The Burgess Shale

Choia carteri

3D animation of Choia ridleyi and other sponges (Diagoniella cyathiformis, Eiffelia globosa, Hazelia conferta, Pirania muricata, Vauxia bellula, and Wapkia elongata) and Chancelloria eros a sponge-like form covered of star-shaped spines.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
Higher Taxonomic assignment: Demospongea (Order: Monaxonida)
Species name: Choia carteri
Remarks:

Choia belongs to an early branch of siliceous sponge, the protomonaxonids at the base of the Demospongea (Rigby, 1986). Demosponges, the same group that are harvested as bath sponges, represent the largest class of sponges today.

Described by: Walcott
Description date: 1920
Etymology:

Choia – derivation unknown, but probably from the Spanish word cholla referring to spiny cacti of the genus Opuntia which resembles the sponge Choia in shape and spiny elements.

carteri – in honor of H. J. Carter, a famous nineteenth century hexactinellid sponge specialist.

Type Specimens: Lectotypes –USNM66482 (C. carteri),USNM66487 (C. ridleyi), in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA. (C. hindei, type and repository information unknown.)
Other species:

Burgess Shale and vicinity: C. ridleyi (Walcott, 1920) from the Walcott Quarry; C. hindei (Dawson, 1896) from the Raymond Quarry.

Other deposits: C. utahensis (Walcott, 1920) from the Middle Cambrian Wheeler and Marjum Formations in Utah (Rigby et al., 2010); C. xiaolantianensis from the Lower Cambrian Chengjiang biota (Hou et al., 1999), C. sp. from the same formation near Haikou, Yunnan Province (Luo et al., 1999); and C.? sriata from the Lower Cambrian Hetang Formation, Anhui Province (Xiao et al., 2005). Choia is also known from the Ordovician of Morocco (Botting, 2007).

Age & Localities:

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

Burgess Shale and vicinity: The Walcott and Raymond Quarries on Fossil Ridge. The Collins Quarry and Trilobite Beds on Mount Stephen.

Other deposits: C. hindei (Dawson, 1896) from the Ordovician of Quebec at Little Métis to the Middle Cambrian Burgess Shale; C. carteri, C. hindei from the Middle Cambrian Wheeler and Marjum Formations in Utah (Rigby et al., 2010).

History of Research:

Brief history of research:

Choia was first described by Walcott (1920) based on specimens from the Burgess Shale, Utah and Quebec. The material from the Burgess Shale was re-examined in detail by Rigby (1986) and Rigby and Collins (2004).

Description:

Morphology:

Choia carteri consists of a flattened elliptical disc, up to 2 cm in diameter (5 cm including the long spicules), formed by fine radiating spicules from which stronger and long spicules up to 30 mm in length radiate. Other species differ in size and spine coarseness. C. ridleyi is generally smaller (less than 1.5 cm) and C. hindei larger (up to 8 cm).

Abundance:

Choia is not common in the Walcott Quarry where it represents only 0.2% of the Walcott Quarry community (Caron and Jackson, 2008). Only one specimen of C. hindei is known from the Burgess Shale (Rigby and Collins, 2004).

Maximum Size:
50 mm

Ecology:

Life habits: Collins Quarry
Feeding strategies: Collins Quarry
Ecological Interpretations:

The sponge was not anchored to the sediment, but simply sat unattached on the sea floor. The long spicules are interpreted to have maintained the sponge above the sediment-water interface. Particles of organic matter were extracted from the water as they passed through canals in the sponges wall.

References:

BOTTING, J. P. 2007. ‘Cambrian’ demosponges in the Ordovician of Morocco: insights into the early evolutionary history of sponges. Geobios, 40: 737-748.

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

DAWSON, J. W. 1896. Additional notes on fossil sponges and other organic remains from the Québec Group of Little Métis on the lower St. Lawrence; with notes on some of the specimens by Dr. G.J. Hinde. Transactions of the Royal Society of Canada, 2: 91-129.

