Figure 8

Evolution of semelparity within cephalopods according to different phylogenetic hypotheses regarding the origin of the Nautilida: (a) from Oncocerida⁶⁵, (b) from Tarphycerida/ Barrandeocerida²⁴ and (c) from Orthocerida⁶⁶. White rectangles represent acquisition of semelparity assuming that iteroparity is the primitive condition. Black rectangles represent an alternative scenario where semelparity is primitive and lost in the Nautilida, which evolved iteroparity instead. Possibly paraphyletic groups are shown in colour: Oncocerida (blue), Tarphycerida (green) and Orthocerida (orange). Fossil groups are assumed to be similar in reproductive strategies to their closest relatives. In all three cases with primitive iteroparity, it is possible that the transition to semelparity occurred after the origin of the Orthocerida and both strategies existed within this group.