerata. Transactions of the Royal Society of Edinburgh-Earth Sciences 94, 169–193.
  • PATERSON, J.R. (2020) The trouble with trilobites: classification, phylogeny and the cryptogenesis problem. Geological Magazine 157, 35–46.
  • PATERSON, J.R., EDGECOMBE, G.D. & LEE, M.S.Y. (2019) Trilobite evolutionary rates constrain the duration of the Cambrian explosion. Proceedings of the National Academy of Sciences of the United States of America 116, 4394–4399.
  • RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116 (5): 1-277.
  • RESSER, C. E. 1942. Fifth contribution to nomenclature of Cambrian trilobites. Smithsonian Miscellaneous Collections, 101 (15): 1-58.
  • ROMINGER, C. 1887. Description of primordial fossils from Mount Stephens, N. W. Territory of Canada. Proceedings of the Academy of Natural Sciences of Philadelphia, 1887: 12-19.
  • RUDKIN, D. M. 1996. The Trilobite Beds of Mount Stephen, Yoho National Park, p. 59-68. In R. Ludvigsen (ed.), Life in Stone – A Natural History of British Columbia’s Fossils. UBC Press, Vancouver.
  • RUDKIN, D. M. 2009. The Mount Stephen Trilobite Beds, p. 90-102. In J.-B. Caron and D. Rudkin (eds.), A Burgess Shale Primer – History, Geology, and Research Highlights. The Burgess Shale Consortium, Toronto.
  • SCHOLTZ, G. AND G. D. EDGECOMBE. 2006. The evolution of arthropod heads: reconciling morphological, developmental and palaeontological evidence. Development Genes and Evolution, 216: 395-415.
  • WALCOTT, C. D. 1888. Cambrian fossils from Mount Stephens, Northwest Territory of Canada. American Journal of Science, Series 3, 36: 163-166.
  • WALCOTT, C. D. 1908. Mount Stephen rocks and fossils. Canadian Alpine Journal, 1:232-248.
Other Links:

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



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Sidneyia inexpectans

3D animation of Sidneyia inexpectans.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Sidneyia inexpectans
Remarks:

Sidneyia is usually considered to be closely related to the chelicerates, but its exact position relative to this group remains unclear (Budd and Telford, 2009). Sidneyia has been variously placed as the sister group to the chelicerates (Hou and Bergström, 1997), close to the crown on the chelicerate stem lineage (Bruton, 1981; Edgecombe and Ramsköld, 1999; Hendricks and Lieberman, 2008), or basal in the chelicerate stem lineage (Briggs and Fortey, 1989; Wills et al., 1998; Cotton and Braddy, 2004).

Described by: Walcott
Description date: 1911
Etymology:

Sidneyia – after Walcott’s son Sidney, who discovered the first specimen in August of 1910.

inexpectans – from the Latin inexpectans, “unexpected,” since Walcott did not expect to find such a fossil in strata older than the Ordovician.

Type Specimens: Lectotype –USNM57487 (S. inexpectans) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: A single specimen from the Chengjiang Fauna in China was used to describe a second species, Sidneyia sinica (Zhang et al. 2002), however this was later shown to be incorrectly attributed to Sidneyia (Briggs et al. 2008).

Age & Localities:

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

Burgess Shale and vicinity: The Walcott, Raymond and Collins Quarries on Fossil Ridge, Mount Field and Mount Stephen – Tulip Beds (S7) and other smaller localities – Odaray Mountain and Stanley Glacier.

Other deposits: Sidneyia has been described from the Wheeler Formation (Briggs and Robison, 1984) and the Spence Shale (Briggs et al. 2008) in Utah, and the Kinzers Formation in Pennsylvania (Resser and Howell, 1938).

History of Research:

Brief history of research:

Sidneyia was the first fossil to be described by Walcott (1911) from the Burgess Shale. Further details were added by Walcott the following year (Walcott, 1912), and Strømer (1944) and Simonetta (1963) made minor revisions to Walcott’s reconstruction. A large appendage found in isolation was originally suggested to be the large frontal appendage of Sidneyia (Walcott, 1911), but this was later found to belong to the anomalocaridid Laggania (Whittington and Briggs, 1985). A major study by Bruton (1981) redescribed the species based on the hundreds of available specimens.

Description:

Morphology:

Sidneyia has a short, wide head shield that is convexly domed and roughly square. The two front lateral corners are notched to allow an antenna and a stalked eye to protrude. Other than the pair of antennae, which are long and thin with at least 20 segments, there are no cephalic appendages. The hemispherical and highly reflective eyes are above and posterior to the antennae.

The thorax of Sidneyia has nine wide, thin body segments that widen from the first to the fourth segment and then get progressively narrower posteriorly. The first four thoracic segments bear appendages with a large, spiny basal segment (the coxa) and 8 thinner segments, ending in a sharp claw. The next five thoracic appendages have a similar appendage but also have flap-like filaments in association with the limbs.

The abdomen consists of three circular rings that are much narrower than the thorax, with a terminal, triangular telson. The last segment of the abdomen has a pair of wide flaps that articulate with the telson to form a tail fan. A trace of the straight gut can be seen in some specimens extending from the anterior mouth to the anus on the telson, and pieces of broken trilobites are sometimes preserved in the gut.

Abundance:

Sidneyia is a relatively common arthropod in the Walcott Quarry, comprising 0.3% of the specimens counted (Caron and Jackson, 2008). Hundreds of specimens have been collected from the Walcott Quarry (Bruton, 1981) and in other nearby localities.

Maximum Size:
160 mm

Ecology:

Life habits: Scavengers
Feeding strategies: Scavengers
Ecological Interpretations:

Sidneyia walked and swam above the sea floor. Its anterior four thoracic appendages were used for walking, and the spiny basal coxa would crush food items and move them towards the mouth. The posterior five thoracic appendages were used for swimming, with the flap-like filaments undulating through the water column to create propulsion. These filaments were also likely used for breathing, like gills.

The predatory nature of Sidneyia is indicated by its spiny coxa used to masticate food, and the presence of crushed fossil debris in its gut. Sidneyia would have walked or swam above the sea floor, using its eyes and antennae to seek out prey, which it would capture and crush with its anterior appendages.

