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Lifestyle of the Octoradiate Eoandromeda in the Ediacaran Lifestyle of the Octoradiate Eoandromeda in the Ediacaran Authors: Wang, Ye, Wang, Yue, Tang, Feng, Zhao, Mingsheng, and Liu, Pei Source: Paleontological Research, 24(1) : 1-13 Published By: The Palaeontological Society of Japan URL: https://doi.org/10.2517/2019PR001 BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Complete website, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/terms-of-use. Usage of BioOne Complete content is strictly limited to personal, educational, and non - commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. 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Downloaded From: https://bioone.org/journals/Paleontological-Research on 15 Feb 2020 Terms of Use: https://bioone.org/terms-of-use Access provided by Bing Search Engine Paleontological Research, vol. 24, no. 1, pp. 1–13, JanuaryEoandromeda 1, 2020 ’s Lifestyle 1 © by the Palaeontological Society of Japan doi:10.2517/2019PR001 Lifestyle of the Octoradiate Eoandromeda in the Ediacaran YE WANG1, YUE WANG1, FENG TANG2, MINGSHENG ZHAO3 and PEI LIU1 1Resource and Environmental Engineering College, Guizhou University, Huanx 550025, Guiyang, Guizhou, China (e-mail: [email protected]) 2Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Street 100037, Beijing, China 3College of Paleontology, Shenyang Normal Univeristy, 253 Huanhe N Street 110034, Shengyang, Liaoning, China Received May 14, 2018; Revised manuscript accepted January 26, 2019 Abstract. The octoradiate Eoandromeda Tang et al. from the Ediacaran of South China and South Australia is poorly understood and there are different interpretations of its morphology and paleoecology. The carbona- ceous compression known as Eoandromeda, which is collected in black shales of the upper Doushantuo Forma- tion in northeastern Guizhou, South China, shows various patterns and complex structures. Eoandromeda is interpreted as an umbrella-shaped metazoan, with a dome-shaped polar structure on the top of its body, eight dextrally spiraling arms and tapering skirts. The spiral arms are differentiated into a main segment consisting of rigid and thick masses and a distal segment consisting of flexible and thin masses. Thus, we consider that the spiral arms may have consisted of gelatinous masses and primarily grew in their distal segments (approximately the tapering skirts). The numerous feather-like structures on the platy spiral arms are regularly arranged into two longitudinal rows. We believe that Eoandromeda lived in a primitive “Seabed Grassland” with an abun- dance and diversity of macroalgae and was capable of swimming in the water column by flapping its feather-like structures. Based on measurements of the maximum diameter of the disk-shaped compression and the maximum width of the spiral arms, Eoandromeda can be divided into a juvenile stage (<10 mm diameter) that has not been found, an adult stage (10–30 mm diameter) with a high growth rate in the width of the spiral arms, and a senes- cent stage (>30 mm diameter) with a slow growth rate in the width of the spiral arms. Fully grown Eoandrom- eda, with thick and rigid spiral arms, may have mostly stayed on the sediment surface, temporarily swimming to seek new habitat or prey. The juveniles, better swimmers, may have had a soft body with soft and thin arms, unlikely to be preserved, and may have been easily transported by water currents. Key words: metazoan, paleoecology, South China, swimming ability, Wenghui biota Introduction nofossil-kind” of Li et al. (1996) and Ding et al. (1996) instead of an ichnogenus, but assigned no ichnospecies, Carbonaceous compressions are abundant and diverse no type ichnospecies and no holotype (see Ding et al., in black shales of the Ediacaran Doushantuo Formation 1996, p. 126–127). The discoidal compression reported from western Hubei (i.e., the Miaohe biota; see Chen and by Wang et al. (2005) in the Wenghui biota was still Xiao, 1991; Chen et al., 1994, 2000; Steiner, 1994; Ding referred to by the ichnofossil-name Eilscaptichnus (Wang et al., 1996; Xiao et al., 2002; Ye et al., 2017), and north- et al., 2005, 2007). However, Wang et al. (2007) consid- eastern Guizhou (i.e., the Wenghui biota; see Wang et al., ered it as a discoidal metazoan, not an ichnofossil. Based 2007, 2008, 2014, 2015, 2016; Wang and Wang, 2008, on the International Code of Zoological Nomenclature 2011; Tang et al., 2008a, b, 2009a), South China (Fig- rules, Tang et al. (2008a) proposed a new genus Eoan- ure 1). Li and Ding (in Ding et al., 1996) first found two dromeda (containing only one species E. octobrachiata) specimens (publishing one of them) of a discoidal com- to replace Eilscaptichnus (nomen nudum) and interpreted pression with octoradiate pattern in the Miaohe biota, and it as an unknown diploblastic