The Burgess Shale

Zacanthoides romingeri

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

Taxonomy:

Class: Trilobita (Order: Corynexochida)
Remarks:

Trilobites are extinct euarthropods, probably stem lineage representatives of the Mandibulata, which includes crustaceans, myriapods, and hexapods (Scholtz and Edgecombe, 2006).

Species name: Zacanthoides romingeri
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:

Period:
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:

Ecological Interpretations:

Zacanthoides romingeri adults very likely walked along the sea bed. The overall spinosity of this species may have served as a deterrent to predators, or possibly helped to break up the visual outline of the animal, making it harder to see on the sea floor (Rudkin, 1996).

References:

RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116 (5): 1-277.

RESSER, C. E. 1942. Fifth contribution to nomenclature of Cambrian trilobites. Smithsonian Miscellaneous Collections, 101 (15): 1-58.

ROMINGER, C. 1887. Description of primordial fossils from Mount Stephens, N. W. Territory of Canada. Proceedings of the Academy of Natural Sciences of Philadelphia, 1887: 12-19.

RUDKIN, D. M. 1996. The Trilobite Beds of Mount Stephen, Yoho National Park, p. 59-68. In R. Ludvigsen (ed.), Life in Stone – A Natural History of British Columbia’s Fossils. UBC Press, Vancouver.

RUDKIN, D. M. 2009. The Mount Stephen Trilobite Beds, p. 90-102. In J.-B. Caron and D. Rudkin (eds.), A Burgess Shale Primer – History, Geology, and Research Highlights. The Burgess Shale Consortium, Toronto.

SCHOLTZ, G. AND G. D. EDGECOMBE. 2006. The evolution of arthropod heads: reconciling morphological, developmental and palaeontological evidence. Development Genes and Evolution, 216: 395-415.

WALCOTT, C. D. 1888. Cambrian fossils from Mount Stephens, Northwest Territory of Canada. American Journal of Science, Series 3, 36: 163-166.

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

Other Links:

Yohoia tenuis

3D animation of Yohoia tenuis.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Class: Unranked clade Megacheira? (stem group arthropods)
Remarks:

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

Species name: Yohoia tenuis
Described by: Walcott
Description date: 1912
Etymology:

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

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

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

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott, Raymond and Collins Quarries on Fossil Ridge.

History of Research:

Brief history of research:

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

Description:

Morphology:

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

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

Abundance:

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

Maximum Size:
23 mm

Ecology:

Ecological Interpretations:

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

References:

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

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

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

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

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

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

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

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

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

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

Other Links:

None

Tubulella flagellum

Tubulella flagellum (ROM 59942) – Proposed Lectotype. Figures 1a of Matthew (1899) and photograph of original specimen (right). Approximate specimen length = 80 mm. Specimen dry – direct light. Trilobite Beds on Mount Stephen.

© ROYAL ONTARIO MUSEUM. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Class: Unranked clade (stem group cnidarians)
Remarks:

This fossil was originally thought to represent the tube of some sedentary polychaete worms (Matthew, 1899; Howell, 1949), but has more recently been compared to the sessile polyp stage of a scyphozoan jellyfish that builds tapered, chitinous tubes fixed to the substrate by an attachment disc (Van Iten et al., 2002).

Species name: Tubulella flagellum
Described by: Matthew
Description date: 1899
Etymology:

Tubulella – from the latin tubulus, “tube, or tubule,” and the suffix –ella, denoting “little.”

flagellum – the Latin for “whip,” in allusion to the long, tapering form of the tubular theca.

Type Specimens: Syntype–ROM59942 in the Royal Ontario Museum, Toronto, ON, Canada.
Other species:

Burgess Shale and vicinity: Many shared similarities suggest that other thecate Burgess Shale fossils such as Byronia annulataSphenothallus sp., Cambrorhytium major, and Cfragilis may be related to Tubulella.

Other deposits: Other species occur worldwide in rocks from the Cambrian period.

Age & Localities:

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

The Trilobite Beds, Tulip Beds (S7) and additional smaller localities on Mount Stephen. The Walcott and Raymond Quarries on Fossil Ridge, Mount Odaray and Monarch Cirque.

History of Research:

Brief history of research:

In August 1887 the Toronto meeting of the British Association for the Advancement of Science was followed by a special geological rail tour to western Canada organized by Byron Edmund Walker (a prominent Canadian banker). One of the excursion highlights was a visit to the Mount Stephen Trilobite Beds, after which Walker loaned his personal collection of Mount Stephen fossils to Canada’s leading Cambrian palaeontologist, George F. Matthew, of Saint John, New Brunswick. In 1899, Matthew published a series of new descriptions based on this material, including Urotheca flagellum, a rare form he interpreted as whip-shaped worm tube, illustrated in two engravings. Walker donated these fossils to the University of Toronto in 1904, and in 1913 they were transferred to the new Royal Ontario Museum of Palaeontology. In 1949, American palaeontologist B. F. Howell found that Matthew’s genus name Urotheca was already in use for a living reptile, so he substituted it for the new name Tubulella. Subsequently, this and similar fossils were reinterpreted as cnidarian polyp thecae. The single best specimen of Walker’s Urotheca flagellum remained unrecognized until it was “rediscovered” in the ROM collections in 2010.

Description:

Morphology:

The chitinous or chitinophosphatic tube (theca) of Tubulella flagellum is a very long and slender cone, with a maximum diameter of about 4 mm. The thecae may be almost straight, or show varying degrees of curvature. The thecal wall is relatively thick and often appears densely black against the shale matrix. The external surface shows very fine transverse growth lines, but usually no strong annular ridges. Often, two or more lengthwise creases or ridges were formed as the result of the crushing and compaction of the tube’s original circular or oval cross section. Some specimens possess a combination of features seen in Tubulella and Byronia, with very narrow thecae bearing both annulae and longitudinal creases. Small clusters of such Tubulella-like thecae are occasionally found closely associated with Byronia annulata, but it is not known whether these were asexually generated “buds” or discrete organisms growing attached to the larger tubes. No soft tissues of Tubulella flagellum have been described to date.

Abundance:

Uncommon in the Trilobite Beds on Mount Stephen. Relatively common in the Walcott Quarry on Fossil Ridge where it represents about 0.25% of the specimens in the community (Caron and Jackson, 2008).

Maximum Size:
100 mm

Ecology:

Ecological Interpretations:

The theca of Tubulella was likely attached to the substrate using an apical disc which is usually broken off. The absence of soft tissue preservation makes the assignment to a particular feeding strategy tentative. By comparison with forms such as Cambrorhytium, a carnivorous or suspension feeding habit seems possible.

References:

BISCHOFF, C. O. 1989. Byroniida new order from early Palaeozoic strata of eastern Australia (Cnidaria, thecate scyphopolyps). Senkenbergiana Lethaea, 69(5/6): 467-521.

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

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

HOWELL, B. F. 1949. New hydrozoan and brachiopod and new genus of worms from the Ordovician Schenectady Formation of New York. Bulletin of the Wagner Free Institute of Science, 24(1): 8 pp.

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, 4: 39-66.

RASETTI, F. 1951. Middle Cambrian stratigraphy and faunas of the Canadian Rocky Mountains. Smithsonian Miscellaneous Collections, 116(5): 277 pp.

VAN ITEN, H., M.-Y. MAO-YAN, AND D.COLLINS 2002. First report of Sphenothallus Hall, 1847 in the Middle Cambrian. Journal of Paleontology, 76: 902-905.

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

ZHU, M.-Y., H. VAN ITEN, R. S. COX, Y.-L. ZHAO AND B.-D. ERDTMANN. 2000. Occurrence of Byronia Matthew and Sphenothallus Hall in the Lower Cambrian of China. Paläontologische Zeitschrift, 74: 227-238.