References:

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

BRIGGS, D. E. G. AND R. A. ROBISON. 1984. Exceptionally preserved non-trilobite arthropods and Anomalocaris from the Middle Cambrian of Utah. The University of Kansas Paleontological Contributions, 111: 1-24.

BRIGGS, D. E. G., B. S. LIEBERMAN, J. R. HENDRICKS, S. L. HALGEDAHL AND R. D. JARRARD. 2008. Middle Cambrian arthropods from Utah. Journal of Paleontology, 82(2): 238-254.

BRUTON, D. L. 1981. The arthropod Sidneyia inexpectans, Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London B, 295: 619-653.

BUDD, G. E. AND M. J. TELFORD. 2009. The origin and evolution of arthropods. Nature, 457(7231): 812-817.

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

CARON, J.-B., R. GAINES, G. MANGANO, M. STRENG, AND A. DALEY. 2010. A new Burgess Shale-type assemblage from the “thin” Stephen Formation of the Southern Canadian Rockies. Geology, 38: 811-814.

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. AND L. RAMSKÖLD. 1999. Relationships of Cambrian Arachnata and the systematic position of Trilobita. Jounral of Paleontology, 73: 263-287.

HENDRICKS , J. R. AND B. S. LIEBERMAN. 2008. Phylogenetic insights into the Cambrian radiation of arachnomorph arthropods. Journal of Paleontology, 82: 585-594.

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

RASSER, C. E. AND B. F. HOWELL. 1938. Lower Cambrian Olenellus zone of the Appalachians. Bulletin of the Geological Society of America, 49: 195-248.

SIMONETTA, A. M. 1963. Osservazioni sugli artropodi non trilobiti della Burgess Shale (Cambriano medio). II. Contributo: I Generai Sidneyia ed Amiella Walcott 1911. Monitore Zoologico Italiano, 70: 97-108.

STØMER, L. 1944. On the relationships and phylogeny of fossil and recent Arachnomorpha. Norsk Videnskaps-Akademi Skrifter I. Matematisk-Naturvidenskaplig Klasse, 5: 1-158.

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

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. AND D. E. G. BRIGGS. 1985. The largest Cambrian animal, Anomalocaris, Burgess Shale, British-Columbia. Philosophical Transactions of the Royal Society of London Series B-Biological Sciences, 309: 569-609.

WILLS, M. A., D. E. G. BRIGGS, R. A. FORTEY, M. WILKINSON AND P. H. A. SNEATH. 1998. An arthropod phylogeny based on fossil and recent taxa, pp. 33-105. In G. D. Edgecombe (ed.), Arthropod fossils and phylogeny. Columbia University Press, New York.

ZHU, X., H. JIAN AND S. DEGAN. 2002. New occurrence of the Burgess Shale arthropod Sidneyia in the Early Cambrian Chengjiang Lagerstätte (South China), and revision of the arthropod Urokodia. Alcheringa: An Australasian Journal of Palaeontology, 26: 1-18.

Other Links:

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



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Selkirkia columbia

3D animation of Selkirkia columbia.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Unranked clade (stem group priapulids)
Species name: Selkirkia columbia
Remarks:

Selkirkia has been compared to the nemathelminth worms (Maas et al., 2007), but most analyses support a relationship with the priapulids at a stem-group level (Harvey et al., 2010; Wills, 1998).

Described by: Walcott
Description date: 1911
Etymology:

Selkirkia – from the Selkirk Mountains, a mountain range in southeastern British Columbia.

columbia – from British Columbia, where the Burgess Shale is located.

Type Specimens: Holotype –USNM57624 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: The genus Selkirkia ranges from the Lower to the Middle Cambrian and is represented by several species, including S. sinica from the Lower Cambrian Chengjiang Biota (Luo et al., 1999; Maas et al., 2007), S. pennsylvanica from the Lower Cambrian Kinzers Formation (Resser and Howell, 1938), Selkirkia sp. cf. and S. spencei from the Middle Cambrian Spence Shale of Utah (Resser, 1939; Conway Morris and Robison, 1986, 1988), and S. willoughbyi from the Middle Cambrian Marjum Formation of Utah (Conway Morris and Robison, 1986).

Age & Localities:

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

Burgess Shale and vicinity: The Walcott, Raymond and Collins Quarries on Fossil Ridge, and smaller localities on Mount Field and Mount Odaray. The Trilobite Beds, the Collins Quarry, the Tulip Beds (S7) and smaller localities on Mount Stephen.

Other deposits: The Middle Cambrian Spence Shale of Utah (Resser, 1939; Conway Morris and Robison, 1986, 1988).

History of Research:

Brief history of research:

Charles Walcott (1908) illustrated a single specimen of a simple tube that he named “Orthotheca major.” He interpreted the fossil as the tube of a polychaete worm, along with another famous species, “O. corrugata,” described by Matthew a decade earlier. O. corrugata is now referred to as Wiwaxia corrugata, which is not the tube of a worm but the scale of an armoured mollusc! The original specimen of “O. major” came from the Trilobite Beds on Mount Stephen, but it was not until the discovery of complete specimens from Fossil Ridge showing soft-bodied worms within the tubes that more details about this animal became available. Walcott (1911) created a new genus name Selkirkia to accommodate the new fossil material. In addition to the type species, S. major, he named two new species, S. gracilis and S. fragilis. In a revision of Walcott’s collections and other fossils discovered by the Geological Survey of Canada, Conway Morris (1977) synonymised Walcott’s three species into one that he called S. columbia, which is still in use today. S. columbia was described as a primitive priapulid worm (Conway Morris, 1977); later studies showed that it belongs to the priapulid stem group (Wills, 1998; Harvey et al., 2010).

Description:

Morphology:

Selkirkia lived in a tube and could reach up to 6 centimetres in length. The body of the worm itself is similar to most priapulids in having a trunk (which remained in the tube) and an anterior mouthpart that could be inverted into the trunk, called a proboscis. The proboscis has different series of spines along its length and is radially symmetrical. Small body extensions called papillae are present along the anterior part of the trunk and probably helped in anchoring the trunk in the tube. The gut is straight and the anus is terminal. The unmineralized tube is slightly tapered, open at both ends, and bears fine transverse lineations.

