The Burgess Shale

Life Habits: Nektonic

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:

Kingdom: Nektonic
Phylum: Nektonic
Class: Dinocarida (Order: Radiodonta, stem group arthropods)
Species name: Stanleycaris hirpex
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).

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:

Life habits: Nektonic
Feeding strategies: Nektonic
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

Sarotrocercus oblita

Reconstruction of Sarotrocercus oblita.

© MARIANNE COLLINS

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Unranked clade (stem group arthropods)
Species name: Sarotrocercus oblita
Remarks:

The phylogenetic affinity of Sarotrocercus is uncertain because its morphology is too poorly known to make a definitive designation. Fryer (1998) suggested it was the most primitive of all arthropods, and it was placed within the Arachnomorpha by Cotton and Braddy (2004). Sarotrocercus has also been aligned with Megacheiran taxa such as Yohoia (e.g. Briggs and Fortey, 1989) and Leanchoilia (e.g., Wills et al. 1995; 1998).

Described by: Whittington
Description date: 1981
Etymology:

Sarotrocercus – from the Greek sarotes, “sweeper”, and kerkops, “a long tailed-monkey”, in reference to the feathery aspect of the tail.

oblita – from the Latin oblitus, “forgotten”, perhaps in reference to the fact that the few specimens of this species were described as part of another species.

Type Specimens: Holotype –USNM144890 (part) and UNSM 272171 (counterpart) 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 Quarry on Fossil Ridge.

History of Research:

Brief history of research:

The genus Sarotrocercus was erected by Harry Whittington in 1981 based on seven specimens originally included within Molaria spinifera (Simonetta and Delle Cave, 1975). No further research has been performed on the fossil material since then, although Sarotrocercus has been included in many studies of arthropod relationships (e.g. Briggs and Fortey, 1989; Wills et al., 1995; Fryer, 1998).

Description:

Morphology:

Sarotrocercus has an oval body consisting of a head shield and nine overlapping trunk segments; a cylindrical posterior segment carries a relatively short, narrow spine ending in a fan-shape cluster of small spikes. The whole animal was about 1.5 cm long. Although the head shield was not very strongly developed, it did bear a pair of large, stalked eyes that poked out from beneath the margin, and a pair of jointed appendages. Each of the nine body segments bore a pair of lobate appendages, with comb-like fringes which might have functioned as gills.

Abundance:

S. oblita is rare in the Burgess Shale. It was originally described on the basis of 7 specimens (Whittington, 1981), and 28 further specimens have been recovered from the Walcott Quarry representing less than 0.1% of the community (Caron and Jackson, 2008).

Maximum Size:
16 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The absence of walking limbs combined with an inferred flexibility of the body imply that the organism swam, probably in an inverted position, using its paddle-like appendages and long tail. Its rarity in the Burgess Shale suggests that it may have spent much time in the water column, thus avoiding submarine landslides that trapped animals living on the sea floor. The absence of sediment in its gut suggest that Sarotrocercus was a filter feeder (Briggs and Whittington, 1985; Whittington, 1981).

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 H. B. WHITTINGTON, 1985. Modes of life of arthropods from the Burgess Shale, British Columbia. Transactions of the Royal Society of Edinburgh. Earth Sciences, 76(2-3): 149-160.

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

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, 94(03): 169-193.

FRYER, G. 1998. A defence of arthropod polyphyly, p. 23. In R. A. Fortey and R. H. Thomas (eds.), Arthropod relationships. Springer, London.

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.

WHITTINGTON, H. B. 1981. Rare arthropods from the Burgess Shale, Middle Cambrian, British Columbia. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 292(1060): 329-357.

WILLS, M. A., D. E. G. BRIGGS, R. A. FORTEY AND M. WILKINSON, 1995. The significance of fossils in understanding arthropod evolution. Verhandlungen den deutschen zoologischen Gesellschaft, 88: 203-216.