Other Links:

None

Stanleycaris hirpex

Stanleycaris hirpex (ROM 59944) – Holotype, part and counterpart. Individual claw. Specimen length = 29 mm. Specimen dry – polarized light. Stanley Glacier.

© ROYAL ONTARIO MUSEUM. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Class: Dinocarida (Order: Radiodonta, stem group arthropods)
Remarks:

Stanleycaris is an anomalocaridid closely related to Hurdia and Laggania. Anomalocaridids have been variously regarded as basal stem-lineage euarthropods (e.g., Daley et al., 2009), basal members of the arthropod group Chelicerata (e.g., Chen et al., 2004), and as a sister group to the arthropods (e.g., Hou et al., 2006).

Species name: Stanleycaris hirpex
Described by: Caron et al.
Description date: 2010
Etymology:

Stanleycaris – from Stanley Glacier, 40 kilometres southeast of the Burgess Shale in Kootenay National Park, where the fossils come from and the Latin caris, meaning “shrimp.” The name Stanley was given after Frederick Arthur Stanley (1841-1908), Canada’s sixth Governor General.

hirpex – from the Latin, hirpex, meaning “large rake,” in reference to the rake-like aspect of the appendage.

Type Specimens: Holotype –ROM59944 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Stanley Glacier in Kootenay National Park.

History of Research:

Brief history of research:

The first fossils of this species were collected by the Royal Ontario Museum in 1996 from talus slopes, but it was not until 2008, during a larger expedition, that specimens were discovered in their proper stratigraphic context. A description of this new genus and species soon followed (Caron et al., 2010).

Description:

Morphology:

Stanleycaris is known from paired or isolated grasping appendages and disarticulated assemblages. The entire animal might have reached 15 centimetres in total length. The grasping appendages range in length from 1.2 cm to 3 cm and have eleven segments (or podomeres), with five spinous ventral blades on the second to sixth segments. Double-pointed dorsal spines are particularly prominent from the second to the sixth segment, decreasing in size towards the distal end of the appendage. The longest of these robust spines is typically two to three times shorter than the ventral blades. The last segment has three curved terminal spines. Mouthparts are represented by circlets of plates bearing teeth around a central square opening. Assemblages are poorly preserved, and the best example consists of a pair of grasping appendages, a mouth part, and remnants of what might represent parts of a carapace or gill structures.

Abundance:

This species is relatively rare and only found near Stanley Glacier.

Maximum Size:
150 mm

Ecology:

Ecological Interpretations:

Stanleycaris is considered a predator or a scavenger, based on the morphology of its frontal appendages and mouth parts. The comb-like ventral blades might have been useful for searching small prey items or disturbing carcasses at the water-sediment interface and within the flocculent level of the mud.

References:

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(9): 811-814.

CHEN, J. Y., L. RAMSKÖLD AND G. Q. ZHOU. 1994. Evidence for monophyly and arthropod affinity of Cambrian giant predators. Science, 264: 1304-1308.

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

DALEY, A. C., G. E. BUDD, J. B. CARON, G. D. EDGECOMBE AND D. COLLINS. 2009. The Burgess Shale anomalocaridid Hurdia and its significance for early euarthropod evolution. Science, 323: 1597-1600.

HOU, X., J. BERGSTRÖM AND P. AHLBERG. 1995. Anomalocaris and other large animals in the Lower Cambrian Chengjiang fauna of Southwest China. GFF, 117: 163-183.

Other Links:

http://geology.geoscienceworld.org/cgi/content/full/38/9/811?ijkey=ZQFY537sTggAw&keytype=ref&siteid=gsgeology

Sphenothallus sp.

Taxonomy:

Sphenothallus sp. (GSC 134789). Fragment of a large specimen showing longitudinal thickenings clearly differentiated near the aperture area (to the right). A Micromitra (Dictyonina) brachiopod is attached to the lower part of the tube. Approximate specimen length = 50 mm. Specimen dry – direct light. Trilobite Beds on Mount Stephen.

