The Burgess Shale

Feeding Strategies: Deposit feeder

Scenella amii

3D animation of Scenella amii.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Unranked clade (stem group molluscs)
Species name: Scenella amii
Remarks:

Scenella is generally classified as a monoplacophoran mollusc (Knight, 1952; Runnegar and Jell, 1976). A position possibly ancestral to brachiopods (Dzik, 2010), or within the Cnidaria, has also been proposed (Babcock and Robison, 1988; Yochelson and Gil Cid, 1984).

Described by: Matthew
Description date: 1902
Etymology:

Scenella – from the Greek word skene, “tent, or shelter,” in reference to its shape.

amii – after Marc Henri Ami from the Geological Survey of Canada.

Type Specimens: Holotype –ROM8048 in the Royal Ontario Museum, Toronto, ON, Canada.
Other species:

Burgess Shale and vicinity: none

Other deposits: Dozens of species are known from the Lower Cambrian to the Lower Ordovician.

Age & Localities:

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

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

History of Research:

Brief history of research:

The limpet-like appearance of Scenella led to its original classification as a mollusc, initially as a pteropod, then as a gastropod (Walcott, 1886). The first fossils of this genus known from the Burgess Shale were collected from the Trilobite Beds on Mount Stephen. These were described as Metoptoma amii by Matthew (1902), but Walcott (1908) considered other specimens from the same locality (and from the Walcott Quarry) to belong to Scenella varians, an earlier named species. Resser (1938) recognized that both species were identical and proposed a new combination, Scenella amii. In the same publication, Resser named a second species from the Trilobite Beds S. columbiana; this was based on a single specimen, originally recognized as a brachiopod with possible spines (Walcott, 1912), and remains highly dubious.

Description:

Morphology:

Each cone-shaped fossil has the form of a flat disc with a central peak, here termed “shell.” Concentric rings surround this peak, and sometimes the shell is also corrugated. The shells are stretched along one axis, making them elliptical rather than circular.

The fossils are often preserved in dense clusters and are usually oriented point-up.

No soft tissue is ever found associated with Scenella. The shell was evidently mineralized as indicated by the three-dimensional preservation and the presence of small cracks suggesting brittleness.

Abundance:

Hundreds of specimens of S. amii are known in the Walcott Quarry (2.27% of the community, Caron and Jackson, 2008). Many of these are found in dense clusters on single slabs.

Maximum Size:
10 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

If a mollusc, Scenella would have been a creeping bottom-dweller, potentially a grazer.

References:

BABCOCK, L. E. AND R. A. ROBISON. 1988. Taxonomy and paleobiology of some Middle Cambrian Scenella (Cnidaria) and hyolithids (Mollusca) from western North America. University of Kansas Paleontological Contributions, Paper, 121: 1-22.

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

DZIK, J. 2010. Brachiopod identity of the alleged monoplacophoran ancestors of cephalopods. Malacologia, 52:97-113.

KNIGHT, J. B. 1952. Primitive fossil gastropods and their bearing on gastropod evolution. Smithsonian Miscellaneous Collections, 117(13): 1–56.

MATTHEW, G. F. 1902. Notes on Cambrian Faunas: Cambrian Brachiopoda and Mollusca of Mt. Stephen, B.C. with the description of a new species of Metoptoma. Transactions of the Royal Society of Canada, 4:107-112.

RASETTI, F. 1954. Internal shell structures in the Middle Cambrian gastropod Scenella and the problematic genus Stenothecoides. Journal of Paleontology, 28: 59-66.

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

Runnegar, B. AND P. A. JELL. 1976. Australian Middle Cambrian molluscs and their bearing on early molluscan evolution. Alcheringa: An Australasian Journal of Palaeontology, 1(2): 109-138.

WALCOTT, C. D. 1886. Second contribution to the studies on the Cambrian faunas of North America. Bulletin of the United States Geological Survey, (30): 11-356.

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

WALCOTT, C. 1912. Cambrian Brachiopoda. United States Geological Survey Monograph, 51: Part 1: 1-872, Part 872: 871-363.

YOCHELSON, E. L. AND D. GIL CID. 1984. Reevaluation of the systematic position of Scenella. Lethaia, 17: 331-340.

Other Links:

None

Ptychagnostus praecurrens

Ptychagnostus praecurrens (USNM 116212). Complete individual originally interpreted as the holotype of Triplagnostus burgessensis by Rasetti (1951). Specimen length = 8 mm. Specimen dry – direct light. Walcott Quarry.

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

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Trilobita (Order: Agnostida)
Species name: Ptychagnostus praecurrens
Remarks:

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

Described by: Westergård
Description date: 1936
Etymology:

Ptychagnostus – from the Greek ptycho, “pleated” (some species have pleat-like furrows on the cephalon), and agnostos, for “unknown” or “unknowable.”

praecurrens – from the Latin prae, “before,” and currens, “to run,” in reference to the old age of this fossil

Type Specimens: Holotype – SGU611; in the Geological Survey of Sweden (Sveriges geologiska undersökning – SGU), Uppsala, Sweden (Westergård, 1936)
Other species:

Burgess Shale and vicinity: none.

