Fig. 6.

Earliest ontogeny of Eohadrotreta from the Cambrian (Series 2) Shuijingtuo Formation, South China. a ventral view of conjunct juvenile valves, marking the shell growth stages, box indicates the area shown in (g). b lateral view of juvenile dorsal valve, marking the shell growth stages. c dorsal view of conjunct juvenile valves, marking the shell growth stages. d posterior view of conjunct valves. e pitting structures on ventral brephic shell. f enlarged pits of (e) show uniform size and orderly distributed pattern. g gradual transition at the boundary between metamorphic shell and mature shell, marking the nick points of mature shell by tailed arrow. h the diminished pitting structures still occur on the halo surface and extend to neanic shell before they eventually vanish. Abbreviations: bs, brephic shell; f, pedicle foramen; ha, halo; mas, mature shell; ms, metamorphic shell; ns, neanic shell; pr, protegulum; ps, post-metamorphic shell. Scale bars: a-c, 100 μm; d, 50 μm; e, h, 5 μm; f, 20 μm; g, 500 nm