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, p. 33-105. In G. D. Edgecombe (ed.), Arthropod fossils and phylogeny. Columbia University Press, New York.

Other Links:

None

Isoxys acutangulus

3D animation of Isoxys carinatus.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Unranked clade (stem group arthropods)
Species name: Isoxys acutangulus
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).

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:

Life habits: Nektonic
Feeding strategies: Nektonic
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

Insolicorypha psygma

Insolicorypha psygma (USNM 198712) – Holotype, part and counterpart. Only known specimen showing the purported head (top) surrounded by a dark stain (probably representing decay fluids), setae, and gut trace. Specimen length = 12 mm. Specimen dry – polarized light (both images). Walcott Quarry.

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

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Unranked clade (stem group polychaetes)
Species name: Insolicorypha psygma
Remarks:

The single specimen (perhaps incomplete, Eibye-Jacobsen, 2004) of this species is too poorly known to allow detailed studies of its affinities.

Described by: Conway Morris
Description date: 1979
Etymology:

Insolicorypha – from the Latin insolitus, “unusual,” and the Greek koryphe, “head,” thus, “unusual head.”

psygma – from the Greek psygma, “fan,” in reference to the fan-like arrangement of the worm’s bristles.

Type Specimens: Holotype –USNM198667 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 Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Only a single specimen is known. This was originally interpreted by Conway Morris (1979) as a complete animal with an abnormal head. Eibye-Jacobsen (2004) later suggested that the specimen represented just the rear part of the animal, and that the ragged edge of the torn body wall formed the illusion of a head.

Description:

Morphology:

This tiny worm (12 mm long) had at least 19 segments, each bearing a pair of lateral projections called parapodia. On the first and perhaps second segment the parapodia are simple (uniramous), while all the other segments have biramous parapodia (divided into two sections of unequal lengths). In the third segment through to the last segment, parapodia support two main bundles of setae, the notosetae (on the upper branch) and the neurosetae (on the lower branch). The notosetae are short while the neurosetae are much longer. The branch bearing the neurosetae has three (two dorsal) and one ventral cirri (representing sensory of secretory organs) and is much longer. The purported front end of the animal has an elongate projection (prostomium) divided into two main sections.

Abundance:

Only a single specimen of Insolicorypha is known and comes from the Walcott Quarry.

Maximum Size:
12 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

Insolicorypha probably had a similar mode of life to modern swimming annelids which also have sensory cirri, but the rarity of this species makes it impossible to conclude exactly how the animal fed. The fans of bristles are clear adaptations to swimming, which may contribute to the organism’s rarity in the Burgess Shale, which primarily preserves bottom-dwelling species.

References:

CONWAY MORRIS, S. 1979. Middle Cambrian Polychaetes from the Burgess Shale of British Columbia. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 285: 227-274.

EIBYE-JACOBSEN, D. 2004. A reevaluation of Wiwaxia and the polychaetes of the Burgess Shale. Lethaia, 37: 317-335.

Other Links:

None

Hurdia victoria

3D animation of Hurdia victoria.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Dinocarida (Order: Radiodonta, stem group arthropods)
Species name: Hurdia victoria
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).

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:

Life habits: Nektonic
Feeding strategies: Nektonic
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.

Other Links:

http://www.sciencemag.org/content/323/5921/1597.abstract

Pikaia gracilens

3D animation of Pikaia gracilens.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Unranked clade (stem group chordates)
Species name: Pikaia gracilens
Remarks:

Pikaia is considered to represent a primitive chordate (Conway Morris, 1979; Conway Morris et al., 1982) possibly close to craniates (Janvier, 1998); a stem-chordate (Smith et al., 2001); or a cephalochordate (Shu et al., 1999). Its exact position within the chordates is still uncertain and this animal awaits a full redescription.

Described by: Walcott
Description date: 1911
Etymology:

Pikaia – from the pika, a small alpine mammal and cousin of the rabbits. Pikas live in the Rocky Mountains, including near the Burgess Shale.

gracilens – from the Latin gracilens, “thin, simple,” in reference to the shape of the body.

