Lee et al.—Rankenella zhangxianensis


3


Figure 3. Outcrop photographs of Rankenella zhangxianensis in Zhangxia Formation, Beiquanzi section. For location, see Figure 2. (1) Bedding-plane view of Epiphyton-R. zhangxianensis-Cambroctoconus orientalis reef. Coin for scale is 20mm in diameter. (2) Bedding-parallel view of R. zhangxianensis within the inter-reef grainstone.


central part of the platform (Fig. 2). Six lithologic units were identified from the Cambrian succession of Shandong Province: Liguan, Zhushadong, Mantou, Zhangxia, Gushan, and Chaomidian formations in ascending order (Chough et al., 2010). The siliciclastic-dominant Liguan Formation (37m thick) was deposited in the eastern part of Shandong Province, unconformably overlying the Precambrian basement of granitic gneiss and sedimentary rocks. The Liguan Formation laterally and vertically changes into the carbonate-dominant Zhushadong Formation (up to 50m thick), representing peritidal environments (Lee and Chough, 2011) with a few small microbial reefs containing various calcified microbes (Lee et al., 2014b). Over- lying the Zhushadong Formation, the siliciclastic-dominant Mantou Formation (ca. 200m thick) was deposited in supratidal to subtidal environments dominated by tidal processes (Lee and Chough, 2011). The Zhangxia Formation is a carbonate-dominated


succession (~180m thick) that formed on top of the Mantou Formation. The formation consists of various carbonate facies including limestone-shale alternation, bioturbated lime mudstone, wackestone, packstone, oolitic/oncolitic/skeletal grainstone, and various microbial reefs including Epiphyton framestone, thrombolites, dendrolites, and stromatolites, deposited on a stable carbonate platform (Woo et al., 2008; Woo, 2009; Wooand Chough, 2010; Howell et al., 2011). It was formed during the Changhian Stage, including trilobite biozones of Lioparia, Crepicephalina, Amphoton-Taizuia, and Damesella-Yabeia, which corresponds to the late Stage 5 to the early Guzhangian of the Cambrian Series 3 (Geyer and Shergold, 2000; Chough et al., 2010; Peng et al., 2012). The reef-building sponges are generally found within the thrombolites throughout the Zhangxia Formation, but mainly in


the basal part (Woo, 2009) (Fig. 2.2). Some sponges also occur in dendrolites (Fig. 2.2). The study materials were collected from the basal part of


the Zhangxia Formation (Lioparia Zone), indicating the late Cambrian Stage 5 (Geyer and Shergold, 2000; Chough et al., 2010) (Fig. 2B). In the Beiquanzi section, where samples were collected, sponges sporadically occur within thrombolites of more than 7m in height and 30m in width. Several buildups are stacked vertically and laterally, causing difficulty in differentiating their outlines. The buildups are surrounded by skeletal and oolitic packstone to grainstone with a relatively sharp boundary. Within the buildups, Rankenella zhangxianensis n. sp. was found together with the calcified microbe (cyanobacteria) Epiphyton Bornemann, 1886 and a stem-group cnidarian Cambroctoconus orientalis Park et al., 2011 (Fig. 3.1). Rankenella zhangxianensis also occasionally occurs within the inter-reef packstone to grainstone (Fig. 3.2).


Systematic paleontology


Class Demospongia Sollas, 1885 Order Orchocladina Rauff, 1895


Family Anthaspidellidae Miller, 1889 Genus Rankenella Kruse, 1983


Type species.—Rankenella mors Gatehouse, 1968. Late Cambrian Stage 4–early Guzhangian, Ranken Limestone, Tindall Limestone, and Thorntonia Limestone, Australia (cf. Kruse and Reitner, 2014).


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