HOU, X., J. BERGSTRÖM, H. WANG, X. FENG AND A. CHEN. 1999. The Chengjiang fauna exceptionally well-preserved animals from 530 million years ago. Yunnan Science and Technology Press, Kunming, 170 p.

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

RIGBY, J. K. 1986. Sponges of the Burgess Shale (Middle Cambrian), British Columbia. Palaeontographica Canadiana, 2: 1-105.

RIGBY, J. K. AND D. COLLINS. 2004. Sponges of the Middle Cambrian Burgess Shale and Stephen Formations, British Columbia, 1, 155 p.

RIGBY, J. K., S. B. CHURCH AND N. K. ANDERSON. 2010. Middle Cambrian Sponges from the Drum Mountains and House Range in Western Utah. Journal of Paleontology, 84: 66-78.

WALCOTT, C. D. 1920. Middle Cambrian Spongiae. Smithsonian Miscellaneous Collections, 67(6): 261-364.

XIAO, S., J. HU, X. YUAN, R. L. PARSLEY AND R. CAO. 2005. Articulated sponges from the Lower Cambrian Hetang Formation in southern Anhui, South China: their age and implications for the early evolution of sponges. Palaeogeography, Palaeoclimatology, Palaeoecology, 220: 89-117.

Other Links:

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: Collins Quarry
Phylum: Collins Quarry
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: Collins Quarry
Feeding strategies: Collins Quarry
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:

Naraoia compacta

Reconstruction of Naraoia compacta.

© MARIANNE COLLINS

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Naraoia compacta
Remarks:

Naraoia is usually compared to the trilobites, but its exact relationships are uncertain (Whittington, 1977). The naraoiids and other trilobite-like arthropods, sometimes referred to as Trilobitoidea, can be grouped together with the trilobites to form the Lamellipedians (Hou and Bergström, 1997; Wills et al. 1998; Edgecombe and Ramsköld, 1999). This group has been variously placed in the upper stem lineage of the arthropods (Budd, 2002), or in the stem lineage of either the mandibulates (Scholtz and Edgecombe, 2006) or the chelicerates (Cotton and Braddy, 2004).

Described by: Walcott
Description date: 1912
Etymology:

Naraoia – from Narao Lakes, near Kicking Horse Pass in Yoho Park, British Columbia. From the Stoney First Nation Nakoda word Narao, meaning “hit in the stomach,” which likely refers to James Hector, who was kicked by a horse while travelling up the Kicking Horse River in 1858.

compacta – from the Latin compactus, “joined together.”

Type Specimens: Lectotype –USNM57687 (N. compacta) and holotypesUSNM83946 (N. spinifer) andUSNM189210 (N. halia) in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: N. spinifer (Walcott, 1931); N. halia (Simonetta and Delle Cave, 1975) from the Walcott Quarry, Burgess Shale.

Other deposits: N. longicaudata and spinosa (Zhang and Hou, 1985) from the Early Cambrian Chengjiang biota of South China, of which N. longicaudata was later placed in its own genus, Misszhouia (Chen et al., 1997); Possible specimens of Naraoia have been found at the Lower Cambrian Emu Bay Shale in Australia (Nedin, 1999). Unlike most Burgess Shale arthropods, Naraoia has also been found in rocks younger than the Cambrian, in the Late Silurian Bertie Formation of Southern Ontario (Caron et al., 2004).

Age & Localities:

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

The Walcott and Raymond Quarries on Fossil Ridge. The Trilobite Beds on Mt. Stephen, Tulip Beds (S7) and Collins Quarry as well as other smaller localities on Mount Stephen.

