SUPPLEMENTARY INFORMATION

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1 SUPPLEMENTARY INFORMATION doi: /nature Supplementary Figures Supplementary Figure 1. Stratigraphic column of the Cambrian Stage 3 (regional Canglangpuan Stage) Xiaoshiba section in the suburb of Kunming. The soft-bodied fossils from the Xiaoshiba biota occur between the Chengjiang (Cf) and Guanshan (Gf) biotas. The local subdivisions of the lower Cambrian follow the scheme proposed by Hu et al. 30. The fossiliferous layers correspond to the lower part of the Canglangpuan Stage, which is a thickbedded sandstone unit, occasionally embedded with thin-bedded siltstones and shales in Kunming area. Chengjiangocaris kunmingensis n. sp., is found in association with the trilobites Yunnanocephalus and Chengjiangaspis, both found in the Yu anshan and Hongjingshao Formations, and Hongshiyanaspis, considered to belong to the Yiliangella trilobite zone, the first biozone of the Canglangpuan 31. Fuxianhuia xiaoshibaensis n. sp. is found in association with the trilobite Zhangsania typica, which is known from the lower Canglangpuan Yiliangella zone 32. The Xiaoshiba biota represents the youngest unequivocal 33 occurrence of fuxianhuiid arthropods to date. 1

2 RESEARCH SUPPLEMENTARY INFORMATION Supplementary Figure 2. Head shield taphonomy in fuxianhuiids. a, Fresh carcasses transported to stagnant anaerobic bottom waters devoid of significant currents or scavengers. b, Decay of soft-tissues via bacterial degradation and autolysis. c, Initial degradation of the connective tissues leading to increased flexibility between exoskeletal elements. In the Xiaoshiba biota, this involves the inversion/rotation, easily distinguished by the position of 2 W W W. N A T U R E. C O M / N A T U R E

3 SUPPLEMENTARY INFORMATION RESEARCH the doublure, and forward repositioning of the head shield ( taphonomic dissection ) most likely associated with the sedimentary event responsible for final burial. Enhanced preservation is associated with those structures in immediate contact with the surrounding sediment. In the absence of such dissection, proximal and/or underlying features are preferentially effaced, with a potential for misinterpretation. d, Rapid burial of the carcasses attenuates further loss of morphological information due to decay and provides a suitable diagenetic environment for exceptional soft tissue preservation. e, YKLP holotype of Chengjiangocaris kunmingensis n. sp. from the Xiaoshiba biota (Hongjingshao Formation) showing exceptional preservation of the head structures due to the effect of the taphonomic dissection of the head region; anterior to the left. f, YKLP Fuxianhuia xiaoshibaensis n. sp. from the Xiaoshiba biota (Hongjingshao Formation) showing effaced preservation of head structures covered by head shield in life position; anterior up. 3

4 RESEARCH SUPPLEMENTARY INFORMATION Supplementary Figure 3. Head shield and specialized post-antennal appendage (SPA) taphonomy in Fuxianhuia and Chengjiangocaris specimens with head preservation (see Supplementary Table 1 for specimen numbers and references). 4

5 SUPPLEMENTARY INFORMATION RESEARCH Supplementary Figure 4. Chengjiangocaris kunmigensis n. sp. (a-c, e, f) and Fuxianhuia xiaoshibaensis n. sp. (d) from the early Cambrian (Canglangpuan) Hongjingshao Formation, Yunnan. a, YKLP articulated specimen in oblique view with taphonomically dissected head region and well-preserved appendage series; anterior to left. Note the presence of several pairs of walking legs per trunk tergite. b, YKLP 12022a articulated complete specimen in oblique view, showing full tergite count; anterior to right. c, Close up of the head region of YKLP (Fig. 1h) showing structural organization of the head and preserved ventral nerve cord; anterior up. d, YKLP articulated complete specimen in dorsal view; anterior up. e, Complete specimen of YKLP (Fig. 1f) in oblique view with taphonomically dissected head region and well preserved anterior walking legs; anterior to right. f, Complete specimen of holotype YKLP (Fig. 1d) in dorsal view with taphonomically dissected head region and full tergite count; anterior to left. Abbreviations: An, articulation n; asc, anterior sclerite; db, doublure; ey, eye; hs, head shield; nc, nerve cord; Pn, podomere n; tf, tail flukes; Tn, tergite n; wl, walking leg. W W W. N A T U R E. C O M / N A T U R E 5