© GEOLOGICAL SURVEY OF CANADA. PHOTO: JEAN-BERNARD CARON

Class: Unranked clade (stem group cnidarians)
Remarks:

Sphenothallus has been compared to some form of tubiculous annelid worm or the sessile polyp stage of a scyphozoan jellyfish that builds tapered, chitinous tubes fixed to the substrate by an attachment disc (Van Iten et al., 2002).

Species name: Sphenothallus sp.
Described by: Van Iten et al.
Description date: 2002
Etymology:

Sphenothallus – from the Greek sphen, “wedge”, and thallos, “branch.”

Species name not determined.

Type Specimens: Not applicable
Other species:

Burgess Shale and vicinity: Many shared similarities suggest that other thecate Burgess Shale fossils such as Byronia annulataCambrorhytium majorCfragilis and Tubulella flagellum, may be related to Sphenothallus sp.

Other deposits: Other species occur worldwide in rocks from the Cambrian to the Silurian periods. Sphenothallus is also known in the Kaili Formation (Zhu et al., 2000).

Age & Localities:

Period:
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:

Two specimens from the Trilobite Beds were illustrated in 2002 (Van Iten et al.). A third previously unrecognized specimen was identified in the Geological Survey of Canada collections in Ottawa (Billings collection) in the Spring of 2010. Owing to the relatively low degree of morphological variations among all known species, it is not currently possible to assign the Burgess Shale form to any particular species without better preserved specimens.

Description:

Morphology:

The chitinophosphatic tube (theca) of Sphenothallus consists of longitudinal thickenings which are particularly obvious towards the aperture area. The tube is gently curved and does not seem to branch. The maximum diameter of the largest specimen is about 4 mm for a length of about 75 mm. A thin wall is present between the longitudinal thickenings and terminates in a smooth margin near the aperture, a couple of millimeters beyond the longitudinal thickenings. The tube is roughly circular in the apical region and is very slender, with the two longitudinal thickenings less differentiated in this area. The surface of the entire tube including thickenings is smooth with no evidence of ridges or annulations. All three specimens lack the apical ends, so it is not evident that this species had a holdfast and there is no evidence of soft-tissue preservation.

Abundance:

Only three specimens known from the Trilobite Beds on Mount Stephen.

Maximum Size:
75 mm

Ecology:

Ecological Interpretations:

The theca of Sphenothallus was likely attached to the substrate via an apical disc as can be seen in other better known species. The absence of soft tissue preservation makes the assignment to a particular feeding strategy tentative. By comparison with possible related forms such as Cambrorhytium, a carnivorous or suspension feeding habit seems possible.

References:

VAN ITEN, H., M.-Y. ZHU AND D. COLLINS. 2002. First report of Sphenothallus Hall, 1847 in the Middle Cambrian. Journal of Paleontology, 76: 902-905.

ZHU, M.-Y., H. VAN ITEN, R. S. COX, Y.-L. ZHAO AND B.-D. ERDTMANN. 2000. Occurrence of Byronia Matthew and Sphenothallus Hall in the Lower Cambrian of China. Paläontologische Zeitschrift, 74: 227-238.

Other Links:

None

Sidneyia inexpectans

3D animation of Sidneyia inexpectans.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Class: Unranked clade (stem group arthropods)
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).

Species name: Sidneyia inexpectans
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:

Period:
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:

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

Selkirkia columbia

3D animation of Selkirkia columbia.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Class: Unranked clade (stem group priapulids)
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).

Species name: Selkirkia columbia
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:

Period:
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:

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

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:

Class: Trilobita (Order: Corynexochida)
Remarks:

Trilobites are extinct euarthropods, probably stem lineage representatives of the Mandibulata, which includes crustaceans, myriapods, and hexapods (Scholtz and Edgecombe, 2006).

