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Liangshanella burgessensis

A tiny arthropod with a bivalved carapace

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Liangshanella burgessensis (USNM 272083) – Holotype. Individual showing the two valves attached from the dorsal side. Specimen length = 2 mm. Specimen dry – direct light. Walcott Quarry.

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

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Taxonomy

Kingdom:

Animalia

Phylum:

Arthropoda

Class:

Unranked clade (Order: Bradoriida, stem group arthropods)

Affinity:

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).

Species name:

Liangshanella burgessensis

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).

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Age

Period:

Middle Cambrian, Bathyuriscus-Elrathina Zone (approximately 505 million years ago).

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Localities

Principal localities:

The Walcott and Raymond Quarries on Fossil Ridge.

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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).

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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

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Ecology

Life habits:

Nektobenthic, mobile

Feeding strategies:

Deposit feeder, or carnivorous

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).

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References

Bibliography:

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.

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