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

Abstract

Classic biogeographical research has shown that the continent of South America supports a diverse and priceless biota, of which ostracods are an important component. The distribution patterns of Oligocene to Recent shelf ostracods, from the Neotropics to Antarctica, are explained in terms of dispersal and vicariant events. The quantitative examination of a newly constructed database, containing over 140 genera, has allowed the measurement of generic similarity and endemicity between biotas of different geographical regions. The measurement of these parameters has aided the construction of a series 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 distribution. It has been demonstrated that changes in the oceanic currents and water-mass temperature are significant in the formation and maintenance of zoogeographical domains in the Oligocene–Recent of the Neotropics and Antarctica. South America was an important centre of origin for ostracods during the Oligocene, however, few genera appear able to disperse northwards towards the Caribbean. The migratory success or failure of benthonic ostracods is closely linked to oceanographical and climatic conditions, and their physiology. Within the Meso-American region, filter and corridor pathways have allowed rapid dispersal of shallow water ostracods which has lead to decreased 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 circulation patterns, subsequent to the closure of the Panamanian portal, may have initiated the development of a `proto' Panamanian Province in the Early Pliocene.