Journal of Paleontology, 92(1), 2018, p. 87–98 Copyright © 2017, The Paleontological Society 0022-3360/18/0088-0906 doi: 10.1017/jpa.2017.40


New material of three-dimensionally phosphatized and microscopic cycloneuralians from the Cambrian Paibian Stage of South China


Yunhuan Liu,1 Qi Wang,1 Tiequan Shao,1 Huaqiao Zhang,2* Jiachen Qin,1 Li Chen,1 Yongchun Liang,1 Cheng Chen,1 Jiaqi Xue,1 and Xiaowen Liu1


1College of Earth Science and Resources, Chang’an University, Xi’an 710054, China ⟨stotto@163.com⟩, ⟨2015127039@chd.edu.cn⟩, ⟨zytqshao@chd.edu.cn⟩, ⟨201327010227@chd.edu.cn⟩, ⟨201427010307@chd.edu.cn⟩, ⟨201427010301@chd.edu.cn⟩,


⟨201427020323@chd.edu.cn⟩, ⟨sxsxjq@163.com⟩, ⟨201427010317@chd.edu.cn⟩ 2State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China ⟨hqzhang@nigpas.ac.cn⟩


Abstract.—Some rare microscopic cycloneuralians are present in the Cambrian of South China, represented by Eopriapulites and Eokinorhynchus (both early Cambrian), fossil embryos of Markuelia (middle to late Cambrian), and palaeoscolecids (early to late Cambrian). Among them, palaeoscolecids are relatively diverse and abundant. Here, we describe new material of three-dimensionally phosphatized and microscopic cycloneuralians from the Paibian Stage of Wangcun Lagerstätte, western Hunan, South China. New material includes fossil embryos assignable to Markuelia sp., two other types of fossil embryos, and three species of palaeoscolecids, including Dispinoscolex decorus Duan, Dong, and Donoghue, 2012, Schistoscolex hunanensis Duan, Dong, and Donoghue, 2012, and Austroscolex sinensis new species. The palaeoscolecid fragments differ mainly in size and armor of the trunk annuli. Since Eokinorhynchus and Eopriapulites occurred the earliest among the Cambrian cycloneuralians, it is proposed here that: (1) cycloneuralians originated in the Cambrian Fortunian small shelly faunas rather than in the early Cambrian macrobenthos, (2) ancestral cycloneuralians may have simple trunk armor, and (3) Eopriapulites represents an ancestral cycloneuralian.


Introduction


Cycloneuralians have relatively strong fossilization potential because of the development of cuticle and thus have abundant fossil records in Cambrian deposits with exceptionally pre- served fossils (Maas, 2013), such as typical Burgess Shale-type Lagerstätten (Conway Morris, 1977; Chen, 2004; Hou et al., 2004; Maas et al., 2007a) and Orsten-type Lagerstätten (Maas et al., 2007b, 2009; Liu et al., 2014; Zhang et al., 2015; Shao et al., 2016). The disassociated armor of their cuticles can also be preserved as small shelly fossils (Bengtson, 1977; Hinz et al., 1990) or small carbonaceous fossils (Smith et al., 2015; Harvey and Butterfield, 2016). It has previously been proposed that the cycloneuralians originated in early Cambrian macro- benthos and that palaeoscolecids might represent ancestral cycloneuralians or even ancestral ecdysozoans (Budd, 2001; Harvey et al., 2010). This hypothesis was challenged by recent discovery of microscopic cycloneuralians from earlier geologi- cal time (Liu et al., 2014; Zhang et al., 2015). It is thus evident that cycloneuralians should have originated in the Cambrian Fortunian Stage or earlier. Cambrian microscopic cycloneuralians in South China are


represented by Eopriapulites sphinx Liu and Xiao in Liu et al., 2014, Eokinorhynchus rarus Zhang et al., 2015, Markuelia hunanensis Dong and Donoghue in Dong et al., 2004, Markuelia qianensis Zhang et al., 2011, and palaeoscolecids. Among them,


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palaeoscolecids are characterized by a high level of abundance and diversity. Here, we describe new material of three- dimensionally phosphatized and microscopic cycloneuralians from the Paibian (Furongian) Bitiao Formation in Wangcun Lagerstätte, western Hunan, South China. These microscopic cycloneuralians, together with the other microscopic cycloneur- alians in the Cambrian, are used as models to test the origin and ancestral type of cycloneuralians.


Materials and methods


The new cycloneuralians illustrated in this paper were recovered from the Bitiao Formation of Wangcun section, western Hunan, South China (Figs. 1, 2). The Wangcun Lagerstätte has yielded a large number of exceptionally preserved microfossils, including the classic Orsten-type fossils, such as Skara hunanensis Dong in Liu and Dong, 2007, phosphatocopid crustaceans (Zhang and Dong, 2009; Zhang et al., 2011a, b, 2012), and a single type A larva (Zhang et al., 2016), as well as bivalved arthropods Cambrolongispina (Zhang et al., 2014). The key horizon yielding the present specimens is a thin-bedded, dark gray limestone (about 5 cm thick; Fig. 1.2) and has been constrained to part of the conodonts Westergaardodina cf. calix–Prooneotodus rotundatus Zone, Bitiao Formation, belonging to Paibian Stage, Furongian Series (traditional upper Cambrian; Peng et al., 2012; Dong and Zhang, 2017). This horizon has previously yielded fossil embryos


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