The “South Gondwana Fauna” in the Jurassic – an example of the utility of marine Ostracods for palaeobiogeography and palaeogeographic researches

Abstract

The present article is a review of a palaeobiogeographic analysis of Jurassic Ostracods from East Africa, India and Madagascar and includes also some general remarks on palaeobiogeography, biodiversity and Ostracod ecology.The palaeobiogeographic study shows the high significance of this microfossil group for the reconstruction of palaeogeographic processes, particularly plate tectonic developments and sea level changes. The “South Gondwana Fauna" (SGF) was established in the early Middle Jurassic in a shallow marine rift basin between Madagascar, India and East Africa (Gulf of Madagascar) which was a result of early rifting processes between East- and West Gondwana. The maximum diversity of this fauna was reached during the late Middle Jurassic due to geographic expansion of the basin caused by successive rifting and rising sea level. The strong endemic character of the fauna was related to the peripheral geographic position of the Gulf of Madagascar at the southern Tethyan margin. In the late Middle and Upper Jurassic the SGF shows a biogeographic separation between East Africa and Madagascar/India and increasing endemism which may be affected by a deepening of the gulf and/or by the appearance of other environmental migration barriers between these areas.