Feeding Strategies: Scavenger



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Zacanthoides romingeri

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

Taxonomy:

Kingdom: Scavenger
Phylum: Scavenger
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: Scavenger
Feeding strategies: Scavenger
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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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: Scavenger
Phylum: Scavenger
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: Scavenger
Feeding strategies: Scavenger
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: Scavenger
Phylum: Scavenger
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: Scavenger
Feeding strategies: Scavenger
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: Scavenger
Phylum: Scavenger
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: Scavenger
Feeding strategies: Scavenger
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: Scavenger
Phylum: Scavenger
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: Scavenger
Feeding strategies: Scavenger
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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Canadaspis perfecta

3D animation of Canadaspis perfecta.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Scavenger
Phylum: Scavenger
Higher Taxonomic assignment: Hymenocarines, Family Canadaspidae (Briggs 1978)
Species name: Canadaspis perfecta
Remarks:

Hymenocarines were early arthropods with bivalved carapaces and mandibles, forming the bulk of the first mandibulates (represented today by myriapods, crustaceans and insects) Canadaspis was originally classified as a Malacostracan crustacean (Walcott 1912; Briggs 1978), but this has since been refuted (Briggs 1992; Legg et al. 2012; Aria and Caron 2017).

Described by: Walcott
Description date: 1912
Etymology:

Canadaspis – from the country Canada, whose name derives from the Saint-Lawrence Iroquoian kanata, “settlement” or “land,” and the Greek aspis, “shield.”

perfecta – from the Latin perfectus, “complete.”

perfecta – from the Latin perfectus, “complete.”

Type Specimens: Lectotype –USNM57703 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none

Other deposits: C. laevigata from the Lower Cambrian Chengjiang biota (Hou and Bergström 1991, 1997). Further material of Canadaspis cf. perfecta has been recovered from additional localities in the USA (Robison and Richards 1981; Lieberman 2003; Briggs et al. 2008). Indeterminate species of Canadaspis have also been recovered from the Guzhangian Fulu Biota of China (Peng et al. 2020), the Wuliuan Kaili Biota (Wang et al. 2009) and the middle Cambrian Pioche Shale (Kimmig et al. 2019).

Age & Localities:

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

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Originally referred to as Hymenocaris by Charles Walcott (1912), the genus Canadaspis was erected by Novozhilov (Orlov 1960). Four species were designated by Simonetta and Delle Cave (1975), but two of them, Canadaspis ovalis and Canadaspis dictynna, have since been redescribed within Perspicaris dictynna (Briggs 1977). A third species, Canadaspis obesa, has been redescribed within Canadaspis perfecta (Briggs 1978). A full study of the fourth and only valid species, Canadaspis perfecta, was published by (Briggs 1978), who posited a crustacean affinity. An additional species, Canadaspis laevigata was later described from the early Cambrian Chengjiang biota (Hou and Bergström 1997). As with other hymenocarines, the crustacean affinity of Canadaspis was challenged by later workers (Briggs 1992; Hou and Bergström 1997; Waloszek 1999), and a position as stem-group euarthropods argued instead (Budd 2002, 2008; Ortega-Hernández et al. 2017). The two pairs of antennae described by Briggs (1978), for example, have been re-interpreted as one pair of antennulae and one pair more frontal, unsegmented appendages (Ortega-Hernández and Budd 2016). The discovery of mandibles in the hymenocarines Branchiocaris (Aria and Caron 2017) and Waptia (Vannier et al. 2018) prompted the classification of Canadaspis as an early mandibulate. Mandibles had originally been observed in Canadaspis by Briggs (1978), but their identity had not been widely accepted (Edgecombe 2017). Further details of these structures, including a teeth-bearing surface and a potential three-segmented palp have since been uncovered (Izquierdo-López and Caron 2022a), further strengthening the mandibulate position of Canadaspis. Thanks to its long history of research, abundance, and comprehensive anatomical reconstruction, Canadaspis has been included in different morphometric (Zeng et al. 2020; Izquierdo-López and Caron 2022b) and palaeoecological analyses (Briggs 1978). Carapace assemblages also suggest that Canadaspis performed coordinated moulting: multiple individuals moulting at the same time and place (Haug et al. 2013).

