The Eastern Mediterranean fish fauna from the Piacenzian deposits of Polis Graben (Cyprus Island)

Abstract

The Mediterranean fish fauna has been affected by the basin changing connections with surrounding seas and climatic changes throughout the geological history of the region. During the Eocene, the area corresponding to the present-day Mediterranean Sea was a biodiversity hotspot (Renema et al., 2008), and it was connected to the Atlantic and Indian Oceans as part of the Neotethys Ocean. Its fish fauna was dominated by tropical–subtropical species (Bellwood, 1996, Girone and Nolf, 2009, Brzobohatý and Nolf, 2011), as the climate was much warmer than today (Burke et al., 2018). The Proto-Mediterranean started to form in the late Oligocene–early Miocene, when it became disconnected from the Indo-Pacific realm (Bialik et al., 2019; Torfstein and Steinberg, 2020, Sun et al., 2021) and this was reflected in the early–middle Miocene fish fauna, which showed clear affinities to the Atlantic, North Sea and Paratethyan faunas (Agiadi et al., 2021). With the Miocene cooling (Herbert et al., 2016, Capella et al., 2019, Vasiliev et al., 2019) and subsequent isolation of the Mediterranean during the Messinian Salinity Crisis (Hsü et al., 1973, Roveri et al., 2014), the marine fish fauna became subtropical and highly endemic (Girone et al., 2010, Agiadi et al., 2017, Lin et al., 2017, Schwarzhans et al., 2020). The early Pliocene fish fauna was predominately a subtropical one with some tropical elements (Nolf and Girone, 2006, Agiadi et al., 2013, Agiadi et al., 2020), and maintained this character until the Early Pleistocene (Girone et al., 2006, Agiadi et al., 2011, Agiadi et al., 2018).

Despite this general overview of the evolution of the Mediterranean marine fish fauna, significant gaps in the fossil record remain, in particular regarding the Piacenzian. The only previous study on the Mediterranean fish fauna of this interval is that of Girone (2006) from the Adriatic area (Rio Merli section, Northern Italy). The purpose of this study is to describe the unknown late Pliocene fish fauna of the eastern Mediterranean and specifically that of the Levantine Sea, as it is revealed by studying otoliths found in the Piacenzian sediments cropping out in the Androlykou section on the island of Cyprus (Fig. 1). Otoliths are aragonitic, incrementally growing structures in the inner ear of teleost fishes that facilitate balance and sound perception (Schulz-Mirbach et al., 2018). They have species-specific morphology and are very common as fossils in Cenozoic marine and lake sediments (Nolf, 1985). In this study, we further use these fossil otoliths to reconstruct the paleoenvironment of west Cyprus in conjunction with a detailed biostratigraphic analysis.