Type Specimens: Syntypes –USNM57628b, 57629 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 Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Pikaia was first described by Walcott based on a couple of specimens in a 1911 monograph dealing with various Burgess Shale worms. Two additional specimens were figured in a posthumous publication (Walcott, 1931). Walcott placed Pikaia in a now defunct group called the Gephyrea with other vermiform fossils such as Banffia, Ottoia and Oesia. Pikaia was later considered to be a primitive chordate (Conway Morris, 1979; Conway Morris et al., 1982), an interpretation which has since been followed to some degree in most discussions about early chordate evolution (e.g., Janvier, 1998). Pikaia played a major part in Gould’s interpretations of the Burgess Shale fossils in Wonderful Life (Gould, 1989; see also Briggs and Fortey, 2005). A full redescription of this animal is currently under way (Conway Morris and Caron, in prep.).

Description:

Morphology:

Pikaia resembles Metaspriggina in outline, another chordate animal from the Burgess Shale, with an elongate body and a small anterior region bearing the head. The body is laterally flattened and there is evidence of a ventral fin towards the posterior. Numerous V-shaped or ziz-zag segments interpreted as myomeres or muscle bands are visible in all specimens. A narrow dorsal structure which runs down the length of the organism might represent a notochord, but this interpretation remains to be confirmed. The head bears two equal lobes and a pair of short and slender tentacle-like structures. There is no evidence of eyes. Just behind the head, on the ventral side of the body, there is a series of up to twelve pairs of small, short, pointed structures on either side of the midline. These are thought to be related to gill openings. The gut is narrow and the anus is terminal.

Abundance:

Pikaia is relatively rare, known from more than 60 specimens, all from the Walcott Quarry where it represents 0.03% of the specimens counted in the community (Caron and Jackson, 2008).

Maximum Size:
55 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The eel-like morphology and musculature of the animal suggest that it was likely free-swimming, although it probably spent time on the sea floor. The tentacles may have had a sensory function, and the presence of mud in its gut suggests that Pikaia was potentially a deposit feeder.

References:

BRIGGS, D. E. G. AND R. A. FORTEY. 2005. Wonderful strife: Systematics, stem groups, and the phylogenetic signal of the Cambrian radiation. Paleobiology, 31(SUPPL.2 ): 94-112.

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

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. H. B. WHITTINGTON, D. E. G. BRIGGS, C. P. HUGHES AND D. L. BRUTON. 1982. Atlas of the Burgess Shale. Palaeontological Association, 31 p. + 23 pl.

GOULD, S. J. 1989. Wonderful Life. The Burgess Shale and the Nature of History. Norton, New York, 347 p.

JANVIER, P. 1998. Les vertébrés avant le Silurien. GeoBios, 30: 931-950.

SHU, D.-G,. H. L. LUO, S. CONWAY MORRIS, X. L. ZHANG, S. X. HU, L. CHEN, J. HAN, M. ZHU, Y. LI AND L. Z. CHEN. 1999. Lower Cambrian vertebrates from south China. Nature, 402(4 November 1999): 42-46.

SMITH, M. P., I. J. SANSOM AND K. D. COCHRANE. 2001. The Cambrian origin of vertebrates, p. 67-84. In P. E. Ahlberg (ed.), Major Events in Early Vertebrate Evolution: Palaeontology, Phylogeny, Genetics and Development. Taylor and Francis, London.

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

WALCOTT, C. 1931. Addenda to descriptions of Burgess Shale fossils. Smithsonian Miscellaneous Collections, 85(3): 1-46.

Other Links:

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

Carnarvonia venosa

Carnarvonia venosa (USNM 57719) – Holotype. Complete valves attached along the hinge line showing the network of vascular-like elements as mirror-like structures, dorsal view. Specimen length = 100 mm. Specimen dry – direct light. Raymond Quarry.

