Early Oligocene fish otoliths from the Castellane area (SE France) and an overview of Mediterranean teleost faunas at the Eocene-Oligocene boundary

The study of Oligocene fish otoliths from the blue marls in the Castellane area allowed the reconstruction of a teleost fauna of 38 taxa of which 16 could be identified at species level. This is the first otolith-based neritic fish fauna known from the Mediterranean Early Oligocene. Additional data for Early Oligocene otolith-based fish faunas of the paleo-Mediterranean Basin are available only from the Liguro-Piemontese Basin, northern Italy, where the associations are dominated by deepwater fishes. Combining the data from both Mediterranean paleoenvironments, one obtains a list of 88 taxa of which 48 could be identified to species level. This is the only available overview on the composition of the otolith-based fish fauna in the Mediterranean realm during the Early Oligocene. It is shown that already in the Oligocene, the neritic fauna shows good affinities with the present-day Mediterranean one, while the deepwater fauna was a circumglobal oceanic one, strongly different from the Recent Mediterranean deepwater fauna. The Early Oligocene and Late Eocene Mediterranean otolith-based teleost faunas are compared to each other and to contemporaneous faunas from the Aquitaine Basin. This provides evidence for a very strong faunal break in both basins, both in the neritic and the mesopelagic fauna, and this faunal turnover is interpreted as a response to the paleoceanographic and climatic changes (cooling) that took place at the Late Eocene-Early Oligocene at global scale. Finally, the results indicate the great homogeneity of the Eastern Atlantic and Mediterranean faunas during the late Eocene. Notwithstanding the strong faunal turnover at the Eocene-Oligocene boundary, the new Oligocene fauna also exhibits a similar homogeneity over a large geographic area which, for this time unit, can be extended to the Paratethys.