Marine planktonic diatoms, as today's ocean main carbon and siliconexporters, are central to developing an understanding of the interplaybetween the evolution of marine life and climate change. The diatom fossilrecord extends as far as the Early Cretaceous, and the late Paleogene toRecent interval is relatively complete and well documented. Their earlyPaleogene record, when diatoms first expanded substantially in the marineplankton, is hampered by decreased preservation (notably an episode ofintense chertification in the early Eocene) as well as by observation bias.In this article, we attempt to correct for the latter by collecting diatomdata in various Paleocene samples from legacy Deep Sea Drilling Project and Ocean Drilling Program deep-sea sedimentsections. The results show a different picture from what previous analysesconcluded, in that the Paleocene deep-sea diatoms seem in fact to have been asdiverse and abundant as in the later Eocene, while exhibiting verysubstantial survivorship of Cretaceous species up until the Eocene.