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

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Unranked clade (stem group arthropods)
Species name: Carnarvonia venosa
Remarks:

Carnarvonia venosa was originally described as a Malacostracan crustacean (Walcott, 1912) based on a single specimen, but its affinities are unclear.

Described by: Walcott
Description date: 1912
Etymology:

Carnarvonia – from Mount Carnarvon (3,040 m), a peak in Yoho National Park. The peak was named by Alexander Burgess in 1900 in honour of Lord Henry Herbert Carnarvon (1831-1890), colonial secretary.

venosa – from the Latin vena, “vein,” referring to the vascular markings on the carapace.

Type Specimens: Holotype –USNM57719 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 Raymond Quarry on Fossil Ridge.

History of Research:

Brief history of research:

This taxon was designated by Walcott in 1912 to describe a single specimen of a bivalved carapace that he believed was from a malacostracan crustacean. Simonetta and Delle Cave (1975) added a possible second specimen, which was later synonymized with Perspicaris recondita by Briggs (1977). The crustacean affinity has been questioned by Conway Morris (1979) and Jones and McKenzie (1980). Vannier et al. (1997) described the supposed vascular structures and compared them with modern malacostracan crustaceans.

Description:

Morphology:

Carnarvonia venosa has a carapace with two semi-circular and non-mineralized valves preserved flat on the shale, and joined along a straight dorsal ridge (hinge line). The outer margin of the carapace has a smooth outline. There are two globular and raised circles in mirrored arrangement on both valves, which Walcott (1912) and Vannier et al. (1997) interpret to be adducted muscle scars (i.e., muscles attaching the carapace to the body of the animal), as well a pair of potential eye sockets (Vannier et al., 1997). Perhaps the most striking feature preserved is a network of vascular-like elements which have left a clear imprint into the inner side of the soft-carapace and now appear as raised, branching canals. The specimen is approximately 10 cm by 9 cm, but no evidence of body structures, such as thorax, abdomen or limbs have been preserved.

Abundance:

Carnarvonia is extremely rare. Only a single specimen was originally described.

Maximum Size:
100 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

Based on similarities to other bivalved carapaces in the Burgess Shale, it is assumed that the carapace of Carnarvonia venosa was an external covering of an arthropod body. If the circular structures are muscle attachment scars, it may indicate that some movement, such as opening and closing of the valves, was possible. The vascular system is comparable to swimming malacostracans and might suggest a nektonic mode of life. A further description of the life habits is impossible without more complete specimens.

References:

BRIGGS, D. E. G. 1977. Bivalved arthropods from the Cambrian Burgess Shale of British Columbia. Palaeontology, 20: 596-612.

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

JONES, P. J. AND K. G. MCKENZIE. 1980. Queensland Middle Cambrian Bradoriida (Crustacea): new taxa, palaeobiogeography and biological affinities. Alcheringa: An Australian Journal of Palaeontology, 4: 203-225.

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.

VANNIER, J. M. WILLIAMS AND D. SIVETER. 1997. The Cambrian origin of the circulatory system of crustaceans. Lethaia, 30: 169-184.

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

Other Links:

None

Opabinia regalis

3D animation of Opabinia regalis.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Dinocarida (Order: Radiodonta, stem group arthropods)
Species name: Opabinia regalis
Remarks:

Opabinia is an anomalocaridid. Anomalocaridids have been variously regarded as basal stem-lineage euarthropods (e.g., Budd, 1996; Zhang and Briggs, 2007, 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)

Described by: Walcott
Description date: 1912
Etymology:

Opabinia – from Opabin Pass (2,606 m) between Mount Hungabee and Mount Biddle in Yoho National Park. From the Stoney First Nation Nakoda word for “rocky,” a descriptive name for the pass given by Samuel Allen in 1894.

regalis – from the Latin regalis, “royal, or regal.”

Type Specimens: Lectotype –USNM57683 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 and Raymond Quarries on Fossil Ridge.