Other deposits: other species occur throughout the world in Middle Cambrian rocks.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Trilobites currently assigned to this genus and species have been described under several name combinations. Originally, Rasetti (1951) described it as Triplagnostus burgessensis, but subsequently (Rasetti, 1967) considered T. burgessensis to be a synonym of Ptychagnostus praecurrens (Westergård, 1936), a name retained by Peng and Robison (2000), despite numerous interim variations.

Description:

Morphology:

Hard parts: adult dorsal exoskeletons reach about 8 mm in length. The semicircular cephalon has a narrow marginal rim around the front and sides and sharply rounded the genal angles. There are no dorsal eyes and no facial sutures. The narrow glabella comes to an ogival point, with a median furrow extending across the short preglabellar field to the anterior margin; a transverse furrow crosses the glabella just in front of a low tubercle located behind the midpoint. Two short thoracic segments carry lateral nodes on the axial rings. A narrowly rimmed pygidium, the same size and general shape as the cephalon, has abruptly angled anterolateral corners. The pygidial axis is broader than the glabella, but of similar outline, with a median tubercle between two transverse furrows. The pointed tip of the axis reaches almost to the rim posteriorly, without a median furrow.

Unmineralized anatomy: not known

Abundance:

Very common in the Walcott Quarry on Fossil Ridge, where it is the most abundant trilobite (Caron and Jackson, 2008).

Maximum Size:
10 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

Adult agnostine trilobites have often been regarded as pelagic organisms that swam or drifted in the water column. Evidence now suggests that most were members of the mobile benthic epifauna, possibly micrograzers or particle feeders, preferentially occupying colder, deeper, offshore waters.

References:

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

PENG, S. C. AND ROBISON, R. A. 2000. Agnostoid biostratigraphy across the middle-upper Cambrian boundary in Hunan, China. Paleontological Society Memoir, no. 53 (supplement to Journal of Paleontology), 74(4), 104 pp.

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

RASETTI, F. 1967. Lower and Middle Cambrian trilobite faunas from the Taconic Sequence of New York. Smithsonian Miscellaneous Collections, 152(4): 112 pp.

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.

WESTERGÅRD, A. H. 1936. Paradoxides oelandicus beds of Oland: with the account of a diamond boring through the Cambrian at Mossberga. Sveriges Geologiska Undersökning. Series C, no. 394, Årsbok 30, no. 1: 1-66.

Other Links:

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

Haplophrentis carinatus

3D animation of Haplophrentis carinatus.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Hyolitha (Order: Hyolithida, stem group molluscs)
Species name: Haplophrentis carinatus
Remarks:

Haplophrentis belongs to a group of enigmatic cone-shaped to tubular fossils called hyoliths that are known only from the Palaeozoic. Their taxonomic position is uncertain, but the Hyolitha have been regarded as a separate phylum, an extinct Class within Mollusca (Malinky and Yochelson, 2007), or as stem-group molluscs.

Described by: Matthew
Description date: 1899
Etymology:

Haplophrentis – from the Greek haploos, “single,” and phrentikos, “wall,” in reference to the single wall within the shell.

carinatus – from the Latin carinatus, “keel-shaped,” referring to the morphological similarity to the bottom of a boat.

Type Specimens: Lectotype –ROM8463a in the Royal Ontario Museum, Toronto, Canada.
Other species:

Burgess Shale and vicinity: none

Other deposits: H. reesei Babcock & Robinson, 1988 (type species), from the lower Middle Cambrian Spence Shale and elsewhere in Utah; H.? cf. carinatus from the Middle Cambrian Kaili deposit in China (Chen et al., 2003).

Age & Localities:

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

The Walcott, Raymond and Collins Quarries on Fossil Ridge, the Trilobite Beds on Mount Stephen and Stanley Glacier in Kootenay National Park.

History of Research:

Brief history of research:

Matthew described Hyolithes carinatus from the Trilobite Beds in 1899 based on five incomplete specimens. Babcock and Robison (1988) reviewed the original fossils, along with additional specimens collected by the Royal Ontario Museum from various Burgess Shale localities. They concluded that the species carinatus didn’t belong in Hyolithes, and established a new genus, Haplophrentis, to accommodate it.

Description:

Morphology:

Like all hyoliths, Haplophrentis had a weakly-mineralized skeleton that grew by accretion, consisting of a conical living shell (conch), capped with a clam-like “lid” (operculum), with two slender, curved and rigid structures known as “helens” protruding from the shell’s opening. The function of these helens is still debated, but one possibility was to allow settlement and stabilization on the sea floor. Haplophrentis had a wiggly gut whose preserved contents are similar to the surrounding mud.

H. carinatus usually grew to around 25 mm in length, although some specimens reached as much as 40 mm; the species is distinguished from H. reesei, its cousin from Utah, by the faint grooves on its upper surface, the more pronounced net-like pattern on its “lid” (operculum), and its wider, more broadly-angled living shell (conch).

Haplophrentis can be distinguished from the similar hyolith genus Hyolithes because it bears a longitudinal wall running down the inner surface of the top of its living-shell.

