Precambrian Research 255 (2014) 266–275 Contents lists available at ScienceDirect Precambrian Research jo ur nal home p ag e: www.elsevier.com/locate/precamres Orbisiana linearis from the early Ediacaran Lantian Formation of South China and its taphonomic and ecological implications Bin Wan a,b , Shuhai Xiao c,∗ , Xunlai Yuan a , Zhe Chen a , Ke Pang a,b , Qing Tang c , Chengguo Guan a,b , Jessica A. Maisano d a State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences, Nanjing 210008, China b University of Chinese Academy of Sciences, Beijing 100039, China c Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA d Jackson School of Geosciences, University of Texas, Austin, TX 78712, USA a r t i c l e i n f o Article history: Received 27 April 2014 Accepted 24 September 2014 Available online 5 October 2014 Keywords: Ediacaran Lantian Formation South China Orbisiana X-ray microCT a b s t r a c t Orbisiana is an Ediacaran fossil characterized by linearly arranged circular or cylindrical units. The genus was first described from the late Ediacaran Redkino Series in the Moscow Syncline of Russia where it is preserved as pyritic molds in siltstone. Here we report Orbisiana linearis, originally described as Seirisphaera lineare, from black shale of the early Ediacaran Lantian Formation in South China. Unlike the type species (O. simplex), O. linearis is preserved as carbonaceous compressions on the bedding sur- face, with rare specimens preserved three-dimensionally, allowing morphological characterization using X-ray microCT techniques. Morphological, paleoecological and taphonomic analysis suggests that O. lin- earis was a chain-like modular organism characterized by uniserially arranged, millimeter-sized, and tangentially contacting circular or cylindrical units. Ontogenetic growth of O. linearis was likely achieved through both accretionary addition of new modules and inflational expansion of existing units, and it appears that inflational growth was determinate. Although its phylogenetic affinity remains uncertain, O. linearis was likely a procumbent epibenthic or semi-endobenthic organism that lived on the seawater- sediment interface or partly buried in sediments. O. linearis in the Lantian Formation was preserved in situ, although some specimens are disarticulated and many are tectonically deformed. Orbisiana joins a growing list of Ediacaran genera that have a remarkable range of stratigraphic, environmental, ecological, and taphonomic distribution. © 2014 Elsevier B.V. All rights reserved. 1. Introduction The Ediacaran Period represents a geological interval when ben- thic eukaryotes increased significantly in size, tiering height, and morphological complexity (Narbonne, 2005; Xiao and Dong, 2006; Xiao and Laflamme, 2009; Narbonne, 2011; Ghisalberti et al., 2014; Xiao, 2014). The early Ediacaran Lantian biota (Yuan et al., 2011) and the middle-late Ediacaran Avalon, White Sea, and Nama assem- blages, the latter three of which are collectively known as the Ediacara biota (Narbonne, 2005), illustrate clearly this evolutionary change. Unlike the Ediacara biota where fossils are typically pre- served as casts and molds in sandstones and siltstones (Narbonne, 2005; Gehling and Droser, 2012), Lantian fossils are preserved as ∗ Corresponding author. Tel.: +1 5402311366. E-mail address: xiao@vt.edu (S. Xiao). carbonaceous compressions in black shales (Xing, 1989; Yan et al., 1992; Chen et al., 1994; Tang et al., 1997; Yuan et al., 1999, 2001, 2002, 2011). Despite their striking difference in depositional envi- ronment and taphonomic mode, comparative studies of Ediacara fossils hosted in sandstones, siltstones, black shales, and carbo- nates have shown that classical Ediacara taxa are found in different taphonomic windows, thus providing important insights into the environmental, ecological, taphonomic, and stratigraphic ranges of these organisms (Grazhdankin et al., 2008; Xiao et al., 2013; Chen et al., 2014). In this paper, we report Orbisiana from the early Ediacaran Lantian Formation in South China. Orbisiana was orig- inally described as pyrite molds from the late Ediacaran Redkino Series of the Moscow Syncline (Sokolov, 1976), but in Russia it may range from the Redkino to Kotlin Series with an estimated temporal range from 579 Ma to 550 Ma (Grazhdankin et al., 2010; Grazhdankin, 2012, 2014). The new material from the Lantian Formation not only significantly broadens the stratigraphic and http://dx.doi.org/10.1016/j.precamres.2014.09.028 0301-9268/© 2014 Elsevier B.V. All rights reserved.