History of Research:

Brief history of research:

The first description of Naraoia was N. compacta by Walcott (1912), who later described a second specimen, N. spinifer (1931). Simonetta and Delle Cave (1975) re-examined the specimens and designated the new species N. halia and N. pammon. A major redescription of all Burgess Shale material was undertaken by Whittington (1977), and N. compactaspecimens from the Marjum Formation in Utah and the Gibson Formation in Idaho were described by Robison (1984), both of whom synonymized N. halia and N. pammon with N. compacta. However, a major restudy of the naraoiids by Zhang et al. (2007) concluded that N. halia is actually a valid species.

Description:

Morphology:

Naraoia consists of two dorsal shields with a convex axial region, including a roughly square head shield and an elongated body shield. A pair of long, multi-jointed antennae emerges from beneath the head shield. Behind the antennae are four pairs of cephalic appendages and 14 pairs of trunk appendages. All these appendages are segmented and branch into two (biramous), with a spiny walking limb made up of seven segments, and a filamentous branch consisting of a thin shaft bearing many lamellae (flexible and elongated plate-like elements). The basal segment of the biramous appendage is composed of a large, spiny plate.

Internal structures of Naraoia are well preserved, with the most conspicuous feature being the complexly branched gut glands visible on the cephalic shield. The gut passes along the whole length of the body, with paired gut glands visible in the anterior half.

Abundance:

Hundreds of specimens of Naraoia are known from the Walcott Quarry, where they make up about 0.74% of the community (Caron and Jackson, 2008). Naraoia is rare in all the other known localities.

Maximum Size:
40 mm

Ecology:

Life habits: Collins Quarry
Feeding strategies: Collins Quarry
Ecological Interpretations:

Naraoia likely spent much of its time walking on the sea floor, since the rigidity of its appendages would only allow for limited periods of swimming. It would have sensed its environment, including food items, using its antennae. Naraoia used the segmented walking limbs of its biramous appendages for walking and for manipulating food items, which were crushed and moved towards the mouth using the spiny basal plate. The filamentous branches of the biramous limb were used for gas exchange and to propel the animal through the water during short burst of swimming. The large gut glands and spiny appendages suggest that Naraoia was a predator or scavenger. Specimens with healed injuries suggest that Naraoia was also a prey item for other larger predators.

References:

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.

CARON, J.-B., D. M. RUDKIN AND S. MILLIKEN. 2004. A new Late Silurian (Pridolian) naraoiid (Euarthropoda: Nektaspida) from the Bertie Formation of southern Ontario, Canada – delayed fallout from the Cambrian explosion. Journal of Paleontology, 78: 1138-1145.

CHEN, J. G. D. EDGECOMBE AND L. RAMSKöLD. 1997. Morphological and ecological disparity in naraoiids (Arthropoda) from the Early Cambrian Chengjiang fauna, China. Records of the Australian Museum, 49: 1-24.

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

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

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

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

ROBISON, R. B. 1984. New occurrence of the unusual trilobite Naraoia from the Cambrian of Idaho and Utah. University of Kansa Paleontological Contribution, 112: 1-8.

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.

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.

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

WHITTINGTON, H. B. 1977. The Middle Cambrian trilobite Naraoia, Burgess Shale, British Columbia. Philosophical Transactions of the Royal Society of London, B, 280: 409-443.

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.

ZHANG, W. AND X. HOU. 1985. Preliminary notes on the occurrence of the unusual trilobite Naraoia in Asia. Acta Palaeontologica Sinica, 24: 591-595.

ZHANG, X., D. SHU AND D. H. ERWIN. 2007. Cambrian naraoiids (Arthropoda): Morphology, ontogeny, systematics and evolutionary relationships. Journal of Paleontology, 81:1-52.

Other Links:

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

Anomalocaris canadensis

3D animation of Anomalocaris canadensis.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
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: Collins Quarry
Feeding strategies: Collins Quarry
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.

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Herpetogaster collinsi

3D animation of Herpetogaster collinsi.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
Higher Taxonomic assignment: Unranked clade Cambroernida (stem group ambulacrarians)
Species name: Herpetogaster collinsi
Remarks:

Herpetogaster, together with other pedunculate or discoidal fossils such as Eldonia, probably belongs in the stem group to a clade known as the Ambulacraria, represented by both echinoderms and hemichordates (Caron et al., 2010).

