The Burgess Shale

Life Habits: Nektobenthic

Oryctocephalus reynoldsi

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

© ROYAL ONTARIO MUSEUM. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Trilobita (Order: Corynexochida)
Species name: Oryctocephalus reynoldsi
Remarks:

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

Described by: Reed
Description date: 1899
Etymology:

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

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

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

Burgess Shale and vicinity: Oryctocephalus burgessensis Resser, 1938.

Other deposits: many other species worldwide.

Age & Localities:

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

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

History of Research:

Brief history of research:

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

Description:

Morphology:

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

Unmineralized anatomy: not known

Abundance:

Rare, both on Mount Stephen and on Fossil Ridge.

Maximum Size:
25 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

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

References:

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.

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

REED, F. R. C. 1899. Woodwardian Museum Notes: a new trilobite from Mount Stephen, Field, B.C. Geological Magazine, New Series (Decade 4), 6: 358-361.

RESSER, C. E. 1938. Fourth contribution to nomenclature of Cambrian fossils. Smithsonian Miscellaneous Collections, 97: 1-43.

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

WALCOTT, C. D. 1886. Second contribution to the studies on the Cambrian faunas of North America. Bulletin of the US Geological Survey, 30: 1-255.

WHITTINGTON, H. B. 1995. Oryctocephalid trilobites from the Cambrian of North America. Palaeontology, 38: 543-562.

Other Links:

None

Caryosyntrips serratus

Caryosyntrips serratus (ROM 57161) – Holotype, part and counterpart. Individual claw. Specimen length = 78 mm. Specimen dry – direct light (top row), dry – polarized light (bottom row). Walcott Quarry.

© Royal Ontario Museum. Photo: Jean-Bernard Caron

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Dinocarida (Order: Radiodonta, stem group arthropods)
Species name: Caryosyntrips serratus
Remarks:

Caryosyntrips 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: Daley and Budd
Description date: 2010
Etymology:

Caryosyntrips – from the Greek karyon meaning “nut,” and syntrips, a mythical fiend who smashed pottery; thus, a nut smasher, referring to the nutcracker-like morphology of the paired appendages

serratus – from the Latin serratus, “saw-edged.”

Type Specimens: Holotype –ROM57161 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott and Raymond Quarries on Fossil Ridge. Also known from the Tulip Beds (S7) on Mount Stephen.

History of Research:

Brief history of research:

This genus was first noticed and illustrated as “Dinocarida A” in Caron (2005), and formally designated as Carysyntrips serratus by Daley and Budd (2010).

Description:

Morphology:

This taxon is known from eleven specimens of isolated appendages. Appendages are straight and tapering in outline, with a length that ranges between 58 mm and 114 mm. Segmentation of the appendage is poor, but at least 12 podomeres (segments) can be distinguished. The appendage is straight and rigid, with no movement occurring at the podomere boundaries. Each podomere has one thick, short spine on the inner surface, and several smaller spines on the outer surface, giving this outer margin a serrated appearance. The distal end of the appendage tapers to a point, and a single terminal spine is slightly curved. Most appendages are isolated, but a single paired specimen shows the appendages arranged in close proximity, with their thick spine margins in opposition. This particular specimen is loosely associated with potential remains of the body of the animal in the form of some cuticular elements. However, these elements are poorly preserved and might not be of the same animal.

Abundance:

Carysyntrips serratus is extremely rare. Most specimens (8) come from the Walcott Quarry.

Maximum Size:
114 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

Carysyntrips serratus is assumed to have had a similar mode of life to the rest of the anomalocaridids, meaning that it swam through the water column actively searching out prey. Its predatory nature is inferred from the morphology of the appendages, which were heavily spined. The straight, rigid appendages may have pivoted at their proximal attachment points to bring the thick-spine edges of the pair appendages together in a grasping or slicing motion.

References:

CARON, J. B. 2005. Taphonomy and community analysis of the Middle Cambrian Greater Phyllopod Bed, Brugess Shale. Unpublished Ph.D. thesis, University of Toronto, Toronto, 316 pp.

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.

DALEY, A. C. AND G. E. BUDD. 2010. New anomalocaridid appendage from the Burgess Shale, Canada. Palaeontology, 53: 721-738.

