Species of the medullosan ovule Stephanospermum from the Lopingian (late Permian) floras of China Alan R.T. Spencer a,⇑ , Shi-Jun Wang b,c , Michael T. Dunn d , Jason Hilton e a Department of Earth Sciences and Engineering, Imperial College London, London SW7 2BP, UK b State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, PR China c State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, PR China d Department of Biological Sciences, Cameron University, Lawton, OK 73505, USA e School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK article info Article history: Received 18 April 2013 Received in revised form 3 July 2013 Accepted 22 July 2013 Available online 7 August 2013 Keywords: Gymnosperm Medullosales Trigonocarp Coal-ball Wangjiazhai Formation Shuicheng abstract The medullosan pteridosperm ovule Stephanospermum Brongniart is a well-known component of Carbon- iferous aged coal-ball and siderite nodule floras from North America and Europe but also occurs in the Permian floras of Cathaysia where it is represented by the Lopingian (late Permian) aged species Stephan- ospermum trunctatum (Li) Wang et al. (2009) from coal-balls in the Wangjiazhai Formation in Southern China. We provide a detailed emendation of S. trunctatum and illustrate it comprehensively for the first time, and document an additional specimen from the Wangjiazhai Formation coal-ball assemblage that we assign to Stephanospermum shuichengensis sp. nov. S. shuichengensis is distinguished from S. truncta- tum by the absence of apical teeth in the sclerotesta and non-obovate base. The two species of Stephan- ospermum from the Wangjiazhai Formation are important as they extend the stratigraphic and geographical range of the genus from the Pennsylvanian of Euramerica into the Lopingian of Southern China, and demonstrate that the genus persisted in wetland, peat forming environments in the run up to the end-Permian mass extinction event. The 44 MY stratigraphic discontinuity between the Euramer- ican and the Cathaysian species, here named the Stephanospermum gap, leads us to infer that the genus was likely to have occurred in the Pennsylvanian–Permian successions of southern Russia and northern China that are geographically and stratigraphically intermediate to the known occurrences but from which the genus has yet to be discovered. Medullosan pteridosperms appear to have become extinct at or immediately prior to the Permian–Triassic boundary that coincides with the Permo–Trias mass extinction event; although the exact causes of this loss in plant diversity remains unknown, a response to regional climatic drying is likely to have been a contributing factor. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Medullosans are a comparatively well characterised group of Late Palaeozoic pteridosperms that were widespread in wetland and moister parts of seasonal wetland settings in the Pennsylva- nian of Europe and North America (DiMichele et al., 2006) and the Permian of China (Wang et al., 2009). As a group they exhibit a range of growth architectures including trees, vines and liana- like plants. In addition DiMichele et al. (2006) suggest that some medullosans may have been cormose, acaulescent plants. How- ever, currently the evidence is lacking for an evolutionary frame- work in which to determine the relationships between taxa with different growth architectures (DiMichele et al., 2006; Hilton and Bateman, 2006). Where known, ovules produced by medullosans conform to the traditionally circumscribed trigonocarpalean concept (senus Seward, 1917) and are large, radially symmetrical, have the nucellus attached to the integument at the chalaza only, and possess a domed or campanulate pollen chamber (Serbet and Rothwell, 1995; Spencer et al., 2013). In the compression/impres- sion record, medullosan ovules are typically placed in the genus Trigonocarpus Brongniart 1828, whereas those known with ana- tomical preservation are variously assigned to the genera Pachytes- ta Brongiart 1874, Stephanospermum Brongniart 1874, Hexapterospermum Brongniart 1874, Polypterospermum Brongniart 1874, Codonospermum Brongniart 1874, Rhynchosperma Taylor and Eggert 1967, and Hexaloba Dunn et al. 2002. The genus Stephanospermum at present includes eight species from the Pennsylvanian to earliest Permian floras of Euramerica plus a single species from the Permian of China (see Wang et al., 2009; Spencer et al., 2013, for a recent review). The species from China occurs in Changhsingian (late Permian) aged coal-balls from 1367-9120/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jseaes.2013.07.030 ⇑ Corresponding author. Tel.: +44 07824325531. E-mail address: a.spencer09@imperial.ac.uk (A.R.T. Spencer). Journal of Asian Earth Sciences 76 (2013) 59–69 Contents lists available at ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes