Fish otoliths from the pre-evaporitic (Early Messinian) sediments of northern Italy: their stratigraphic and palaeobiogeographic significance

The study of otolith assemblages from the pre-evaporitic Messinian deposits allows the reconstruction of a fauna of 79 taxa of which 35 could be identified at the specific level. Three of these are new: Diaphus rubus, Myctophum coppa, and Uranoscopus ciabatta. The assemblages reflect mainly a neritic environment influenced by the oceanic realm. Analysis of the global present-day geographic distribution of 42 of the recognised Messinian genera indicates that 88% of these are still living in the Mediterranean, 98% in the Atlantic and 78% in the Indo-Pacific realm. These results are in good agreement with the evolutionary trends documented for the Oligocene and Miocene teleost fauna, specifically an increase in percentage of genera inhabiting the modern Mediterranean, a very high percentage of Atlantic and Indo-Pacific genera, and a slight fall of the importance of present-day Indo-Pacific genera from the Rupelian up to the Late Miocene. Analysing the composition of the Early Messinian fauna at the level of nominal species indicates that about 53% of the species represented in the assemblages are still living in the Recent Mediterranean, and that a significant number of these were already present in the Tortonian. It is interesting that these species are mainly neritic. This seems to confirm that the close affinity of the fossil assemblage with the present-day Mediterranean neritic fauna, which was already recorded at the genus level for the Rupelian fauna, persists during the Neogene and continues until the Pleistocene.