Abundance:

Haplophrentis is relatively common on Fossil Ridge and in the Walcott Quarry in particular, accounting for 0.35% of the community there (Caron and Jackson, 2008).

Maximum Size:
40 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

Haplophrentis probably moved very little; its helens appear unsuited for use in locomotion (See Butterfield and Nicholas, 1996; Martí Mus and Bergström, 2005; Runnegar et al., 1975). Whilst Haplophrentis feeding mode remains somewhat conjectural, it probably consumed small organic particles from the seafloor. Numerous specimens have been found in aggregates or in the gut of the priapulid worm Ottoia prolifica suggesting Haplophrentis was actively preyed upon and ingested (Conway Morris, 1977; Babcock and Robison, 1988).

References:

BABCOCK, L. E. AND R. A. ROBISON. 1988. Taxonomy and paleobiology of some Middle Cambrian Scenella (Cnidaria) and hyolithids (Mollusca) from western North America. University of Kansas Paleontological Contributions, Paper, 121: 1-22.

BUTTERFIELD, N. J. AND C. NICHOLAS. 1996. Burgess Shale-type preservation of both non-mineralizing and “shelly” Cambrian organisms from the Mackenzie Mountains, Northwestern Canada. Journal of Paleontology, 70: 893-899.

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

CHEN, X. Y. ZHAO AND P. WANG. 2003. Preliminary research on hyolithids from the Kaili Biota, Guizhou. Acta Micropalaeontologica Sinica, 20: 296-302.

CONWAY MORRIS, S. 1977. Fossil priapulid worms. Special Papers in Palaeontology, 20: 1-95.

MALINKY, J. M. AND E. L. YOCHELSON. 2007. On the systematic position of the Hyolitha (Kingdom Animalia). Memoir of the Association of Australasian Palaeontologists, 34: 521-536.

MARTÍ MUS, M. AND J. BERGSTRÖM. 2005. The morphology of hyolithids and its functional implications. Palaeontology, 48:1139-1167.

MATTHEW, G. F. 1899. Studies on Cambrian faunas, No. 3. Upper Cambrian fauna of Mount Stephen, British Columbia. The trilobites and worms. Transactions of the Royal Society of Canada, Series 2, 4: 39-66.

RUNNEGAR, B., J. POJETA, N. J. MORRIS, J. D. TAYLOR, M. E. TAYLOR AND G. MCCLUNG. 1975. Biology of the Hyolitha. Lethaia, 8: 181-191.

Other Links:

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

http://www.kumip.ku.edu/cambrianlife/Utah-Mollusks-Hyolithids.html

Pikaia gracilens

3D animation of Pikaia gracilens.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

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

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

Described by: Walcott
Description date: 1911
Etymology:

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

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

Type Specimens: Syntypes –USNM57628b, 57629 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

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

Description:

Morphology:

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

Abundance:

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

Maximum Size:
55 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

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

References:

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

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

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

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

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

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

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

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

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

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

Other Links:

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

Fieldia lanceolata

Fieldia lanceolata (ROM 32572) – Part (left) and counterpart (right). Complete specimen with anterior section burried vertically, the posterior is to the left on the part. Specimen length (preserved) = 38 mm. Specimen wet – direct light (top row), wet – polarized light (bottom row). Walcott Quarry talus.

© Royal Ontario Museum. Photos: Jean-Bernard Caron

 

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Unranked clade (stem group priapulids)
Species name: Fieldia lanceolata
Remarks:

Fieldia belongs to the priapulid worm stem group (Harvey et al., 2010; Wills, 1998).

Described by: Walcott
Description date: 1912
Etymology:

Fieldia – from Field, the mountain peak (2,643 m) and small town near Fossil Ridge, British Columbia, Canada. The name was given by William Cornelius Van Horne (General Manager of the Canadian Pacific Railway), to honour Cyrus West Field, a promoter of the first telegraph cable across the Atlantic Ocean.

lanceolata – from the Latin lanceolatus, “lance-shaped,” in reference to the shape of the worm.

Type Specimens: Holotype –USNM57717 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: none.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge.

History of Research:

Brief history of research:

Walcott (1912) was the first to describe Fieldia, which he mistook for the carapace of a crustacean. He later classified a different specimen with the priapulid Ancalagon (known then as “Ottoia minor” Walcott, 1931). Conway Morris (1977) re-described the genus as a primitive priapulid worm based on new material he had found in the Smithsonian’s collections; later studies showed that it belonged to the priapulid stem group (Harvey et al., 2010; Wills, 1998).

Description:

Morphology:

Fieldia is a cylindrical worm about five centimeters in length, with a spine-covered body (trunk) and a rather small, eversible mouthpart, called a proboscis. The proboscis is lined with small spines at the front and several rows of hooks posteriorly. It is not known if the proboscis could be fully retracted or inverted as in other fossil and Recent priapulid worms. The gut is often preserved with a mud infill, and runs along the centre of the body. The trunk does not have annulations and is divided into an anterior, middle and a posterior part. The mud infill is most conspicuous in the middle part of the trunk.

Abundance:

This species is very rare. Only a single specimen was originally described by Walcott (1912) and about a dozen specimens were studied by Conway Morris (1977).

