SE Asian Cenozoic Larger Foraminifera:Taxonomic Questions,Apparent Radiation and Abrupt Extinctions

The Cenozoic larger foraminifera are important for biostratigraphy in SE Asia.This review examines the taxonomic inconsistencies of this group and especially the confusion over concepts of evolution,migration,radiation and extinction.It is proposed that from the Mediterranean to Indo-Pacific,Latest Eocene through Miocene,larger foraminifera populations were more homogenous than previously believed.Lineages show a slow morphological radiation interrupted by several extinctions.This pattern is superimposed on a long-term decline in larger foraminiferal abundance.The dating of the major biostratigraphic events are qualified.The main lineages of larger foraminifera can be classified by their evolutionary style.The classically“large”genera have highly peramorphic trends achieved through strong orthoselection,and these lineages were the most severely hit by a series of Mid-Eocene to Mid-Miocene extinction events.Other carbonate facies taxa that are traditionally grouped with the larger foraminifera are characterised by weak paramorphism,and these were much less affected by the extinction events.Some of these weakly peramorphic forms underwent Latest Miocene to recent radiation to and locally become rock-forming organisms.The three major and one minor larger foraminiferal extinction events since the Mid Eocene coincide with abrupt tectonic events across SE Asia.However,there are probably multiple causes for these extinctions,including global climatic changes.