Fig. 9 in New insights into the origin and relationships of blastoid echinoderms

Fig. 9. Thecal plating in the callocystitid Lepadocystis moorei (Meek, 1871), Late Ordovician, Ohio, USA, illustrating typical extraxial plate arrangement in callocystitid and glyptocystitoid rhombiferans. Plates are arranged in four circlets, basals (B, BB), infra-laterals (IL, ILL), laterals (L, LL), and radials (R, RR), plus the orals which are largely axial in origin (see Fig. 5). All glyptocystitoids have four BB, five ILL and LL, and originally six RR. In all callocystitids R5 is absent. In Lepadocystis L5 interrupts the radial circlet and the periproct (P) is surrounded by four plates, IL4, IL5, L4, and L5. Lepadocystis has five, short ambulacra (dashed outlines below letters A–E) on the thecal plates and five pectinirhombs (Rh) across plate sutures B2:IL2, R1:L2, R3:L3, R3:L4, and R6:L1. Currents entered slits in the first mentioned plate and exited from the other plate. For plate homologies see Table 2. Redrawn and relabelled from Kesling 1967: S207, fig. 106.2c.