Abundance:

Selkirkia is the most abundant priapulid in the Walcott Quarry community, representing 2.7% of the entire community (Caron and Jackson, 2008); thousands of specimens are known, mostly isolated tubes.

Maximum Size:
60 mm

Ecology:

Life habits: Scavengers
Feeding strategies: Scavengers
Ecological Interpretations:

The well developed proboscis and strong spines suggest a carnivorous feeding habit. Comparisons with modern tube-building priapulids suggest Selkirkia was capable of only limited movement, and spend most of the time buried vertically or at an angle to the sediment-water interface, where they might have “trap fed” on live prey. Empty tubes were often used as a substrate for other organisms to colonize, for example, brachiopods, sponges and primitive echinoderms (see Echmatocrinus).

References:

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

CONWAY MORRIS, S. 1977. Fossil priapulid worms. Special Papers in Palaeontology, 20: 1-95.

CONWAY MORRIS, S. AND R. A. ROBISON. 1986. Middle Cambrian priapulids and other soft-bodied fossils from Utah and Spain. The University of Kansas paleontological contributions, 117: 1-22.

CONWAY MORRIS, S. AND R. A. ROBISON. 1988. More soft-bodied animals and algae from the Middle Cambrian of Utah and British Columbia. University of Kansas Paleontological Contributions, Paper, 122: 23-48.

HARVEY, T. H. P., X. DONG AND P. C. J. DONOGHUE. 2010. Are palaeoscolecids ancestral ecdysozoans? Evolution & Development, 12(2): 177-200.

LUO, H., S. HU, L. CHEN, S. ZHANG AND Y. TAO. 1999. Early Cambrian Chengjiang fauna from Kunming region, China. Yunnan Science and Technology Press, Kunming, 162 p.

MAAS, A., D. HUANG, J. CHEN, D. WALOSZEK AND A. BRAUN. 2007. Maotianshan-Shale nemathelminths – Morphology, biology, and the phylogeny of Nemathelminthes. Palaeogeography, Palaeoclimatology, Palaeoecology, 254(1-2): 288-306.

RESSER, C. E. AND B. F. HOWELL. 1938. Lower Cambrian Olenellus Zone of the Appalachians. Geological Society of America, Bulletin, 49: 195-248.

RESSER, C. E. 1939. The Spence Shale and its fauna. Smithsonian Miscellaneous Collections, 97(12):1-29.

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

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

WILLS, M. A. 1998. Cambrian and Recent disparity: the picture from priapulids. Paleobiology, 24(2): 177-199.

Other Links:

None



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Kootenia burgessensis

Kootenia burgessensis (ROM 60761). Disarticulated specimen. Specimen dry – direct light (left) and coated with ammonium chloride sublimate to show details (right). Specimen length = 44 mm. Walcott Quarry.

© Royal Ontario Museum. Photo: Jean-Bernard Caron

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Class Trilobita, Order Corynexochida
Species name: Kootenia burgessensis
Remarks:

Trilobites are, by a large margin, the most diverse of extinct arthropod classes, encompassing more than 2000 species, although the biomineralization of their cuticle is likely largely responsible for their much better-known diversity. A recent probabilistic analysis of trilobite relationships suggests that many of the diagnostic traits used for the taxonomy of the main groups remain highly variable across lineages (Paterson, Edgecombe & Lee, 2019), which explains long-standing difficulties in resolving the trilobite evolutionary tree. The kinship of trilobites relative to other arthropod groups has been a historical dilemma also (Cotton & Braddy, 2004; Aria, Caron & Gaines, 2015; Paterson, 2020). Antennules and some other characters, on the one hand, would ally them with mandibulate arthropods (the Gnathomorpha or Antennulata hypothesis), while others would place them within the chelicerate lineage (the Arachnomorpha hypothesis). Recent phylogenetic results have brought increased support to Arachnomorpha, but there is still no consensus on the question (Aria, 2022).

Described by: Resser
Description date: 1942
Etymology:

Burgess Shale and vicinity: Kootenia dawsoni. However, see below regarding a possible synonymy with the genus Olenoides.

Other deposits: other species attributed to Kootenia are widespread in the Cambrian of North America, and have been recorded in Greenland, China, Australia, and elsewhere.

Type Specimens: Holotype (K. burgessensis) – USNM65511 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA (Resser, 1942); Type status under review – (K. dawsoni), University of Michigan Museum of Paleontology, Ann Arbor, Michigan, USA.
Other species:

Burgess Shale and vicinity: Kootenia dawsoni; Olenoides serratus. (Species of Kootenia are no longer considered different enough from those in Olenoides to warrant placement in a separate genus, but Kootenia is retained here for ease of reference to historical literature).

Other deposits: other species attributed to Kootenia are widespread in the Cambrian of North America, and have been recorded in Greenland, China, Australia, and elsewhere.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge, and nearby localities on Mount Field; K. dawsoni is known from the Trilobite Beds and elsewhere on Mount Stephen.

History of Research:

Brief history of research:

Kootenia burgessensis was established by Charles Resser based on material Walcott included in K. dawsoni. Kootenia originally appeared as a subgenus of Bathyuriscus in Walcott’s 1889 paper revising many of Rominger’s Mount Stephen trilobite identifications. Walcott named B. (Kootenia) dawsoni after G. M. Dawson of the Geological Survey of Canada as a replacement for what Rominger had illustrated as Bathyurus (?) in 1887. In 1908, Walcott followed G. F. Matthew (1899) in calling this Dorypyge (Kootenia) dawsoni, but regarded Kootenia as a full genus in 1918. Harry Whittington included Kootenia burgessensis in his 1975 redescription of Burgess Shale appendage-bearing trilobites, illustrating a single specimen showing biramous thoracic limbs on one side. In 1994, Melzak and Westrop pointed out that the diagnostic character of Kootenia (depth of “interpleural” furrows on the pygidium) showed intraspecific variability, and argued that Kootenia—and perhaps other dorypygids trilobites—may have to be subsumed within Olenoides. We maintain Kootenia as a separate genus here pending formal taxonomic clarification.