Described by: Caron and Conway Morris
Description date: 2010
Etymology:

Herpetogaster – from the Greek, herpo, “to creep,” and gaster, “stomach.” The name refers to the creeping aspect of the animal and the large stomach.

collinsi – after Desmond Collins, a former curator of palaeontology at the Royal Ontario Museum who led expeditions to the Burgess Shale between 1975-2000.

Type Specimens: Holotype –ROM58051 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. The Collins Quarry on Mount Stephen and Stanley Glacier in Kootenay National Park.

History of Research:

Brief history of research:

Herpetogaster was described in 2010 as a possible member of the ambulacrarians (Caron and Conway Morris, 2010).

Description:

Morphology:

Herpetogaster consists of a main body with a pair of tentacles at the front and a flexible stolon. The body is divided into thirteen segments and coils clockwise when seen dorsally. The tentacles are long and flexible and branch several times. The stomach is the most conspicuous portion of the gut and is often preserved as a highly reflective film, as in Eldonia, a closely related form. The anus is terminal and the mouth is located between the tentacles. The stolon sometimes exceeds the length of the main body, and terminates with a flat disk. This structure was evidently used for anchoring the organism to the seabed, or to other organisms).

Abundance:

This animal is known from 101 specimens. Only 6 come from the Walcott Quarry, where it represents only 0.011% of the specimens counted in the community (Caron and Jackson, 2008); most specimens (68) come from the Raymond Quarry.

Maximum Size:
48 mm

Ecology:

Life habits: Collins Quarry
Feeding strategies: Collins Quarry
Ecological Interpretations:

Specimens of Herpetogaster were found associated with the sponge Vauxia, suggesting the animal lived on or near the seabed. It is not clear if Herpetogaster was permanently anchored, and whether or not it fed only on particulate matter in the water column, or could hunt small preys using its prehensile tentacles.

References:

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., S. CONWAY MORRIS AND D. SHU. 2010. Tentaculate fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) interpreted as primitive deuterostomes. PLoS ONE, 5(3): e9586.

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Xanioascus canadensis

Reconstruction of Xanioascus canadensis.

© MARIANNE COLLINS

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
Higher Taxonomic assignment: Unranked clade (stem group ctenophores)
Species name: Xanioascus canadensis
Remarks:

Xanioascus is regarded as a very primitive ctenophore, possibly representing a stem-group member (Conway Morris and Collins, 1996).

Described by: Conway Morris and Collins
Description date: 1996
Etymology:

Xanioascus – from the Greek xanion, “comb,” in reference to the shape and presence of comb-rows, and askos, “a leather bag used as a bottle.”

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

Type Specimens: Holotype –ROM43186 in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Collins Quarry on Mount Stephen.

History of Research:

Brief history of research:

Xanioascus canadensis was described by Conway Morris and Collins in 1996 from fossils discovered by the Royal Ontario Museum at a new locality on Mount Stephen; no additional studies have been published since then.

Description:

Morphology:

Xanioascus is bag-like in overall shape and bears 24 comb-rows. The comb-rows are well developed and extend close to the presumably large, but poorly preserved, mouth area. A distinctive feature of this species is the presence of ovoid structures within the body, but their identity remains speculative.

Abundance:

Only 8 specimens of this species are known.

Maximum Size:
125 mm

Ecology:

Life habits: Collins Quarry
Feeding strategies: Collins Quarry
Ecological Interpretations:

The presence of comb-rows suggests the animal was an active swimmer. Its mode of feeding is more conjectural as the mouth is not well preserved and there is no evidence of tentacles.

References:

CONWAY MORRIS, S. AND D. COLLINS. 1996. Middle Cambrian ctenophores from the Stephen Formation, British Columbia, Canada. Philosophical Transactions of the Royal Society of London, Series B, 351: 279-308.

