Supplementary Figures

a, The Late Cambrian Anatolepis sp. fragment from central Texas Wilberns Formation (TC-1021). b, the holotype of Aglaspis franconensis USNM PAL 98916 the Late Cambrian Anatolepis sp. fragment from central Texas Wilberns Formation (TC-1021) from which a fragment was removed for scanning.c, Dorsal view of a translucent three-dimensional reconstruction of Anatolepis fragment with a distribution of horizontal canals that surround the tubricles. d, Dorsal view of a translucent three-dimensional reconstruction of Aglaspis franconensis fragment with a distribution of horizontal canals that surround the tubercles. e,f, Segmented horizontal canals showing how they sometimes are attached to the cuticular organs, in Anatolepis and Aglaspis franconensis respectively. Abbreviations: co, cuticular organ; hc, horizontal canal; tb, tubercle.