Maximum Size:
53 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

Fieldia is commonly preserved with mud inside its gut, suggesting that it fed directly on the sea-floor sediments. Its tubular body-shape is well adapted for burrowing; it probably used its spines to pull itself through the mud.

References:

CONWAY MORRIS, S. 1977. Fossil priapulid worms. Special Papers in Palaeontology, 20: 1-95.

HARVEY, T. H. P., X. DONG AND P. C. J. DONOGHUE. 2010. Are palaeoscolecids ancestral ecdysozoans? Evolution & Development, 12(2): 177-200.

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

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

WILLS, M. A. 1998. Cambrian and Recent disparity: the picture from priapulids. Paleobiology, 24(2): 177-199.

Other Links:

None

Elrathina cordillerae

Elrathina cordillerae (ROM 53273). Complete individual; a presumed carcass with free cheeks in place (coated with ammonium chloride sublimate to show details). Specimen length = 24 mm. Specimen dry – direct light. Mount Stephen Trilobite Beds on Mount Stephen.

© Royal Ontario Museum. Photo: Jean-Bernard Caron

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Trilobita (Order: Ptychopariida)
Species name: Elrathina cordillerae
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:

Elrathina – unspecified.

cordillerae – in reference to the Western Cordillera (Canadian Rocky Mountain ranges), derived from the Spanish cordilla, the diminutive of cuerda, meaning “cord.”

Type Specimens: Type status under review – UMMP 4883 (6 specimens), University of Michigan Museum of Paleontology, Ann Arbor, Michigan, USA.
Other species:

Burgess Shale and vicinity: Elrathina parallela, E. brevifrons, E. spinifera, and E. marginalis have been described from similar stratigraphic horizons at nearby sites on Mount Field, Mount Stephen, and Mount Odaray.

Other deposits: Other species of Elrathina have been reported from the Cambrian of North America and Greenland.

Age & Localities:

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

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

History of Research:

Brief history of research:

E. cordillerae was originally described under the genus name Conocephalites in Rominger’s 1887 publication on trilobites from Mount Stephen. In 1888 Walcott reallocated the species to Ptychoparia where it remained until Charles Resser, Walcott’s former assistant at the United States National Museum, established the new replacement genus Elrathina (Resser, 1937). Other workers have subsequently suggested that Elrathina is indistinguishable from Ptychoparella (see Blaker and Peel, 1997).

Species of Elrathina, along with those of the corynexochid Bathyuriscus, were found to be very abundant in a narrow interval of Middle Cambrian rocks throughout western North America, forming the basis of the Bathyuriscus-Elrathina Zone erected by Charles Deiss (1940).

Description:

Morphology:

Hard parts: adult dorsal exoskeletons average about 2 cm long. The semicircular cephalon is about one-third the length of the entire dorsal shield, bordered by a well-defined narrow rim, and with rounded genal angles. Weak transverse eye ridges extend to the small eyes, which are located just forward of cephalic mid-length. The slightly anteriorly narrowing glabella is rounded in front and exhibits three pairs of shallow lateral furrows; the pre-glabellar field is about the same width as the narrow anterior rim. The long, tapering thorax with a narrow axial lobe contains between 17 and 19 straight-sided segments, flexed gently downwards a short distance from the rounded tips. The tiny elliptical pygidium usually features two segments.

Unmineralized anatomy: rare specimens from the Walcott Quarry on Fossil Ridge retain tantalizing evidence of soft parts, including a pair of slender uniramous antennae, followed by very delicate looking biramous limbs beneath the cephalon, thorax and pygidium. These and other individuals of E. cordillerae are occasionally associated with a dark stain adjacent to the exoskeleton, presumably representing fluidized decay products.

Abundance:

Relatively common on Fossil Ridge and locally very abundant in the Walcott Quarry, where it represents about 25% of all trilobites collected (Caron and Jackson, 2008).

Maximum Size:
28 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

Like similar-looking ptychoparioid trilobites, E. cordillerae may be interpreted as a fully mobile, epibenthic deposit (particle) feeder adapted to very low oxygen levels.

References:

BLAKER, M. R. AND J. S. PEEL. 1997. Lower Cambrian trilobites from North Greenland. Meddeleser om Grønland, Geoscience, 35, 145 p.

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

DEISS, C. 1940. Lower and Middle Cambrian stratigraphy of southwestern Alberta and southeastern British Columbia. Bulletin of the Geological Society of America, 51: 731-794.

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

RESSER, C. E. 1937. Third contribution to nomenclature of Cambrian trilobites. Smithsonian Miscellaneous Collections, 95(22): 29 p.

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. 1989. Trilobites with appendages from the Middle Cambrian Stephen Formation of British Columbia. 28th International Geological Congress, Washington, D.C. July 9-19, 1989. Abstracts: 2-729.

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. 1918. Cambrian Geology and Paleontology IV. Appendages of trilobites. Smithsonian Miscellaneous Collections, 67(4): 115-216.

WALCOTT, C. D. 1924. Cambrian and Lower Ozarkian trilobites. Smithsonian Miscellaneous Collections, 75(2): 53-60.