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Sanctacaris uncata

Reconstruction of Sanctacaris uncata.

© MARIANNE COLLINS

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Sanctacaris uncata
Remarks:

Sanctacaris was originally considered to belong to the crown-group chelicerates (Briggs and Collins, 1988), but subsequent analyses have aligned it with the arachnomorphs (Dunlop and Seldon, 1997; Wills et al., 1998; Sutton et al., 2002) or placed it in the stem lineage of the euarthropods (Budd, 2002).

Described by: Briggs and Collins
Description date: 1988
Etymology:

Sanctacaris – from the Latin sanctus, “holy, or saint,” (referring to Santa from the field name “Santa Claws”) and caris, “crab, or shrimp.”

uncata – from the Latin uncata meaning “hooked, or barbed,” referring to the numerous claws.

Type Specimens: Holotype –ROM43502 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 Collins Quarry on Mount Stephen.

History of Research:

Brief history of research:

Sanctacaris was first described by Briggs and Collins in 1988, and has since been included in several studies on arthropod relationships (e.g. Briggs and Fortey, 1989; Dunlop and Seldon, 1997; Wills et al. 1998; Sutton et al. 2002; Budd, 2002).

Description:

Morphology:

Sanctacaris has a wide head shield with six pairs of head appendages projecting forward that are segmented and branch into two (biramous). The body trunk has eleven divisions, and a wide telson. Its body length ranges from 4.6 cm to 9.3 cm. The head shield is convex in the middle, and has two wide, triangular extensions on either side. A pair of eyes is located on the head shield near the lateral side of the anterior margin. The six biramous head appendages have thin, antenna-like branches in association with a spiny raptorial appendage. The rest of the body is divided into eleven segments. Each segment has a raised central region with wide lateral projections and is associated with one pair of biramous limbs. Each biramous limb consists of a wide flap with a fringe of setae and a thin, segmented walking branch. The telson is wide and paddle-shaped, with a posterior fringe of setae.

Abundance:

Sanctacaris is known from five specimens from Mount Stephen.

Maximum Size:
93 mm

Ecology:

Life habits: Collins Quarry
Feeding strategies: Collins Quarry
Ecological Interpretations:

Sanctacaris may have lived on or just above the sea floor. The presence of the frontal appendages and eyes indicate that Sanctacaris would have been a free-swimming predator. The broad flaps of the trunk appendages would have been used to propel the animal through the water, with the telson and the lateral projections of the head and body being used to stabilize and steer. The raptorial branches of the biramous head appendages would have served to actively grab prey items, while the antennae-like branches would have been used to sense the environment.

References:

BRIGGS, D. E. G. AND D. COLLINS. 1988. A Middle Cambrian chelicerate from Mount Stephen, British Columbia. Palaeontology, 31: 779-798.

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.

DUNLOP, J. A. AND P. A. SELDEN. 1997. The early history and phylogeny of chelicerates, pp. 221-235. In R. A Fortey and R. Thomas (eds.), Arthropod phylogeny. Chapman and Hall, London.

SUTTON, M. D., D. E. G. BRIGGS, D. J. SIVETER, D. J. SIVETER AND P. J. ORR. 2002. The arthropod Offacolus kingi (Chelicerata) from the Silurian of Herefordshire, England: computer based morphological reconstructions and phylogenetic affinities. Proceedings of the Royal Society of London, Series B, 269: 1195-1203.

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:

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Plenocaris plena

Reconstruction of Plenocaris plena.

© MARIANNE COLLINS

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Plenocaris plena
Remarks:

The affinity of Plenocaris is poorly known. It has been assigned to the Class Malacostraca (Whittington, 1974), but no phylogenetic analysis of this species has been carried out.

Described by: Walcott
Description date: 1912
Etymology:

Plenocaris – from the Latin plenus, “full,” and caris, “shrimp.”

plena – from the Latin plenus, “full.”