6 RESEARCH SUPPLEMENTARY INFORMATION 2. Supplementary Table Taxon Head shield in situ Fuxianhuia protensa CN / NIGPAS [8, 34] CN [8, 20] CN [8] CN [8] CN [8] CN [8] CN * [8] RCCBYU [20] RCCBYU [20] ELRC [3, 4] ELRC 19250a* [3] ELRC [3] ELRC 19254a [3, 4] ELRC 19255b [3, 10] ELRC [3, 4] NIGP a [3] NIGPA [4] SK [4] YKLP 11321[11] YKLP [12] YKLP [12] YKLP [12] YKLP [12] YKLP 15004* [12] YKLP [12] YKLP [11, 12] YKLP [12] YKLP 15010* [12] YKLP [12] N = 29 Chengjiangocaris longiformis CN / NIGPAS * [8, 34] CN * [8, 20] RCCBYU [3, 10, 20] N = 3 Fuxianhuia xiaoshibaensis n.sp. GJS 0040a, b GJS 0041 GJS 0043a, b GJS 0045a, b GJS 0046 GJS 0068 GJS 0456 GJS 0457a, b N = 8 GJS 0042 N = 1 Chengjiangocaris kunmingensis n.sp. GJS 0022a, b* GJS 0025* GJS 0069* GJS 0460* N = 4 GJS 0001a, b GJS 0002a, b GJS 0004* GJS 005a, b* GJS 0008a, b GJS 0009a, b* GJS 0011 GJS 0012 GJS 0014 GJS 0015* GJS 0021 GJS a, b N = 12 Taphonomically dissected head region Supplementary Table 1 Specimens of Fuxianhuia and Chengjiangocaris with cephalic preservation examined for this study. Source references are marked in brackets. Symbol key: SPAs and articulation A2 visible, italic bold; articulations not preserved, normal text; Asterisk denotes specimens in that the SPAs not preserved or are not clearly observable (see also Supplementary Fig. 3). Institutional abbreviations: CN, Catalogue Number, Academia Sinica, Nanjing; ELRC, Early Life Research Centre, Chengjiang, China; NIGP / NIPGAS, Nanjing Institute of Geology and Palaeontology, Academia Sinica; RCCBUY, Research Centre for the Chengjiang Biota, Yunnan University, China; SK, Field Station of the Early Life Research Centre at Chengjiang; YKLP, Key Laboratory for Palaeobiology, Yunnan University. 6

7 SUPPLEMENTARY INFORMATION RESEARCH 3. Additional References 30. Hu, S.-X., Zhang, Z.-F., Holmer, L. E. & Skovsted, C. B. Soft-part preservation in a linguliform brachiopod from the lower Cambrian Wulongqing Formation (Guanshan Fauna) of Yunnan, South China. Acta Palaeontol. Pol. 55, (2010). 31. Luo, H.-L., et al. Early Cambrian Malong fauna and Guanshan fauna from Eastern Yunnan, China. Yunnan Sci, Technol. Press, Kunming, pp (2008). 32. Zhou, Z.-Y. & Yuan, J.-L. Lower Cambrian trilobite succession in Southwest China. Acta Palaeontol. Sin. 19, (1980). 33. Zhu, M.-Y., Vannier, J., Iten, H. V., & Zhao, Y.-L. Direct evidence for predation on trilobites in the Cambrian. Proc. R. Soc. Lond. B. 271, S277 S280 (2004). 34. Hou, X.-G. & Bergström, J. in The early evolution of Metazoa and the significance of problematic taxa (eds Simonetta, A. M. & Conway-Morris, S.) (Cambridge Univ. Press, Cambridge, 1991). 7