Other Links:

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

http://www.geological-supplies.com/burgess/abstracts/balint

http://gsa.confex.com/gsa/2008AM/finalprogram/abstract_149017.htm

Elrathia permulta

Elrathia permulta (ROM 60762). Complete individual; a presumed carcass with free cheeks in place. Specimen length = 27 mm. Specimen dry – direct light (left) and coated with ammonium chloride sublimate to show details (right). Walcott Quarry.

© Royal Ontario Museum. Photo: Jean-Bernard Caron

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Trilobita (Order: Ptychopariida)
Species name: Elrathia permulta
Remarks:

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

Described by: Walcott
Description date: 1918
Etymology:

Elrathia – unspecified.

permulta – from the Latin per, “very much”, and multus, “many”.

Type Specimens: Holotype –USNM65517 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: other species occur, sometimes abundantly, elsewhere in the Cambrian of North America and Greenland.

Age & Localities:

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

The Walcott Quarry on Fossil Ridge. Elrathia sp. has been reported from localities on Mount Stephen.

History of Research:

Brief history of research:

The concept of Elrathia permulta is quite confused. Walcott named the species Ptychoparia permulta in 1918 and illustrated two specimens, one clearly designated as the type. Resser (1937) noted that the illustrated specimens were quite different, moved both to Walcott’s 1924 genus Elrathia, and proposed the name Elrathia dubia for the second species. Unfortunately, he based this on the original type of permulta; Rasetti (1951) declared dubia invalid, returned the type specimen to Elrathia permulta, and designated the other of Walcott’s specimens as a paratype of Ehmaniella burgessensis. The holotype of permulta, however, lacks many of the diagnostic characters of Elrathia, and Robison (1964) suggested it represents a new genus.

Description:

Morphology:

Hard parts: the adult dorsal exoskeleton is up to 25 mm long, with a large semicircular cephalon occupying about one-third the total length. The cephalon is bordered by a rounded rim and broad inner furrow; genal angles are produced into sharp triangular spines extending back to the fourth thoracic segment. There is a relatively long field between the narrow, tapered, and anteriorly rounded glabella and the frontal rim. Eyes are small and transverse eye ridges are very weak. Three pairs of shallow lateral furrows mark the glabella. The thorax comprises 14 segments, and tapers back more rapidly over the posterior half to a small rounded pygidium. The surface of the exoskeleton is variably granulate.

Unmineralized anatomy: not known.

Abundance:

Rare in the Walcott Quarry on Fossil Ridge, and elsewhere.

Maximum Size:
25 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

E. permulta may, like similar small ptychoparioid trilobites, be interpreted as a mobile, epibenthic deposit (particle) feeder adapted to low oxygen levels.

References:

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

RESSER, C. E. 1937. Third contribution to nomenclature of Cambrian trilobites. Smithsonian Miscellaneous Collections, 95(22): 29 p.

ROBISON, R. A. 1964. Late Middle Cambrian faunas from western Utah. Journal of Paleontology, 38:510-566.

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. 1918. Cambrian Geology and Paleontology IV. Appendages of trilobites. Smithsonian Miscellaneous Collections, 67(4): 115-216.

WALCOTT, C. D. 1924. Cambrian and Lower Ozarkian trilobites. Smithsonian Miscellaneous Collections, 75(2): 53-60.

Other Links:

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

Eldonia ludwigi

3D animation of Eldonia ludwigi.

Animation by Phlesch Bubble © Royal Ontario Museum

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Unranked clade Cambroernida (stem group ambulacrarians)
Species name: Eldonia ludwigi
Remarks:

Eldonia, together with other discoidal or pedunculate fossils such as Herpetogaster, 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: Walcott
Description date: 1911
Etymology:

Eldonia – from Eldon, a train stop on the Canadian Pacific Railway 30 km east of Field. Eldon is named after a town in County Durham, England, and means “Aelle’s hill.”

ludwigi – after Hubert Ludwig, a German echinoderm expert who described many fossil holothurians.

Type Specimens: Lectotype –USNM57540 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: Stellostomites eumorphus (Sun and Hou, 1987), from the Lower Cambrian Chengjiang fauna, was redescribed as Eldonia eumorpha (Chen et al., 1995). However, S. eumorphus is retained in the literature as the only valid species (Zhu et al. 2002); E. berbera was described from the Upper Ordovician of Morocco (Alessandrello and Bracchi, 2003). If confirmed it would be the youngest stratigraphic occurrence for the genus.

Age & Localities:

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

Burgess Shale and vicinity: Walcott and Raymond Quarries on Fossil Ridge.

Other deposits: Middle Cambrian Spence Shale and Marjum Formation in Utah (Conway Morris and Robison, 1988).

