Fig. 5 in Fossil coleoid cephalopod from the Mississippian Bear Gulch Lagerstätte sheds light on early vampyropod evolution

Fig. 5 Overview of coleoid shell evolution, showing our interpretations of the gladius/proostracum. Early coleoids, such as Gordoniconus13, add the primordial rostrum85 and proostracum14; vampyropods lose the phragmocone and primordial rostrum, the proostracum is now a gladius14; belemnoids and early decabrachians lose the body chamber86 and add the rostrum85; oegopsids lose the rostrum, some retain a demineralized primordial rostrum85 and phragmocone71, the proostracum is now a gladius14. Structures only labeled when they appear (solid black line) or are lost (dashed black line). Shell tissues: orange = phragmocone + body chamber (dashed = demineralized), blue = proostracum/gladius, green = primordial rostrum (dashed = demineralized), yellow = rostrum.