Biochronological framework for the late Galerian and early-middle Aurelian Mammal Ages of peninsular Italy

Abstract

Following a recent chronostratigraphic revision of 17 fossiliferous sites hosting assemblages constituting local faunas of the Aurelian Mammal Age (AMA) for peninsular Italy, we provide a re-structured biochronological framework and discuss the current validity and significance of the Middle Pleistocene Faunal Units (FU) for this region. In contrast with the previous model of a wide faunal renewal during Marine Isotope Stage (MIS) 9 (~330 ka), the First Occurrences (FO) of several species of the Torre in Pietra FU are significantly backdated and referred to the Fontana Ranuccio FU (530-400 ka). We show that the faunal renewal was more gradual and occurred earlier than previously assumed. Many taxa that are typical of the Late Pleistocene register their FO in the Fontana Ranuccio FU, latest Galerian, which is characterized by the almost total disappearance of Villafranchian taxa and by the persistence of typical Galerian taxa such as Dama clactoniana, Bison schoetensacki and Ursus deningeri, and by the FO of Stephanorhinus kirchbergensis, S. hemitoechus, Hippopotamus amphibius, Cervus elaphus eostepahnoceros, Ursus spelaeus, Canis lupus, and Vulpes vulpes. The next Torre in Pietra FU is characterized only by the FO of Megaloceros giganteus and of Mustela putorius. However, we observe that MIS 9 marks the actual moment when the faunal assemblages of this region are represented only by those taxa characterizing the late Middle Pleistocene and Late Pleistocene. For this reason, we propose to consider the Torre in Pietra (lower levels) local fauna still as a conventional boundary for the Galerian-Aurelian transition. Finally, we remark that the strong faunal renewal in MIS 13, with six FOs, coincides with the temperate climatic conditions due to the absence of marked glacial periods that could have favored the FOs and the subsequent spread of these taxa.