History of Research:

Brief history of research:

Described by Walcott in 1911, Eldonia was originally interpreted as a holothurian (sea cucumber within the echinoderms), a view that was accepted by some eminent experts at the time (Clark A.H., 1913) and upheld by later re-examination of the material (Durham, 1974). However, this interpretation has always had detractors (Clark H.L., 1912; Dzik, 1991, 1997; Madsen, 1956, 1957, 1962; Paul and Smith, 1984), and the lack of key echinoderm features prohibits a close relationship with that group (Conway Morris, 1993; see also Zhu et al., 2002). Despite their resemblance to jellyfish (scyphozoans) there is a wide consensus that eldoniids do not share any affinities with cnidarians. A connection to “lophophorates” (e.g., brachiopods, phoronids) has been argued in more detail (Chen et al., 1995, Dzik, 1997), but this status remains rather problematic. The description of Eldonia’s close relative Herpetogaster provides a possible link to the Ambulacraria, a group that contains the echinoderms and hemichordates (Caron and Conway Morris, 2010).

Fragments of the reflective gut have been extracted by acid maceration and analyzed for taphonomic studies (Butterfield, 1990).

Description:

Morphology:

Eldonia has a discoidal body with both anus and mouth opening ventrally. Fine rays radiate from a central point within the disc. The gut coils clockwise (viewed from the dorsal surface) around the centre of the organism and is clearly separated into a pharynx, stomach (the darker area), and narrow intestine. There is a pair of relatively stout tentacles around the mouth which probably were used for feeding.

Abundance:

Walcott collected hundreds of specimens of Eldonia in a single fossil layer within the Phyllopod Bed that he called the Great Eldonia Layer. Additional specimens have since been collected from the Walcott Quarry, where they comprise 0.4% of the community (Caron and Jackson, 2008).

Maximum Size:
150 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

Eldonia has conventionally been interpreted as a free-floating filter-feeder. However, based on its morphology, preservational patterns, and its similarity with Herpetogaster, a benthic lifestyle has also been proposed, with its tentacles either collecting food from the water, or sweeping the sea floor for particles of detritus (Caron and Conway Morris, 2010). It is unclear whether the animal could move at least occasionally or was permanently stationary (sessile).

References:

ALESSANDRELLO, A. AND G. BRACCHI. 2003. Eldonia berbera n. sp. a new species of the enigmatic genus Eldonia Walcott, 1911 from the Rawtheyan (Upper Ordovician) of Anti-Atlas (Erfoud, Tafilalt, Morocco). Atti della Società italiana di scienze naturali e del Museo civico di storia naturale in Milano, 144(2): 337-358.

BUTTERFIELD, N. J. 1990. Organic preservation of non-mineralizing organisms and the taphonomy of the Burgess Shale. Paleobiology, 16(3): 272-286.

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.

CHEN, J.-Y., M.-Y. ZHU AND G.-Q. ZHOU. 1995. The early Cambrian medusiform metazoan Eldonia from the Chengjiang Lagerstätte. Acta Palaeontologica Polonica, 40: 213-244.

CLARK, H. L. 1912. Fossil holothurians. Science, 35(894): 274-278.

CLARK, A. H. 1913. Cambrian holothurians. American Naturalist, 48: 488-507.

CONWAY MORRIS, S. AND R. A. ROBISON. 1988. More soft-bodied animals and algae from the Middle Cambrian of Utah and British Columbia. The University of Kansas Paleontological Contributions, 122: 23-84.

CONWAY MORRIS, S. 1993. The fossil record and the early evolution of the Metazoa. Nature, 361(6409): 219-225.

DURHAM, J. W. 1974. Systematic Position of Eldonia ludwigi Walcott. Journal of Paleontology, 48(4): 751-755.

DZIK, J. 1991. Is fossil evidence consistent with traditional views of the early metazoan phylogeny?, p. 47-56. In A. M. Simonetta and S. Conway Morris (eds.), The Early Evolution of Metazoa and the Significance of Problematic Taxa. Cambridge University Press, Cambridge.

DZIK, J. Y., L. ZHAO AND M. Y. ZHU. 1997. Mode of life of the Middle Cambrian eldonioid lophophorate Rotadiscus. Palaeontology, 40(2):385-396.

MADSEN, F. J. 1956. Eldonia, a Cambrian siphonophore-formerly interpreted as a holoturian[sic]. Videnskabelige meddelelser fra Dansk naturhistorisk forening i Københaven, 118: 7-14.

MADSEN, F. J. 1957. On Walcott’s supposed Cambrian holothurians. Journal of Paleontology, 31(1): 281-282.

MADSEN, F. J. 1962. The systematic position of the Middle Cambrian fossil Eldonia. Meddelelser fra Dansk Geologisk Førening, 15: 87-89.

PAUL, C. R. C. AND A. B. SMITH. 1984. The early radiation and phylogeny of echinoderms. Biological Reviews, 59(4): 443-481.

WALCOTT, C. 1911. Cambrian Geology and Paleontology II. Middle Cambrian holothurians and medusae. Smithsonian Miscellaneous Collections, 57(3): 41-68.

ZHU, M. Y., Y. L. ZHAO AND J. Y. CHEN. 2002. Revision of the Cambrian discoidal animals Stellostomites eumorphus and Pararotadiscus guizhouensis from South China. Geobios, 35(2): 165-185.

