File:Representative stem-group chordates and comparisons with Pikaia.png

English: Figure 3 Representative stem-group chordates and comparisons with Pikaia

Hide caption (A–E) Yunnanozoon. (A) RCCBYU 10310, showing gut tube, posterior segments, and filamentous arches. (B) YKLP 13005. (C) YKLP 13032. (D) YKLP 13016. Black arrows denote separation between dorsal “segments.” (E) Schematic anatomical reconstruction after Cong et al. and Tian et al. (F) Pikaia, schematic reconstruction illustrating dorsoventrally inverted anatomical reinterpretation. (G) Hypothetical cross-sections of trunk segments in Pikaia3 under the new dorsoventrally inverted interpretation, showing dorsal and ventral “fins.”3 Color legend on the right applies to (E)–(I). (H) USNM 198688, detail of the anterior region showing bilobed head, anterior appendages, pharyngeal cavity, and dorsal nerve cord. (I) Schematic reconstruction of the anterior region of Pikaia under the new anatomical interpretation, showing the anterior appendages as dorsally directed gills. (J and K) Banffia constricta. (J) ROMIP 49914. (K) ROMIP 49898, photographed under ammonium chloride sublimate to highlight relief of lateral grooves and segmental boundaries.

RCCBYU, Research Center of Chengjiang Biota, Yunnan University, Kunming; YKLP, Yunnan Key Laboratory for Palaeobiology, Kunming; USNM, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution; ROMIP, Royal Ontario Museum, Invertebrate Palaeontology; Ps, posterior segments; Gu, gut; ?Go, possible gonads; Fa, filamentous arches; ct, connective tissue, integument; am, axial musculature; ds, digestive system; nc, dorsal nerve cord; aa, anterior appendages; ?no, hypothetical notochord; My, myomeres; Ph, pharynx; Lg, lateral grooves; Cs, constriction; Ts, tail segments; Mo, mouth opening. Scale bars, 5 mm (A, C, and D); 10 mm (B, J, and K); 1 mm (H).