History of Research:

Brief history of research:

Opabinia regalis was first described by Walcott (1912) as the most primitive of all Burgess Shale arthropods. Owing to its unique morphology with a bizarre frontal “nozzle,” Opabinia became a flagship fossil for the Burgess Shale, leading to much speculation on its affinity and lifestyle. One famous reconstruction shows the animal swimming upside down as an anostracan crustacean (Hutchinson, 1930).

It wasn’t until the major redescription by Whittington (1975) that the morphology of Opabinia was revealed to be truly one of the most enigmatic of all fossils. It was so unusual, in fact, that when Whittington showed an early version of his reconstruction in a meeting of palaeontologists in 1972, the whole room burst out laughing!

Further work by Bergström (1986) identified similarities between Opabinia and the recently discovered whole-body specimens of Anomalocaris (Whittington and Briggs, 1985), and updated the morphology of the gills and frontal proboscis. Budd (1996) was the first to place Opabinia in the stem lineage of the euarthropods (just below the anomalocaridids), and also suggested the animal had trunk limbs, though this idea was contested by Zhang and Briggs (2007). The issue of whether Opabinia had trunk limbs remains controversial (Budd and Daley, 2011).

Description:

Morphology:

Opabinia has five eyes, a frontal “nozzle,” or proboscis, a body with serially repeated lateral lobes and gills, and a prominent tail fan. The whole body length ranges between 4.3 and 7.0 cm (excluding proboscis). The head has a rounded anterior margin, with five bulbous compound eyes on short stalks clustered on the dorsal surface of the head. The annulated frontal proboscis is four times longer than the head. It is highly flexible, and has a fused pair of appendages at the distal end, consisting of two opposing claws with five or six spines each. The mouth was ventral and faced to the rear.

The trunk was divided into 15 segments, each bearing a pair of lateral lobes in association with gill structures consisting of a series of lanceolate blades. There is some controversy as to the exact location of the gills (dorsal, ventral or posterior) relative to the lobes. The tail fan consists of three pairs of upward-directed flaps. The central region of the body shows an outline of the main body cavity, and a dark line representing a trace of the gut runs along the length of the body, starting with a U-shaped bend near the rearward opening ventral mouth. Paired spherical structures next to the alimentary canal could represent gut glands. There are also controversial triangular features in the central region of the body, which have alternatively been interpreted as lobopod-like walking limbs (Budd, 1996), or as undifferentiated diverticula or extensions of the gut (Whittington, 1975; Zhang and Briggs, 2007).

Abundance:

Opabinia is rare, with only 42 specimens known from all collections. In the Walcott Quarry, Opabinia represents only 0.006% of the community (Caron and Jackson, 2008).

Maximum Size:
101 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

Opabinia was a swimmer. Undulatory waves along its lateral lobes propelled it forward, while it used its tail fan to steer. Opabinia probably employed the distal claws on its flexible nozzle to grasp soft food items and carry them towards its ventral mouth.

References:

BERGSTRÖM, J. 1986. Opabinia and Anomalocaris, unique Cambrian ‘arthropods.’ Lethaia, 19: 241-46.

BUDD, G.E. 1996: The morphology of Opabinia regalis and the reconstruction of the arthropod stem group. Lethaia, 29: 1-14.

BUDD, G.E. AND A. DALEY. 2011. The lobes and lobopods of Opabinia regalis from the middle Cambrian Burgess Shale. Lethaia, DOI: 10.1111/j.1502-3931.2011.00264.x.

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

HUTCHINSON, G.E. 1930. Restudy of some Burgess Shale fossils. Proceedings of the U.S. National Museum, 78: 1-11.

WALCOTT, C. D. 1912. Middle Cambrian Branchiopoda, Malacostraca, Trilobita and Merostomata. Smithsonian Miscellaneous Collections, 57: 145-228.

WHITTINGTON, H.B. 1975. The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences, 271: 1-43.

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.