Other Links:

None

Ehmaniella burgessensis

Ehmaniella burgessensis (ROM 60759) – Part and counterpart. Complete specimen. Specimen length = 6 mm. Specimen dry – direct light (left) and coated with ammonium chloride sublimate to show details (middle, right). Walcott Quarry

© Royal Ontario Museum. Photo: Jean-Bernard Caron

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Trilobita (Order: Ptychopariida)
Species name: Ehmaniella burgessensis
Remarks:

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

Described by: Rasetti
Description date: 1951
Etymology:

Ehmaniella – modification of Ehmania, a trilobite genus name coined in 1935 by C. E. Resser to honour Philip Ehman (Montana) for his geological assistance.

burgessensis – from the Burgess Shale.

Type Specimens: Holotype (E. burgessensis) – USNM116245; Holotype (E. waptaensis) – USNM116243 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: Ehmaniella waptaensis Rasetti, 1951.

Other deposits: other species have been reported from elsewhere in the Cambrian of North America.

Age & Localities:

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

The Walcott, Raymond and Collins Quarries on Fossil Ridge. The Trilobite Beds on Mount Stephen, and smaller localities on Mount Odaray.

History of Research:

Brief history of research:

Walcott illustrated two Burgess Shale trilobite specimens in establishing Ptychoparia permulta in 1918. Resser (1937) saw that the two individuals belonged in different species, but erroneously used Walcott’s clearly designated primary type of permulta to found the new combination Elrathia dubia. Rasetti (1951) declared Resser’s dubia invalid, left the original type of permulta in Elrathia, and employed Walcott’s other specimen as a paratype of a new species (burgessesnsis), which he assigned to Resser’s 1937 genus Ehmaniella. Ehmaniella waptaensis, also described by Rasetti in 1951, is nearly indistinguishable.

Description:

Morphology:

Hard parts: adult dorsal exoskeletons may reach 2.8 cm long. The semicircular cephalon is about one-third the length of the dorsal shield, bordered by a well-defined rounded rim; wide free cheeks often show anastomosing ridges and carry short, sharp genal spines. Strong transverse eye ridges extend to relatively large eyes, which are located at or behind cephalic mid-length. The bluntly rounded glabella tapers evenly forward and bears three pairs of shallow lateral furrows; the pre-glabellar field is short. A thorax of thirteen parallel-sided segments has a barrel-shaped outline and a rather broad axial lobe. The short, wide, rounded triangular pygidium usually shows 4 or 5 axial rings with corresponding pleurae. The surface of the exoskeleton is variably granulate.

Unmineralized anatomy: rare specimens of Ehmaniella from the Walcott Quarry and above on Fossil Ridge preserve a pair of slender uniramous antennae (Walcott, 1918; Rudkin 1989). These are sometimes associated with a dark stain adjacent to the exoskeleton, presumably representing fluidized decay products.

Abundance:

Relatively common on Fossil Ridge and locally abundant in the Walcott Quarry (fourth most common trilobite with about 400 specimens observed, only 13 of which are E. waptaensis, Caron and Jackson, 2008).

Maximum Size:
28 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

Like similar-looking ptychoparioid trilobites, Ehmaniella may be interpreted as a fully mobile, epibenthic deposit (particle) feeder.

References:

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

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

RESSER, C. E. 1935. Nomenclature of some Cambrian trilobites. Smithsonian Miscellaneous Collections, 95(22): 29 p.

RESSER, C. E. 1937. Third contribution to nomenclature of Cambrian trilobites. Smithsonian Miscellaneous Collections, 93(5): 46 p.

RUDKIN, D. M. 1989. Trilobites with appendages from the Middle Cambrian Stephen Formation of British Columbia. 28th International Geological Congress, Washington, D.C. July 9-19, 1989. Abstracts: 2-729.

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. 1918. Cambrian Geology and Paleontology IV. Appendages of trilobites. Smithsonian Miscellaneous Collections, 67(4): 115-216.

Other Links:

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

Liangshanella burgessensis

3D animation of Liangshanella burgessensis.

ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM

Taxonomy:

Kingdom: Deposit feeder
Phylum: Deposit feeder
Class: Unranked clade (Order: Bradoriida, stem group arthropods)
Species name: Liangshanella burgessensis
Remarks:

Liangshanella is a bradoriid belonging to the family Svealutidae (Siveter and Williams, 1997). The bradoriids were traditionally compared to other bivalved arthropods, such as Recent ostracods (e.g. Sylvester-Bradley, 1961) and Cambrian phosphatocopids (e.g. Maas et al., 2003). However, they are thought to be in the stem-lineage or in a sister group position relative to the Crustaceans (e.g. Hou et al., 1996; Shu et al., 1999; Hou et al., 2010).

Described by: Siveter and Williams
Description date: 1997
Etymology:

Liangshanella – from Liangshan, a region in South Shaanxi, China.

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

Type Specimens: Holotype –USNM272083 in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.
Other species:

Burgess Shale and vicinity: none.

Other deposits: L. circumbolina from the Flinders Ranges in South Australia; L. liangshanensis, L. rotundata, L. orbicularis, L. yunnanensis and L. baensis from southern China; L. lubrica from the Tongying Formation in Hubei, China; L. sayutinae from the Trans-Baikal area in the Russian Far-East and Greenland; L. birkenmajeri from Antarctica. See references in Siveter and Williams (1997).