Other Links:

None

Canadia spinosa

3D animation of Canadia spinosa.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Unranked clade (stem group polychaetes)
Species name: Canadia spinosa
Remarks:

Canadia was briefly compared to modern chrysopetalids (Family: Palmyridae) but the similarities were thought to be too general to allow the inclusion of this species to this group (Conway Morris, 1979). Canadia is now regarded as a stem-group polychaete (Eibye-Jacobsen, 2004).

Described by: Walcott
Description date: 1911
Etymology:

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

spinosa – from the Latin spinosus, “full of spines,” reflecting its spiny appearance.

Type Specimens: Lectotype –USNM57654 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: One specimen known from the Spence Shale (Middle Cambrian of Utah) and described as Canadia sp. (Robison, 1969).

Age & Localities:

Age:
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:

Walcott (1911) described two different species of Canadia (C. setigera and C. spinosa) in his initial census of the Burgess Shale, and a more detailed description was produced from his notes after his death by Resser (Walcott, 1931) adding several additional species (C. grandis, C. irregularis, C. sparsa, C. dubia, and C. simplex). Conway Morris (1979) synonymised C. irregularis and C. grandis with C. spinosa, while the other species have all been reinterpreted as different genera. Nick Butterfield (1990) succeeded in isolating individual scales by dissolving fossils in acid. These scales were compared with the sclerites of Wiwaxia, suggesting a possible affinity between the two taxa. Wiwaxia is now regarded as a primitive mollusc (Caron et al., 2006) implying the scales of Canadia and sclerites of Wiwaxia are probably convergent. Like Burgessochaeta, Canadia has proven useful in calculating the extent of decay in fossil assemblages (Caron and Jackson, 2006).

Description:

Morphology:

Canadia is a bristled worm around 2 to 4 cm long and slightly dorsoventrally flattened. A long pair of smooth, tentacles protrudes from the front of its head. The variation in shape seen among these tentacles suggests that the organism could contract and extend them. The rest of the body consists of 20 to 22 trunk segments, each bearing a pair of lateral projections called parapodia. On the first segment the parapodia are simple (uniramous), while all the other segments have biramous parapodia (divided into two sections). All parapodia bear bristles called setae. In the second segment through to the last segment they form two main bundles, the notosetae (dorsal) and the neurosetae (lateral). Gills (branchiae) are situated between these two bundles of setae. The notosetae cover the organism asymmetrically, with the longest, widest setae closest to the midline. The lateral surface of the larger setae is serrated, and all the setae bear a finely spaced patterning of ridges, which may have given Canadia an iridescent lustre in life (Parker, 1998). The animal had a straight gut, and an eversible soft proboscis.

Abundance:

Canadia is relatively rare in the Walcott Quarry representing only 0.05% of the specimens counted in the community (Caron and Jackson, 2008).

Maximum Size:
45 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

Canadia probably lived close to the seafloor and could have swum by using its bristle-fans as paddles and by undulating its body. It would have used its tentacles primarily as sensory organs, and its proboscis for feeding on live or dead organisms.

References:

BUTTERFIELD, N. J. 1990. A reassessment of the enigmatic Burgess Shale fossil Wiwaxia corrugata (Matthew) and its relationship to the polychaete Canadia spinosa Walcott. Paleobiology, 16(3): 287-303.

CARON, J.-B. AND D. A. JACKSON. 2006. Taphonomy of the Greater Phyllopod Bed Community, Burgess Shale. PALAIOS, 21: 451-465.

CARON, J.-B., A. H. SCHELTEMA, C. SCHANDER, AND D. RUDKIN. 2006. A soft-bodied mollusc with radula from the Middle Cambrian Burgess Shale. Nature, 442: 159-163.

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. 1979. Middle Cambrian polychaetes from the Burgess Shale of British Columbia. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences, 285(1007): 227-274.

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

PARKER, A. R. 1998. Colour in Burgess Shale animals and the effect of light on evolution in the Cambrian. Proceedings of the Royal Society of London, Biological Sciences. 265: 967-972.

ROBISON, R. A. 1969. Annelids from the Middle Cambrian Spence Shale of Utah. Journal of Paleontology, 43: 1169-1173.

WALCOTT, C. D. 1911. Middle Cambrian annelids. Smithsonian Miscellaneous Collections, 57(2): 109-144.