Description:

Morphology:

Hard parts: adult dorsal exoskeletons may reach 5.5 cm in length and are broadly oval in outline. In most general features, Kootenia burgessensis resembles the co-occurring Olenoides serratus, with a semi-circular cephalon bearing genal spines, a thorax of seven segments, and a semi-circular pygidium. In Kootenia, however, spines on the thoracic pleural tips and shorter and blunter, as are those around the margin of the pygidium; interpleural furrows on the pygidium are absent to very faint.

Unmineralized anatomy: based on evidence from just a few specimens, Kootenia burgessensis, like Olenoides serratus, had a pair of flexible, multi-jointed “antennae” followed by three pairs of biramous limbs on the cephalon. Pairs of similar biramous appendages were attached under each thoracic segment, with a smaller number under the pygidium. No specimens, however, show any evidence of posterior antenna-like cerci as in Olenoides.

Abundance:

Kootenia burgessensis is moderately common in the Walcott Quarry section on Fossil Ridge, as is Kootenia dawsoni in the Mount Stephen Trilobite Beds.

Maximum Size:
55 mm

Ecology:

Life habits: Scavengers
Feeding strategies: Scavengers
Ecological Interpretations:

Adult Kootenia burgessensis walked along the sea bed, possibly digging shallow furrows to locate small soft-bodied and weakly-shelled animals or carcasses. Kootenia could probably swim just above the sea bed for short distances. Tiny larvae and early juveniles probably swam and drifted in the water column.

References:

  • ARIA, C. (2022) The origin and early evolution of arthropods. Biological Reviews 97, 1786–1809.
  • 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.
  • COTTON, T.J. & BRADDY, S.J. (2004) The phylogeny of arachnomorph arthropods and the origin of the Chelicerata. Transactions of the Royal Society of Edinburgh-Earth Sciences 94, 169–193.
  • PATERSON, J.R. (2020) The trouble with trilobites: classification, phylogeny and the cryptogenesis problem. Geological Magazine 157, 35–46.
  • PATERSON, J.R., EDGECOMBE, G.D. & LEE, M.S.Y. (2019) Trilobite evolutionary rates constrain the duration of the Cambrian explosion. Proceedings of the National Academy of Sciences of the United States of America 116, 4394–4399.
  • MATTHEW, G. F. 1899. Studies on Cambrian faunas, No. 3. Upper Cambrian Fauna of Mount Stephen, British Columbia: The trilobites and worms. Transactions of the Royal Society of Canada, Series 2, Vol. 5, Section IV:39-66.
  • MELZAK, A. AND S. R. WESTROP. 1994. Mid-Cambrian (Marjuman) trilobites from the Pika Formation, southern Canadian Rocky Mountains, Alberta. Canadian Journal of Earth Sciences, 31:969-985.
  • 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.
  • 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.
  • 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. 1889. Description of new genera and species of fossils from the Middle Cambrian. United States National Museum, Proceedings for 1888:441-446.
  • WALCOTT, C. D. 1908. Mount Stephen rocks and fossils. Canadian Alpine Journal, 1: 232-248.
  • WALCOTT, C. 1918. Cambrian Geology and Paleontology IV. Appendages of trilobites. Smithsonian Miscellaneous Collections, 67(4): 115-216.
  • WHITTINGTON, H. B. 1975. Trilobites with appendages from the Middle Cambrian, Burgess Shale, British Columbia. Fossils and Strata, No. 4: 97-136.
Other Links:

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



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Pagetia bootes

Pagetia bootes (ROM 60756). Complete individual. Specimen length = 4.5 mm. Specimen dry – direct light (left) and coated with ammonium chloride sublimate to show details (right). Walcott Quarry.

© ROYAL ONTARIO MUSEUM. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Artiopoda, Order Agnostida
Species name: Pagetia bootes
Remarks:

Pagetia is a member of Agnostida, small arthropods characterized by a pygidium (tail plate) similar in size and shape to the head and only two or three thoracic segments in adults. Unlike some other agnostids, Pagetia has dorsal eyes and moulting sutures. In this respect, its morphology is intermediate between that of presumably more derived agnostids (e.g. Peronopsis) and other trilobites (Cotton and Fortey 2005). A phylogenetic analysis recovered the group including Pagetia and related species to have been one of the first to branch off among trilobites (Paterson et al. 2019).

Described by: Walcott
Description date: 1916
Etymology:

Genus – unspecified, presumably from Paget Peak (2565 m) in Yoho National Park, named for the Very Reverend Dean Paget, founding member of the Alpine Club of Canada, who made the first recorded ascent in 1904.

species – unspecified, probably from the Greek Boötes meaning herdsman or ploughman; name of a northern constellation.

Type Specimens: Syntypes (P. bootes) – USNM 62855-61; Holotype (P. walcotti) – USNM 146310; in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: P. walcotti Rasetti, 1966.

Other deposits: other species occur throughout the world in Lower to Middle Cambrian rocks.

Age & Localities:

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

The Walcott and Raymond Quarries on Fossil Ridge. The Trilobite Beds on Mount Stephen. Mount Odaray.

History of Research:

Brief history of research:

Pagetia bootes was first named by Walcott (1916). Öpik was the first to recognize the hypostome (1952). Rasetti later provided the first detailed description (1966). The species has been featured in numerous works discussing trilobite biogeography, biostratigraphy, and phylogeny, e.g. (Rasetti 1951, 1952; Cotton and Fortey 2005; Paterson et al. 2019). Chatterton and colleagues described several Burgess Shale specimens preserved within Selkirkia tubes (2003).