ZHANG, X.-G. AND D. E. G. BRIGGS. 2007: The nature and significance of the appendages of Opabinia from the Middle Cambrian Burgess Shale. Lethaia, 40: 161-173.

Other Links:

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

Odaraia alata

3D animation of Odaraia alata.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Unranked clade (stem group arthropods)
Species name: Odaraia alata
Remarks:

The affinity of Odaraia is uncertain because, while it was historically considered as a crustacean (Walcott, 1912; Briggs, 1981; Briggs and Fortey, 1989; Hou and Bergström, 1997; Wills et al., 1998), more recent studies have placed it in the upper stem lineage to the arthropods (Budd, 2002, 2008).

Described by: Walcott
Description date: 1912
Etymology:

Odaraia – from Odaray Mountain (3,159 m) in Yoho Park, which was named by J. J. McArthur in 1887 from the Stoney First Nation Nakoda expression for “many waterfalls.”

alata – from the Latin ala, “wing,” referring to the wing-like fins of the tail.

Type Specimens: Lectotype –USNM57722 (O. alata) 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 and Raymond Quarries on Fossil Ridge.

History of Research:

Brief history of research:

Odaraia was first described by Walcott (1912), and was re-examined briefly by Simonetta and Delle Cave (1975). A major restudy of Odaraia was published by Briggs (1981), and it has since been included in several studies on arthropod evolution (Briggs and Fortey, 1989; Hou and Bergström, 1997; Wills et al. 1998; Budd, 2002). New morphological features of the gut and the head region were described by Butterfield (2002) and Budd (2008) respectively.

Description:

Morphology:

Much of the body of Odaraia is contained within a prominent bivalved carapace that, unusually, has its hinge line along the dorsal midline of the animal with the valves meeting on the ventral surface. The carapace forms a tube open at the front and back. The head protrudes from the front of this carapace tube, and consists of a small anterior plate, or sclerite, that bears a pair of large, spherical eyes on short stalks. On the head between the two large eyes are three small, highly reflective spots that have been interpreted as median eyes.

Behind the head, the body consisted of approximately 47 narrow segments, each bearing a pair of appendages. The appendages on the first two body segments are thin, segmented walking branches, but all appendages behind this are segmented and branch into two (biramous). These biramous appendages have a segmented inner branch that has a large spine at its base and splits into two walking branches distally, and an outer branch with filamentous blades. The tail or telson has three blades or flukes, two of which extend laterally and the third of which extends vertically. The gut is typically straight and has paired midgut glands.

Abundance:

Odaraia typically makes up less than 0.5% of the community in Walcott Quarry, from which over 200 specimens have been collected (Caron and Jackson, 2008). About a dozen specimens are known from Raymond Quarry.

Maximum Size:
150 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The tubular carapace of Odaraia would have enclosed the ventral appendages, making it impossible for the animal to use its appendages for walking on the sea floor. It therefore seems to have swum through the water column by waving the inner segmented branches of its biramous appendages. The outer filamentous branches were likely used for respiration.

The large eyes and gut glands suggest that Odaraia was an active predator, seeking out floating or swimming organisms and sieving them out the water as the current passed through the tubular carapace. To minimize the drag created by its dorsal hinge, it is quite likely that Odaraia swam on its back, similar to the modern horseshoe crab. The large telson would have been used to stabilize the animal while swimming to prevent it from rolling, and to help with steering and braking.

References:

BRIGGS, D. E. G. 1981. The arthropod Odaraia alata Walcott, Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London B, 291: 541-582.

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.

BUDD, G. E. 2008. Head structures in upper stem-group euarthropods. Palaeontology, 51: 561-573.

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

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

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.

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

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, p. 33-105. In G. D. Edgecombe (ed.), Arthropod fossils and phylogeny. Columbia University Press, New York.

Other Links:

None

Anomalocaris canadensis

3D animation of Anomalocaris canadensis.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Nektonic
Phylum: Nektonic
Class: Dinocarida (Order: Radiodonta, stem group arthropods)
Species name: Anomalocaris canadensis
Remarks:

Anomalocaris is an anomalocaridid. 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).

