The transition from the Paleocene to the Eocene epoch - approximately 55 million years ago - represents a critical moment in the Earth’s history, when the planet experienced the warmest climatic episode of the Cenozoic era. This sudden global warming resulted in a major turnover among the Earth’s marine and terrestrial organisms. Covering mammals, reptiles, invertebrates and plants as well as the spectrum of marine biota, this text documents both the well-established and the lesser-known turnovers, such as those of the calcareous nannoplankton and terrestrial mollusks.