Species name: Kootenia burgessensis
Described by: Resser
Description date: 1942
Etymology:

Kootenia – unspecified, but almost certainly for the Kootenay region of southeast British Columbia, or the derivative Kootenay River, both based upon the Ktunaxa or Kutenai First Nation of the same area.

burgessensis – from the Burgess Shale.

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:

Period:
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 concluded that Kootenia could not be consistently discriminated from Olenoides using traditional characters of the spinose pygidium.

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:

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:

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:

Isoxys acutangulus

3D animation of Isoxys carinatus.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Class: Unranked clade (stem group arthropods)
Remarks:

The affinity of Isoxys is uncertain because for a long time it was known only from empty carapaces. Recent descriptions of soft parts show that the frontal appendage is similar to that of some megacheiran, or “great appendage,” taxa such as Leanchoilia, Alalcomenaeus, and Yohoia (Vannier et al., 2009; García-Bellido et al., 2009a). The affinity of Megacheira as a whole is uncertain, but it has been suggested that they either sit within the stem-lineage to the euarthropods (Budd, 2002) or they are stem-lineage chelicerates (Chen et al., 2004; Edgecombe, 2010).

Species name: Isoxys acutangulus
Described by: Walcott
Description date: 1908
Etymology:

Isoxys – from the Greek isos, “equal,” and xystos, “smooth surface”; thus referring to the pair of smooth valves.

acutangulus – from the Latin acutus, “sharp, pointed,” and angulus, “angle”; thus referring to the acute angle of the cardinal spines.

Type Specimens: Type status under review –USNM56521 (I. acutangulus) and Holotype –USNM189170 (I. longissimus) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: I. longissimus from Walcott, Raymond and Collins Quarries on Fossil Ridge.

Other deposits: I. chilhoweanus from the Chilhowee Group, Tennessee, USA; I. auritus, I. paradoxus and I. curvirostratus from the Maotianshan Shale of China; I. bispinatus from the Shuijingtuo Formation, Hubei, China; I. wudingensis from the Guanshan fauna of China; I. communis and I. glaessneri from the Emu Bay Shale of Australia; I. volucris from the Buen Formation, Sirius Passet in Greenland; I. carbonelli from the Sierro Morena of Spain, and I. zhurensis from the Profallotaspis jakutensis Zone of Western Siberia. Undescribed species from Canada; Mount Cap Formation in the Mackenzie Mountains, Northwest Territories and the Eager Formation near Cranbrook. Other undescribed species in the Kaili Formation, Guizhou Province, China and the Kinzers Formation, Pennsylvania, USA. See references in Briggs et al., 2008; García-Bellido et al., 2009a,b; Stein et al., 2010; Vannier and Chen, 2000.

Age & Localities:

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

The Walcott, Raymond and Collins Quarries on Fossil Ridge. Additional localities are known on Mount Field, Mount Stephen – Tulip Beds (S7) and the Trilobite Beds, and near Stanley Glacier.

History of Research:

Brief history of research:

Walcott gave the name Isoxys to specimens from the lower Cambrian Chilhowee Group of Tennessee, USA, in 1890. He then later designated the first species from the Trilobite Beds on Mount Stephen, Anomalocaris? acutangulus (Walcott, 1908), although he placed it erroneously in the genus Anomalocaris. Simonetta and Delle Cave (1975) renamed it Isoxys acutangulus and discovered a second Burgess Shale species, I. longissimus. The original designations were based on carapaces only, making research on the ecology and affinity of Isoxys difficult. Soft parts have recently been described from the Burgess Shale taxa (Vannier et al. 2009, García-Bellido et al. 2009a).