Description:

Morphology:

The carapace of Canadaspis covers half of its total body length. Carapace valves are suboval in outline and taper towards the anterior, more pronounced than in the closely related Perspicaris. Valves connect dorsally, and do not form an anterior process, but often form a small posterior process. The length of the bivalved carapaces ranges in size from 0.8-5.2 cm in length. The head protrudes slightly from behind the carapace valves, and its outline is generally rounded. Canadaspis has one pair of small, elongate eyes, as well as one pair of elongate unsegmented appendages located between the eyes. Other head appendages include a pair of antennulae, a pair of mandibles, a possible pair of maxillae and two pairs of limbs incorporated into the head (cephalothorax). The antennulae are short and thick and have at least 12 segments, all fringed with long spines. The mandibles are rounded and have a dentate inner edge. A following cephalic appendage may represent a small three-segmented palp fringed with setae. The morphology of the maxillae is currently not clear. The thorax has 8 segments, each with a two-branched limb (biramous). Each limb has a multisegmented base (basipod). In thoracic legs, each segment bears a small spine. The basipod bears an inner walking branch (endopod), divided into 7 segments, with the terminal one ending in a complex three-clawed structure. The outer branch (exopod) is a large flap with lamellae, interpreted to be gills. Posterior to the thorax there are 7 segments that do not bear legs (the abdomen). The edge of each segment is spinose. The last segment is highly spinose and bears a pair of larger spinose processes. The gut of Canadaspis is sometimes preserved, with mid-gut glands giving it a segmented appearance (Butterfield 2002).

Abundance:

Canadaspsis is abundant, with over 5,000 specimens known; it comprises 8.6% of the Walcott Quarry community (Caron and Jackson, 2008).

Maximum Size:
About 5.2 cm (largest carapace)

Ecology:

Life habits: Scavenger
Feeding strategies: Scavenger
Ecological Interpretations:

Canadaspis was likely to have lived closed to the sea floor, walking on its biramous appendages by moving them in a rippling motion. This would also waft water past the gills that form the outer branches of its biramous limbs, allowing for respiration. This movement may have also propelled Canadaspis through the water column. The inner surfaces of its legs were covered with spines that would have assisted in feeding by directing food particles to the organism’s mouth. The mandibles would have been used to help consume the coarse particles found on the sediment surface or aid in tearing and manipulating other sources of food. The synchronized moulting strategy of Canadaspis (Haug et al. 2013) is part of an increasing evidence of the complexity of behaviours in Cambrian bivalved arthropods, which also includes the ability to take care of eggs seen in Waptia (Caron and Vannier 2016) or Chuandianella (Ou et al. 2020), or the chain-like associations seen in Synophalos (Hou et al. 2009).

