Belemnites are nektopelagic cephalopods which developed a widespread pattern of distribution in the Jurassic, and most authors have accepted that their centre of origin was Europe. Available data suggest that the belemnites developed a global distribution only in the Toarcian, some 15 Ma after their first appearence in the European Hettangian. Development of the Boreal and Tethyan belemnite realms took place in the Middle Jurassic and continued through to the Cretaceous. New data from Argentina and the Antarctic Peninsula reaffirms the development of the global distribution of belemnites in the Toarcian, and sheds new light on the biogeographical patterns for the Jurassic of the southern hemisphere. This has considerable implications for understanding the development of faunal realms in the Mesozoic.