Age & Localities:

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

The Walcott and Raymond Quarries on Fossil Ridge.

History of Research:

Brief history of research:

Liangshanella liangshanensis is the type species of this genus and was first described by Huo (1956) from Lower Cambrian rocks of south China. Further species have since been described in China (Zhang, 1974; Li, 1975; Qian and Zhang, 1983; Zhang, 2007), Russia and Greenland (Melnikova, 1988), Australia (Topper et al., in press) and Antarctica (Wrona, 2009). Liangshanella burgessensis from the Burgess Shale was described by Siveter and Williams (1997), and the genus has been included in studies on the biogeography, evolution and affinity of the bradoriids (e.g. Shu and Chen, 1994; Williams et al., 2007).

Description:

Morphology:

Like all bradoriids, Liangshanella burgessensis has a small bivalved carapace with a straight dorsal hinge held together by a band of cuticle. The carapaces range in length from 0.66 mm – 4.25 mm and were soft and unmineralized. The bivalved carapace of L. burgessensis is sub-circular, with the anterior end being slightly narrower than the posterior end. There is a marginal ridge along the lateral surface of the valves. A centrally situated, sub-circular muscle scar composed of numerous small pits can be seen inside the valve. No evidence of soft parts has been found.

Abundance:

Liangshanella burgessensis is known from thousands of specimens and is the most common taxon in the Walcott Quarry (11.8% of the community, Caron and Jackson, 2008).

Maximum Size:
10 mm

Ecology:

Life habits: Deposit feeder
Feeding strategies: Deposit feeder
Ecological Interpretations:

Liangshanella was likely epibenthic, living on and within the first few metres of the soft muddy seafloor. Like other bradoriids, Liangshanella was probably a deposit feeder, and may have even been scavenging or predating on microscopic non-mineralized animals (Williams et al., 2007). Most specimens of Liangshanella found are empty carapaces, being left over from when the animal moulted its exoskeleton. Bradoriids are extremely common in Cambrian rocks, suggesting they played important roles in recycling nutrients in the seabed (Shu et al., 1999). They were also important food sources for larger animals, as indicated by their common presence in coprolites (e.g. Vannier and Chen, 2005).

References:

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

HOU, X., D. J. SIVETER, M. WILLIAMS, D. WALOSSEK AND J. BERGSTRÖM. 1996. Preserved appendages in the arthropod Kunmingella from the early Cambrian of China: its bearing on the systematic position of the Bradoriida and the fossil record of the Ostracoda. Philosophical Transactions of the Royal Society, B351: 1131-1145.

HOU, X., M. WILLIAMS, D.J. SIVETER, D.J. SIVETER, R.J. ALDRIDGE AND R.S. SANSOM. 2010. Soft-part anatomy of the Early Cambrian bivalve arthropods Kunyangella and Kunmingella: significance for the phylogenetic relationships of Bradoriida. Proceedings of the Royal Society, B277: 1835-1841.

HUO, S. 1956. Brief notes on lower Cambrian Archaeostraca from Shensi and Yunnan. Acta Palaeontologica Sinica, 4: 425-445.

LI, Y. 1975. Cambrian Ostracoda and other new descriptions from Sichuan, Yunnan and Shaanxi. Professional Papers of Stratigraphy and Palaeontology, 2: 37-72.

MAAS, A., D. WALOSZEK AND K.J. MÜLLER. 2003. Morphology, ontogeny and phylogeny of the Phosphatocopina (Crustacea) from the Upper Cambrian “Orsten” of Sweden. Fossils and Strata, 49: 1-238.

MELNIKOVA, L. M. 1988. Nekotoryye bradoriidy (Crustacea) iz botomskogo yarusa vostochnogo Zabaykal’ya. Paleontologicheskiy Zhurnal, 1: 114-117.

QIAN, Y. AND S. ZHANG. 1983. Small shelly fossils from the Xihaoping Member of the Tongying Formation in Fangxian County of Hubei Province and their stratigraphical significance. Acta Palaeontologica Sinica, 22: 82-94

SHU, D. AND L. CHEN. 1994. Cambrian palaeobiogeography of Bradoriida. Journal of Southeast Asian Earth Sciences, 9: 289-299.

SHU, D., J. VANNIER, H. LUO, L. CHEN, X. ZHANG AND S. HU. 1999. Anatomy and lifestyle of Kunmingella (Arthropoda, Bradoriida) from the Chengjiang fossil Lagerstätte (Lower Cambrian, Southwest China). Lethaia, 35: 279-298.

SIVETER, D.J. AND M. WILLIAMS. 1997. Cambrian Bradoriid and Phosphatocopid Arthropods of North America. Special Papers in Palaeontology, 57: 1-69.

SYLVESTER-BRADLEY, P. C. 1961. Archaeocopida, p. Q100-103. In R. C. Moore, and C. W. Pitrat (Eds.), Treatise on Invertebrate Paleontology Part Q, Arthropoda 3, Crustacea, Ostracoda. Geological Society of America and University of Kansas Press, Boulder, Colorado and Lawrence, Kansas.

Other Links:

None