Fig. 2: Gordoniconus beargulchensis holotype AMNH 43264, part.

a Complete specimen, showing suggested proostracum (blue), body chamber (orange), septate phragmocone (red) and primordial rostrum (yellow); scale = 1 cm. b Purple boxed region of Fig. 1a, showing structure interpreted as gills/gonads. c Green boxed posterior region of Fig. 1a, showing phragmocone and primordial rostrum; note the thin siphuncle and numerous complete septa, not all are marked. Image credit: S. Thurston.