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. 1977. Bivalved arthropods from the Cambrian Burgess Shale of British Columbia. Palaeontology, 20: 595–621.
  • BRIGGS, D. E. G. 1978. The morphology, mode of life, and affinities of Canadaspis perfecta (Crustacea: Phyllocarida), middle Cambrian, Burgess Shale, British Columbia. Phylosophical Transactions of The Royal Society of London, 281: 439–487.
  • BRIGGS, D. E. G. 1992. Phylogenetic significance of the Burgess Shale crustacean Canadaspis. Acta Zoologica, 73: 293–300.
  • BRIGGS, D. E. G., LIEBERMAN, B. S., HENDRICKS, J. R., HALGEDAHL, S. L. and JARRARD, R. D. 2008. Middle Cambrian arthropods from Utah. Journal of Paleontology, 82: 238–254.
  • BUDD, G. E. 2002. A palaeontological solution to the arthropod head problem. Nature, 417: 271–275.
  • BUDD, G. E. 2008. Head structure in upper stem-group euarthropods. Palaeontology, 51: 561–573.
  • BUTTERFIELD, N. J. 2002. Leanchoilia guts and the interpretation of three-dimensional structures in Burgess Shale-type fossils. Paleobiology, 28: 155–171.
  • CARON, J. B. and VANNIER, J. 2016. Waptia and the diversification of brood care in early arthropods. Current Biology, 26: 69–74.
  • EDGECOMBE, G. D. 2017. Palaeontology: the cause of jaws and claws. Current Biology, 27: R807–R810.
  • HAUG, J. T., CARON, J. B. and HAUG, C. 2013. Demecology in the Cambrian: synchronized molting in arthropods from the Burgess Shale. BMC Biology, 11: 1–10.
  • HOU, X. and BERGSTRÖM, J. 1991. The arthropods of the Lower Cambrian Chengjiang fauna, with relationships and evolutionary significance. In SIMONETTA, A. M. and CONWAY-MORRIS, S. (eds.) The Early Evolution of Metazoan and the Significance of Problematic Taxa, Cambridge University Press, Cambridge, 179–187 pp.
  • HOU, X. and BERGSTRÖM, J. 1997. Arthropods of the lower Cambrian Chengjiang fauna, southwest China. Fossil and Strata, 45: 1–116.
  • HOU, X., SIVETER, D. J., ALDRIDGE, R. J. and SIVETER, D. J. 2009. A new arthropod in chain-like associations from the Chengjiang Lagerstätte (Lower Cambrian), Yunnan, China. Palaeontology, 52: 951–961.
  • IZQUIERDO-LÓPEZ, A. and CARON, J.-B. 2022a. The problematic Cambrian arthropod Tuzoia and the origin of mandibulates revisited. Royal Society Open Science, 9:.
  • IZQUIERDO-LÓPEZ, A. and CARON, J.-B. 2022b. Extreme multisegmentation in a giant bivalved arthropod from the Cambrian Burgess Shale. IScience, 25, 104675:.
  • KIMMIG, J., COUTO, H., LEIBACH, W. W. and LIEBERMAN, B. S. 2019. Soft-bodied fossils from the upper Valongo Formation (Middle Ordovician: Dapingian-Darriwilian) of northern Portugal. Science of Nature, 106:.
  • 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.
  • LIEBERMAN, B. S. 2003. A new soft-bodied fauna: The Pioche formation of Nevada. Journal of Paleontology, 77: 674–690.
  • ORLOV, Y. A. 1960. Osnovy Paleontologii. In Arthropoda, Trilobitomorpha and Crustacea, Moscow: Nedra.
  • ORTEGA-HERNÁNDEZ, J. and BUDD, G. E. 2016. The nature of non-appendicular anterior paired projections in Palaeozoic total-group Euarthropoda. Arthropod Structure and Development, 45: 185–199.
  • ORTEGA-HERNÁNDEZ, J., JANSSEN, R. and BUDD, G. E. 2017. Origin and evolution of the panarthropod head – A palaeobiological and developmental perspective. Arthropod Structure and Development, 46: 354–379.
  • OU, Q., VANNIER, J., YANG, X., CHEN, A., MAI, H., SHU, D., HAN, J., FU, D., WANG, R. and MAYER, G. 2020. Evolutionary trade-off in reproduction of Cambrian arthropods. Science Advances, 6: 3376–3405.
  • PENG, S. C., YANG, X. F., LIU, Y., ZHU, X. J., SUN, H. J., ZAMORA, S., MAO, Y. Y. and ZHANG, Y. C. 2020. Fulu biota, a new exceptionally-preserved Cambrian fossil assemblage from the Longha Formation in southeastern Yunnan. Palaeoworld, 29: 453–461.
  • ROBISON, R. A. and RICHARDS, B. C. 1981. Larger bivalve arthropods from the Middle Cambrian of Utah. Paleontological Contributions of the University of Kansas, 106: 1–19.
  • SIMONETTA, A. M. and DELLE CAVE, L. 1975. The Cambrian non trilobite arthropods from the Burgess Shale of British Columbia. A study of their comparative morphology, taxonomy and evolutionary significance. Palaeontographia italica, 69 (n.s. 3: 1–37.
  • 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:
  • WALCOTT, C. D. 1912. Cambrian geology and paleontology II: Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57: 145–228.
  • WALOSZEK, D. 1999. On the Cambrian diversity of Crustacea. In SCHRAM, F. R. and VON VAUPEL KLEIN, J. C. (eds.) Crustaceans and the Biodiversity Crisis, Brill, Leiden, 3–27 pp.
  • WANG, Y., LIN, J., ZHAO, Y. and ORR, P. J. 2009. Palaeoecology of the trace fossil Gordia and its interaction with nonmineralizing taxa from the early Middle Cambrian Kaili Biota, Guizhou province, South China. Palaeogeography, Palaeoclimatology, Palaeoecology, 277: 141–148.
  • ZENG, H., ZHAO, F.-C., YIN, Z.-J. and ZHU, M.-Y. 2020. A new early Cambrian bivalved euarthropod from Yunnan, China and general interspecific morphological and size variations in Cambrian hymenocarines. Palaeoworld, 30(3): 387–397.
Other Links:

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



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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: Scavenger
Phylum: Scavenger
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: Scavenger
Feeding strategies: Scavenger
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.
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  • 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



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Tuzoia burgessensis

Outlines of Tuzoia canadensis (left), Tuzoia burgessensis (middle) and Tuzoia retifera (right).

