Understanding biogeographic processes is fundamental to understanding how the marine fauna of the Southern Ocean will be impacted by a changing climate. Here I draw on a large phylogenetic dataset across a class of marine invertebrates (brittle stars) - reinforced by the fossil record, tectonic models and oceanographic hindcasts - to show how regional marine faunas around the Southern Ocean have been structured over the Cenozoic. In particular, the focus will be on the biogeographic importance of the southern subtropical gyres, how they have transported lineages across oceans, and how they mediate the interaction between temperate and polar biomes.