Highly diverse bryozoan faunas from the Plio-Pleistocene of the Greek island of Rhodes

With an estimated 300 species, the Plio-Pleistocene bryozoan faunas of Rhodes arc very diverse, especially when compared with the about 300 potentially fossilizable species described in the whole present-day Mediterranean, lite studied bryozoans arc classified into several palace biogctt graphic groups. The largest one consists of species with an eastern Atlantic/Mediterranean distribution. Smaller groups are the Mediterranean endemics, the cosmopolitan species, and the rare Indo-Pacific species. Two other groups are lacking from the present-day Mediterranean: the boreal-Atlantic and the tropical species.. Their presence and the high biodiversity could be due to several factors. During colder periods some species entered the Mediterranean from the North Atlantic, but the warmer and stable climate of the relatively isolated Aegean, also permitted tropical species to survive. Due to tectonic movements and giacio-custatic variations, several cycles of regression and transgression occurred. Together with temperature oscillations this could have made more habitats available and thus explain most of the observed uncommon biodiversity.