The palaeozoogeography of Oligocene to Recent marine Ostracoda from the Neotropics (mid- and South America) and Antarctica

Classic biogeographical research has shown that the continent of South Amer ica supports a diverse and priceless biota, of which ostracods are an impor tant component. The distribution patterns of Oligocene to Recent shelf ostr acods, from the Neotropics to Antarctica, are explained in terms of dispers al and vicariant events. The quantitative examination of a newly constructe d database, containing over 140 genera, has allowed the measurement of gene ric similarity and endemicity between biotas of different geographical regi ons. The measurement of these parameters has aided the construction of a se ries of palaeoendemicity and communality maps. These maps emphasise changes in the spatio-temporal distribution of mid to Late Tertiary ostracods, and can aid in the recognition of abiotic mechanisms that modify genera distri bution. It has been demonstrated that changes in the oceanic currents and w ater-mass temperature are significant in the formation and maintenance of z oogeographical domains in the Oligocene-Recent of the Neotropics and Antarc tica. South America was an important centre of origin for ostracods during the Oligocene, however, few genera appear able to disperse northwards towar ds the Caribbean. The migratory success or failure of benthonic ostracods i s closely linked to oceanographical and climatic conditions, and their phys iology. Within the Meso-American region, filter and corridor pathways have allowed rapid dispersal of shallow water ostracods which has lead to decrea sed endemism. Although a distinctive ostracod assemblage was established in the Oligocene of Antarctica, the expansion of the Drake Passage permitted a new suite of cryophilic genera to emerge on the continent during the ?Mio -Pliocene. Within the Meso-American region the alteration of oceanic circul ation patterns, subsequent to the closure of the Panamanian portal, may hav e initiated the development of a 'proto' Panamanian Province in the Early P liocene. (C) 1999 Elsevier Science B.V. All rights reserved.