Aboral structures and mouth formation of C. subdepressus.

A Skeletal plates on the aboral surface of a 2 d old juvenile under polarized light. B Aboral view showing the distribution of miliary spines (arrow). C Detail of a miliary (left) and primary (right) spine. D Pair of ophicephalous pedicellariae (arrows) at the posterior region of the juvenile. E Digestory track of the juvenile and fecal pellet (arrow) being released by the anus. F Side view of the mouth (arrowhead) after the opening of the peristomial membrane. G Oral view showing the mouth and peristomial membrane 7 dpm. H Juvenile 120 dpf during locomotion with podia extended anteriorly and the characteristic longer pair of posterior spines (arrows). Scale bars =  (C, G); (A, D, E, F); (B); (H)