Latitudinal range fluctuations in the marine realm through geological time.

Our concept of polar marine faunas as having evolved in comparative isolation over long periods may need to be revised. New evidence from the Southern Ocean, in particular, suggests that a number of taxa may have had connections with lower-latitude regions in the comparatively recent past. Opportunities for high-low latitude faunal interchange were enhanced considerably by reduced meridional temperature gradients over the greater part of the last 100 million years. Indeed, such is the nature and scope of past latitudinal range fluctuations that they could be major determinants of regional patterns in taxonomic diversity.