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

Other Links:

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

Olenoides serratus

3D animation of Olenoides serratus.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Trilobita (Order: Corynexochida)
Species name: Olenoides serratus
Remarks:

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

Described by: Rominger
Description date: 1887
Etymology:

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

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

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

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

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

Age & Localities:

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

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

History of Research:

Brief history of research:

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

Description:

Morphology:

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

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

Abundance:

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

Maximum Size:
90 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

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

References:

KOBAYASHI, T. 1935. The Cambro-Ordovician formations and faunas of south Chosen. Paleontology, Part 3: Cambrian faunas of south Chosen with a special study on the Cambrian trilobite genera and families. Journal of the Faculty of Science, Imperial University of Tokyo, Section II. 4(2): 49-344.

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

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

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

WALCOTT, C. D. 1912. Cambrian Geology and Paleontology, II. No. 6. – Middle Cambrian Branchiopoda, Malacostraca, Trilobita, and Merostomata. Smithsonian Miscellaneous Collections, 57(6): 145-228.

WHITTINGTON, H. B. 1975. Trilobites with appendages from the Middle Cambrian, Burgess Shale, British Columbia. Fossils and Strata, No. 4: 97-136.

WHITTINGTON, H. B. 1980. Exoskeleton, moult stage, appendage morphology, and habits of the Middle Cambrian trilobite Olenoides serratus. Palaeontology, 23: 171-204.

Other Links:

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

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

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

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

Canadaspis perfecta

3D animation of Canadaspis perfecta.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Canadaspis perfecta
Remarks:

Canadaspis was originally classified as a Malacostracan crustacean (Walcott, 1912; Briggs, 1978), but this has been widely debated (e.g. Hou and Bergström, 1997; Boxshall, 1998; Walossek, 1999; Butterfield, 2002). It has also been placed in the upper euarthropod stem-lineage (Edgecombe, 2010), forming a clade with other bivalved arthropods such as Perspicaris (Bergström and Hou, 1998; Waloszek et al., 2007), and possibly including Fuxianhuia (Budd, 2002; Budd and Telford, 2009).

Described by: Walcott
Description date: 1912
Etymology:

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

perfecta – from the Latin perfectus, “complete.”

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

Burgess Shale and vicinity: none.

Other deposits: C. laevigata from the Lower Cambrian Chengjiang biota (Hou and Bergström, 1991, 1997). Further material of Canadaspis cf. perfecta has been recovered from additional localities in the USA (Robison and Richards, 1981; Lieberman, 2003; Briggs et al., 2008).

Age & Localities:

Age:
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:

Originally referred to as Hymenocaris by Charles Walcott (1912), the genus Canadaspis was erected by Novozhilov (1960). Four species were designated by Simonetta and delle Cave (1975), but two of them, Canadaspis ovalis and Canadaspis dictynna have since been redescribed within Perspicaris dictynna (Briggs, 1977). A third species, Canadaspis obesa was redescribed within Canadaspis perfecta (Briggs, 1978). A full study of the fourth and only valid species, Canadaspis perfecta was published by Briggs (1978), who posited a crustacean affinity. This was rebuffed by later workers (Hou and Bergström, 1997; Boxshall, 1998; Walossek, 1999), and a close relationship with other bivalved Burgess Shale taxa in the arthropod stem lineage, including Branchiocaris, Perspicaris and Odaraia, was suggested (Budd, 2002; Budd, 2008).

Description:

Morphology:

Canadaspis is composed of a bivalved carapace covering a body with an appendage-bearing head region, an abdomen of 8 segments with associated limbs that are segmented and branch into two (biramous), and a thorax of 7 segments with a spiny telson or tail. The length of the bivalved carapaces ranges in size from 0.8-5.2 cm. The carapace valves are suboval in outline and taper towards the anterior, with a straight hinge line connecting them towards the back of the upper surface (dorsally).

