Did fossil cephalopods reproduce in the same way as modern squids and octopuses?
This is unclear. Cephalopods today are divided into the nautiluses, which reproduces many times, and the coleoids which reproduce only once (usually). It is generally assumed that the fossil nautiloids were very much like the modern species, with a long lifespan and numerous reproductive periods, but the evidence is lacking. Hatching size of the Mesozoic and Tertiary nautiloids is broadly similar to the living species. Ammonites seem to be different, with a hatching size much more like that of the coleoids. Sexual dimorphism is pronounced. Some writers have suggested that ammonites grew quite quickly—perhaps in as little as a year for the small species—and died after spawning. In some ammonites the shell eventually coils back on itself, almost sealing off the aperture. It has been suggested that like the modern octopus, the female ammonite brooded the eggs within the security of the shell, but didn’t feed, and eventually died after the hatchlings swam away. On the other hand, some esti
