Zeng et al.—Radiodontan oral cone from Guanshan Lagerstätte
(Cong et al., 2014, fig. 1a–d, f) and L. trilobus (Cong et al., 2016, figs. 1.1–1.3, 1.5, 2.1–2.3), both from the Chengjiang Lagerstätte, and the circular plates of Schinderhannes bartelsi Kühl et al., 2009 from the Early Devonian Emsian Hunsrück Slate. Moreover, a mouth apparatus exactly like Omnidens amplus Hou et al., 2006 from Chengjiang was recently identified in the ‘gilled lobopodian’ Pambdelurion whittingtoni Budd, 1998 from the Cambrian Stage 3 Sirius Passet Lagerstätte, Greenland (Vinther et al., 2016), sug- gesting that its supposed radiodontan identity (Chen et al., 1994, 1996; Chen, 2004) may be problematic. In this paper, we present a new radiodontan oral cone
morphotype from the Guanshan Lagerstätte (Cambrian Series 2, Stage 4) in the Wulongqing Formation, Gaoloufang section, Kunming, eastern Yunnan, South China. The frontal appendages of two radiodontans, Anomalocaris kunmingensis Wang et al., 2013 and Paranomalocaris multisegmentalis Wang et al., 2013, have already been described fromthis Lagerstätte (Hu et al., 2010, 2013). The taxonomic identity of this new oral cone cannot be determined because it is preserved in isolation, not associatedwith frontal appendages or other body
parts.Because the new oral cone combines features seen in both Anomalocaris and Peytoia oral cones, we regard it as a transitional form that has the potential to illuminate themorphological variations, feeding mechanisms, and evolution of these unique feeding structures.
Geologic setting
As with the better known Chengjiang Lagerstätte (e.g., Zhao et al., 2012), the Guanshan Lagerstätte is a Burgess Shale-type deposit that is widely distributed in eastern Yunnan Province (Fig. 1) and has yielded abundant and diverse well-preserved soft-bodied fossils (Luo et al., 2008; Hu et al., 2010, 2013; Liu et al., 2012). Soft-bodied Guanshan fossils are found within yellowish- to-greenish mudstones intercalated with thinly bedded siltstone layers in the Wulongqing Formation (Hu et al., 2010, 2013).
Locality and imaging.—The isolated radiodontan oral cone (NIGPAS 162529) described here was collected from the Gaoloufang section at Guangwei in Kunming,Yunnan Province, China, one of themainGuanshan Lagerstätte localities (Fig. 1; Hu et al., 2010, 2013). Photographs of this fossil were made using a Nikon AF-S VR 105mm f/2.8G macro lens mounted on a Nikon D300s digital single lens reflex camera, employing low-angle incident light to show the relief of structures; interpretative drawings were based on high-resolution photographs in Adobe
smooth surfaces and include four perpendicularly situated large plates separated by 28 small plates. The two morphotypes of oral cones can only be distinguished by the presence of a set of extra inner teeth within the central opening in Hurdia (Daley et al., 2009, 2013a; see Discussion). In contrast, the oral cone in A. canadensis comprises three large plates intercalated by medium and small ones, all of which have scale-like nodes and furrowed folds toward their outer margins. In addition, an almost identical A. canadensis-type oral cone has also been identified in A. saron Houetal.,1995fromtheCambrian Stage 3 Chengjiang Lagerstätte, Yunnan, South China (Chen et al., 1994, fig. 2; Daley and Bergström, 2012), as well as in an unidentified and isolated speci- men from the Cambrian Stage 4 Emu Bay Shale, Kangaroo Island, South Australia (McHenry and Yates, 1993, fig. 8; Daley et al., 2013b, fig. 4). Other radiodontan oral cones described in the literature include examples of a partially preserved Hurdia sp. (Daley et al., 2013a, fig. 24a) and Peytoia cf. P. nathorsti (Conway Morris and Robison, 1982) from the Cambrian Stage 5 Spence Shale and DrumianWheeler Formation, both in Utah,USA, in addition to several other fragmentary or indeterminate examples (Masiak and Żylińska, 1994, fig. 7; Lieberman, 2003, figs. 8.1, 9; Briggs et al., 2008, figs. 1, 2.1). Structures present around mouth openings that are probably related to oral cones include the con- centric ridges and triangular areas of Lyrarapax unguispinus
41
Figure 1. Map to show the main fossil localities of the Guanshan Lagerstätte in eastern Yunnan Province, South China, including the Gaoloufang section, the sampling site in this paper. Fossil localities are from Hu et al. (2013, fig. 3).
Two trilobite assemblage zones, the lower Palaeolenus Assemblage Zone and the upper Megapalaeolenus Assemblage Zone, have been identified within the Wulongqing Formation (e.g., Luo et al., 2008); biostratigraphically, the Guanshan Lager- stätte belongs to the late period of the early Cambrian Canglang- puan Stage of South China (e.g., Lin, 2008), dated to the global Cambrian Series 2, Stage 4 (Steiner et al., 2005). Detailed dis- cussion of the stratigraphy, sedimentology, and taphonomy of the Guanshan Lagerstätte can be found in Hu et al. (2010, 2013).
Materials and methods
Repository and institutional abbreviation.—The single speci- men described in this paper is housed in the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing, China (NIGPAS).
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