© MARIANNE COLLINS

Taxonomy:

Kingdom: Scavenger
Phylum: Scavenger
Higher Taxonomic assignment: Hymenocarines, Family Tuzoiidae
Species name: Tuzoia burgessensis
Remarks:

Tuzoia is known as one of the most diverse and widespread hymenocarines, but, besides isolated carapaces, other soft-tissues are scarce. Tuzoia may represent one of the earliest hymenocarine representatives.

Described by: Resser
Description date: 1929
Etymology:

Tuzoia – from Mount Tuzo, in the Valley of the Ten Peaks, named in 1907 after Henrietta Tuzo, who was the first to climb this mountain.

burgessensis – from Mount Burgess (2,599 m), a mountain peak in Yoho National Park. Mount Burgess. The name was given in 1886 by Otto Klotz, the Dominion topographical surveyor, after Alexander Burgess, a former Deputy Minister of the Department of the Interior.

Type Specimens: Holotypes –USNM80477b (T. burgessensis),USNM57720 (T. retifera),USNM80478b (T. canadensis) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale: T. retifera and T. canadensis from the Tuzoia layer above the Raymond Quarry, the Raymond and Walcott Quarries on Fossil Ridge, and other sites on Mount Field and Stanley Glacier. (See Vannier et al., 2007 for references).

Other deposits: T. australis from the Lower Cambrian Emu Bay Shale of Australia (Glaessner 1979; García-Bellido et al. 2009). T. bispinosa from the Lower Cambrian Balang Formation of China (Wen et al. 2019) and the Wuliuan Kaili Formation of China (Yuan and Zhao 1999; Wen et al. 2015). T. guntheri from the Middle Cambrian Marjum and Pioche Formations of Utah and Nevada (Robison and Richards 1981; Lieberman 2003). T. jianheensis from the Lower Cambrian Tsinghsutung Formation of China (Chen et al. 2017). T. lazizhaeiensis from the Lower Cambrian Balang Formation of China (Wen et al. 2019). T. polleni from the Lower Cambrian Eager Formation of British Columbia (Resser 1929), the Lower Cambrian Kinzers Formation of Pennsylvania (Resser 1929; Vannier et al. 2007), the Lower Cambrian Parker Quarry in Vermont (Pari et al. 2022) and the Wuliuan Pioche Formation of Utah and Nevada (Resser and Howell 1938). Other species of Tuzoia are known (e.g., T. manchuriensis), albeit poorly documented or with open nomenclature. (See Lieberman 2003; Vannier et al. 2007; Wen et al. 2019; Izquierdo-López and Caron 2022a for references).

Age & Localities:

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

The Walcott and Raymond Quarries, the Tuzoia layer above the Raymond Quarry and the Collins Quarry on Fossil Ridge. The Tulip Beds (S7) on Mount Stephen. Marble Canyon and Stanley Glacier in Kootenay National Park.

History of Research:

Brief history of research:

Tuzoia was first described by Charles Walcott (1912) based on a single carapace specimen from the Burgess Shale, which was later expanded in more detail by Resser (1929). Since then, Tuzoia has been described from multiple other Cambrian sites: Utah (Robison and Richards 1981) and Nevada (Lieberman 2003) in the USA, Australia (Glaessner 1979; Luo et al. 1999; Yuan and Zhao 1999; Wen et al. 2015, 2019; Wu and Liu 2022), the Czech Republic (Chlupáč and Kordule 2002), and multiple localities in China (Pan 1957; Shu 1990; Luo et al. 1999; Yuan and Zhao 1999; Wen et al. 2015, 2019; Wu and Liu 2022) ), making it one of the geographically most widespread arthropod species of that period (Hendricks et al. 2008). Given its distribution, more than 20 species of Tuzoia have been historically defined, but major redescriptions have reduced this number to lower than 10 (Vannier et al. 2007; Wen et al. 2019). Several species, though, remain poorly known or with open nomenclature. In 2021, a new genera to the family tuzoiidae, Duplapex, was described from the Qingjiang Biota of China (Ma et al. 2021). Soft parts such as eyes, potential antennae and gut structures were first reported by Vannier et al. (2007), and were followed by new information on the anatomy of the head (Wen et al. 2019) and legs (Caron et al. 2010; Wen et al. 2019; Du et al. 2020), albeit generally poorly preserved. A re-study of Tuzoia, including new material from the Marble Canyon and adjacent outcrops at the Burgess Shale (Caron et al. 2014) found fully-preserved legs and a tailpiece, as well as new details of the head, allowing for a first comprehensive reconstruction of its anatomy and evaluation of its affinities (Izquierdo-López and Caron 2022).

Description:

Morphology:

The most prominent feature of Tuzoia is its large, bivalved carapace. The two dome-shaped carapace valves have convexly rounded ventral margins and are joined along a straight dorsal margin that usually extends at the front and back into pointed spines, or cardinal processes. Most species of Tuzoia have two main spines on the mid-posterior and posteroventral margin of the carapace. Smaller spines are usually present along the posterior, ventral and dorsal side of the carapace; they vary in number, size, and orientation between species. A lateral ridge passes horizontally, perpendicular to the surface of the carapace valves, which is often spinose. The carapaces are covered in a polygonal pattern. The head bears a pair of large, spherical eyes on short stalks, and projects forwards from underneath the carapace and bears a pair of antennae and a pair of lobes between the eyes. The trunk is short, and is completely covered by the carapace. It bears a total of 12 thick biramous legs. Each leg is divided into a base (basipod), which is elongated and bears a few isolated spines and an inner branch (endopod), divided into seven segments, with the terminal one having a claw-like shape. The basipod of the first anterior legs may bear dentate projections (endites), and all segments of the endopod bear spines. The remaining, more posterior legs do not show these projections, and spines are limited to a couple of segments. The legs may also have a paddle-like outer branch (exopod), although its shape is not clear. The body terminates into two pairs of broad fan-like appendages (caudal rami). Besides the carapace, anatomical details are a composite between different species of Tuzoia from the Burgess Shale formation, mainly T. burgessensis and T. retifera. Possible anatomical differences across species are currently unknown.

Abundance:

As the name suggests, the Tuzoia beds between the Raymond and Collins Quarries on Fossil Ridge yield abundant Tuzoia burgessensis specimens, with over 160 specimens found so far. T. burgessensis is also found rarely in Raymond Quarry, where T. retifera is more common, with 87 known specimens. Tuzoia is also found rarely in other sites on Mount Field and Mount Stephen. Tuzoia is also found at Stanley Glacier and in the Marble Canyon and Tokumm Creek localities, albeit not highly abundant.

Maximum Size:
About 20 cm.

Ecology:

Life habits: Scavenger
Feeding strategies: Scavenger
Ecological Interpretations:

Tuzoia is suggested to be free-swimming animal. The midposterior and posteroventral spines probably acted as a keel to provide directional stability to the animal while swimming, and the lateral ridge may have allowed directional control to improve the streamlining of the animal while preventing sinking. The reticulate pattern of the carapace is interpreted as a way of strengthening the carapace without adding so much weight that the animal would be unable to swim. Spines and the lateral ridge may also have provided protection from predation. The legs end in claw-like structures, suggesting that Tuzoia may have also been able to walk on the benthos or anchor itself to structures such as carcasses. If that was the case, the carapace must have been able to open partially. The large, frontally-directed eyes, as well as the spines on the anterior legs, also reinforce the idea that it was a predator or scavenger. The spines present on the more posterior legs could have also been used to attach to surfaces or manipulate food.

References:

  • ARIA, C. and CARON, J. B. 2017. Burgess Shale fossils illustrate the origin of the mandibulate body plan. Nature, 545: 89–92.
  • CARON, J. B., GAINES, R. R., MÁNGANO, M. G., STRENG, M. and DALEY, A. C. 2010. A new Burgess Shale-type assemblage from the “thin” Stephen Formation of the southern Canadian Rockies. Geology, 38: 811–814.
  • 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: 3210.
  • CHEN, W. Y., ZHAO, Y. L., YANG, X. L. and WEN, R. Q. 2017. Tuzoia Walcott, 1912 from the Cambrian ‘Tsinghsutung Formation’ of Guizhou, China. Palaeontologica Sinica, 56: 301–311.
  • CHLUPÁČ, I. and KORDULE, V. 2002. Arthropods of Burgess Shale type from the Middle Cambrian of Bohemia (Czech Republic). Vestnik Ceskeho Geologickeho Ustavu, 77: 167–182.
  • DU, K.-S., ORTEGA-HERNÁNDEZ, J., YANG, J., YANG, X., GUO, Q., WEI, L., HE, J., LI, K., DU, J., HOU, J. and ZHANG, X. 2020. A new early Cambrian Konservat-Lagerstätte expands the occurrence of Burgess Shale-type deposits on the Yangtze Platform. Earth-Science Reviews, 211:.
  • GARCÍA-BELLIDO, D. C., PATERSON, J. R., EDGECOMBE, G. D., JAGO, J. B., GEHLING, J. G. and LEE, M. S. Y. 2009. The bivalved arthropods Isoxys and Tuzoia with soft-part preservation from the lower Cambrian Emu Bay Shale lagerstätte (Kangaroo Island, Australia). Palaeontology, 52: 1221–1241.
  • GLAESSNER, M. G. 1979. Lower Cambrian Crustacea and annelid worms from Kangaroo Island, South Australia. Alcheringa, 3: 21–31.
  • HENDRICKS, J. R., LIEBERMAN, B. S. and STIGALL, A. L. 2008. Using GIS to study palaeobiogeographic and macroevolutionary patterns in soft-bodied Cambrian arthropods. Palaeogeography, Palaeoclimatology, Palaeoecology, 264: 163–175.
  • IZQUIERDO-LÓPEZ, A. and CARON, J.-B. 2022. The problematic Cambrian arthropod Tuzoia and the origin of mandibulates revisited. Royal Society Open Science, 9:.
  • LIEBERMAN, B. S. 2003. A new soft-bodied fauna: The Pioche formation of Nevada. Journal of Paleontology, 77: 674–690.
  • LUO, H.-L., HU, S.-X., CHEN, S., ZHANG, S. S. and TAO, Y. H. 1999. Early Cambrian Chengjiang Fauna from Kunming Region, China. .
  • MA, J., LIN, W., LIU, C., SUN, A., WU, Y., WU, Y. and FU, D. 2021. A new bivalved arthropod from Cambrian (Stage 3) Qingjiang biota expands the palaeogeographical distribution and increases the diversity of Tuzoiidae. Journal of the Geological Society, 179(1):
  • PAN, K. 1957. On the discovery of Homopoda from South China. Palaeontologica Sinica, 5: 523–526.
  • PARI, G., BRIGGS, D. E. G. and GAINES, R. R. 2022. The soft-bodied biota of the Cambrian Series 2 Parker Quarry Lagerstätte of northwestern Vermont, USA. Journal of Paleontology, 1–21.
  • RESSER, C. E. 1929. New Lower and Middle Cambrian Crustacea. Proceedings of the U.S. National Museum, 76: 1–18.
  • RESSER, C. E. and HOWELL, B. F. 1938. Lower Cambrian Olenellus Zone of the Appalachians. Geological Society of America Bulletin, 49: 195–248.
  • ROBISON, R. A. and RICHARDS, B. C. 1981. Larger bivalve arthropods from the Middle Cambrian of Utah. Paleontological Contributions of the University of Kansas, 106: 1–19.
  • SHU, D. G. 1990. Cambrian and Lower Ordovician Bradoriida from Zhejiang. Northwest University Press, Xian, Hunan and Shaanxi Provinces.
  • 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.
  • WALCOTT, C. D. 1912. Cambrian geology and paleontology II: Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57: 145–228.
  • WEN, R., BABCOCK, L. E., PENG, J., LIU, S. and LIANG, B. 2019. The bivalved arthropod Tuzoia from the Balang Formation (Cambrian Stage 4) of Guizhou, China, and new observations on comparative species. Papers in Palaeontology, 5: 719–742.
  • WEN, R. Q., ZHAO, Y. L. and PENG, J. 2015. Morphology and ontogeny of Tuzoia bispinosa from the Kaili Biota (Cambrian Stage 5) of eastern Guizhou, China. Palaeoworld, 24: 61–70.
  • WU, Y. and LIU, J. 2022. New data on the bivalved arthropod Tuzoia from the Cambrian (Series 2 , Stage 4) Guanshan Biota in Kunming, Yunnan, Southwest China. Frontiers in Earch Sciences, 10:862679: 1–11.
  • YUAN, J. L. and ZHAO, Y. L. 1999. Tuzoia (bivalved arthropods) from the Lower-Middle Cambrian Kaili Formation of Taijiang, Guizhou. Palaeontologica Sinica, 38: (Suppl.), 88-93.
Other Links:

http://www.bioone.org/doi/abs/10.1666/pleo05070.1