Description:

Morphology:

Adult dorsal exoskeletons reach about 10 mm in length (including the pygidial spine). The semicircular cephalon has a narrow marginal rim around the front and sides and acute genal angles. The border is divided perpendicularly by a series of shallow furrows. The cephalon laterally bears a pair of proparian moulting sutures and compound eyes, connected to the axis by narrow, arcing eye ridges. The eyes of Pagetia and related genera are structurally unique among trilobites, having relatively few lenses separated by gaps (Jell 1975). The narrow glabella comes to an ogival point, with a median furrow extending across the short preglabellar field to the anterior margin. Faint traces of segmentation are visible on the glabella. The occipital lobe at the posterior or the cephalic axis emits an elongate spine, directed posteriad. The thorax contains two short segments with pleural furrows. A narrowly rimmed pygidium, the same size and general shape as the cephalon, has abruptly angled anterolateral corners. The pygidial axis shows six well-developed segments. The first five each bear a median tubercle while the terminal segment emits a long spine, directed posteriad. An elongate, convex hypostome is present ventrally, unfused to the headshield. Appendages are unknown.

Abundance:

P. bootes is very common in the Walcott Quarry. It is the third most common trilobite with at least 1000 specimens observed (Caron and Jackson, 2008), prompting Rasetti (1951) to define the “Pagetia bootes faunule” as the conventional shelly fossil assemblage associated with the exceptionally preserved soft-bodied biota. The co-occurring P. walcotti is very rare.

Maximum Size:
About 10 mm.

Ecology:

Life habits: Scavengers
Feeding strategies: Scavengers
Ecological Interpretations:

The mode of life of agnostids has been extensively debated (Fortey and Owens 1999). Their small size, degenerate eyes, adaptations for enrollment, and wide geographic occurrence have been proposed to support a pelagic lifestyle (Jell 1975; Fortey 1985). However, most specimens at the Burgess Shale are found in unrolled position, suggesting they did not live permanently enrolled. Further, Pagetia is sometimes found in groups, occasionally entombed inside the tubes of Selkirkia, which suggests the animal was spending at least part of its life cycle near the benthos (Chatterton et al. 2003; Lin and Yuan 2009). Due to the absence of appendage preservation, less is known about the mode of life of Pagetia than other Burgess Shale agnostids (Moysiuk and Caron 2019).

References:

  • CHATTERTON, B. D. E., COLLINS, D. H. and LUDVIGSEN, R. 2003. Cryptic behaviour in trilobites: Cambrian and Silurian examples from Canada, and other related occurrences. Special Papers in Palaeontology, 70: 157–173.
  • COTTON, T. J. and FORTEY, R. A. 2005. Comparative morphology and relationships of the Agnostida. In KOENEMANN, S. and JENNER, R. (eds.) Crustacea and Arthropod Relationships, CRC Press, 95–136 pp.
  • FORTEY, R. A. 1985. Pelagic trilobites as an example of deducing the life habits of extinct arthropods. Earth and Environmental Science Transactions of The Royal Society of Edinburgh, 76: 219–230.
  • FORTEY, R. A. and OWENS, R. M. 1999. Feeding habits in trilobites. Palaeontology, 42: 429–465.
  • JELL, P. A. 1975. The abathochroal eye of Pagetia, a new type of trilobite eye. Fossils and Strata, 4: 33–43.
  • LIN, J. P. and YUAN, J. L. 2009. Reassessment of the mode of life of Pagetia Walcott, 1916 (Trilobita: Eodiscidae) based on a cluster of intact exuviae from the Kaili Formation (Cambrian) of Guizhou, China. Lethaia, 42: 67–73.
  • MOYSIUK, J. and CARON, J.-B. 2019. Burgess Shale fossils shed light on the agnostid problem. Proceedings of the Royal Society B: Biological Sciences, 286: 20182314.
  • 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.
  • ÖPIK, A. A. 1952. The hypostoma of Pagetia. Journal of Paleontology, 26: 272–274.
  • PATERSON, J. R., EDGECOMBE, G. D. and LEE, M. S. Y. 2019. Trilobite evolutionary rates constrain the duration of the Cambrian explosion. Proceedings of the National Academy of Sciences of the United States of America, 116: 4394–4399.
  • RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116: 1–277.
  • RASETTI, F. 1952. Revision of the North American trilobites of the family Eodiscidae. Journal of Paleontology, 26: 434–451.
  • RASETTI, F. 1966. Revision of the North American species of the Cambrian Trilobite genus Pagetia. Journal of Paleontology, 40: 502–511.
  • WALCOTT, C. D. 1916. Cambrian geology and paleontology, III, No. 5; Cambrian trilobites. Smithsonian Miscellaneous Collections, 64: 303–456.
Other Links:

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

2D reconstruction – see: http://www.trilobites.info/galagnostida.htm



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Oryctocephalus reynoldsi

Oryctocephalus burgessensis (ROM 49962). Complete small individual; a presumed carcass with free cheeks in place. Specimen length = 5.5 mm. Specimen dry – direct light (left) and coated with ammonium chloride sublimate to show details (right). Walcott Quarry talus.

© ROYAL ONTARIO MUSEUM. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Class Trilobita, Order Corynexochida
Species name: Oryctocephalus reynoldsi
Remarks:

Trilobites are, by a large margin, the most diverse of extinct arthropod classes, encompassing more than 2000 species, although the biomineralization of their cuticle is likely largely responsible for their much better-known diversity. A recent probabilistic analysis of trilobite relationships suggests that many of the diagnostic traits used for the taxonomy of the main groups remain highly variable across lineages (Paterson, Edgecombe & Lee, 2019), which explains long-standing difficulties in resolving the trilobite evolutionary tree. The kinship of trilobites relative to other arthropod groups has been a historical dilemma also (Cotton & Braddy, 2004; Aria, Caron & Gaines, 2015; Paterson, 2020). Antennules and some other characters, on the one hand, would ally them with mandibulate arthropods (the Gnathomorpha or Antennulata hypothesis), while others would place them within the chelicerate lineage (the Arachnomorpha hypothesis). Recent phylogenetic results have brought increased support to Arachnomorpha, but there is still no consensus on the question (Aria, 2022).

Described by: Reed
Description date: 1899
Etymology:

Oryctocephalus – from the Greek oryktos, “dug” or “burrowed,” and kephalos, “head.”

reynoldsi – after Mr. S. H. Reynolds, who collected and donated the type specimen to the Woodwardian Museum of the University of Cambridge (now in the Sedgwick Museum of Earth Sciences).

