English: Diversity of Cambrian non-biomineralizing stem-group vertebrates. (a,b) Nuucichthys rhynchocephalus gen. et sp. nov., Drumian Marjum Fm., Utah, USA. (a) Holotype UMNH.IP.6084, general view (dry, direct light). (b) Morphological reconstruction; note

that the presence of dorsal branchial bars in this taxon is uncertain. (c,d) Metaspriggina walcotti Simonetta & Ineson [37], Wuliuan Burgess Shale Formation, British Columbia, Canada. (c) ROMIP 65347, general view (dry, polarized light); this specimen is incompletely preserved anterodorsally, resulting in the absence of the anteriormost myomeres and branchial bars. (d) Morphological reconstruction. (e,f) Emmonsaspis cambrensis (Walcott) [42], Cambrian Stage 4 Parker Slate Fm., Vermont, USA. (e) USNM 15314a (specimen 1), general view (dry, polarized light); this specimen only preserves the trunk. (f) Morphological reconstruction. (g,h) Myllokunmingia fengjiaoa Shu et al. [in 31], Cambrian Stage 3 Chiungchussu Fm., Yunnan, China. (g) RCCBYU 10200a, general view (dry, low-angle direct light); note that some details of the anterior head are not visible in this specimen. (h) Morphological reconstruction. (i,j) Yunnanozoon lividum Hou et al. [43], Cambrian Stage 3 Chiungchussu Formation Fm., Yunnan, China. (i) RCCBYU 10310a, general view (dry, direct); note that the caudal process is missing in this specimen. (j) Morphological reconstruction; note that the number and distribution of the myomeres are tentative. The reconstructions in (b,d,f,h,j) only illustrate some discriminating anatomical features discussed in the text, as they would be preserved in fossils (i.e. including decay changes, such as the shrinkage of myomeres), rather than the living organisms. Images in (c,e,i) were mirrored to facilitate comparison with the new fossil, and those in (g,i) were first

published in [38] and [44], respectively. Credits: J.-B. Caron for (c,e) and D. J. Siveter for (g,i).