Trophic relationships in the Early Miocene Upper Marine Molasse of Baden-Württemberg, Southwest Germany, with special emphasis on the elasmobranch fauna

Abstract

The Early Miocene Upper Marine Molasse (OMM) in south-western Germany contains a diverse fossil ecosystem in which elasmobranch teeth are especially abundant. However, the scarcity of outcrops and sometimes poor preservation of fossils resulted in scant recent literature about the OMM. Here, we focus on the elasmobranch fauna to determine the trophic relationships within the OMM, using fossil teeth as proxies for diet and trophic levels based on functional morphology and an actualistic species- or genus-level approach. Herein we present a fresh and comprehensive palaeoecological reconstruction of the OMM ecosystem in Baden-Württemberg. All five outcrop areas available for the present analysis (Baltringen, Meßkirch-Rengetsweiler, Meßkirch-Walbertsweiler, Ulm-Ermingen, and Ursendorf) exhibit a similar faunal composition, with the apex predator being Otodus (Megaselachus) sp. Among the other elasmobranchs, there are mostly piscivorous and malacophagous species; taxa that feed on a variety of other invertebrates or amniotes (including marine mammals) are also present. The OMM sediments deposited in shallow-water settings, but there are fossils of more oceanic species that might, at times, have approached the shore. With a soft bottom, partly covered by sea grass, the OMM environment would have been like the present-day warm-waters settings of the Mediterranean.