The head has two pairs of antennae, small eyes, spiny mouth parts and two pairs of biramous appendages. The first antennae are short and unsegmented, while the second antennae are much longer, have at least 12 segments and are fringed with long spines. The small eyes were borne on short, blunt stalks. A series of spines behind the antennae are interpreted as mandibles, arthropod mouth parts used for cutting food. The ten pairs of biramous limbs of the head and abdomen consist of a segmented inner walking limb, and a large outer flap with lamellae, interpreted to be gills. The segmented abdomen does not bear appendages, and ends in a spiny telson. The gut of Canadaspis is sometimes preserved, with mid-gut glands giving it a segmented appearance (Butterfield, 2002).

Abundance:

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

Maximum Size:
52 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

Canadaspis was likely to have lived on the sea floor, walking on its biramous appendages by moving them in a rippling motion. This would also waft water past the gills that form the outer branches of its biramous limbs, allowing for respiration. This movement may also propelled Canadaspis through the water column. The biramous appendages on Canadapsis’ head are tipped with a pair of claws that were probably used in feeding. The inner surfaces of its legs were covered with spines that would have assisted in feeding by directing food particles to the organism’s mouth. The mandibles would have been used to help consume the coarse particles found on the sediment surface. Canadapsis’ spiny head-shield probably protected it from predators.

References:

BERGSTRÖM, J. AND X. HOU. 1998. Chengjiang arthropods and their bearing on early arthropod evolution, p. 151-184. In G. D. Edgecombe (ed.), Arthropod Fossils and Phylogeny. Columbia University Press, New York.

BOXSHALL, G. 1998. Comparative limb morphology in major crustacean groups: the coax-basis joint in postmandibular limbs, p. 155-167. In R. A Fortey and R. Thomas (eds.), Arthropod phylogeny. Chapman & Hall, London.

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

BRIGGS, D. E. G. 1978. The morphology, mode of life, and affinities of Canadaspis perfecta (Crustacea: Phyllocarida), Middle Cambrian, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London, Series B, 281(984): 439-487.

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.

BUDD, G. E. 2002. A palaeontological solution to the arthropod head problem. Nature, 417(6886): 271-275.

BUDD, G. E. 2008. Head structure in upper stem-group euarthropods. Palaeontology, 51(3): 561-573.

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

BUTTERFIELD, N. J. 2002. Leanchoilia guts and the interpretation of three-dimensional structures in Burgess Shale-type fossils. Paleobiology, 28(1): 155-171.

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

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.

HOU, X. AND J. BERGSTRÖM. 1991. The arthropods of the Lower Cambrian Chengjiang fauna, with relationships and evolutionary significance p. 179-187. In A. M. Simonetta and S. Conway Morris (eds.), The Early Evolution of Metazoa and the Significance of Problematic Taxa. Cambridge University Press, Cambridge.

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

LIEBERMAN, B. S. 2003. A new soft-bodied fauna: the Pioche Formation of Nevada. Journal of Paleontology, 77(4): 674-690.

NOVOZHILOV. N. I. 1960. Principles of Paleontology: arthropods, trilobites and crustaceans. In Y. A. Orlov (ed.). Gos. Nauchno-Techn. Izdvo, Moscow.

ROBISON, R. A. AND B. C. RICHARDS. 1981. Larger bivalve arthropods from the Middle Cambrian of Utah. The University of Kansas Paleontological Contributions, 106: 1-28.

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. Middle Cambrian Branchiopoda, Malacostraca, Trilobita, and Merostomata, pp. 145-228, Cambrian Geology and Paleontology, 2.Volume 57 (6). Smithsonian Miscellaneous Collections.

WALOSZEK, D. 1999. On the Cambrian diversity of Crustacea, p. 3-27. In F. R. Schram and J. C. von Vaupel Klein (eds.), Crustaceans and the biodiversity crisis. Volume 1. Brill, Leiden.

WALOSZEK, D. MAAS, A. CHEN, J. AND M. STEIN. 2007. Evolution of cephalic feeding structures and the phylogeny of Arthropoda. Palaeogeography, Palaeoclimatology, Palaeoecology, 254: 273-287.

Other Links:

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

Bathyuriscus rotundatus

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

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

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Trilobita (Order: Corynexochida)
Species name: Bathyuriscus rotundatus
Remarks:

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

Described by: Rominger
Description date: 1887
Etymology:

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

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

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

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

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

Age & Localities:

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

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

History of Research:

Brief history of research:

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

Description:

Morphology:

Hard parts: adult dorsal exoskeletons may be up to 5 cm long and are narrowly oval in outline, with a semicircular cephalon, a thorax of nine segments ending in blade-like tips with short spines, and a semicircular pygidium without spines.

