Caudal vertebrae of Oksoko avarsan. Reconstruction (A) of caudal series showing which vertebrae are represented by which specimens. Vertebrae shaded blue are preserved only in MPC-D 102/11.a (B), whereas those shaded red (the pygal vertebrae) are preserved only in MPC-D 102/12 (C). Vertebrae shaded purple are represented by both specimens. Articulated caudal series of MPC-D 102/11.a in left lateral view (B). Articulated caudal series of MPC-D 102/12 in right lateral view (C), mirrored to match the orientation of MPC-D 102/11. Proximal caudal vertebra of MPC-D 102/12 (D, E) in right lateral (D) and dorsal (E) views. Pygal vertebrae of MPC-D 102/11.a (F) and MPC-D 102/12 (G), showing incorporation of additional vertebrae into the pygostyle. Distal caudal of MPC-D 102/12 (H–J) in left lateral (H), dorsal (I), and anterior (J) views. Abbreviations: idpf, infradiapophyseal fossa; nc, neural canal; ns, neural spine; p1–p3, first to third pygal vertebrae; post, postzygapophysis; pre, prezygapophysis; rpl, resorbed pleurocoel; spdf, supradiapophyseal fossa; tp, transverse process.