Described by: Whiteaves
Description date: 1892
Etymology:

Anomalocaris – from the Greek anomoios, “unlike,” and the Latin caris, “crab” or “shrimp,” thus, “unlike other shrimp.”

canadensis – from Canada, the country where the Burgess Shale is located.

Type Specimens: Lectotype – GSC3418 in the Geological Survey of Canada, Ottawa, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: A. pennsylvanica from the Early Cambrian Kinzers Formation in Pennsylvania (Resser, 1929); A. saron (Hou et al., 1995) from the Early Cambrian Chengjiang biota; A. briggsi (Nedin, 1995) from the Early Cambrian Emu Bay Shale of Australia.

Age & Localities:

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

The Collins, Raymond and Walcott Quarries on Fossil Ridge. The Trilobite Beds, Tulip Beds (S7) and the Collins Quarry on Mount Stephen. Additional localities on Mount Field, Mount Stephen, near Stanley Glacier and in the Early Cambrian Cranbrook Shale, Eager Formation, British Columbia.

History of Research:

Brief history of research:

Anomalocaris has a complex history of description because parts of its body were described in isolation before it was realized they all belonged to the same animal. The frontal appendage of Anomalocaris was described by Whiteaves (1892) as the body of a shrimp. The mouth parts were described by Walcott (1911) as a jellyfish called Peytoia nathorsti. A full body anomalocaridid specimen was originally described as the sea cucumber Laggania cambria (Walcott, 1911), and re-examined by Conway Morris (1978) who concluded it was a superimposition of the “jellyfish” Peytoia nathorsti on top of a sponge. Henriksen (1928) attached Anomalocaris to the carapace of Tuzoia, but Briggs (1979) suggested instead that it was the appendage of an unknown arthropod, an idea that turned out to be correct.

In the early 1980s, Harry Whittington was preparing an unidentified Burgess Shale fossil from the Geological Survey of Canada by chipping away layers of rock to reveal underlying structures, when he solved the mystery of Anomalocaris‘s identity. Much to his surprise, Whittington uncovered two Anomalocaris “shrimp” attached to the head region of a large body, which also had the “jellyfish” Peytoia as the mouth apparatus. Similar preparations of other fossils from the Smithsonian Institution in Washington DC revealed the same general morphology, including the Laggania cambria specimen Conway Morris (1978) thought to be the superimposition of the Peytoia jellyfish on a sponge, which was actually a second species of Anomalocaris. Thus, Whittington and Briggs (1985) were able to describe two species: Anomalocaris canadensis, which had a pair of the typical Anomalocaris appendages, and Anomalocaris nathorsti, which has a different type of frontal appendage and includes the original specimen of Laggania cambria. Bergström (1986) re-examined the morphology and affinity of Anomalocaris and suggested it had similarities to the arthropods.

Collecting at the Burgess Shale by the Royal Ontario Museum in the early 1990s led to the discovery of several complete specimens, which Collins (1996) used to reconstruct Anomalocaris canadensis with greater accuracy. This led to a name change of Anomalocaris nathorsti to Laggania cambria. Anomalocaris has since been the subject of many studies discussing its affinity (e.g., Hou et al., 1995; Chen et al., 2004; Daley et al., 2009), ecology (e.g., Rudkin, 1979; Nedin, 1999) and functional morphology (e.g., Usami, 2006).

Description:

Morphology:

Anomalocaris is a bilaterally symmetrical and dorsoventrally flattened animal with a non-mineralized exoskeleton. It has a segmented trunk, with at least 11 lateral swimming flaps bearing gills, and a prominent tailfan, which consists of three pairs of prominent fins that extend upward from the body. Paired gut glands are associated with the body segments in some specimens. The head region bears one pair of anterior appendages, two eyes on stalks, and a ventrally oriented circular mouth apparatus with many spiny plates. The frontal appendages are elongated and have 14 segments, each with a pair of sharp spikes projecting from the ventral surface. The stalked eyes are dorsal and relatively large. The ventral mouth apparatus has 32 rectangular plates, four large and 28 small, arranged in a circle, with sharp spines pointing into a square central opening. The most complete Anomalocaris specimen is 25 cm in length, although individual fragments suggest individuals could reach a larger size, perhaps up to 100 cm.