The long glabella reaches almost to the anterior cephalic border; the posterior portion is narrow and parallel-sided, while the anterior third expands rapidly forward. There are four pairs of lateral glabellar furrows, with the two front pairs angled forward and the posterior pair directed obliquely back. The eyes are relatively long and lie close to the glabella. Broad free cheeks are extended back into short genal spines. The pygidium is slightly smaller than the cephalon, with a well-defined narrow axial lobe of five rings and a terminal piece; four pairs of pygidial ribs are usually visible. The exoskeleton is mostly smooth externally, but very well preserved specimens may show faint anastomosing ridges on the free cheeks.

Unmineralized anatomy: not known.

Abundance:

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

Maximum Size:
50 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

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

References:

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

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

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

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

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

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

WALCOTT, C. D. 1916. Cambrian Geology and Paleontology III. Cambrian Trilobites. Smithsonian Miscellaneous Collections, 64(5): 303-456.

Other Links:

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

Nectocaris pteryx

3D animation of Nectocaris pteryx.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Cephalopoda (stem group molluscs)
Species name: Nectocaris pteryx
Remarks:

Nectocaris is regarded as an early stem-group mollusc close to the cephalopods. This stem-group also includes Vetustovermis from the Middle Cambrian Emu Bay Shale of Australia, and the Lower Cambrian Petalilium from the Chengjiang deposit in China (Smith and Caron, 2010).

Described by: Conway Morris
Description date: 1976
Etymology:

Nectocaris – from the Greek nekto, “swimming,” and the Latin caris, “shrimp,” based on its original interpretation as an arthropod.

pteryx – from the Greek pteryx, “fins,” in reference to the presence of fins.

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:

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

The Walcott, Raymond and Collins Quarries on Fossil Ridge.

History of Research:

Brief history of research:

As with Odontogriphus, another Burgess Shale animal related to molluscs, Walcott collected the first specimen of Nectocaris between 1909 and 1924. The fossil was photographed by Walcott, and its print sat with the unidentified specimen in the Smithsonian collections until noticed and described by Simon Conway Morris in 1976. Due to the lateral compression of the fossil, his resulting reconstruction was laterally-oriented. The funnel, bent back over the front, resembled the head-shield of an arthropod, and yet the fin, folded along the top of the organism, looked much like the ray-bearing dorsal fin of a chordate. A chordate affinity was further suggested by the myomere-like appearance of the bars, and although Conway Morris did not offer a firm diagnosis, Simonetta (1988) promoted a chordate status (Insom et al., 1995).

Meanwhile, Glaessner had described Vetustovermis, based on an ill-preserved specimen from Australia’s Emu Bay Shale, and because of its segmented appearance he suggested an affinity with annelid worms (Glaessner, 1979). Other workers noted the similarity of some Chengjiang fossils to this specimen and described them as slug-like relatives of the molluscs (Chen et al., 2005). During this period, the Royal Ontario Museum had been collecting similar fossils, which Desmond Collins recognized as representatives of Nectocaris. These were eventually described as stem-group cephalopods (Smith and Caron, 2010). The relationships among members of this clade are difficult to determine, and it may require further fossil finds to establish their diversity and range. The absence of a shell in Nectocarisindicates that cephalopods, which were previously thought to have evolved later in the Cambrian from snail-like monoplacophorans, did not require a buoyant shell to start swimming, but derived their shell independently of other mollusc lineages.

Description:

Morphology:

The body of Nectocaris is kite-shaped and can reach up to 72 mm in length, including two flexible tentacles that extend forwards from the head, which also bears a pair of camera-type eyes on short stalks. A long, nozzle-like funnel originates under the base of the head. The main body has wide lateral fins with transverse bars; a large axial cavity contains paired gills.

Abundance:

Nectocaris is known from 90 specimens on Fossil Ridge, mostly from the Collins Quarry; it is rare or absent at most other Burgess Shale localities. Only two specimens, including the holotype, have been found in the Walcott Quarry.

