The Cenozoic diversity of Antarctic Bivalves does not reflect Southern Ocean environmental changes after the Antarctic thermal isolation

Abstract

Environmental changes occurred in Southern Hemisphere in response to the separation of Antarctica from Australia, around Eocene/Oligocene boundary, and from South America, during the late Oligocene, greatly affected biodiversity in Southern Ocean. Although it is generally accepted that the Antarctic thermal isolation affected the Cenozoic biodiversity by changing environmental conditions, there is no available study concerning the Cenozoic dynamics of Antarctic bivalve diversity in relation to climatic changes. In this study, an assembling of all available bivalve family and genera described from Antarctic Cenozoic deposits as well as modern bivalve family and genera were analyzed in order to evaluate possible effects of Cenozoic environmental changes on Antarctic bivalve diversity along the Cenozoic. The main conclusion of this work is that the currently known Cenozoic record of the Antarctic bivalves does not reflect Cenozoic environmental changes. This is probably related to the restricted record of Antarctic bivalves, and therefore to the scarce knowledge on the Cenozoic diversity of the group. The analysis also revealed that Cenozoic intervals of highest diversity are attributed to few areas in Antarctica that are available for paleontological exploration. Besides, the large number of recorded bivalve taxa in some Cenozoic intervals may be related to the stratigraphic control of deposits.