Sirenia inhabited the coastal waters of Europe and North Africa from the Eocene until the end of the Pliocene. They are the only herbivorous marine mammals, and their presence in the European/North African realm is supported by almost 400 fossil records. Their dependence on seagrass, as well as their ecological needs, limited their capability to adapt to the climate changes that occurred during the Cenozoic. Their disappearance from European and Mediterranean shores occurred in two different steps: 1) the European Atlantic extinction, related to global cooling and fragmentation of the seagrass meadows, which greatly reduced sirenia habitats and resources; 2) their disappearance from the Mediterranean, linked not to declining resources but to the onset of continental glaciations in the northern hemisphere.