Description:

Morphology:

The most prominent feature of Isoxys is the non-mineralized carapace, which ranged in length from 1 cm to almost 4 cm, and covered most of the body. It was folded to give two equal hemispherical valves, and had pronounced spines at the front and back. A pair of bulbous, spherical eyes protrudes forward and laterally from under the carapace. They are attached to the head by very short stalks. A pair of frontal appendages that are segmented and non-branching (uniramous) is adjacent to the eyes. The flexible appendages are curved with a serrated outline and five segments in total, including a basal part, three segments with stout outgrowths, and a pointed terminal segment.

The trunk of the body has 13 pairs of evenly spaced appendages that are segmented and branch into two (biramous), with slender, unsegmented walking limbs and large, paddle-like flaps fringed with long setae. The telson has a pair of lateral flaps. A cylindrical gut passes from the head to the ventral terminus of the telson, and is lined by paired, lobate gut glands. I. longissimus is distinguished from I. acutangulus by the presence of extremely long spines and an elongated body shape.

Abundance:

Isoxys is known from hundreds of specimens collected on Fossil Ridge. In the Walcott Quarry, Isoxys acutangulus is relatively common and represents about 0.35% of the community whereas Isoxys longissimus is extremely rare (Caron and Jackson, 2008).

Maximum Size:
40 mm

Ecology:

Ecological Interpretations:

The streamlined body, thin carapace, and the presence of large paddle-shaped flaps in the appendages all suggest that Isoxys was a free-swimming animal. The spines and wide telson would have been use for steering and stability in the water column. A predatory lifestyle is indicated by the large eyes, frontal appendage, and gut glands. Isoxys would have swum just above the sea floor, seeking out prey in the water column and at the sediment-water interface.

References:

BRIGGS, D. E. G., B. S. LIEBERMAN, J. R. HENDRICK, S. L. HALGEDAHL AND R. D. JARRARD. 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.

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

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

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

GARCÍA-BELLIDO, D. C., J. VANNIER AND D. COLLINS. 2009a. Soft-part preservation in two species of the arthropod Isoxys from the middle Cambrian Burgess Shale of British Columbia, Canada. Acta Palaeontologica Polonica, 54: 699-712.

GARCÍA-BELLIDO, D. C., J. R. PATERSON, G. D. EDGECOMBE, J. B. JAGO, J. G. GEHLING AND M. S. Y. LEE. 2009b. The bivavled arthropods Isoxys and Tuzoia with soft-part preservation from the lower Cambrian Emu Bay Shale Lagerstätte (Kangaroo Island, Australia). Palaeontology, 52: 1221-1241.

SIMONETTA, A.M. AND L. DELLE CAVE. 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: 1-37.

STEIN, M., J. S. PEEL, D. J. SIVETER AND M. WILLIAMS. 2010. Isoxys (Arthropoda) with preserved soft anatomy from the Sirius Passet Lagerstätte, lower Cambrian of North Greenland. 2010. Lethaia, 43: 258-265.

VANNIER, J. AND J.-Y. CHEN. 2000. The Early Cambrian colonization of pelagic niches exemplified by Isoxys (Arthropoda). Lethaia, 35: 107-120.

VANNIER, J., D. C. GARCÍA-BELLIDO, S. X. HU AND A. L. CHEN. 2009. Arthropod visual predators in the early pelagic ecosystem: evidence from the Burgess Shale and Chengjiang biotas. Proceedings of the Royal Society of London Series B, 276: 2567-2574.

WALCOTT, C. D. 1890. The fauna of the Lower Cambrian or Olenellus Zone. Reports of the U.S. Geological Survey, 10: 509-763.

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

WILLIAM, M., D. J. SIVETER AND J. S. PEEL. 1996. Isoxys (Arthropoda) from the early Cambrian Sirius Passet Lagerstätte, North Greenland. Journal of Paleontology, 70: 947-954.

Other Links:

None

Hurdia victoria

3D animation of Hurdia victoria.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Class: Dinocarida (Order: Radiodonta, stem group arthropods)
Remarks:

Hurdia is an anomalocaridid, and is usually considered to represent either a basal stem-lineage euarthropod (e.g. Daley et al., 2009), a member of the crown-group arthropods (e.g. Chen et al., 2004), or a sister group to the arthropods (Hou et al., 2006).