Abundance:

The Anomalocaris frontal appendage is extremely common at the Mount Stephen Trilobite Beds, and several hundred specimens of isolated frontal appendages and mouth parts have been collected from Mount Stephen and the Raymond Quarry on Fossil Ridge. These parts are relatively rare at Walcott Quarry, where fewer than 50 specimens are known (Caron and Jackson, 2008). Several dozen disarticulated assemblages and five complete body specimens are known from the Raymond Quarry.

Maximum Size:
1000 mm

Ecology:

Life habits: Nektonic
Feeding strategies: Nektonic
Ecological Interpretations:

The streamlined body would have been ideal for swimming. Undulatory movements of the lateral flaps propelled the animal through the water column and might have also served in gill ventilation. While swimming, Anomalocaris‘s frontal appendages would hang below the body, but it would thrust its head and appendages forward 180° to attack prey as needed.

A predatory lifestyle is suggested by the large eyes, frontal appendages with spines, gut glands, and spiny mouth apparatus. The circular mouth part is unique in the animal kingdom. It seems unlikely that it was used to bite prey by bringing lateral plates into opposition, rather, it grasped objects either by pivoting the plates outwards or contracting them inward. It has been suggested that Anomalocaris may have preyed on trilobites because some Cambrian trilobites have round or W-shaped healed wounds, interpreted as bite marks (Rudkin, 1979), and large fecal pellets composed of trilobite parts have been found in the Cambrian rock record; anamalocaridids are the only known animals large enough to have produced such pellets. The anomalocaridids could have fed by grasping one end of the trilobite in the mouth apparatus and rocking the other end back and forth with the frontal appendages until the exoskeleton cracked (Nedin, 1999). However, the unmineralized mouth apparatus of Anomalocaris would have probably been too weak to penetrate the calcified shell of trilobites in this manner, and the mouth parts do not show any sign of breakage or wear. Thus, Anomalocaris may have been feeding on soft-bodied organisms including on freshly moulted “soft-shell” trilobites (Rudkin, 2009).

References:

BERGSTRÖM, J. 1986. Opabinia and Anomalocaris, unique Cambrian ‘arthropods’. Lethaia, 19: 241-46.

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

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.

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.

CONWAY MORRIS, S. 1978. Laggania cambria Walcott: a composite fossil. Journal of Paleontology, 52: 126-131.

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.

HENRIKSEN, K. L. 1928. Critical notes upon some Cambrian arthropods described from Charles D. Walcott. Videnskabelige Meddelelser fra Dansk Naturhistorisk Forening: Khobenhavn, 86: 1-20.

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.

NEDIN, C. 1999. Anomalocaris predation on nonmineralized and mineralized trilobites. Geology, 27: 987-990.

RESSER, C. E. 1929. New Lower and Middle Cambrian Crustacea. Proceedings of the United States National Museum, 76: 1-18.

RUDKIN, D. M. 1979. Healed injuries in Ogygosis klotzi (Trilobita) from the Middle Cambrian of British Columbia. Royal Ontario Museum, Life Sciences Occasional Paper, 32: 1-8.

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.

USAMI, Y. 2006. Theoretical study on the body form and swimming pattern of Anomalocaris based on hydrodynamic simulation. Journal of Theoretical Biology, 238: 11-17.

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

WHITEAVES, J. F. 1892. Description of a new genus and species of phyllocarid Crustacea from the Middle Cambrian of Mount Stephen, B.C. Canadian Record of Science, 5: 205-208.

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.

Other Links:

www.trilobites.info/anohome.html

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