Type Specimens: Holotype (O. reynoldsi) – SM A1425, Sedgwick Museum of Earth Sciences, University of Cambridge, Cambridge, UK. Holotype S17 (O. burgessensis) –USNM96487, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: Oryctocephalus burgessensis Resser, 1938.

Other deposits: many other species worldwide.

Age & Localities:

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

The Trilobite Beds and smaller localities on Mount Stephen. The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

The genus Oryctocephalus was established by Charles Walcott in 1886 to include the species O. primus, based on isolated cranidia and pygidia from the Middle Cambrian of Nevada. Reed named and described O. reynoldsi in 1899 from a complete specimen (including the articulated thorax), probably collected at the Mount Stephen Trilobite Beds. In the same year as Reed’s paper appeared, G. F. Matthew also had a publication in press, describing O. walkeri from collections on Mount Stephen. Although minor differences between O. reynoldsiand O. walkeri were noted (Matthew, 1899), they are almost certainly one and the same, and Reed’s name has publication priority. In 1938, Resser erected a new species, O. burgessensis, for specimens from the Walcott Quarry. Rasetti (1951) illustrated O. reynoldsiand O. burgessensis and named another new species, O. matthewi, from both localities. Whittington reassessed the Burgess Shale species of Oryctocephalus in 1995, and found that Rasetti’s O. matthewi was indistinguishable from O. reynoldsi.

Description:

Morphology:

Hard parts: both Oryctocephalus reynoldsi and O. burgessensis are small trilobites, with adult exoskeletons generally 15-20 mm long, excluding pygidial spines. Dorsal shields are ovoid in outline, slightly narrower posteriorly. O. reynoldsi has a broad semicircular cephalon, with the genal angles drawn out and back into long slender spines extending almost to the pygidium. The distinctive glabella widens slightly forwards to a rounded front at the anterior border. Three pairs of pits lie forward of the occipital ring, just inside the axial furrows; the posterior pair is joined by a shallow transverse furrow. Faint eye ridges swing back from near the front of the glabella to the long crescentic eye lobes far out on the cheeks. The thorax contains seven wide segments with strong, curving pleural furrows and long terminal spines directed obliquely rearward. The unmistakable pygidium is semicircular, narrower than the cephalon, with a tapering axis of five rings and a terminal piece ending well inside the posterior margin. Six radially disposed pleurae all end in spines, the fourth pair being much broader at the base and very long, directed out and back to at least twice the length of the pygidium. The short fifth and sixth spine pairs extend straight back. O. burgessensis can be distinguished mainly by its subtly shorter genal and fourth pygidial spines; the genal spine also appears to arise slightly farther forward than in O. reynoldsi.

Unmineralized anatomy: not known

Abundance:

Rare, both on Mount Stephen and on Fossil Ridge.

Maximum Size:
25 mm

Ecology:

Life habits: Scavengers
Feeding strategies: Scavengers
Ecological Interpretations:

Very similar species of Oryctocephalus are found in Middle Cambrian rocks of deeper water origin in many places around the world, suggesting that these cosmopolitan trilobites typically inhabited open ocean settings.

References:

  • ARIA, C. (2022) The origin and early evolution of arthropods. Biological Reviews 97, 1786–1809.
  • 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.
  • COTTON, T.J. & BRADDY, S.J. (2004) The phylogeny of arachnomorph arthropods and the origin of the Chelicerata. Transactions of the Royal Society of Edinburgh-Earth Sciences 94, 169–193.
  • MATTHEW, G. F. 1899. Studies on Cambrian faunas, No. 3. Upper Cambrian Fauna of Mount Stephen, British Columbia: The trilobites and worms. Transactions of the Royal Society of Canada, Series 2, Vol. 5, Section IV: 39-66.
  • PATERSON, J.R. (2020) The trouble with trilobites: classification, phylogeny and the cryptogenesis problem. Geological Magazine 157, 35–46.
  • PATERSON, J.R., EDGECOMBE, G.D. & LEE, M.S.Y. (2019) Trilobite evolutionary rates constrain the duration of the Cambrian explosion. Proceedings of the National Academy of Sciences of the United States of America 116, 4394–4399.
  • RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116 (5): 1-277.
  • REED, F. R. C. 1899. Woodwardian Museum Notes: a new trilobite from Mount Stephen, Field, B.C. Geological Magazine, New Series (Decade 4), 6: 358-361.
  • RESSER, C. E. 1938. Fourth contribution to nomenclature of Cambrian fossils. Smithsonian Miscellaneous Collections, 97: 1-43.
  • 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. 1886. Second contribution to the studies on the Cambrian faunas of North America. Bulletin of the US Geological Survey, 30: 1-255.
  • WHITTINGTON, H. B. 1995. Oryctocephalid trilobites from the Cambrian of North America. Palaeontology, 38: 543-562.
Other Links:

None



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Olenoides serratus

3D animation of Olenoides serratus.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Class Trilobita, Order Corynexochida
Species name: Olenoides serratus
Remarks:

Trilobites are, by a large margin, the most diverse of extinct arthropod classes, encompassing more than 2000 species, although the biomineralization of their cuticle is likely largely responsible for their much better-known diversity. A recent probabilistic analysis of trilobite relationships suggests that many of the diagnostic traits used for the taxonomy of the main groups remain highly variable across lineages (Paterson, Edgecombe & Lee, 2019), which explains long-standing difficulties in resolving the trilobite evolutionary tree. The kinship of trilobites relative to other arthropod groups has been a historical dilemma also (Cotton & Braddy, 2004; Aria, Caron & Gaines, 2015; Paterson, 2020). Antennules and some other characters, on the one hand, would ally them with mandibulate arthropods (the Gnathomorpha or Antennulata hypothesis), while others would place them within the chelicerate lineage (the Arachnomorpha hypothesis). Recent phylogenetic results have brought increased support to Arachnomorpha, but there is still no consensus on the question (Aria, 2022).

