Figure 4. Sanducystis sinensis from the Sandu Formation (Furongian Series, upper Cambrian) South China. General views of different slabs showing different states of preservation. (a) Slab NIGPAS163198 with eight partially complete

Figure 5. Sanducystis sinensis from the Sandu Formation (Furongian Series, upper Cambrian) South China. Note that all specimens (with the exception of specimens i, l, n and o) are at the same scale to emphasize changes along ontogeny

Figure 3 — Guangxiaspis guangxiensis Zhou, 1977 , Sandu Formation, Guole, Jingxi, Guangxi. 1–2 , NIGPAS148317, latex cast and internal mold of incomplete meraspid degree 2 exoskeleton respectively. Note the division between thorax and transitory pygidium indicated by white arrow. X13.5; 3–4

Figure 4 — Guangxiaspis guangxiensis Zhou, 1977 , Sandu Formation, Guole, Jingxi, Guangxi. 1 , NIGPAS148326, latex cast of complete early holaspid exoskeleton. Note the termination of exoskeleton indicated by white arrow. X6.5; 2–5 , NIGPAS148327: 2 , internal mold of complete early holaspid

Figure 5 — Guangxiaspis guangxiensis Zhou, 1977 , Sandu Formation, Guole, Jingxi, Guangxi. 1–2 , NIGPAS148334, latex cast and internal mold of complete early holaspid exoskeleton, X3.2; 3 , NIGPAS148335, internal mold of complete later holaspid exoskeleton, X2.1; 4 , NIGPAS148336, latex cast

, middle Marjum Formation, Utah, USA. 3, solutan indet., Secret Canyon Formation, Nevada, USA. 4, Pahvanticystis utahensis , upper Weeks Formation, Utah, USA. 5, solutan indet., Conasauga Formation, Alabama, USA. 6, solutan indet., Sandu Formation, Guangxi, South China. 7, Minervaecystis ? sp., Whipple

of tergites, Probinacunaspis nasalis–Peichiashania hunanensis Zone, upper Cambrian (Furongian, Stage 9), Sandu Formation, Guole Section, Guangxi Province, China, dorsal views. (f, g) Specimen immersed under ethanol; (f) general view; (g) detail of the left

Fig. 1. (A) Map of China, with the South China paleoplate outlined by a thick line; (B) inset box enlarged as a map of the Guiyang–Sandu region, Guizhou Province; the star in (B) shows the location of (C) the Xiayangao section of the Tonggao Formation (only the lower and middle parts are shown

Fig. 2. Green clay micro-concretions in the “green-spotted” silty mudstone, Tonggao Formation, Xiayangao section, Sandu. (A) Transmitted plane-polarized light image of silty mudstone with authigenic green clay micro-concretions. Internal laminations within the micro-concretions, interpreted

Fig. 3 Authigenic minerals in the silty mudstone, Tonggao Formation, Xiayangao section, Sandu. (A, B) Light grey, acicular or lath-shaped clay minerals, probably formed as pseudomorphs of gypsum, and larger, pale green, prismatic to subcubic minerals (chlorite-rich). (C) Thin section cut

threshold values discussed in the text. Data sources: 1, Jiulongwan ( Li et al. 2010 ; Och et al. 2016 ); 2, Three Gorges core #1 ( Kendall et al. 2015 ); 3, Rongxi ( Sahoo 2015 ); 4, Wuhe ( Sahoo et al. 2016 ); 5, Sandu (this study); 6, Jinjiadong ( Huang et al. 2017 ); 7, Long'e ( Huang et al

Fig. 1. Geological background of study sections. ( a ) Global palaeogeography showing the location of the South China Block from c. 635 to 510 Ma (modified from Zhang et al. 2015 ). ( b ) Geological map of the Yangtze platform during deposition of the Ediacaran Doushantuo Formation (modified

Fig. 9 Nereidella originata n. sp., lower part of the Tonggao Formation, Xiayangao section, Sandu. (A) NIGP141353, paratype, dorsal internal mould; (B) NIGP141354, holotype, dorsal internal mould; (C) NIGP141355, paratype, dorsal internal mould; (D) NIGP141356, paratype, dorsal internal mould