Figure 3

Vertical magnetic resonance imaging (MRI) sections of various sea urchin specimens. The virtual sections depict the axial complex (arrow). A Cidaris cidaris (Cidaroida). B Caenopedina mirabilis (Pedinoida). C Plesiodiadema indicum (Aspidodiadematidae). D Salenocidaris hastigera (Salenioida). E Strongylocentrotus purpuratus (Echinoida). F Lytechinus variegatus (Echinoida). G Genocidaris maculata (Temnopleuroida). H Echinoneus cyclostomus (Holectypoida). I Cassidulus caribearum ("Cassiduloida"). J Echinolampas depressa ("Cassiduloida"). K Echinarachnius parma (Clypeasteroida). Tables 1 & 2 list resolutions for each MRI dataset.