ABSTRACT: The nature and timing of mechanisms and events that shaped the deep-sea biodiversity are still debated. The present contribution provides an analysis and discussion of the distribution of off-shelf ostracods in the Late Paleozoic-Early Mesozoic. A taxonomic revision introduces Kozuria gen. nov. to accommodate Triassic species of Acanthoscapha, traditionally seen as Devonian-Carboniferous holdover archetypal of the Middle Triassic deep-sea of the western Tethys. The taxonomic composition as well as the temporal and geographic distribution of Permian and Triassic off-shelf assemblages are summarized and discussed in the light of climatic and biotic events. This analysis illustrates the Triassic uniformization of the composition of off-shelf assemblages and two possible periods of offshore migration in the late Permian (Changhsingian) and Middle Triassic (Anisian).