| Summary: | Diatoms are a large and widespread group of phytoplankton with an important role in ecosystems as primary producers. They are of great use in biostratigraphic and paleoclimatic studies, namely in the Bering Sea, where they are abundantly preserved in sediments. Proboscia barboi, Proboscia curvirostris and Thalassiosira jouseae are Plio-Pleistocene centric diatoms of mid to high latitudes of the North Pacific and North Atlantic Oceans, and are important biostratigraphic markers and datums in these regions. In this study, the biostratigraphy of these species at IODP Site U1340 (Bowers Ridge, Bering Sea) is refined and their abundance record interpreted in light of the paleoclimatic context of the North Pacific during the Plio-Pleistocene, using environmental information from the diatom assemblage in order to better understand the ecology of these extinct species. On a morphological approach, T. jouseae and its close related species Thalassiosira nidulus are described based on specimens of Site U1340 and their differences discussed. In addition, evidence for the evolutionary link between P. barboi and P. curvirostris is provided and discussed.
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