Abstract. Marine planktonic diatoms, as today's ocean main carbon and silicon exporters, are central to developing an understanding of the interplay between the evolution of marine life and climate change. The diatom fossil record extends as far as the Early Cretaceous, and the late Paleogene to Recent interval is relatively complete and well documented. Their early Paleogene record, when diatoms first expanded substantially in the marine plankton, is hampered by decreased preservation (notably an episode of intense chertification in the early Eocene) as well as by observation bias. In this article, we attempt to correct for the latter by collecting diatom data in various Paleocene samples from legacy Deep Sea Drilling Project and Ocean Drilling Program deep-sea sediment sections. The results show a different picture from what previous analyses concluded, in that the Paleocene deep-sea diatoms seem in fact to have been as diverse and abundant as in the later Eocene, while exhibiting very substantial survivorship of Cretaceous species up until the Eocene.