Fauna Development of Larger Benthic Foraminifera in the Cenozoic of Southeast Asia

Abstract

The central part of the Indo-West Pacific (IWP) harbours the highest marine biodiversity, but only few data of its origin are available. In this paper the Cenozoic records of large benthic foraminifera are reviewed. Since many groups need species level revision, the occurrences of genera were reviewed based on records from literature. It is acknowledged that using genus level data is susceptible to differences in interpretation between authors, but the observed patterns are tested against morphological disparity and the number of taxa observed in a single locality. The analyses show a longitudinal shift in diversity from the western Tethys in the Eocene to the central IWP in the Miocene and younger. Oligocene faunas were relatively homogenous between these two regions. During the Eocene radiation occurred in the western Tethys, and abundant and often stratigraphically long-ranging species migrated east and reached Indonesia. This pattern reversed from the Late Eocene onwards, continuing in the Oligocene, and especially the Miocene. However, although the same genera were observed in Oligocene deposits from the western and eastern Tethys lineages showing similar morphological trends evolved independently and at different rates in the two regions. The observed patterns compare very well with the availability of suitable habitat in shallow tropical seas, and are fine-tuned by environmental parameters such as temperature and nutrient availability.