Maximum Size:
72 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

A free-swimming predator or scavenger, Nectocaris would have fed on small prey items with its prehensile tentacles in a similar fashion to squid today. Its primary mode of propulsion would have been in the flexing of its fins; it may have supplemented this by squirting water from its funnel. The funnel was also used to inhale and exhale water, which entered the animal’s body cavity to oxygenate the large internal gills.

References:

CHEN, J.-Y., D.-Y. HUANG AND D. J. BOTTJER. 2005. An Early Cambrian problematic fossil: Vetustovermis and its possible affinities. Proceedings of the Royal Society B: Biological Sciences, 272(1576): 2003-2007.

CONWAY MORRIS, S. 1976. Nectocaris pteryx, a new organism from the Middle Cambrian Burgess Shale of British Columbia. Neues Jahrbuch für Geologie und Paläontologie, Monatshefte, 12: 703-713.

GLAESSNER, M. F. 1979. Lower Cambrian Crustacea and annelid worms from Kangaroo Island, South Australia. Alcheringa, 3(1): 21-31.

INSOM, E. A. PUCCI AND A. M. SIMONETTA. 1995. Cambrian Protochordata, their origin and significance. Bollettino di Zoologia, 62(3): 243-252.

SIMONETTA, A. M. 1988. Is Nectocaris pteryx a chordate? Bollettino di Zoologia, 55(1-2): 63-68.

SMITH, M. AND J.-B. CARON. 2010. Primitive soft-bodied cephalopods from the Cambrian. Nature, 465: 469-472.

Other Links:

http://www.nature.com/nature/journal/v465/n7297/full/nature09068.html

Mollisonia symmetrica

Mollisonia symmetrica (USNM 57659) – Holotype. Exoskeleton preserved in dorsal view. Specimen length = 48 mm. Specimen dry – direct light (with different angles of low angle light). Trilobite Beds on Mount Stephen.

© SMITHSONIAN INSTITUTION – NATIONAL MUSEUM OF NATURAL HISTORY. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Mollisonia symmetrica
Remarks:

The affinity of Mollisonia has not been considered in detail because the appendages are unknown and the specimens are poorly preserved.

Described by: Walcott
Description date: 1912
Etymology:

Mollisonia – from Mount Mollison (2,952 m), southwest of Field in British Columbia, named by Joseph H. Scattergood in 1898 after the Mollison sisters, who managed some of the Canadian Pacific Railway hotels in the Rocky Mountains.

symmetrica – from the Greek syn, “plus,” and metron, “measure,” referring to the symmetrical nature of the body.

Type Specimens: Holotype –USNM57659 (M. symmetrica) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: A possible new species from Stanley Glacier (Caron et al., 2010).

Other deposits: M. sinica from the Middle Cambrian Kaili Formation of southwest China (Zhang et al., 2002).

Age & Localities:

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

The Walcott Quarry on Fossil Ridge. A few specimens potentially representing different species are known from the Trilobite Beds on Mount Stephen and Stanley Glacier.

History of Research:

Brief history of research:

Two definite species of Mollisonia were originally described by Walcott (1912), M. symmetricaand M. gracilis, based on one specimen each. A second specimen of M. gracilis discovered in 1925 and preserved with soft-tissues was removed from the genus and renamed Houghtonites gracilis by Raymond (1931). A third possible species, Mollisonia? rara, was described from several fragmentary specimens. Simonetta and Delle Cave (1975) restudied these specimens and synonymized Mollisonia? rara with M. symmetrica. Specimens of M. symmetrica have also been found in the Wheeler Formation and Spence Shale of Utah (Robison, 1991; Briggs et al. 2008).

Description:

Morphology:

The body of M. symmetica is elongated and symmetrical, with a convex dorsal surface. The rounded head shield has two anterior projections and several pairs of central oval structures. The body consists of seven thoracic segments that are all of equal width. The tail shield is rounded and of similar shape to the head shield, but with three posterior projections.

Abundance:

One specimen of M. symmetrica is known from the Mount Stephen Trilobite beds. A few dozen specimens are known from the Walcott Quarry where itrepresents less than 0.04% of the community (Caron and Jackson, 2008).

Maximum Size:
79 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

Mollisonia symmetrica is too poorly known to allow detailed studies of its ecology but comparisons with a related form called Hougthonites gracilis suggest a nektobenthic lifestyle.

References:

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.

