De Nederlandse fossiele zeezoogdieren. Een overzicht

In this article the Cetacea (wales and delphins), the Pinnipedia (seals, sea lions and walrusses) and the Sirenia (sea cows) are united under the term sea mammals. Fossils of sea mammals are found to a lesser extent than those of land mammals. In addition to their rareness, their appearance is restricted to specific areas also: recent and fossil sea bottoms and beaches. Therefore, still little is known about the evolution of sea mammals, so the genus and species determination often is difficult or even impossible. Furthermore, especially older literature appears to contain incorrect information, and, in addition, to mention a huge amount of different names for the same genera and species. Thus, it is not amazing that fossil sea mammals are not a center of interest, neither in science or in popular areas. The Netherlands and the adjoining North Sea belong to the richest locations of the world of fossil sea mammals. How could it be different, with such a geological history abounding in water! The ever changing shore lines of the North Sea during Miocene, Pliocene, Pleistocene and the early Holocene in combination with the mouths of the many large rivers have left behind a very variated sea mammal fauna. For example, nowhere on the world so many fossils are found of the Pleistocene walrus as in the Netherlands! However, these fossils have bee neglected by scientists since the end of the nineteenth century, in spite of their quantity and quality. The collections are often in a bad condition and often the accompagnying data have been lost.