Type Specimens: Holotype –USNM57700 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 and Raymond Quarries on Fossil Ridge. The Collins Quarry on Mount Stephen.

History of Research:

Brief history of research:

Plenocairs was first described by Walcott (1912) as Yohoia plena. Whittington (1974) invalidated Y. plena, upgrading it to its own genus, Plenocaris plena, leaving Y. tenuis as the only species of Yohoia.

Description:

Morphology:

The body of Plenocaris is elongated and consists of a head region and 13 body segments ending in a paddle-shaped telson. The head bears a pair of simple antennae. The trunk segments 2 to 4 bear a pair of uniramous, elongate appendages whereas the other segments have no appendages. A carapace is loosely connected to the rest of the body and dorsally and laterally covers the head region and anterior of trunk.

Abundance:

Plenocaris represent a trivial proportion (0.2%) of specimens counted in the Walcott Quarry (Caron and Jackson, 2008) and is extremely rare elsewhere.

Maximum Size:
17 mm

Ecology:

Life habits: Collins Quarry
Feeding strategies: Collins Quarry
Ecological Interpretations:

Some specimens of Plenocaris have a sediment-filled gut, suggesting that this animal lived near the benthos and was a deposit feeder. In the absence of swimming appendages, swimming and steering was only possible thanks to its long trunk and large lobate tail.

References:

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

WHITTINGTON, H. B. 1974. Yohoia Walcott and Plenocaris n. gen. arthropods from the Burgess Shale, Middle Cambrian, British Columbia. Geological Survey of Canada Bulletin, 231: 1-27.

Other Links:

None

Branchiocaris pretiosa

Reconstruction of Branchiocaris pretiosa.

© Marianne Collins

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
Higher Taxonomic assignment: Unranked clade (stem group arthropods)
Species name: Branchiocaris pretiosa
Remarks:

Branchiocaris is considered to represent either a stem-lineage euarthropod (Budd, 2002; 2008) or a primitive branchiopod crustacean (crown-group arthropod) (Resser, 1929; Hou and Bergström, 1997; Briggs et al., 2008), perhaps closely related to Marrella (Briggs et al., 1992; Wills et al., 1998).

Described by: Resser
Description date: 1929
Etymology:

Branchiocaris – from the Greek branchion, “gill,” and the Latin caris, “crab” or “shrimp,” thus, gilled shrimp.

pretiosa – from the Latin pretiosus, “precious” or “attractive.”

Type Specimens: Holotype –USNM80483 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: Branchiocaris has also been found in the Cambrian sediments of Utah (Briggs et al., 2008), and a possible second species, Branchiocaris? yunnanensis, has been described from the Lower Cambrian Chengjiang biota (Hou, 1987).

Age & Localities:

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

The Walcott and Raymond Quarries on Fossil Ridge. The Tulip Beds (S7) and Collins Quarry on Mount Stephen.

History of Research:

Brief history of research:

This animal was originally described as Protocaris pretiosa by Charles Resser in 1929, the second species to be placed in the genus established by Charles Walcott in 1884. Resser (1929) considered it to be a phyllocarid crustacean, but Raymond (1935) and Størmer (1944) suggested it had affinities to trilobites.

A major redescription was undertaken by Briggs (1976), who removed P. pretiosa to a new genus, Branchiocaris, based on differences in carapace outline and telson morphology. While Briggs (1976) acknowledged similarities between Branchiocaris and the branchiopod crustaceans, he did not assign this animal to any extant group of arthropods. Hou and Bergström (1997) suggested that Branchiocaris was a calmanostracan branchiopod, while other phylogenetic analyses placed it close to Marrella (Briggs et al., 1992; Wills et al., 1998). A reassessment of the head structures in Branchiocaris led Budd (2002, 2008) to suggest that it is a stem-lineage euarthropod, belonging to a clade with Odaraia, Fuxianhuia, Perspicaris and Canadaspis.

