Current approaches to foraminiferal paleoecology are based on concepts borrowed from modern ecolcgy. Pioneering studies of the 1930’s (Natland, 1933) showed that many late Neogene species have living representatives which provide a means for deducing paleoecolcgic conditions. This approach was expanded in the 1950’s as knowledge of modern distributional patterns provided empiric models useful in reconstructing marine paleoenvironments. Relationships such as faunal trends in species diversity and abundance, planktic to benthic ratios, abundances of porcelaneous and agglutinated species, species depth hiofacies and the upper depth limits of isobathyal species have been widely applied as paleoecologic tools, especially in estimating paleobathymetry. The use of modern faunal concepts to interpret extinct fossil faunas res s on the assumption that modern distributional patterns are analogous to those of the past and that homeomorphs of modern species, and especially groups of species, had similar environmental adaptations. Furthermore, paleodepth estimates based on living species assume that species depth habitats have not changed with time. While the general correlation of form, structure and environment observed in modern and fossil faunas supports these assumptions, it does not prove them. Recent evidence suggests that deep sea and continental margin species experienced major shifts in depth distribution during the Pleistocene. Similar changes involving both bathymetric migration and evolutionary turnover accompanied middle Tertiary changes in ocean environments and suggest that the present-day distribution patterns have evolved concomitantly with the development of the modern ocean over the last 14 million years.