Described by: Rominger
Description date: 1887
Etymology:

Olenoides – from Olenus, in Greek mythology a man who, along with his wife Lethaea, was turned to stone. Olenus was used for a trilobite genus name in 1827; the suffix –oides(“resembling”) was added later.

serratus – from the Latin serratus, “saw-shaped,” probably referring to the spinose margin of the pygidium.

Type Specimens: Type status under review – UMMP 4882 (11 specimens), University of Michigan Museum of Paleontology, Ann Arbor, Michigan, USA.
Other species:

Burgess Shale and vicinity: Kootenia dawsoni; Kootenia burgessensis. (Species of Kooteniaare no longer considered different enough from those in Olenoides to warrant placement in a separate genus, but Kootenia is retained here for ease of reference to historical literature).

Other deposits: species of Olenoides are widespread in the Cambrian of North America and Greenland, and have been recorded in Siberia, China, and elsewhere.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge. The Trilobite Beds and other localities on Mount Stephen.

History of Research:

Brief history of research:

Olenoides serratus was among the first Burgess Shale animals to be named and described. The fossils used in Rominger’s original 1887 description were collected from the Mount Stephen Trilobite Beds in 1886. Rominger coined the name Ogygia serrata for this trilobite, illustrating one complete specimen in accompanying engravings. Following several intermediate changes, the name now in use was first published by Kobayashi in 1935. Spectacular appendage-bearing specimens discovered during Walcott’s Fossil Ridge excavations in 1910-1911 brought Olenoides serratus (then called Neolenus serratus) attention worldwide as one of the most anatomically complete trilobites known. This iconic Burgess Shale species has been thoroughly redescribed by Harry Whittington (1975, 1980), who also concluded that Nathorstia transitans (named by Walcott in 1912) was a “soft shell” moult stage of Olenoides serratus.

Description:

Morphology:

Hard parts: adult dorsal exoskeletons may reach 9 cm long and are broadly oval in outline, with a semi-circular cephalon, a thorax of seven segments ending in spines, and a semi-circular pygidium with marginal spines. The cephalon, thorax and pygidium are of approximately equal length. The parallel-sided glabella is rounded in front and reaches almost to the anterior border. Thin eye ridges swing back from the front of the glabella to the small, outwardly-bowed eyes. The free cheeks narrow back into straight, slender genal spines reaching to the third pleurae. Tips of the pleurae also extend into needle-like spines. The spiny pygidium has six axial rings decreasing in size backwards; five pairs of marginal spines point rearward. The whole exoskeleton has a variably granulate outer surface with fine ridges and cusps near the margins.

Unmineralized anatomy: Olenoides serratus had a pair of flexible, multi-jointed cephalic “antennae.” Behind these, three pairs of biramous limbs were attached beneath the cephalon on either side of the mid-line. Each inner branch had a large spiny blade-shaped coxa and six spinose cylindrical podomeres that tapered away from the body, the last carrying three short “claws” at the tip. The outer limb branch was composed of many flat, overlapping filaments sweeping back from a long lobe, with a small oval, hair-fringed lobe at the outer end. Pairs of similar biramous appendages were attached under each thoracic segments; four to six pairs were attached under the pygidium, becoming shorter and more slender to the rear. Unique among all trilobites preserving limbs, Olenoides serratus also had a pair of antenna-like appendages (cerci; singular = cercus) emerging from under the pygidium behind the last biramous limbs.

Abundance:

Olenoides serratus is moderately common, especially at the Mount Stephen Trilobite Beds, where thousands of pieces and hundreds of partial to complete exoskeletons have been observed or collected. Olenoides is the largest and most conspicuous trilobite in the Walcott Quarry section on Fossil Ridge, where specimens with preserved appendages have been found.

Maximum Size:
90 mm

Ecology:

Life habits: Scavengers
Feeding strategies: Scavengers
Ecological Interpretations:

Adults of Olenoides serratus walked along the sea bed, possibly digging shallow furrows to locate small soft-bodied and weakly-shelled animals or carcasses. Prey items were shredded between the spiny limb bases and passed forward to the rear-facing mouth. Olenoides could probably swim just above sea bed for short distances. Some Olenoides fossils show unmistakable evidence of healed injuries, suggesting they may have been preyed upon, likely in their “soft-shell” growth phase, by larger arthropods such as Anomalocaris. Tiny larvae and early juveniles of Olenoides probably swam and drifted in the water column above the sea bed.

References:

  • ARIA, C. (2022) The origin and early evolution of arthropods. Biological Reviews 97, 1786–1809.
  • 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.
  • COTTON, T.J. & BRADDY, S.J. (2004) The phylogeny of arachnomorph arthropods and the origin of the Chelicerata. Transactions of the Royal Society of Edinburgh-Earth Sciences 94, 169–193.
  • KOBAYASHI, T. 1935. The Cambro-Ordovician formations and faunas of south Chosen. Paleontology, Part 3: Cambrian faunas of south Chosen with a special study on the Cambrian trilobite genera and families. Journal of the Faculty of Science, Imperial University of Tokyo, Section II. 4(2): 49-344.
  • PATERSON, J.R. (2020) The trouble with trilobites: classification, phylogeny and the cryptogenesis problem. Geological Magazine 157, 35–46.
  • PATERSON, J.R., EDGECOMBE, G.D. & LEE, M.S.Y. (2019) Trilobite evolutionary rates constrain the duration of the Cambrian explosion. Proceedings of the National Academy of Sciences of the United States of America 116, 4394–4399.
  • RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116 (5): 1-277.
  • 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.
  • 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. 1912. Cambrian Geology and Paleontology, II. No. 6. – Middle Cambrian Branchiopoda, Malacostraca, Trilobita, and Merostomata. Smithsonian Miscellaneous Collections, 57(6): 145-228.
  • WHITTINGTON, H. B. 1975. Trilobites with appendages from the Middle Cambrian, Burgess Shale, British Columbia. Fossils and Strata, No. 4: 97-136.
  • WHITTINGTON, H. B. 1980. Exoskeleton, moult stage, appendage morphology, and habits of the Middle Cambrian trilobite Olenoides serratus. Palaeontology, 23: 171-204.
Other Links:

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

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

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

http://pakozoic.deviantart.com/art/Olenoides-serratus-3D-77550691



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Bathyuriscus rotundatus

Bathyuriscus rotundatus (USNM 116232b) – Plesiotype. Nearly complete individual with right free cheek in place. Specimen length = 14 mm. Specimen dry – direct light. Trilobite Beds on Mount Stephen.

