The Greater Antilles harbor a diverse fauna with high levels of endemism. Two major models of historical biogeography have been proposed. The vicariance model proposes that a proto-Antillean fauna connecting North and South America in the late Cretaceous fragmented by plate tectonics to form the current island faunas. The dispersal model suggests that organisms dispersed over water during the Cenozoic to reach the islands. A variation on the dispersal model proposes that a dry land bridge connected the Greater Antilles with South America for a short time during the mid-Cenozoic facilitating dispersal into the Antilles. Most biogeographic studies addressing these models have been based on well-studied groups of vertebrates. Two lines of evidence suggest that dispersal is responsible for the origin of most lineages. First, most West Indian animal groups are depauperate at the higher taxonomic levels yet they often have some unusually large radiations of species. This taxonomic pattern, which is reflected in the fossil record, suggests that niches left vacant by groups absent from the Antilles have been filled by other groups present. Secondly, times of divergence estimated by molecular clocks indicate that most lineages arrived during the Cenozoic at times when there were no continental connections with the islands. These two lines of evidence are congruent with the nearly unidirectional current flow in the West Indies that probably brought flotsam from rivers in South America to these islands throughout the Cenozoic. Despite this general pattern, a few groups appear to have arrived very early and may represent ancient relicts of the proto-Antilles.