The Rauenberg fossil Lagerstätte (Baden-Württemberg, Germany): A window into early Oligocene marine and coastal ecosystems of Central Europe

The Oligocene was a period of profound climatic and biotic changes, coinciding with a shift from a mostly ice-free warmhouse world at the Eocene-Oligocene boundary to a globally cooler, more seasonal climate. The Rauenberg locality (Baden-Württemberg, Germany) is one of the most significant early Oligocene fossil assemblages in Europe, containing both marine and terrestrial elements of fauna and flora. Preservation is often superb and comprises complete and articulated skeletons with soft tissue preservation. The diverse assemblage provides critical insights into the paleoenvironment of the Upper Rhine Valley. We reassess diversity at the locality, resulting in a list of 302 taxa found at the site, 207 of which are marine (52% of taxa represented by macrofossils). The rest are interpreted as originating from the coastal environment. Molluscan, echinoderm, and plant macrofossil diversity are assessed here for the first time. Based on these new results, we interpret Rauenberg as representing a fully marine assemblage deposited in a moderately shallow, low-energy tropical-subtropical environment. Productivity was high, and seafloor anoxia was intermittently developed. There is no evidence for long-term brackish influence or mangrove swamps, and no direct evidence for the development of seagrass meadows. On land, warm, frost-free conditions permitted the development of prevailingly evergreen sclerophyllous broad-leaved forests along with pine and palm-rich coastal forests on sandy soils. The marine invertebrate fauna shows more northerly affinities, whereas the vertebrate fauna is distinctly Paratethyan.