3D animation of Liangshanella burgessensis.
ANIMATION BY PHLESCH BUBBLE © ROYAL ONTARIO MUSEUM
Liangshanella is a bradoriid belonging to the family Svealutidae (Siveter & Williams 1997). The bradoriids were traditionally compared to other bivalved arthropods within or close to crustaceans, such as Recent ostracods (e.g. Sylvester-Bradley, 1961) and Cambrian phosphatocopids (e.g. Maas et al. (2003)). More recently, authors have argued bradoriids to represent more basal members of the arthropod stem group (e.g. Hou et al. (1996); Shu et al. (1999); Hou et al. (2010)). A recent reexamination of appendage morphology in the bradoriid Kunmingella supports a placement of these arthropods outside of crown groups (Zhai et al. 2019), but their exact phylogenetic placement remains unclear.
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.
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).
The Walcott and Raymond Quarries on Fossil Ridge.
Liangshanella liangshanensis is the type species of this genus and was first described by Huo (1956) from Lower Cambrian rocks of south China. urther 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). The most recent insight on the morphoanatomy of these arthropods comes from computed tomographic imagery of Kunmingella species from the Chengjiang biota (Zhai et al. 2019), which confirms both the presence of biramous enditic appendages and the lack of clear crown-group synapomorphies.
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. Based on appendicular evidence from other bradoriid taxa, L. burgessensis would have possessed short, spinose antennules, very reduced eyes—if at all present—, and biramous post-frontal appendages characterized by the presence of well-developed “fingers” on the inner side, called endites.
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).
Williams et al. (2007) considered bradoriids to be most likely epibenthic dwellers feeding on organic detritus or small non-biomineralized prey items; an ecology comparable to that of ostracods. These authors also pointed out that the large disparity of carapace shapes probably reflected a variety of different sub-niches and lifestyles. Their size and abundance would have made them in turn a common food source for larger animals, as indicated by coprolite composition (Vannier & Chen 2005).
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