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

Taxonomy:

Kingdom: Scavengers
Phylum: Scavengers
Higher Taxonomic assignment: Class Trilobita, Order Corynexochida
Species name: Bathyuriscus rotundatus
Remarks:

Trilobites are, by a large margin, the most diverse of extinct arthropod classes, encompassing more than 2000 species, although the biomineralization of their cuticle is likely largely responsible for their much better-known diversity. A recent probabilistic analysis of trilobite relationships suggests that many of the diagnostic traits used for the taxonomy of the main groups remain highly variable across lineages (Paterson, Edgecombe & Lee, 2019), which explains long-standing difficulties in resolving the trilobite evolutionary tree. The kinship of trilobites relative to other arthropod groups has been a historical dilemma also (Cotton & Braddy, 2004; Aria, Caron & Gaines, 2015; Paterson, 2020). Antennules and some other characters, on the one hand, would ally them with mandibulate arthropods (the Gnathomorpha or Antennulata hypothesis), while others would place them within the chelicerate lineage (the Arachnomorpha hypothesis). Recent phylogenetic results have brought increased support to Arachnomorpha, but there is still no consensus on the question (Aria, 2022).

Described by: Rominger
Description date: 1887
Etymology:

Bathyuriscus – a variation of the earlier trilobite genus name Bathyurus, originally based on the Greek bathys, “deep,” and the Greek oura, “tail,” thus, a trilobite with a deep tail.

rotundatus – from the Latin rotundus, “round,” presumably alluding to the rounded outline of the dorsal shield.

Type Specimens: Type status under review – UMMP 4884 (9 specimens), University of Michigan Museum of Paleontology, Ann Arbor, Michigan, USA.
Other species:

Burgess Shale and vicinity: Bathyuriscus adaeus Walcott, 1916, from several localities higher in the Bathyuriscus-Elrathina Zone on Mount Stephen, Mount Odaray, and Park Mountain.

Other deposits: other species of Bathyuriscus have been described from numerous localities elsewhere in the Cambrian of North America.

Age & Localities:

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

The Trilobite Beds and other localities on Mount Stephen. Fossil Ridge in sections stratigraphically below the Walcott Quarry.

History of Research:

Brief history of research:

Bathyuriscus rotundatus was first described in the same 1887 publication as several other important Mount Stephen trilobites. Carl Rominger initially used the name Embolimus rotundata for partial specimens of this trilobite, and named a second similar species in his collection Embolimus spinosa (now known as Zacanthoides romingeri). In 1908, Walcott revised Rominger’s original species name to yield the combination Bathyuriscus rotundatus, still in use today (Walcott, 1908). Along with the co-occurring Elrathina cordillerae, B. rotundatus is a signature fossil for the Middle Cambrian Bathyuriscus-Elrathina Zone in the southern Canadian Rockies.

Description:

Morphology:

Hard parts: adult dorsal exoskeletons may be up to 5 cm long and are narrowly oval in outline, with a semicircular cephalon, a thorax of nine segments ending in blade-like tips with short spines, and a semicircular pygidium without spines. The long glabella reaches almost to the anterior cephalic border; the posterior portion is narrow and parallel-sided, while the anterior third expands rapidly forward. There are four pairs of lateral glabellar furrows, with the two front pairs angled forward and the posterior pair directed obliquely back. The eyes are relatively long and lie close to the glabella. Broad free cheeks are extended back into short genal spines. The pygidium is slightly smaller than the cephalon, with a well-defined narrow axial lobe of five rings and a terminal piece; four pairs of pygidial ribs are usually visible. The exoskeleton is mostly smooth externally, but very well-preserved specimens may show faint anastomosing ridges on the free cheeks. Unmineralized anatomy: not known.

Abundance:

Extremely common in the Mount Stephen Trilobite Beds, where it rivals Ogygopsis klotzi in abundance.

Maximum Size:
50 mm

Ecology:

Life habits: Scavengers
Feeding strategies: Scavengers
Ecological Interpretations:

Bathyuriscus rotundatus was a mobile epibenthic trilobite. Because we have no direct evidence of limb structure, its feeding habits are uncertain. It may have been a deposit feeder and opportunistic scavenger. Like Ogygopsis, Bathyuriscus may occur as fully intact individuals (probably carcasses), with the free cheeks missing, inverted, or rotated (presumed moults), and as scattered pieces. Some show evidence of healed injuries that may be predation scars (Rudkin, 2009).

References:

  • ARIA, C. (2022) The origin and early evolution of arthropods. Biological Reviews 97, 1786–1809.
  • 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.
  • COTTON, T.J. & BRADDY, S.J. (2004) The phylogeny of arachnomorph arthropods and the origin of the Chelicerata. Transactions of the Royal Society of Edinburgh-Earth Sciences 94, 169–193.
  • PATERSON, J.R. (2020) The trouble with trilobites: classification, phylogeny and the cryptogenesis problem. Geological Magazine 157, 35–46.
  • PATERSON, J.R., EDGECOMBE, G.D. & LEE, M.S.Y. (2019) Trilobite evolutionary rates constrain the duration of the Cambrian explosion. Proceedings of the National Academy of Sciences of the United States of America 116, 4394–4399.
  • RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116 (5): 1-277.
  • 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. 2009. The Mount Stephen Trilobite Beds, pp. 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 EDGECOMBE, G. D. 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: 163-166.
  • WALCOTT, C. D. 1908. Mount Stephen rocks and fossils. Canadian Alpine Journal, 1: 232-248.
  • WALCOTT, C. D. 1916. Cambrian Geology and Paleontology III. Cambrian Trilobites. Smithsonian Miscellaneous Collections, 64(5): 303-456.
Other Links:

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