Deinotherium levius and Tetralophodon longirostris (Proboscidea, Mammalia) from the Late Miocene hominid locality Hammerschmiede (Bavaria, Germany), and their biostratigraphic significance for the terrestrial faunas of the European Miocene

Abstract

During the Miocene, proboscideans reached their greatest diversification, and due to their marked evolutionary changes in dental size and morphology, they comprise an important biostratigraphic/biochronological tool. In this article, we study the proboscideans from the Late Miocene hominid locality Hammerschmiede (Germany), whose fossiliferous layers HAM 6, HAM 4 and HAM 5 are dated to 11.42, 11.44 and 11.62 Ma, respectively. The studied material consists of mandibular, tusk and cheek tooth specimens, which are attributed to the deinothere Deinotherium levius and the tetralophodont gomphothere Tetralophodon longirostris. An almost complete juvenile mandible of D. levius was CT-scanned and revealed that the erupting lower tusks represent the permanent ones. The mandible is most possibly associated with a lower deciduous tusk, and therefore these specimens capture the rare, and short in duration, moment of transition between deciduous and permanent lower tusks in fossil proboscideans and represent the first such example in deinotheres. The chronologically well-constrained proboscidean fauna from Hammerschmiede and the examination of other assemblages from European localities indicate that the coexistence of D. levius and T. longirostris characterizes the late Astaracian–earliest Vallesian, while Hammerschmiede may showcase the transition from the Middle Miocene trilophodont (Gomphotherium)-dominated faunas of central Europe to the Late Miocene tetralophodont-dominated ones. Finally, in order to decipher the dietary preferences of the Hammerschmiede Tetralophodon we performed dental mesowear angle analysis, which revealed a mixed-feeding diet with an important browsing component, significantly different from the heavily browsing one of Deinotherium known from other localities. Such distinct feeding habits between the taxa indicate niche partitioning, which allowed their sympatry.