Species name: Hurdia victoria
Described by: Walcott
Description date: 1912
Etymology:

Hurdia – from Mount Hurd (2,993 m), a mountain northeast of the now defunct Leanchoil railway station on the Canadian Pacific Railway in Yoho National Park. The peak was named by Tom Wilson for Major M. F. Hurd, a CPR survey engineer who explored the Rocky Mountain passes starting in the 1870s.

victoria – unspecified; perhaps from Mount Victoria (3,464 m) on the border of Yoho and Banff National Parks, named by Norman Collie in 1897 to honour Queen Victoria.

Type Specimens: Lectotypes –USNM57718 (H. victoria) andUSNM57721 (H. triangulata) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: Hurdia triangulata.

Other deposits: Potentially other species are represented in Utah (Wheeler Formation) (Briggs et al., 2008), the Jince Formation in the Czech Republic (Chlupáč and Kordule 2002) and the Shuijingtuo Formation in Hubei Province, China (Cui and Huo, 1990) and possibly Nevada (Lieberman, 2003).

Age & Localities:

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

The Walcott, Raymond and Collins Quarries on Fossil Ridge. Also known from other localities on Mount Field, Mount Stephen – Tulip Beds (S7) – and near Stanley Glacier.

History of Research:

Brief history of research:

Hurdia is a relative newcomer to the anomalocaridids. Although isolated parts of its body were first identified in the early 1900s, no affinity could be determined until the description of whole body specimens by Daley et al. in 2009. Hurdia victoria was the name originally given to an isolated triangular carapace that Walcott (1912) suggested belonged to an unknown arthropod. Proboscicaris, another isolated carapace, was originally described as a phyllopod arthropod (Rolfe, 1962). Hurdia’s frontal appendages were first described by Walcott (1911a) as the feeding limbs of Sidneyia, but were later removed from this genus and referred to as “Appendage F” with unknown affinity (Briggs, 1979).

Like other anomalocaridids, the mouth parts were first described as the jellyfish Peytoia nathorsti (Walcott, 1911b). When Whittington and Briggs (1985) discovered the first whole body specimens of Anomalocaris, the mouth part identity of Peytoia was recognized and “Appendage F” was determined to be the frontal appendage of Anomalocaris nathorsti (later renamed Laggania cambria by Collins (1996). When describing Anomalocaris, Whittington and Briggs (1985) also figured a mouth apparatus with extra rows of teeth.

After two decades of collecting at the Burgess Shale, Desmond Collins from the Royal Ontario Museum (ROM) discovered that this extra-spiny mouth part actually belonged to a third type of anomalocaridid, which also had an “Appendage F” pair and a frontal carapace structure consisting of one Hurdia carapace and two Proboscicaris carapaces (Daley et al., 2009). This is the Hurdia animal. ROM specimens of “Appendage F” showed that it has three distinct morphologies, two of which belongs to the Hurdia animal (known from two species, victoria and triangulata) and one to Laggania cambria.

Description:

Morphology:

Hurdia has a bilaterally symmetrical body that is broadly divisible into two sections of equal lengths. The anterior region is a complex of non-mineralized carapaces consisting of one dorsal triangular H-element (previously called Hurdia) and two lateral subrectangular P-elements (or Proboscicaris). This complex is hollow and open ventrally. It attaches near the anterior margin of the head and protrudes forward. The surfaces of the H- and P-elements are covered in a distinctive polygonal pattern similar to that seen on Tuzoia carapaces. A pair of oval eyes on short stalks protrudes upwards through dorsal-lateral notches in the overlapping posterior corners of the H- and P-elements.

