Fishes and the Break-up of Pangaea: An introduction
There is general agreement that a tight relationship exists between evolutionary histories of living lineages and the shifting geography of the Earth during the Phanerozoic, but how to depict that link has been much disputed in recent decades. The issue is fundamental, as it involves two supposedly-irreconcilable paradigms for how we interpret past and present distributions: the Darwin–Wallace biogeographic paradigm that involves dispersal from centres of origin, and the vicariance paradigm. When dealing with extinct organisms, for which we have only sparse and fragmentary fossil remains, the limit between the two paradigms becomes blurred. Here, all available data about time (stratigraphy) and space (palaeogeography) need to be gathered in order to detect biogeographical signals.
Because of the incompleteness of the fossil record, the analyses may lead to storytelling style descriptions of biogeographic scenarios (phylogenies are often weakly supported, datings are frequently vague and occurrences are sparse). But these scenarios are always open to refutation if new fossils are found and, accordingly, are genuine scientific hypotheses. The Darwin–Wallace biogeographic paradigm and the vicariance paradigm have been described as the extreme points of a pendulum; in this book, examples of relationships between the evolutionary history of fish clades and the break-up of Pangaea are described using approaches that lie between these extreme points of the pendulum.