Description:

Morphology:

Branchiocaris has a prominent bivalved carapace covering most of the narrowly-segmented body, which has many trunk limbs and a distinctive two-bladed telson. It ranges in total body length from 7 cm to over 9 cm. The sub-oval carapace has a straight dorsal hinge line with a pointed spine at each corner. The carapace surface is smooth except for a narrow border along the margin, consisting of 150-200 small, irregularly spaced and elongated pits.

The bivalved carapace covers most of the head and the anterior part of the body, extending partly over the lateral side of the animal. The frontmost structure of the head is a semicircular anterior sclerite, behind which two pairs of cephalic appendages are located. The foremost pair consists of stout but highly flexible antennae that attach towards the front of the upper surface (anterodorsally) and taper gradually towards the rear. Each antenna is made up of at least 20 segments. Behind the antennae is a pair of claw-like (subchelate) appendages. Each has at least seven segments, the last of which is elongated into a spine with a central furrow.

There is no evidence of eyes in this animal. The body trunk had at least 44 divisions or segments, and appendages were attached to a ridge running along the ventrolateral side of the animal. The trunk segments bear appendages that consist of a wide triangular flap, bearing gill blades (lamellae) and hair-like bristles (setae), and a short proximal area with up to seven segments. The posterior end of the body terminates in a large segment, or telson, that is sub-oval and has two broad lanceolate processes extending from its ventral surface. Traces of the alimentary canal are visible along the length of some specimens, as either a highly reflective dark stain or a raised ridge.

Abundance:

Branchiocaris is very rare in the Walcott Quarry on Fossil Ridge, where it makes up a negligible percentage (0.008%) of the community (Caron and Jackson, 2008). It is more common on Mount Stephen in rocks of the slightly older Glossopleura Zone (Collins et al., 1983).

Maximum Size:
155 mm

Ecology:

Life habits: Collins Quarry
Feeding strategies: Collins Quarry
Ecological Interpretations:

The trunk appendages are poorly suited for walking, but the wide flaps would have been ideal for propelling the animal through the water column by wave-like movements. This type of swimming may have set up a water current running along the ventral surface of the animal, assisting in the function of the lamellae as gills. The telson probably aided in propulsion and steering while swimming. The subchelate frontal appendages were most likely use to grasp food material from the sea floor and pull it towards the mouth. The antennae presumably served a sensory function. Since Branchiocaris apparently lacks eyes, it seems unlikely to be an active predator. It was probably a deposit feeder, swimming just above the sea floor gathering food.

References:

BRIGGS, D. E. G. 1976. The arthropod Branchiocaris n. gen. Middle Cambrian, Burgess Shale, British Columbia. Geological Survey of Canada Bulletin, 264: 1-29.

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

BRIGGS, D. E. G., R. A. FORTEY, M. A. WILLS. 1992. Morphological disparity in the Cambrian. Science, 256: 1670-3.

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.

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.

COLLINS, D., D. BRIGGS AND S. CONWAY MORRIS. 1983. New Burgess Shale fossil sites reveal Middle Cambrian faunal complex. Science, 222: 163-167.

HOU, X. 1987. Early Cambrian large bivalved arthropods from Chengjiang, eastern Yunnan. Acta Palaeontologica Sinica, 26: 286-298.

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

HOU, X., R. J. ALDRIDGE, J. BERGSTRÖM, D. J. SIVETER, D. J. SIVETER, AND X. FENG. 2004. The Cambrian Fossils of Chengjiang, China. The Flowering of Early Animal Life. Blackwell, Oxford.

RAYMOND, P. E. 1935. Leanchoilia and other Mid-Cambrian Arthropoda. Harvard University Museum of Comparative Zoology Bulletin, 76: 205-230.

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

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

WALCOTT, C. D. 1884. On a new genus and species of Phyllopoda from the Middle Cambrian, p. 330-331. In On the Cambrian faunas of North America, preliminary studies. U.S. Geological Survey Bulletin, 30.