Mouth parts are on the ventral surface of the head, and consist of a circlet of 32 tapering and overlapping plates, 4 large and 28 small, with spines lining the square inner opening. Within the central opening are up to five inner rows of toothed plates. A pair of appendages flanks the mouth part, each with nine thin segments with short dorsal spines and seven elongated ventral spines. The posterior half of the body consists of a series of seven to nine reversely imbricated lateral lobes that extend ventrally into triangular flaps. Dorsal surfaces of the lateral lobes are covered in a series of elongated blades interpreted to be gill structures. The body terminates abruptly in two rounded lobes, and lacks a tailfan. Complete specimens are up to 20 cm in length, although disarticulated fragments may suggest a larger body size up to 50 cm long. Hurdia triangulata differs from Hurdia victoria by having a wider and shorter H-element.

Abundance:

Over 700 specimens of Hurdia have been identified, most of which are disarticulated. Hurdia is found in all Burgess Shale quarries on Fossil Ridge, and is particularly abundant in Raymond Quarry, where it makes up almost 1% of the community (240 specimens). A total of 7 complete body specimens exist.

Maximum Size:
500 mm

Ecology:

Ecological Interpretations:

Hurdia was likely nektonic, since there are no trunk limbs for walking, and the numerous gills suggest an active swimming lifestyle. The animal propelled itself through the water column by waving its lateral lobes and gills. The large eyes, prominent appendages and spiny mouth parts suggest that Hurdia actively sought out moving prey items. Although the function of the frontal carapace remains unknown, it may have played a role in prey capture. If Hurdia were swimming just above the sea floor, it could have used the tip of its frontal carapace to stir up sediment and dislodge prey items, which would then be trapped beneath its frontal carapace. Prey items were funneled towards the mouth by a sweeping motion of the long ventral blades of the frontal appendages, which formed a rigid net or cage. Like other anomalocaridids, Hurdia likely ingested soft-bodied prey.

References:

BRIGGS, D. E. G. 1979. Anomalocaris, the largest known Cambrian arthropod. Palaeontology, 22: 631-663.

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

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

CHLUPÁČ, I. AND V. KORDULE. 2002. Arthropods of Burgess Shale type from the Middle Cambrian of Bohemia (Czech Republic). Bulletin of the Czech Geological Survey, 77: 167-182.

COLLINS, D. 1996. The “evolution” of Anomalocaris and its classification in the arthropod class Dinocarida (nov) and order Radiodonta (nov). Journal of Paleontology, 70: 280-293.

CUI, Z. AND S. HUO. 1990. New discoveries of Lower Cambrian crustacean fossils from Western Hubei. Acta Palaeontologica Sinica, 29: 321-330.

DALEY, A. C., G. E. BUDD, J. B. CARON, G. D. EDGECOMBE AND D. COLLINS. 2009. The Burgess Shale anomalocaridid Hurdia and its significance for early euarthropod evolution. Science, 323: 1597-1600.

HOU, X., J. BERGSTRÖM AND P. AHLBERG. 1995. Anomalocaris and other large animals in the Lower Cambrian Chengjiang fauna of Southwest China. GFF, 117: 163-183.

HOU, X., J. BERGSTRÖM AND Y. JIE. 2006. Distinguishing anomalocaridids from arthropods and priapulids. Geological Journal, 41: 259-269.

LIEBERMAN, B. S. 2003. A new soft-bodied fauna: The Pioche Formation of Nevada. Journal of Paleontology, 77: 674-690.

ROLFE, W. D. I. 1962. Two new arthropod carapaces from the Burgess Shale (Middle Cambrian) of Canada. Breviora Museum of Comparative Zoology, 60: 1-9.

WALCOTT, C. D. 1911a. Middle Cambrian Merostomata. Cambrian Geology and Paleontology II. Smithsonian Miscellaneous Collections, 57: 17-40.

WALCOTT, C. D. 1911b. Middle Cambrian holothurians and medusae. Cambrian Geology and Paleontology II. Smithsonian Miscellaneous Collections, 57: 41-68.

WALCOTT, C. D. 1912. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57: 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.

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