Biogeographical patterns are an outcome of the combined influences of earth history and ecology. Dispersal has been of particular importance to the assembly of the New Zealand biota, the predominantly dispersal fauna being superimposed on any surviving residues of a biota already present when Zealandia separated from eastern Gondwana in the late Cretaceous. The relative roles of Gondwanan vicariance and dispersal in generating the biota have been robustly argued, but there is now a strong consensus that most of the modern biota has dispersal origins, with, at most, just a few relictual Gondwanan taxa. Some geologists argue for New Zealand being completely submerged in ocean in the Oligocene, though many biologists argue for some small emergent islands, based in part on evidence from DNA sequencing, the biological clock and also the low likelihood that some biotic elements could have dispersed across the sea. The implication of complete submergence is that the entire biota has dispersal derivations.