WILLS, M. A., D. E. G. BRIGGS, R. A. FORTEY, M. WILKINSON, AND P. H. 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:

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Alalcomenaeus cambricus

Reconstruction of Alalcomenaeus cambricus.

© Marianne Collins

Taxonomy:

Kingdom: Collins Quarry
Phylum: Collins Quarry
Higher Taxonomic assignment: Unranked clade Megacheira? (stem group arthropods)
Species name: Alalcomenaeus cambricus
Remarks:

Alalcomenaeus is closely related to Leanchoilia, and together with Yohoia and some Chengjiang taxa, they form the “great appendage” arthropods, or Megacheira (Hou and Bergström, 1997; Wills et al., 1998; Cotton and Braddy, 2004). The phylogenetic placement of the megacheirans is uncertain and they are considered to be either stem-lineage chelicerates (Chen et al., 2004; Edgecombe, 2010) or upper stem-lineage euarthropods (Budd, 2002).

Described by: Simonetta
Description date: 1970
Etymology:

Alalcomenaeus – from the Greek Alalcomenae, the birthplace of the goddess Athena.

cambricus – of Cambrian age, derived originally from Cambria in Wales.

Type Specimens: Holotype –USNM155658 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: Possibly one species from the Lower Cambrian Chengjiang biota, China, described originally as Alalcomenaeus? illecebrosus (referred to as Leanchoilia illecebrosa by Hou and Bergström, 1997).

Age & Localities:

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

The Collins Quarry on Mount Stephen, and the Walcott and Raymond Quarries on Fossil Ridge.

History of Research:

Brief history of research:

Simonetta (1970) described this organism on the basis of a handful of specimens originally collected by Walcott on Fossil Ridge. The taxon was redescribed by Whittington (1981), who accepted only two of Simonetta’s original specimens as Alalcomenaeus. The recovery of over 300 new specimens from Collins Quarry on Mount Stephen allowed for a more detailed description of the taxon (Briggs and Collins, 1999).

Description:

Morphology:

The largest specimens of Alalcomenaeus reach about 6 cm in length, excluding the anterior great appendages. The head has a trapezoidal head shield, a pair of ventral pedunculate eyes, three (or possibly five) median eyes, one pair of large frontal appendages (the “great appendage”) and two pairs of smaller biramous appendages. Each great appendage has three long whip-like extensions. The outer branch of the biramous limb is flap-like and the inner branch bears spines. The trunk is composed of eleven segments, each bearing a pair of biramous appendages, and the paddle-like tail is fringed with short, sharp spines.

Abundance:

Just a few dozen specimens of Alalcomenaeus have been found in the Burgess Shale at several horizons on Fossil Ridge. Alalcomenaeus represents 0.04% of the Walcott Quarry community (Caron and Jackson, 2008). It is more common in the Glossopleura Zone on Mount Stephen, where over 300 specimens have been found in one single locality (Collins Quarry), but in general this species is rare.

Maximum Size:
60 mm

Ecology:

Life habits: Collins Quarry
Feeding strategies: Collins Quarry
Ecological Interpretations:

The primary mode of locomotion was probably swimming, powered both by the wave-like fanning of its lateral flaps and flicks of its tail. The outer leg branches also served as gills. The spiny inner branches are not well suited to walking, but might have been used to macerate food. The long filaments of the great appendages were probably sensory and suggest an active predatory habit, consistent with the large, downward-facing stalked eyes and spinose inner leg branches. Alalcomenaeus most likely hunted organisms that lived either in or on the sediment.

References:

BRIGGS, D. E. G. AND D. COLLINS. 1999. The Arthropod Alalcomenaeus cambricus Simonetta, from the Middle Cambrian Burgess Shale of British Columbia. Palaeontology, 42(6): 953-977.

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

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

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

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

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

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

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

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: 329-357.

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