OLIGOCENE-MIOCENE BIOGEOGRAPHY OF THE WESTERN INDIAN OCEAN AND THE MYTH OF FAUNISTIC EXCHANGE WITH THE MEDITERRANEAN SEA (Invited Presentation)
Biogeographically, these faunas witness a pronounced provinciality during Oligocene and Early Miocene times, differing markedly from the much more homogeneous modern faunas. Oligocene faunas are known from Arabia, Pakistan and N-India. Throughout the Oligocene, several of the species are also found in the Western Tethys, documenting a still passable seaway for nearshore molluscs. Already at that time a clear biogeographic separation from the Western Tethys is evident. Moreover, the similarities between Indo-Pakistani faunas and Arabian ones are surprisingly low suggesting a further provincialism. During the Aquitanian the West-East interrelation drops to zero despite the passage having been open during this interval. Only the Burdigalian assemblages of N-India witness a very minor re-appearance of Western Tethys taxa, due to the re-establishment of rather ineffective migration pathways prior to the final closure of the Tethyan Seaway. During the Early Miocene, a distinct Central East African Province (CEAP) is distinguished from an Eastern-African-Arabian Province (EAAP) and a Western Indian Province (WIP) ranging along the western margin of India. All have only limited similarities with coeval faunas of the Proto-Indo-Polynesian Province (PIPP), usually ranging below 10% of shared species. No faunistic relation with the proto-Mediterranean Sea was established for eastern Africa and southern India during Miocene times pointing against any immigration of “Indo-Pacific” elements into the circum-Mediterranean area.