metazoan with eight dex- regarded them as an ichnofossil formed by a worm dig- trally spiraling arms. Tang et al. (2008b) suggested that ging spirally on the sediment surface. Based on the code Eoandromeda may have been a coelenterate. Based on the of ichnofossil nomenclature of Li et al. (1996) and Ding central area on the discoidal compressions and the numer- et al. (1996), they named the discoidal compression as ous feather-like structures on the spiral arms, Wang et al. Eilscaptichnus Li and Ding in Ding et al., 1996, an “ich- (2008) proposed that Eoandromeda, with its octoradiate Downloaded From: https://bioone.org/journals/Paleontological-Research on 15 Feb 2020 Terms of Use: https://bioone.org/terms-of-use Access provided by Bing Search Engine 2 Ye Wang et al. Figure 1. Locations and horizons of Eoandromeda Tang et al. from black shales of the upper Doushantuo Formation of the Ediacaran, South China. A, Ediacaran palaeogeographical configuration of the Yangtze region (modified from Liu and Xu, 1994 and Jiang et al., 2011), showing the comparable paleogeographical settings of both Wenghui and Miaohe biotas; B, location of the measured section at Wenghui, Jiangkou, Guizhou, China; C, D, columnar sections of the Doushantuo Formation exposed at Wenghui, Jiangkou, northeastern Guizhou (C) and Miaohe, Zigui, western Hubei (D), showing horizons bearing Eoandromeda. symmetry, may have been a ctenophore. Coincidentally, morphies of the crown group, such as tentacles, statoliths, another preservation type (a cast and mold) of Eoandrom- polar fields, and biradial symmetry, and interpreted it as eda was reported in the Ediacara Member in the lower part an early stem-group ctenophore. At present, the metazoan of the Rawnsley Quartzite in South Australia (Zhu et al., interpretation is accepted by multiple researchers (e.g. 2008). Based on the Chinese and Australian specimens, Wang et al., 2009, 2011, 2014, 2015, 2016; Tang et al., Zhu et al. (2008) suggested that Eoandromeda may have 2009a, 2011a, b, 2014; Xiao et al., 2013; MacGabhann, been a diplobastic-grade animal, sharing some features 2014), though its systematic classification is still contro- with ctenophores and cnidarians. Tang et al. (2011a, b) versial. On the other hand, few paleoecological studies considered that Eoandromeda apparently lacks synapo- on Eoandromeda have addressed the problem of whether Downloaded From: https://bioone.org/journals/Paleontological-Research on 15 Feb 2020 Terms of Use: https://bioone.org/terms-of-use Access provided by Bing Search Engine Eoandromeda’s Lifestyle 3 it was benthonic (Tang et al., 2008a, b, 2009a; Zhu et reposited in the Institute of Geology, Chinese Academy al., 2008) or planktonic or swimming (Wang et al., 2008, of Geological Science. 2009, 2010, 2011, 2015; Tang et al., 2011a, b, 2014). Examination of all collected specimens in black shales Morphological features and biological of the upper Doushantuo Formation at the Wenghui sec- interpretations tion of Jiangkou County, Guizhou Province, South China (Figure 1B) shows that these carbonaceous compressions Body appearance exhibit various patterns and possess complex structures. All specimens of Eoandromeda octobrachiata from Here we attempt to infer the lifestyle of Eoandromeda the Wenghui section are separately preserved on the bed- from its morphological characters. ding planes of the Doushantuo black shales. Most of them show circular disk-shaped (Figures 2A–D, 3A, C, G, I, Geological settings 4C, E, H) and symmetrically or asymmetrically oval disk- shaped (Figures 2E–H, 3E, 4A, G, I) compressions, which At the Wenghui section (27°50′07″N , 109°01′20″E), led to Eoandromeda being regarded as a discoidal meta- the Ediacaran Doushantuo Formation (>71 m thick), zoan in early publications (see Wang et al., 2007, 2008; overlying the diamictites of the Nantuo Formation and Tang et al., 2008a, b, 2009a, b). The Australian specimens underlying the bedded cherts of the Liuchapo Formation, preserved as cast and mold in siliciclastic sedimentary can be subdivided into four members (Figure 1C). The rocks were interpreted by Zhu et al. (2008) as a dome- lowest Member I is a 4.1-m-thick dolostone (cap carbon- shaped organism. However, the bell-shaped outline of E. ates). The Member II is composed of muddy dolostones octobrachiata (Figure 2I–K), which was reported in the and black shales. The overlying Member III consists of Wenghui biota and interpreted as a lateral compression dolostones and muddy dolostones, with interbedded black (Wang et al., 2009), indicates that Eoandromeda may shales. The uppermost Member IV is more than 31 m have had an umbrella-shaped body (Wang et al., 2009, thick and characterized by fossiliferous black shales, con- 2010, 2011, 2015; Tang et al., 2011a, b) because it was taining the Wenghui biota.
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