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.

RAYMOND, P. E. 1931. Notes on invertebrate fossils, with descriptions of new species. Bulletin of the Museum of Comparative Zoology, Harvard University, 55: 165-213.

ROBISON, R. A. 1991. Middle Cambrian biotic diversity: Examples from four Utah Lagerstätten, p. 77-98. In A. Simonetta and S. Conway Morris (eds.), The Early Evolution of Metazoa and the Significance of Problematic Taxa. Cambridge University Press, Cambridge.

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.

ZHANG, X., Y. ZHAO, R. YANG AND D. SHU. 2002. The Burgess Shale arthropod Mollisonia(M. sinica new species): New occurrence from the Middle Cambrian Kaili fauna of southwest China. Journal of Paleontology, 76: 1106-1108.

Other Links:

None

Anomalocaris canadensis

3D animation of Anomalocaris canadensis.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: 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:

Age:
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: Nektobenthic
Feeding strategies: Nektobenthic
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

Metaspriggina walcotti

Metaspriggina walcotti (USNM 198611) – Holotype, part and counterpart. Lateral specimen showing clear myomeres; anterior to the right. Specimen length = 43 mm. Specimen dry – direct light (left column), dry – polarized light (right column). Walcott Quarry.

© SMITHSONIAN INSTITUTION – NATIONAL MUSEUM OF NATURAL HISTORY. PHOTOS: JEAN-BERNARD CARON

Taxonomy:

Kingdom: Nektobenthic
Phylum: Nektobenthic
Higher Taxonomic assignment: Unranked clade (stem group chordates)
Species name: Metaspriggina walcotti
Remarks:

Metaspriggina is considered to represent a primitive chordate, possibly transitional between cephalochordates and the earliest vertebrates (Conway Morris, 2008).

Described by: Simonetta and Insom
Description date: 1993
Etymology:

Metaspriggina – from the Greek meta, “in company with, or later in time,” and the morphologically similar Ediacaran organism Spriggina (which is no longer thought to be related). Spriggina honours Reg Sprigg, discoverer of the Precambrian fossils of the Ediacara Hills in Australia.

walcotti – after Charles Walcott, discoverer of the Burgess Shale.

Type Specimens: Lectotype –USNM198612 and former holotype 198611 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Set aside by Walcott for further study, the two known specimens of this species were briefly examined by Conway Morris (1979). Simonetta and Insom (1993) described one of the two specimens (the original holotype specimen) as a potential relative of the Ediacaran organism Spriggina, whereas the second specimen (now the lectotype) was interpreted as a potential chordate. A chordate interpretation for both specimens was proposed (Janvier, 1998; Smith et al., 2001) and a detailed redescription was eventually instigated by Conway Morris (2008) with both specimens being included in the same genus and species.

Description:

Morphology:

Metaspriggina is elongate in shape with a small anterior cranial region and a long triangular and laterally flattened trunk; there is no evidence of fins. The larger of the two known fossil specimens is around 7 cm in length. Both specimens possess numerous V-shaped or zig-zag segments interpreted as myomeres or muscle bands. A narrow central structure runs down the length of the organism and is interpreted as a gut. The front of one specimen appears to show a rudimentary cranium which is poorly preserved and seems to have lacked eyes.

Abundance:

M. walcotti is very rare in the Walcott Quarry, known from just two specimens.

Maximum Size:
69 mm

Ecology:

Life habits: Nektobenthic
Feeding strategies: Nektobenthic
Ecological Interpretations:

With only two specimens, and poor preservation of the head, the diet and feeding habits of Metaspriggina remain a mystery. The rarity of fossils suggests that the animal was likely free-swimming, which is consistent with its musculature, although it is possible that it also spent some time on the sea floor.

References:

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

CONWAY MORRIS, S. 2008. A redescription of a rare chordate, Metaspriggina walcottiSimonetta and Insom, from the Burgess Shale (Middle Cambrian), British Columbia, Canada. Journal of Paleontology, 82(2): 424-430.

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

SIMONETTA, A. M. AND E. INSOM. 1993. New animals from the Burgess Shale (Middle Cambrian) and their possible significance for the understanding of the Bilateria. Bolletino di Zoologia, 60(1): 97 – 107.

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.

Other Links:

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